Performance information

• Change in Thermodynamic Entropy and Free Volume of Epoxy Resin During Tensile Deformation　　　　　　　　　　　　　　　
  Takuma Inoue; Yutaka Oya; Jun Koyanagi; Takenobu Sakai
  Polymers, Volume：17, Number：4, Feb. 2025
  The relationship between thermodynamic entropy generation and free volume changes during the tensile deformation of epoxy resin was investigated. Thermodynamic entropy generation was evaluated using differential scanning calorimetry (DSC) for samples at various strain levels, while free volume changes were measured with positron annihilation lifetime spectroscopy (PALS). Volumetric strain was assessed through the digital image correlation (DIC) method. The results showed that both thermodynamic entropy and free volume increase during tensile deformation, and the average free volume radius becomes more uniform. It was observed that thermodynamic entropy generation and free volume each exhibit a linear relationship with volumetric strain. Additionally, thermodynamic entropy generation increased linearly with free volume. These findings suggest that the increase in thermodynamic entropy during tensile deformation is attributed to irreversible changes, such as the expansion of free volume within the material.
  Scientific journal
  DOI：https://doi.org/10.3390/polym17040477
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85219006444&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85219006444&origin=inward
  DOI ID：10.3390/polym17040477, eISSN：2073-4360, SCOPUS ID：85219006444
• Mechanical Behavior Dependence on Geotextiles Interweave Configuration Used in Coastal Restoration　　　　　　　　　　　　　　　
  Carlos Rolando RIOS-SOBERANIS; Takenobu SAKAI; Shuichi WAKAYAMA; Emilio PEREZ-PACHECO; Jorge Carlos; CANTO-PINTO
  Advanced Experimental Mechanics, Volume：9, First page：3, Last page：10, Jan. 2025, [Reviewed], [Invited]
  English, Scientific journal
  DOI：https://doi.org/10.11395/aem.24-0017
  DOI ID：10.11395/aem.24-0017
• Comparation of Polyethylene and Polypropylene on the Time-Temperature Superposition Principle by Molecular Dynamics Simulations　　　　　　　　　　　　　　　
  Yuan Shihong; Takenobu Sakai
  Advanced Experimental Mechanics, Volume：10, First page：1, Last page：6, Jan. 2025, [Reviewed], [Last]
  English, Scientific journal
  DOI：https://doi.org/10.11395/aem.25-0001
  DOI ID：10.11395/aem.25-0001, 共同研究・競争的資金等ID：30455017
• Molecular Dynamics Study on Effect of Contamination on Mechanical Properties of CFRP Joints
  Takenobu SAKAI; Reimon TERAZAWA; Kensuke KAGEYAMA
  Journal of the Japan Society for Composite Materials, Volume：50, Number：5, First page：177, Last page：184, Sep. 2024, [Reviewed], [Lead, Corresponding]
  The Japan Society for Composite Materials, Japanese, Scientific journal
  DOI：https://doi.org/10.6089/jscm.50.177
  DOI ID：10.6089/jscm.50.177, ISSN：0385-2563, eISSN：1884-8559, 共同研究・競争的資金等ID：30455017
• Investigating the influence of free volume and temperature on time-temperature superposition principle by MD simulation
  Yuan Shihong; Takenobu Sakai
  Mechanical Engineering Journal, Volume：11, Number：6, First page：24, Last page：00242, Sep. 2024, [Reviewed], [Last]
  Japan Society of Mechanical Engineers, English, Scientific journal
  DOI：https://doi.org/10.1299/mej.24-00242
  DOI ID：10.1299/mej.24-00242, eISSN：2187-9745, 共同研究・競争的資金等ID：30455017
• Analyzing the Sound of Materials: Application of Acoustic Emission Technique for Monitoring Material Behavior
  Carlos Rolando Ríos-Soberanis; Takenobu Sakai; Shuichi Wakayama
  Materials Science Forum, Volume：1118, First page：111, Last page：117, Mar. 2024, [Reviewed]
  During the last years, some concerns have arisen in relation to the outcome of mechanisms of failure in composite materials according to its mechanical behavior. Such interest resulted in the development of new complex structures in order to enhance its mechanical resistance and the controlling of damage processes. Nevertheless, it is imperative to understand the degree of mechanical performance that these materials can achieve when under external stresses. In this regard, applying Acoustic Emission (AE) technique is widely known as a very effective technology for identifying and monitoring damage progression on different kind of materials and structures providing valuable information. AE is a non-destructive technique (NDT) capable of detecting micro damage initiation and propagation along several types of failure modes such as reinforcement/matrix interfacial debonding, matrix cracking, delamination, fracture, etc. This paper examines applications of AE regarding to composite materials where fracture processes are generally more complex and data interpretation is correspondingly more difficult. Finally, in order to continuously improve the reliability of this technique, several researches have advanced its trustworthiness through innovations in AE technology. Some perspectives are discussed.
  Trans Tech Publications, Ltd., English, Scientific journal
  DOI：https://doi.org/10.4028/p-hk3qly
  DOI ID：10.4028/p-hk3qly, eISSN：1662-9752
• Evaluation of the curing reaction of epoxy resins by electrochemical measurement and molecular orbital method
  Koki Matsumura; Tetsuya Morimoto; Takenobu Sakai
  Advanced Composite Materials, First page：1, Last page：15, Mar. 2024, [Reviewed], [Last, Corresponding]
  Informa UK Limited, English, Scientific journal
  DOI：https://doi.org/10.1080/09243046.2024.2325639
  DOI ID：10.1080/09243046.2024.2325639, ISSN：0924-3046, eISSN：1568-5519
• Evaluation of Volumetric Strain on Polyamide 6 by Thermodynamic Entropy Generation
  Takenobu Sakai; Yutaka Oya; Jun Koyanagi
  Experimental Mechanics, Volume：64, Number：1, First page：105, Last page：111, Nov. 2023, [Reviewed], [Lead, Corresponding]
  Springer Science and Business Media LLC, English, Scientific journal
  DOI：https://doi.org/10.1007/s11340-023-01009-x
  DOI ID：10.1007/s11340-023-01009-x, ISSN：0014-4851, eISSN：1741-2765
• Effects of different loading methods in molecular dynamics on deformation behavior of polymer crystals　　　　　　　　　　　　　　　
  Koki Yoshida; Kensuke Kageyama; Takenobu Sakai
  Mechanics of Time-Dependent Materials, Sep. 2023, [Reviewed], [Last, Corresponding]
  English, Scientific journal
  共同研究・競争的資金等ID：30455019;30455017
• Application of AE Method to Crack Tip Location and Damage Mode Evaluation on Mode-I and Mode-II Tests for CFRP　　　　　　　　　　　　　　　
  Takenobu SAKAI; Kakeru MIURA; Kensuke KAGEYAMA
  Journal of the Japanese Society for Experimental Mechanics, Volume：23, Number：2, First page：132, Last page：137, Jul. 2023, [Reviewed], [Lead, Corresponding]
  Japanese, Scientific journal
  DOI：https://doi.org/10.11395/jjsem.23.132
  DOI ID：10.11395/jjsem.23.132
• Identification of invisible fatigue damage of thermosetting epoxy resin by non-destructive thermal measurement using entropy generation
  Natsuko Kudo; Ryohei Fujita; Yutaka Oya; Takenobu Sakai; Hosei Nagano; Jun Koyanagi
  Advanced Composite Materials, Volume：33, Number：2, First page：233, Last page：249, Jun. 2023, [Reviewed]
  Informa UK Limited, English, Scientific journal
  DOI：https://doi.org/10.1080/09243046.2023.2230687
  DOI ID：10.1080/09243046.2023.2230687, ISSN：0924-3046, eISSN：1568-5519
• Effect of the Frequency Characteristics of AE Sensor on the Evaluation of CFRP Damage Modes　　　　　　　　　　　　　　　
  Tomohisa SHIRAISHI; Takenobu SAKAI; Kensuke KAGEYAMA
  Volume：23, Number：2, First page：145, Last page：151, Jun. 2023, [Reviewed], [Corresponding]
  Japanese, Scientific journal
  DOI：https://doi.org/10.11395/jjsem.23.145
  DOI ID：10.11395/jjsem.23.145
• Effect of Crystallization Treatment Method on CFRPA6's Damage Behavior　　　　　　　　　　　　　　　
  Takenobu Sakai; Fei Chunhao; Kensuke Kageyama
  Volume：69, Number：4, First page：167, Last page：172, Apr. 2023, [Reviewed], [Lead]
  Japanese, Scientific journal
• Fabrication and characteristics of electret using fine silica powder and its application of ultrasonic sensor　　　　　　　　　　　　　　　
  Kensuke Kageyama; Kakeru Kobayashi; Yoshiaki Kawada; Takenobu Sakai
  ELECTRONICS AND COMMUNICATIONS IN JAPAN, Volume：105, Number：3, Sep. 2022
  Electrets were prepared by spin-coating the dispersion of fine silica powders, and their charge retention characteristics were investigated. Finer silica aggregates were formed on the PTFE surface layer by spin-coating the dispersed solution of fine silica powder than those formed by spray-coating colloidal silica. Electrets using fine silica powder also showed better charge retention characteristics than those using colloidal silica. Such an improvement in the charge retention might be due to the suppression of discharge in the excessive gap caused by coarse silica aggregates. Then, ECSs were fabricated using the prepared electrets, and their transmitting and receiving characteristics of airborne ultrasound were also investigated. The peak sensitivity of the ECS using a spin coating of fine powdered silica dispersion was slightly improved from those using spray coating of colloidal silica. On the other hand, the peak frequency and frequency band were greatly improved using spin coating of fine powdered silica dispersion. Therefore, ECS using fine silica powder is expected to be applied as a broadband airborne ultrasonic sensor.
  WILEY, English, Scientific journal
  DOI：https://doi.org/10.1002/ecj.12372
  DOI ID：10.1002/ecj.12372, ISSN：1942-9533, eISSN：1942-9541, Web of Science ID：WOS:000840118200001
• Relation between CFRP Stacking Sequence and AE Peak Frequency by Wavelet Analysis　　　　　　　　　　　　　　　
  Takenobu Sakai; Ren Kawaguchi; Yohei Yamada; Kensuke Kageyama
  Volume：68, Number：8, First page：315, Last page：320, Aug. 2022, [Reviewed], [Lead]
  Japanese, Scientific journal
• Elucidation of the Time-Temperature Superposition Principle of Polyethylene
  Shihong Yuan; Ayako Mano; Kensuke Kageyama; Takenobu Sakai
  Journal of the Japan Society for Composite Materials, Volume：48, Number：4, First page：149, Last page：155, Jul. 2022, [Reviewed]
  The Japan Society for Composite Materials, Japanese, Scientific journal
  DOI：https://doi.org/10.6089/jscm.48.149
  DOI ID：10.6089/jscm.48.149, ISSN：0385-2563, eISSN：1884-8559
• Evaluation of viscoelastic non-isochoric plastic behavior of PBT and PA6
  Yoshihiko Sato; Sayaka Masumizu; Kenichi Sakaue; Jun Koyanagi; Akio Ohtani; Takenobu Sakai
  Mechanics of Time-Dependent Materials, Apr. 2022, [Last]
  Springer Science and Business Media LLC, Scientific journal
  DOI：https://doi.org/10.1007/s11043-022-09552-1
  DOI ID：10.1007/s11043-022-09552-1, ISSN：1385-2000, eISSN：1573-2738
• A Possibility for Quantitative Detection of Mechanically-Induced Invisible Damage by Thermal Property Measurement via Entropy Generation for a Polymer Material　　　　　　　　　　　　　　　
  Takenobu Sakai; Naohiro Takase; Yutaka Oya; Jun Koyanagi
  Materials, Volume：15, Number：3, First page：737, Jan. 2022, [Reviewed], [Lead]
  English, Scientific journal
• CFRTPの曲げ特性に及ぼすひずみ速度依存性の粘弾性および結晶構造的考察　　　　　　　　　　　　　　　
  福嶋 遼太; 蔭山 健介; 坂井 建宣
  Sep. 2021, [Reviewed], [Last, Corresponding]
  Japanese, Scientific journal
• 大気中熱処理がCFRTPの動的粘弾性特性に及ぼす影響　　　　　　　　　　　　　　　
  福嶋 遼太; 蔭山 健介; 坂井 建宣
  Volume：21, Number：2, Jul. 2021, [Reviewed], [Last, Corresponding]
  Japanese, Scientific journal
• CFRPの破壊モード分類のための時間周波数解析法の選定　　　　　　　　　　　　　　　
  白石 知久; 蔭山 健介; 坂井 建宣
  Volume：67, Number：4, First page：133, Last page：134, Apr. 2021, [Reviewed]
• Molecular Dynamics Simulation for Evaluating Fracture Entropy of a Polymer Material under Various Combined Stress States　　　　　　　　　　　　　　　
  Naohiro Takase; Jun Koyanagi; Kazuki Mori; Takenobu Sakai
  Materials, Volume：14, Number：8, First page：1884, Apr. 2021, [Reviewed], [Last]
  English, Scientific journal
• Molecular Dynamics Simulation of Weak Bonds in Carbon Fiber Reinforced Plastic Adhesive Joints　　　　　　　　　　　　　　　
  Reimon Terazawa; Atsushi Tamura; Kensuke Kageyama; Takenobu Sakai
  Advanced Composite Materials, Mar. 2021, [Reviewed], [Last, Corresponding]
  English, Scientific journal
• Effect of heat treatment on mechanical properties of carbon-fiber-reinforced themoplastic
  Ryota Fukushima; Yohei Yamada; Kensuke Kageyama; Takenobu Sakai
  Advanced Composite Materials, Volume：30, Number：6, First page：527, Last page：543, Mar. 2021
  Informa UK Limited, Scientific journal
  DOI：https://doi.org/10.1080/09243046.2021.1893886
  DOI ID：10.1080/09243046.2021.1893886, ISSN：0924-3046, eISSN：1568-5519
• Formulation of non-linear viscoelastic–viscoplastic constitutive equation for polyamide 6 resin　　　　　　　　　　　　　　　
  Jun Koyanagi; Kodai Hasegawa; Akio Ohtani; Takenobu Sakai; Kenichi Sakaue
  Heliyon, Volume：7, Number：2, First page：e06335, Last page：e06335, Feb. 2021
  Elsevier BV, Scientific journal
  DOI：https://doi.org/10.1016/j.heliyon.2021.e06335
  DOI ID：10.1016/j.heliyon.2021.e06335, ISSN：2405-8440
• Molecular dynamics simulation for the quantitative prediction of experimental tensile strength of a polymer material　　　　　　　　　　　　　　　
  Jun Koyanagi; Naohiro Takase; Kazuki Mori; Takenobu Sakai
  Composites Part C: Open Access, Volume：2, First page：100041, Last page：100041, Oct. 2020, [Reviewed], [Last]
  Elsevier BV, Scientific journal
  DOI：https://doi.org/10.1016/j.jcomc.2020.100041
  DOI ID：10.1016/j.jcomc.2020.100041, ISSN：2666-6820
• Effect of matrix crystallinity of carbon fiber reinforced polyamide 6 on static bending properties
  Takenobu Sakai; Nur Safiah Binti Shamsudim; Ryota Fukushima; Kensuke Kageyama
  Advanced Composite Materials, First page：1, Last page：14, Aug. 2020, [Reviewed], [Lead, Corresponding]
  Informa UK Limited, Scientific journal
  DOI：https://doi.org/10.1080/09243046.2020.1802805
  DOI ID：10.1080/09243046.2020.1802805, ISSN：0924-3046, eISSN：1568-5519
• AEと環境の同時測定によるトマトの乾燥ストレス応答評価の検討　　　　　　　　　　　　　　　
  蔭山 健介; 林 由将; 菅野 アナム; 坂井 建宣
  Volume：32, Number：1, First page：1, Last page：5, Feb. 2020, [Reviewed], [Last]
  Scientific journal
• Effect of Crystallization on Mechanical Properties of CFRTP　　　　　　　　　　　　　　　
  Takenobu Sakai; Nur Safiah Binti Shamsudim
  Conference Proceedings of the Society for Experimental Mechanics Series, First page：45, Last page：46, 2020
  Carbon fiber reinforced thermoplastics are consisted with the carbon fiber and thermos plastics such as PP, PA6, PI, and PC and so on. Mechanical properties, especially viscoelasticity, of CFRTP were depended on the matrix resin, therefore, if the mechanical properties of matrix resin has changed, CFRTP’s properties will be also changed. In this study, carbon fiber reinforced polyamide 6 was used for evaluate the effect of crystallization. The materials were heat treated for crystallization, and the crystallization was controlled by heat treatment time. As the result of dynamic mechanical analysis, storage modulus was decreased with the increase in the heat treatment time, however, longer heat treatment time made the storage modulus increased. As the results of DSC measurement, the peak shape of melting point was different each other. The double peak was observed with the longer heat treatment time, however, the single peak was observed with the short heat treatment time. This is because the mechanical properties of CFRTP was dominated by the peak shape and peak area of the melting point.
  Springer, English, International conference proceedings
  DOI：https://doi.org/10.1007/978-3-030-29986-6_7
  DOI ID：10.1007/978-3-030-29986-6_7, ISSN：2191-5652, SCOPUS ID：85087179263
• Investigation of Drought Stress Response in Tomato Plants by Simultaneous Measurement of AE and Environment　　　　　　　　　　　　　　　
  Kensuke Kageyama; Yoshimasa Hayashi; Anamu Kanno; Takenobu Sakai
  ECO-ENGINEERING, Volume：32, Number：1, First page：1, Last page：5, 2020
  Simultaneous measurement system of AE at the stem and illuminance, temperature and humidity of the ground surface in greenhouse cultivation tomatoes was developed and the simultaneous measurement were carried out at two sites. AE occurrence rate tended to decrease in winter similar to humidity deficit HD. Most AE occurred in the daytime though the daily fluctuation behavior of HD and AE events differed by the site. The rank correlation coefficients, RV1h and RV6h using hourly differentials of AE events and HD, and those from 6h moving average values, respectively were derived. As the result, the strong correlation found between average value of RV1h of the whole period and yield Y, and there was also the weak correlation between monthly average value of RV1h and Y.
  SOC ECO-ENGINEERING, ENV SCI & TECH, GRAD SCH LIFE & ENV SCI, Japanese, Scientific journal
  DOI：https://doi.org/10.11450/seitaikogaku.32.1
  DOI ID：10.11450/seitaikogaku.32.1, ISSN：1347-0485, eISSN：1880-4500, Web of Science ID：WOS:000510837400001
• 一方向性CFRPの損傷発生挙動のひずみ速度・温度依存性　　　　　　　　　　　　　　　
  坂井 建宣; 安部 聡; 蔭山 健介
  Volume：46, Number：2, First page：54, Last page：61, 2020, [Reviewed], [Lead, Corresponding]
  Scientific journal
• Development of an Impulse Response Method for Assessing Knee Osteoarthritis at the Femorotibial Joint: Comparison Between Healthy Young Adults and Older Women with Clinical Knee Osteoarthritis
  Keita Aimoto; Susumu Ota; Kazunori Hase; Takenobu Sakai; Katsuya Kodama; Hiroaki Nakamura
  Journal of Medical and Biological Engineering, Volume：40, Number：1, First page：35, Last page：40, 2019, [Reviewed]
  © 2019, Taiwanese Society of Biomedical Engineering. Purpose: Because in patients with knee osteoarthritis (OA), the knee joint properties such as cartilage, meniscus, soft tissue and bone formation are assumed to degeneration change, the shock absorb might also decrease. The transmission of impulse from femur and tibia is thought to change in the knee joint. The purpose of the present study was to determine the differences between young healthy women and elderly women with knee OA using the impulse response method. Methods: Twenty-six older women with clinically diagnosed knee OA (OA group, age: 69 ± 6 years) and 26 young women without knee OA (young control [YC] group, age: 21 ± 1 years) participated in the study. The OA group fulfilled the knee OA classification criteria based on clinical findings. An input device provided an impulse to the subject while standing. The output value was measured using a single-axis accelerometer. The outcome measures were the input–output ratio and power spectrum. Results: The input–output ratio did not significantly differ between the groups. The power spectrum at 21–30 Hz was significantly greater (p = 0.036) in the OA group than in the control group. Additionally, the power spectrum at 21–30 Hz correlated with knee pain (r = 0.39, p = 0.049). At 21–30 Hz, transmission of impulse from femur and tibia in the knee joint was lower in the OA group than in the control group. Conclusion: The IR method used in the present study could detect the transmission of impulse in early knee OA.
  Springer Science and Business Media LLC, Scientific journal
  DOI：https://doi.org/10.1007/s40846-019-00484-9
  DOI ID：10.1007/s40846-019-00484-9, ISSN：1609-0985, eISSN：2199-4757, SCOPUS ID：85068919681
• 廃タイヤ強化ポリ乳酸複合材料の機械的特性評価　　　　　　　　　　　　　　　
  坂井建宣; 川井喬介; 蔭山健介; 立山耕平; 山田浩
  Volume：64, Number：1, First page：31, Last page：35, 2019, [Reviewed], [Lead, Corresponding]
  Scientific journal
• Estimating the creep behavior of glass-fiber-reinforced polyamide considering the effects of crystallinity and fiber volume fraction　　　　　　　　　　　　　　　
  Takenobu Sakai; Yuto Hirai; Satoshi Somiya
  Volume：4, Number：5, First page：1, Last page：9, 2019, [Reviewed], [Lead, Corresponding]
  Scientific journal
• 分子動力学シミュレーションによるポリカーボネートの体積クリープの静水圧依存性評価　　　　　　　　　　　　　　　
  坂井 建宣; 鈴木 将士; 蔭山 健介
  Volume：45, Number：1, First page：26, Last page：33, 2019, [Reviewed], [Lead, Corresponding]
• Experimental studies on the mechanical behavior of Mayan archeological rocks　　　　　　　　　　　　　　　
  V.J. Ley-Paredes; C.R. R?os-Soberanis; E. Perez-Pacheco; C. Vinajera-Reyna; S. Wakayama; T. Sakai
  Volume：86, Number：208, First page：227, Last page：233, 2019, [Reviewed], [Last]
• 炭素繊維強化ポリアミドの結晶化が静的曲げ特性に及ぼす影響　　　　　　　　　　　　　　　
  坂井 建宣; Nur Safiah; Binti Shamsudim; 福嶋遼太; 蔭山健介
  Volume：45, Number：6, First page：223, Last page：229, 2019, [Reviewed], [Lead, Corresponding]
  Scientific journal
• Evaluation of Degradation State of Used Bedsore Preventing Mattress　　　　　　　　　　　　　　　
  Takenobu Sakai; Ryoichiro Ito; Kensuke Kageyama
  2018 IEEE 7th Global Conference on Consumer Electronics, GCCE 2018, First page：447, Last page：450, Dec. 2018
  Bedsore preventing mattress needs body pressure dispersibility, and this properties related to the mattress's viscoelasticity. In the hospital and rental shop of mattress, the judgement of the degradation of mattress was carried out by manual operation, however, there is no quantitative evaluation method of the degradation has existed. In this study, degradation state of used bedsore preventing mattress was evaluated using dynamic mechanical analysis (DMA) which can measure the material's viscoelasticity.
  Institute of Electrical and Electronics Engineers Inc., English, International conference proceedings
  DOI：https://doi.org/10.1109/GCCE.2018.8574712
  DOI ID：10.1109/GCCE.2018.8574712, SCOPUS ID：85060271944
• Performance Evaluation of Flexible Electret Sensor Array for Ultrasonic Object Detection in Short Distance　　　　　　　　　　　　　　　
  Kensuke Kageyama; Tsubasa Okawa; Takenobu Sakai
  2018 IEEE 7TH GLOBAL CONFERENCE ON CONSUMER ELECTRONICS (GCCE 2018), First page：824, Last page：825, 2018
  Ultrasonic object detection in short distance could contribute the monitoring of human life activity and remote operation of home appliances. In this study, Ultrasonic sensor array using flexible electret elements were fabricated to detect objects in short distance. The reflection waves were clearly detected at short distance. The object (PVC pipe) detection was examined using the ultrasound generated by the ECS array. The estimated distance was good agreement with the true value though large errors were observed for the estimated angles because only three receivers were used for ECS array.
  IEEE, English, International conference proceedings
  ISSN：2378-8143, Web of Science ID：WOS:000459859500291
• 超音波センサに適した極薄PTFE層を有するシリカ凝集体エレクトレットの製作と特性評価　　　　　　　　　　　　　　　
  蔭山健介; 折笠健; アハマド ザリフ; アフィック ビン; ジャマルディン; 坂井建宣
  Volume：138, Number：9, First page：441, Last page：447, 2018, [Reviewed], [Last]
• Accelerated creep and creep-rupture testing of transverse unidirectional carbon/epoxy lamina based on the stepped isostress method　　　　　　　　　　　　　　　
  Jonathon Tanks; Katherine Rader; Stephen Sharp; Takenobu Sakai
  COMPOSITE STRUCTURES, Volume：159, First page：455, Last page：462, Jan. 2017, [Reviewed], [Last]
  Accelerated methods for measuring long-term viscoelastic properties of fiber reinforced polymer (FRP) composites are important for reducing the time needed to characterize material behavior. Most of them are based on the time-temperature-stress superposition principle (TTSSP), or some variation. This paper investigates the applicability of the stepped isostress method (SSM) to study tensile creep of unidirectional carbon FRP (CFRP) lamina used in rehabilitating prestressed concrete structures. The SSM employs a load-stepping approach, typically with three to five steps for a single specimen resulting in creep-rupture. Theoretical analysis of the experimental method (previously lacking) is discussed and modifications to the testing and analysis protocol are shown to improve validity of the master curves compared to conventional creep curves and traditional TTSSP creep master curves at room temperature. Finally, three failure criteria are compared for predicting creep-rupture of CFRP laminates based on the accelerated testing method. (C) 2016 Elsevier Ltd. All rights reserved.
  ELSEVIER SCI LTD, English, Scientific journal
  DOI：https://doi.org/10.1016/j.compstruct.2016.09.096
  DOI ID：10.1016/j.compstruct.2016.09.096, ISSN：0263-8223, eISSN：1879-1085, Web of Science ID：WOS:000386759100043
• Time-Temperature Dependence of Bending Creep for a Carbon Fiber Reinforced Thermoplastic Polyimide Composite　　　　　　　　　　　　　　　
  岡田瑞生; 上田政人; 後藤健; 小林訓史; 坂井建宣; 荒井広明
  Volume：43, Number：2, First page：41, Last page：47, 2017, [Reviewed]
  Japanese
  ISSN：0385-2563, CiNii Articles ID：40021134702, CiNii Books ID：AN00196748
• Development of Vibration Measurement System for Chest Surface Using Flexible Circuit　　　　　　　　　　　　　　　
  坂井建宣; 柴山正輝; 野方文雄; 蔭山健介
  Volume：17, Number：1, First page：39, Last page：44, 2017, [Reviewed], [Lead, Corresponding]
  Japanese
  ISSN：1346-4930, CiNii Articles ID：40021181929, CiNii Books ID：AA11822914
• Visualization of Heart Motion and Position Location of Heart Valve based on Micro-vibration Analysis of the Chest Surface　　　　　　　　　　　　　　　
  坂井建宣; 林和輝; 河村洋子; 横田康成; 野方文雄
  Volume：17, Number：1, First page：45, Last page：51, 2017, [Reviewed]
  Japanese
  ISSN：1346-4930, CiNii Articles ID：40021181938, CiNii Books ID：AA11822914
• Study on high functionality of carbon/carbon composites based on waste CFRP　　　　　　　　　　　　　　　
  高橋智彦; 坂井建宣; 宗宮詮
  Volume：63, Number：5, First page：233, Last page：238, 2017, [Reviewed]
  Japanese
  ISSN：0452-9685, CiNii Articles ID：40021224117, CiNii Books ID：AN00058449
• Evaluation of damage behavior of spread glass fiber reinforced plastics by AE measurement　　　　　　　　　　　　　　　
  喜多村竜太; 浅野忠明; 伊丹康人; 井口英明; 小泉浩二; 坂井建宣; 荻原慎二
  Volume：63, Number：9, First page：451, Last page：457, 2017, [Reviewed]
  Japanese
  ISSN：0452-9685, CiNii Articles ID：40021339854, CiNii Books ID：AN00058449
• Evaluation of Fracture Process of Carbon Fiber Reinforced Thermoplastic Polyimide Using Acoustic Emission Technique　　　　　　　　　　　　　　　
  坂井建宣; 安部聡; 後藤健; 小林訓史; 上田政人; 荻原慎二; 若山修一; 蔭山健介
  Volume：17, Number：1, First page：27, Last page：33, 2017, [Reviewed]
  Japanese
  ISSN：1346-4930, CiNii Articles ID：40021181916, CiNii Books ID：AA11822914
• Fabrication and Characteristic Evaluation of Electret Condenser Sensor for Measurement of Acoustic Emission in Living Tree　　　　　　　　　　　　　　　
  KAGEYAMA Kensuke; LU Ziyao; SUGAWARA Takuya; SAKAI Takenobu
  Journal of the Japanese Society for Experimental Mechanics, Volume：16, Number：4, First page：295, Last page：300, 2017, [Reviewed]
  <p> Electret condenser sensors (ECS) is suitable for detection of ultrasounds propagating air and soft materials because it has an air gap in the element. In this study, ECS were fabricated to detect artificial acoustic emission (AE) propagating a wood plate and AEs at a trunk of acerola. ECS demonstrated the higher S/N ratio from 40 to 100 kHz for the detection of the artificial AEs than a piezoelectric AE sensor (PS) and a wideband acceleration sensor (AC). The AEs detected by ECS showed several frequency peak from 50 to 200 kHz at the AE measurement at a trunk of acerola while the AE detected by PS also showed wide frequency from 100 to 500 kHz. Furthermore, the ECS had the same degree of sensitivity as PS at AE measurement at the trunk of acerola while AC hardly detected the AEs. The AE behavior of ES, however, did not partially coincide with the significant increase of AE events of PS. Hence, the long-term reliability of ES must be investigated for practical use of AE measurement of woody plants.</p>
  The Japanese Society for Experimental Mechanics, Japanese
  DOI：https://doi.org/10.11395/jjsem.16.295
  DOI ID：10.11395/jjsem.16.295, ISSN：1346-4930, CiNii Articles ID：130005300055, CiNii Books ID：AA11822914
• Sensitivity Enhancement of FBG Sensors for Acoustic Emission Using Waveguides　　　　　　　　　　　　　　　
  Takenobu Sakai; Satomi Suzuki; Shuichi Wakayama
  EXPERIMENTAL MECHANICS, Volume：56, Number：8, First page：1439, Last page：1447, Oct. 2016, [Reviewed]
  Sensors created from optical fibers are often used to measure strain due to their high accuracy. However, they are not used as often for higher frequency applications as a result of low sampling rates in their data acquisition systems. Recently, acquisition systems have been developed that satisfy the required specifications for use in acoustic emission (AE), but these types of sensors are not used due to their low signal-to-noise (S/N) ratios. However, there are many studies on the sensitivity enhancement conferred by the fiber Bragg grating sensor (FBG sensor). This sensor is easy to use and does not require specific reference fibers when sensing. In this study, acoustic waveguides, which are usually used in ultrasonic microscopes, were fabricated and used in FBG AE sensors to enhance the S/N ratio. Two types of waveguides were designed; the refraction type and the reflection type. FBG fibers were attached to the waveguides, which were then secured using adhesive to a thin aluminum plate. Impulses were inputted into the sensor by breaking pencil lead on the plate. The results showed that the amplitude of the first wave was increased using these waveguides. Using finite-element method (FEM) analysis, the enhancement of the wave amplitude was also evaluated such that the acoustic waveguide could be used for enhancement of the S/N ratio of FBG sensors.
  SPRINGER, English, Scientific journal
  DOI：https://doi.org/10.1007/s11340-016-0178-6
  DOI ID：10.1007/s11340-016-0178-6, ISSN：0014-4851, eISSN：1741-2765, Web of Science ID：WOS:000383599900011
• Fracture behavior of wasted activated carbon powder composites　　　　　　　　　　　　　　　
  Takenobu Sakai; Tomohiko Gushiken; C. R. Rios-Soberanis; Tomoki Masuko; Satoshi Matsushima; Satoshi Kobayashi; Satoru Yoneyama; Shuichi Wakayama
  ADVANCED COMPOSITE MATERIALS, Volume：25, Number：4, First page：375, Last page：384, Aug. 2016, [Reviewed]
  At the Waterworks Bureau (Tokyo Metropolitan Government), activated carbon has been used for filtering water. After being used for the filtering process, it is normally disposed or burned for thermal recycling. However, CO2 emissions occur during the thermal recycling. This work focuses on the identification of mechanical behavior of recycled wasted activated carbon (WAC) in order to elaborate smart materials having mechanical electrical functions. Acoustic emission technique (AE) was used intensively as characterization support in which sensors were attached to detect microdamage during bending tests. At first, the resonant frequencies of the specimens were measured using the through-transmission test. The resonant frequencies of the specimens containing low weight fractions of WAC powder were less in comparison to the frequencies of the specimens with higher volume fraction. The frequency analysis was carried out with the projected wavelet transform on the signals detected during bending tests. Obtained data showed that, typically, the first major peaks showed the resonant frequency of the sensors, while the second major peaks exhibited signals indicative of resin cracking. The surfaces of the fractured specimens were analyzed by optical microscopy in order to visualize the crack formation and propagation on the activated carbon composite under flexural stresses. Consequently, fractographic and AE analyses provide better understanding of the failure mechanisms involved.
  TAYLOR & FRANCIS LTD, English, Scientific journal
  DOI：https://doi.org/10.1080/09243046.2015.1011049
  DOI ID：10.1080/09243046.2015.1011049, ISSN：0924-3046, eISSN：1568-5519, Web of Science ID：WOS:000377425400006
• Damage behavior evaluation of thermoplastic resin based CF/PA6 laminate composites with fiber discontinuity　　　　　　　　　　　　　　　
  Koyo Koyanagi; Ryuta Kitamura; Akira Matsuba; Yosuke Kouno; Hayato Nakatani; Takenobu Sakai; Shinji Ogihara
  Zairyo/Journal of the Society of Materials Science, Japan, Volume：65, Number：8, First page：561, Last page：566, Aug. 2016, [Reviewed]
  The tensile tests of the unidirectional CFRP laminate composites (CF/PA6) with fiber discontinuity were performed, and mechanical properties were obtained. The laminate stacking sequence of the specimens is [024], and the specimens have fiber discontinuity of 6, 12 and 18 layers. And, the damage growth behaviors were investigated by microscopic observation and acoustic emission (AE) monitoring. Furthermore, the delamination onset stresses were predicted by the simple analysis model. As a result, the stress-strain curves showed nonlinear behavior, and nonlinear starting points became early with increase of the fiber discontinuity layers. It is found that the initial damage of the specimen was the crack between fiber discontinuity end/resin interface by microscopic observation and AE monitoring. And, the delamination between continuous/discontinuous ply around the resin occurred. After that, the resin at the fiber discontinuity was broken at the time of maximum applied stress, then the delamination grew extensively in the specimen, finally the specimens was broken. In addition, the delamination onset stresses were predicted by analysis model using energy release rate, and these stresses were almost agree with experimental values.
  Society of Materials Science Japan, Japanese, Scientific journal
  DOI：https://doi.org/10.2472/jsms.65.561
  DOI ID：10.2472/jsms.65.561, ISSN：1880-7488, CiNii Articles ID：40020938488, SCOPUS ID：84983606002
• Damage accumulation studied by acoustic emission in bone cement prepared with core-shell nanoparticles under fatigue　　　　　　　　　　　　　　　
  O. F. Pacheco-Salazar; Shuichi Wakayama; Takenobu Sakai; C. R. Rios-Soberanis; J. V. Cauich-Rodriguez; J. M. Cervantes-Uc
  JOURNAL OF MATERIALS SCIENCE, Volume：51, Number：12, First page：5635, Last page：5645, Jun. 2016, [Reviewed]
  Analysis of acoustic emission signals generated during the fatigue testing of core-shell nanoparticles filled acrylic bone cements is reported. Core-shell nanoparticles composed of a poly(butyl acrylate) rubbery core and a poly(methyl methacrylate-co-styrene) (P(MMA-co-St)) outer glassy shell with varying compositions (20/80, 30/70, 40/60, and 50/50) were incorporated into the solid phase of bone cement at 10 wt%. Acoustic emission data revealed that the damage accumulation process was discontinuous for all bone cement formulations, being less pronounced in formulations with higher fatigue resistance (20/80 and 30/70) which emitted a higher number of events before the final fracture. The capability of both 20/80 and 30/70 core-shell nanoparticles to hinder the microcracks or crazes propagation was attributed to their poor interfacial adhesion with the matrix in comparison with formulations with 40/60 and 50/50 core-shell nanoparticles. Based on the acoustic emission data and SEM micrographs, a crack propagation scheme for bone cements containing core-shell nanoparticles was proposed. In this regard, core-shell nanoparticles had a double role on the bone cement as reported for other systems; firstly, the nanoparticles promoted nucleation sites for crazes or microcracks, and secondly, they could also hinder the propagation of these defects, acting as a barrier to their growth. Crack propagation mechanism consisted mainly in crazing ahead of the cracks tip as well as the coalescence of these cracks which were responsible of the acoustic emission detected.
  SPRINGER, English, Scientific journal
  DOI：https://doi.org/10.1007/s10853-016-9865-z
  DOI ID：10.1007/s10853-016-9865-z, ISSN：0022-2461, eISSN：1573-4803, Web of Science ID：WOS:000373626000006
• 熱可塑性樹脂を母材とした繊維不連続有する一方向強化 CF/PA6積層板の損傷挙動評価　　　　　　　　　　　　　　　
  小柳興瑶; 喜多村竜太; 松葉 朗; 河野洋輔; 中谷隼人; 坂井建宣; 荻原慎二
  Volume：54, Number：8, First page：555, Last page：560, 2016, [Reviewed]
• Preliminary study of optimal measurement location on vibroarthrography for classification of patients with knee osteoarthritis　　　　　　　　　　　　　　　
  Ota S; Ando S; Tozawa Y; Nakamura T; Okamoto S; Sakai T; Hase K
  Volume：28, First page：2904, Last page：2908, 2016, [Reviewed]
• Spin test of three-dimensional composite rotor using polymer ring as a connection device for high-speed flywheel　　　　　　　　　　　　　　　
  HIROSHIMA Noboru; HATTA Hiroshi; NAGURA Yuuichi; KOYAMA Masashi; SAKAI Takenobu; KOGO Yasuo
  Mechanical Engineering Journal, Volume：3, Number：4, First page：1, Last page：12, 2016, [Reviewed]
  

  A method for connecting a driving shaft to a three-dimensional composite disk via a polymer ring was examined to achieve stable rotation at high rotation speeds. Polyoxymethylene (POM) was adopted as the polymer ring material. Compression test was conducted to determine the limit of linear viscoelasticity, and creep resistance of POM was examined to evaluate its long-term durability. Structural design using finite element analysis including long-term creep resistance has shown that this method was predicted to be effective up to a tip speed of 1210 m/s. A three-dimensional composite disk was reinforced to three directions in accordance with the cylindrical coordinates. A trial composite disk with outer and inner diameters of 304 and 41 mm, respectively, was manufactured and tested up to a tip speed of 908 m/s. Vibration amplitudes were measured using gap and laser sensors. The vibration phenomenon and methods of suppressing vibration were discussed for higher rotation speeds.

  
  The Japan Society of Mechanical Engineers, English
  DOI：https://doi.org/10.1299/mej.16-00261
  DOI ID：10.1299/mej.16-00261, CiNii Articles ID：130005169886
• Detection of Cavitation in Stem of Miniature Tomato using Acceleration Sensor　　　　　　　　　　　　　　　
  Kageyama, K; Iman; B. A. H; Kimura, K; Sakai, T
  Volume：1, First page：214, Last page：218, 2016, [Reviewed]
• Charge Retention of Silica-Agglomerate Electret using Electrostatic Spraying at Elevated Temperatures　　　　　　　　　　　　　　　
  Chenye WU; Kensuke KAGEYAMA; Takenobu SAKAI
  Volume：1, First page：120, Last page：125, 2016, [Reviewed]
• Evaluation of Irrigation Response using AE Method for Management of High-Frequency Irrigation of Hydroponic Miniature-Tomato　　　　　　　　　　　　　　　
  Kensuke Kageyama; Takenobu Sakai
  Volume：34, First page：65, Last page：70, 2016, [Reviewed]
• 樹木のアコースティック・エミッション測定を目的としたエレクとレットセンサの製作と特性評価　　　　　　　　　　　　　　　
  蔭山健介; 魯子 暁; 菅原拓也; 坂井建宣
  Volume：16, Number：3, First page：9, Last page：14, 2016, [Reviewed]
• Estimation of creep and recovery behavior of a shape memory polymer　　　　　　　　　　　　　　　
  Takenobu Sakai; Takayuki Tao; Satoshi Somiya
  MECHANICS OF TIME-DEPENDENT MATERIALS, Volume：19, Number：4, First page：569, Last page：579, Nov. 2015, [Reviewed]
  The shape recovery and shape fixity properties of shape memory polymers (SMPs), advanced functional materials, were investigated in this study. Although the shape recovery behavior of these polymers has been examined from a viscoelastic point of view, questions remain with regard to quantifying the recovery behavior of SMPs. SMPs can recover their shape after the molding process; this recovery occurs via creep recovery and/or shape recovery; an estimation of SMP recovery requires a good understanding of both processes. In this study, the time-temperature superposition principle was applied to the creep and shape recovery behavior of SMPs. The creep behavior was estimated using an experimentally obtained master curve and time-temperature shift factors. Our estimated results were in good agreement with the experimental data. However, the estimation of the creep recovery with changing temperature below or above the glass transition temperature was not successful due to the lack of consideration of the shape recovery behavior. The time and temperature dependency of the shape recovery were confirmed for creep behavior, using the master curve for the recovery ratio and the corresponding shift factors for shape recovery. The values of the shape recovery shift factors differed from those for the time-temperature shift factors obtained for creep behavior. Therefore, these shape recovery shift factors were used in the estimation of creep and shape recovery behavior using the master curve for the creep tests. The estimated results were closer to the results obtained experimentally. Moreover, our results indicated that the recovery behavior above was dominated by shape recovery as a result of polymer viscoelasticity.
  SPRINGER, English, Scientific journal
  DOI：https://doi.org/10.1007/s11043-015-9279-3
  DOI ID：10.1007/s11043-015-9279-3, ISSN：1385-2000, eISSN：1573-2738, Web of Science ID：WOS:000365423600007
• Evaluation of damage progression and mechanical behavior under compression of bone cements containing core-shell nanoparticles by using acoustic emission technique　　　　　　　　　　　　　　　
  O. F. Pacheco-Salazar; Shuichi Wakayama; Takenobu Sakai; J. V. Cauich-Rodriguez; C. R. Rios-Soberanis; J. M. Cervantes-Uc
  JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS, Volume：46, First page：137, Last page：147, Jun. 2015, [Reviewed]
  In this work, the effect of the incorporation of core-shell particles on the fracture mechanisms of the acrylic bone cements by using acoustic emission (AE) technique during the quasi-static compression mechanical test was investigated. Core-shell particles were composed of a poly(butyl acrylate) (PBA) rubbery core and a methyl methacrylate/styrene copolymer (P(MMA-co-St)) outer glassy shell. Nanoparticles were prepared with different core-shell ratio (20/80, 30/70, 40/60 and 50/50) and were incorporated into the solid phase of bone cement at several percentages (5, 10 and 15 wt%). It was observed that the particles exhibited a spherical morphology averaging ca. 125 nm in diameter, and the dynamic mechanical analysis (DMA) thermograms revealed the desired structuring pattern of phases associated with core-shell structures. A fracture mechanism was proposed taking into account the detected AE signals and the scanning electron microscopy (SEM) micrographs. In this regard, core-shell nanoparticles can act as both additional nucleation sites for microcracks (and crazes) and to hinder the microcrack propagation acting as a barrier to its growth; this behavior was presented by all formulations. Cement samples containing 15 wt% of core-shell nanoparticles, either 40/60 or 50/50, were fractured at 40% deformation. This fact seems related to the coalescence of microcracks after they surround the agglomerates of core-shell nanoparticles to continue growing up. This work also demonstrated the potential of the AE technique to be used as an accurate and reliable detection tool for quasi-static compression test in acrylic bone cements. (C) 2015 Elsevier Ltd. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.jmbbm.2015.02.028
  DOI ID：10.1016/j.jmbbm.2015.02.028, ISSN：1751-6161, eISSN：1878-0180, Web of Science ID：WOS:000353752100014
• Analysis of Fiber-Matrix Interfacial Stresses Using Experimental-numerical Hybrid Technique　　　　　　　　　　　　　　　
  坂井建宣; 飯原靖憲; 米山聡
  実験力学, Volume：15, Number：3, First page：169-174 (J-STAGE), Last page：174, 2015
  In this study, the single fiber composite was used to evaluate the stress transfer between a single fiber and a matrix. Single steel fiber was inserted to the epoxy resin, and the tensile load was applied to the steel fiber. Applied load was varied from 0N to 177N, and then the photoelastic images were taken by a digital CCD camera. On the photoelastic analysis, the stress separation was carried out using an experimental-numerical hybrid method. The boundary conditions for a local finite element model, that is, the tractions along boundaries were inversely determined from photoelastic fringes. After determining the boundary conditions for the local finite element model, the stresses could be obtained by finite element direct analysis. The maximum shear stress were placed on the side surface of the steel fiber near the end of fiber, and the maximum normal stress difference was measured near the surface of the end of fiber. The results of stress distribution on the interface between the fiber and the resin indicated that the stress concentration was observed on the middle part of the end of fiber and the side surface near the end of fiber.
  日本実験力学会, Japanese
  DOI：https://doi.org/10.11395/jjsem.15.169
  DOI ID：10.11395/jjsem.15.169, ISSN：1346-4930, J-Global ID：201502205211245825, CiNii Articles ID：130005102012, CiNii Books ID：AA11822914
• Improvement of heat resistance of silica-agglomerate electret using electrostatic spraying　　　　　　　　　　　　　　　
  WU Chenye; KAGEYAMA Kensuke; SAKAI Tatenobu
  Mechanical Engineering Journal, Volume：2, Number：3, First page：1, Last page：15, 2015, [Reviewed]
  The silica-agglomerate electret could be obtained after spraying negatively charged solution of colloidal silica on a fluororesin film using an electrostatic spraying technique. The surface electric potential was measured after spraying to investigate which method was suitable for preparing the electret. As a result, the method in which a spray gun was installed to a conventional corona-charging setup delivered the electret with the amplitude of the electric surface potential over 0.8 kV. The silica agglomerates using an electrostatic spraying technique (ES electret) showed larger diameter D and lower point density N than those using conventional technique (corona-charging after spraying, CC electret). Furthermore, the prepared electrets were heated to examine the improvement of the heat resistivity by the electrostatic spraying. Then, the obtained silica-agglomerate electret showed better heat resistivity than the conventional silica-agglomerate electret. Then, the charge retention at 250°C R250 of ES electrets prepared in this study was higher than 57 % when the electrets suffered high temperature from 200 to 250 °C for 12.5 min at the heating test. Consequently, it can be concluded that the electrostatic spraying was excellent technique to obtain the silica-agglomerates electret with high heat resistance.
  The Japan Society of Mechanical Engineers, English
  DOI：https://doi.org/10.1299/mej.15-00064
  DOI ID：10.1299/mej.15-00064, ISSN：2187-9745, CiNii Articles ID：130005071473
• Characterization of crack growth resistance under thermal shock on silicon nitride with various microstructure　　　　　　　　　　　　　　　
  SAKAI Takenobu; WAKAYAMA Shuichi; KAMETANI Go; YOSHIDA Katsumi; AKATSU Takashi
  Mech Eng J (Web), Volume：1, Number：1, First page：SMM0002-SMM0002 (J-STAGE), Last page：SMM0002, 2014
  The crack growth resistance under thermal shock loading on silicon nitride was characterized using Disc-on-Rod test which was developed by the authors. The microdamage during thermal shock fracture was monitored by acoustic emission (AE) technique. Specimens were composed of β-Si₃N₄ with an acicular structure. Cylinders of silicon nitride with various microstructures were sintered at different temperatures. A pre-crack was introduced using Knoop indentation. In the Disc-on-Rod test, the specimens were uniformly heated to 850 ºC, and only the center of circular specimen was quenched by contacting with a copper rod. Within a fraction of a second after contacting, crack propagated in an unstable manner, at the same time, a high amplitude AE signal was detected. Subsequently, stable crack propagation was observed, and several low amplitude AE signals were generated corresponding to crack propagation. The specimen sintered at higher temperature showed lower crack growth resistance. From the results of microstructure observation and the fracture mechanical consideration, it is suggested that larger grains with > 1.5 μm in minor axes contribute to the toughening of materials. Consequently, the results of this study provide fundamental insights for the development of ceramic materials with high resistance to thermal shock fracture.
  The Japan Society of Mechanical Engineers, English
  DOI：https://doi.org/10.1299/mej.2014smm0002
  DOI ID：10.1299/mej.2014smm0002, ISSN：2187-9745, J-Global ID：201402248521643971, CiNii Articles ID：130003398611
• Evaluation of Mechanical Behaviour of Bone Cements by Using Acoustic Emission Technique　　　　　　　　　　　　　　　
  C. R. Rios-Soberanis; S. Wakayama; T. Sakai; J. M. Cervantes-Uc; A. May-Pat
  MATERIAL SCIENCE AND ENGINEERING TECHNOLOGY II, Volume：856, First page：246, Last page：+, 2014, [Reviewed]
  Biomaterials such as acrylic bone cements are widely applied in orthopaedic surgery for the fixation of artificial joints. Therefore, the mechanical behavior of such materials under external stresses is of special interest in order to achieve long-term in vivo performance. Fracture process can be attributed to diverse random microscopic damage modes. As the load increases, new damage modes appear and the existing ones can transition into others depending on the nature of the material. However, limitation exists in detailing the understanding of the micromanage initiation and development, and, consequently, in optimizing biomaterials performance. This paper focuses in the study of the emission of acoustic signals from bone cements in order to monitor the evolution of the internal defects that are believed to dominate in vivo failure.
  TRANS TECH PUBLICATIONS LTD, English, International conference proceedings
  DOI：https://doi.org/10.4028/www.scientific.net/AMR.856.246
  DOI ID：10.4028/www.scientific.net/AMR.856.246, ISSN：1022-6680, Web of Science ID：WOS:000336337600047
• Photoelastic Stress Analysis of the Fiber/Matrix Interface in a Single-Fiber Composite　　　　　　　　　　　　　　　
  Takenobu SAKAI; Yasunori IIHARA; Satoru YONEYAMA
  Volume：14, First page：213, Last page：216, 2014, [Reviewed]
• シリカ凝集体を用いたPFAフィルムエレクトレットの耐熱性向上　　　　　　　　　　　　　　　
  蔭山 健介; 三村 昌平; 坂井 建宣
  Volume：135, Number：4, First page：122, Last page：128, 2014, [Reviewed]
• Damage accumulation behavior of non-crimp fabric-reinforced epoxy composite under static and cyclic tensile loading
  T. Sakai; S. Wakayama; E. Pérez-Pacheco; J. Rodriguez-Laviada; C. R. Rios-Soberanis
  Advanced Composite Materials, Volume：22, Number：4, First page：281, Last page：297, Aug. 2013
  A non-crimp fabric with a stacking sequence of [0°,+45°,90°,- 45°] embedded in epoxy resin matrix was analyzed. Samples for mechanical test were obtained from laminates at different orientations depending on the textile architecture direction at 0°, 45°, and 90°in order to study the relationship between damage initiation and propagation with fabric geometry. Tension mode tests (static and cyclic) were carried out to evaluate the evolution of damage using as a main tool, the acoustic emission technique that allows monitoring the mechanical behavior of the materials during the test in real time. Results show that there is a remarkable mechanical influence of the reinforcement textile in the composite and that damage generation and progression (mechanisms of fracture) is highly dependent of the direction in which the stress is applied in relation with the architecture of the fabric. In static tensile mode, samples at 0°exhibited better mechanical parameters than samples at 90°, while at 45°orientation was lesser. The effect of textile geometry was demonstrated to have an influence in such mechanisms. In cyclic tensile mode, Kaiser effect is observed at low stresses, while the experimental results showed that the Felicity effect became clearer along with the increasing of stress level. © 2013 Japan Society for Composite Materials, Korean Society for Composite Materials and Taylor &
  Francis.
  English, Scientific journal
  DOI：https://doi.org/10.1080/09243046.2013.809636
  DOI ID：10.1080/09243046.2013.809636, ISSN：0924-3046, SCOPUS ID：84879658619
• Mechanical evaluation and damage sequence identification of multiaxial textile reinforced composites　　　　　　　　　　　　　　　
  C. R. Rios-Soberanis; S. Wakayama; T. Sakai; E. Perez-Pacheco; J. Rodriguez-Laviada
  Annual Technical Conference - ANTEC, Conference Proceedings, Volume：1, First page：393, Last page：397, Jan. 2013
  Mechanical properties and damage pattern of a multiaxial textile reinforced epoxy composite was evaluated by tension and bending test. A non crimp fabric (NCF) of [0°,+45°, 90°, - 45°] stacking sequence was used as reinforcement. Through the identification of the initiation sites and the coalescence of cracks was possible to correlate the damage with the textile geometry and its effect on the mechanical properties. Fractography was used as a tool to identify governing mechanisms and link these to the material internal structure and the textile geometry. Acoustic emission technique was employed to identify the mechanisms of fracture by correlating the signals of mechanical waves produced my damage with fracture stages. Additionally the effect of textile architecture on the composite mechanical properties and damage pattern was correlated with its damage initiation and propagation. Through a combination of experimental work and theoretical studies the mechanisms controlling the mechanical behavior are explained.
  SCOPUS ID：84903544243
• Manufacture of partially biodegradable composite materials based on PLA-tires powder: Process and characterization　　　　　　　　　　　　　　　
  Carlos Rolando Rios-Soberanis; Shuchi Wakayama; Takenobo Sakai; José De Los Ángeles Rodriguez-Laviada; Emilio Pérez-Pacheco
  International Journal of Polymer Science, Volume：2013, First page：1, Last page：8, 2013, [Reviewed]
  This research work focuses on the processability and mechanical characterization of blends of polylactic acid (PLA) and tire (elastomeric part). Wasted tires used as filler in the PLA matrix were reduced by two different processes (thermal shock and pyrolysis) in order to acquire the solid residuals in powder to be characterized and compared. Elastomeric solids obtained from scraped tires were used as filler in the PLA matrix and mixed in a Brabender 60 cc mixer at different concentrations ranging from 0% to 60% of filler volume fraction. The blend was laminated, and then samples were obtained in order to undertake mechanical properties at tension and Izod impact tests. A fully detailed analysis on the solid powders by Differential Scanning Calorimeter (DSC), thermogravimetric analysis (TGA), infrared analysis (IR), and scanning electron microscopy analysis (SEM) identified them as a rich source of carbon. Blends were characterized thermally and mechanically showing a direct effect due to the tire nature (thermoset rubber) and concentration. Fracture mechanisms were also identified. © 2013 Carlos Rolando Rios-Soberanis et al.
  English, Scientific journal
  DOI：https://doi.org/10.1155/2013/514951
  DOI ID：10.1155/2013/514951, ISSN：1687-9422, SCOPUS ID：84878694786
• Characterization of Damage Process of Rabbit Tendon by Acoustic Emission Technique in Vitro　　　　　　　　　　　　　　　
  Takenobu SAKAI; Satomi SUZUKI; Shuichi WAKAYAMA; Satoru YONEYAMA; Ei YAMAMOTO
  Volume：13, First page：213, Last page：216, 2013, [Reviewed]
• Estimating the creep behavior of polycarbonate with changes in temperature and aging time　　　　　　　　　　　　　　　
  Takenobu Sakai; Satoshi Somiya
  MECHANICS OF TIME-DEPENDENT MATERIALS, Volume：16, Number：3, First page：241, Last page：249, Aug. 2012, [Reviewed]
  Thermoplastic resins are typically used without any kind of physical aging treatment. For such materials, creep behavior and physical aging, which depend on time and temperature, occur simultaneously. The effects of these processes are evident after quenching and are recorded in the material as a thermal history. This history strongly influences mechanical properties and creep behavior in particular. Thus, a more thorough understanding of the physical aging process is desirable. We examined the creep deformation of polycarbonate (PC) to reveal the effects of physical aging on creep behavior. The effects were dependent on both time and temperature. The relationship between physical aging and creep behavior exemplified superposition principles with regard to time and both pre-test aging time and pre-test aging temperature. The superposition principles allowed the calculation of creep deformations at a given temperature; the calculated results were corroborated by experimental data.
  SPRINGER, English, Scientific journal
  DOI：https://doi.org/10.1007/s11043-011-9154-9
  DOI ID：10.1007/s11043-011-9154-9, ISSN：1385-2000, Web of Science ID：WOS:000307555200001
• Creep Analysis Considering Fiber Volume Fraction and Crystallinity and of Carbon Fiber Reinforced Poly (ether-ether-ketone)　　　　　　　　　　　　　　　
  SAKAI Takenobu; KAWABATA Yukiko; SOMIYA Satoshi
  Proceedings of the Japan Society for Photoelasticity, Volume：12, Number：2, First page：94, Last page：100, Jun. 2012
  The Poly (ether-ether-ketone) (PEEK) resin is a kind of super engineering thermoplastics, and has good mechanical properties and high heat resistance. Recently it has been used for the matrix of Carbon Fiber Reinforced Plastics (CFRP) as a substitute material for thermosetting plastics at high temperature because of its fine moldability. For such occasion, it is very important for reliability of these materials to reveal the visco-elastic behavior of polymer materials. In this study, linearity for creep behavior of PEEK and CFRPEEKs were discussed, and the relationship between time and temperature, fiber volume fractions and crystallinity was revealed.<br>   Bending creep tests were performed on the crystallized PEEK resin and its CFRPs. It was found that master curves of creep compliance were obtained, and the Arrhenius type time -temperature superposition principle was applied for crystallized PEEK resin and its crystallized CFRPs. Effects of crystallinity and fiber volume fractions on creep behavior were considered by making grand master curves and great grand master curve.Great grand master curve and the shift factors for making great grand master curve were approximated with prony-series equation and quadratic expressions. Using these equations, the creep analyses were carried out. The results have a good agreement with the experimental data. And the estimation data was determined with great accuracy.
  The Japanese Society for Experimental Mechanics, Japanese
  DOI：https://doi.org/10.11395/jjsem.12.94
  DOI ID：10.11395/jjsem.12.94, ISSN：1346-4930, J-Global ID：201202206296603664, CiNii Articles ID：10030800757, CiNii Books ID：AA11822914
• Effect of Z-yarn on Bending Behavior of Non-crimp Fabric Composites　　　　　　　　　　　　　　　
  坂井 建宣; C-R Rios Rolando; 若山 修一
  Volume：30, First page：35, Last page：40, 2012, [Reviewed]
  Japanese
  ISSN：0286-6013, CiNii Articles ID：40019240282, CiNii Books ID：AN00027831
• 炭素繊維強化ポリエーテルエーテルケトンの繊維および結晶化を考慮したクリープ解析　　　　　　　　　　　　　　　
  坂井 建宣; 川畑 有紀子; 宗宮 詮
  Volume：12, Number：2, First page：26, Last page：32, 2012, [Reviewed]
• Estimation of fatigue life of cortical bone considering viscoelastic properties and damage mechanics　　　　　　　　　　　　　　　
  Takenobu Sakai; Keita Yasui; Shuichi Wakayama
  Conference Proceedings of the Society for Experimental Mechanics Series, Volume：3, First page：289, Last page：294, Dec. 2011
  Recently, the Osteoporosis victims increase in the senior citizen. Therefore, the danger of the stress fracture due to the decrease in bone strength is pointed out. Especially, the damage accumulation behavior of the bone in the cyclic load becomes a problem for the fatigue of the bone. Moreover, it is necessary to consider the viscoelastic property for the prediction of the fatigue behavior, because the bone is a viscoelastic material. In this study, our objective is to estimate the fatigue behavior that considers the viscoelasticity behavior and the damage accumulation behavior as damage mechanics. The viscoelastic properties were revealed with the strain rate tests, and we calculated the 3-mode Maxwell parameters with these results. The damage accumulation behaviors were measured with the Acoustic Emission method. Using these results, we could estimate the fatigue behavior of cortical bone with the viscoelastic parameter and cumulative AE energy.
  ISSN：2191-5644, SCOPUS ID：84857852242
• Effect of fabric architecture (NCF) on bending and creep test of textile composites　　　　　　　　　　　　　　　
  T. Sakai; S. Wakayama; C. R. Rios-Soberanis; C. R. Rios-Soberanis; J. Rodriguez-Laviada; E. Pérez-Pacheco
  ICCM International Conferences on Composite Materials, Dec. 2011, [Reviewed]
  SCOPUS ID：84875936059
• Analysis of damage progression in textile reinforced composite in tension (static and cyclic) mode using acoustic emission　　　　　　　　　　　　　　　
  T. Sakai; S. Wakayama; C. R. Rios-Soberanis; C. R. Rios-Soberanis; J. Rodriguez-Laviada; E. Pérez-Pacheco
  Annual Technical Conference - ANTEC, Conference Proceedings, Volume：1, First page：442, Last page：446, Aug. 2011
  A non crimp fabric (NCF) with a stacking sequence of [0°,+45°, 90°,-45°] embedded in epoxy resin matrix was analyzed. Samples for mechanical test were obtained from laminates at different orientations depending on the textile direction at 0°, 45° and 90° in order to identify the failure mechanisms. Tension mode tests (static and cyclic) were carried out to evaluate the evolution of damage using as a main tool the acoustic emission technique that allows monitoring the mechanical behavior of the materials during the test in "real time".
  SCOPUS ID：80051757622
• Analysis of creep behavior in thermoplastics based on visco-elastic theory　　　　　　　　　　　　　　　
  Takenobu Sakai; Satoshi Somiya
  MECHANICS OF TIME-DEPENDENT MATERIALS, Volume：15, Number：3, First page：293, Last page：308, Aug. 2011, [Reviewed]
  Plastics and fiber-reinforced plastics (FRP) are used in the aerospace industry because of their mechanical properties. However, despite their excellent high-temperature mechanical properties, plastics and FRP eventually deform visco-elastically at high temperatures. Most of the research has focused on the creep behavior of FRPs, but few studies have investigated the linear visco-elastic behavior. Linear visco-elastic behavior and non-linear visco-elastic behavior occur with physical aging in these plastics. In this study, the non-linear visco-elastic behavior of plastics and FRP was investigated based on the bending creep deformation of polycarbonate (PC) and polyoxymethylene (POM). Moreover, the effects of the fiber volume fraction on the creep characteristics were investigated using glass fiber-reinforced polycarbonate (GFRPC). The creep deformation was calculated using the linear visco-elastic theory based on these effects, and comparison between experimental and estimated data showed that the creep analysis sufficiently predicted the creep behavior.
  SPRINGER, English, Scientific journal
  DOI：https://doi.org/10.1007/s11043-011-9136-y
  DOI ID：10.1007/s11043-011-9136-y, ISSN：1385-2000, Web of Science ID：WOS:000293911800005
• Effect of crystallinity and fiber volume fraction on creep behavior of glass fiber reinforced polyamide　　　　　　　　　　　　　　　
  坂井 建宣; 平井 悠斗; 宗宮 詮
  Materials system., Volume：29, First page：53, Last page：59, Jan. 2011
  金沢工業大学材料システム研究所, Japanese
  ISSN：0286-6013, J-Global ID：201102295123267680, CiNii Articles ID：40018708300, CiNii Books ID：AN00027831
• Effect of crystallinity and fiber volume fraction on creep behavior of glass fiber reinforced polyamide　　　　　　　　　　　　　　　
  Takenobu Sakai; Yuto Hirai; Satoshi Somiya
  Conference Proceedings of the Society for Experimental Mechanics Series, Volume：3, First page：159, Last page：164, 2011
  Thermoplastic Polyamide (PA) is known as Nylon®, and its FRP are one of the engineering plastics. It is very important for them to reveal accurately the visco-elastic behavior. Furthermore, PA is a crystalline polymer, and it is necessary to consider the effect of crystallization on mechanical properties. The purpose of this study was to make clear the effect of crystallization and fiber volume fraction on creep behavior of PA and its composites. The creep test was performed using the materials which adjusted crystallinity on each fiber volume fraction. As a result, these materials conformed to Arrhenius type of time-temperature superposition principle, and these effects on creep behavior had the time retardation effect. To compare the creep behavior on these effects, we made the grand master curves for crystallinity and fiber volume fraction. Obtained two grand master curves were compared each other, the shapes of these curves are similarly, and we can superposed them. It is therefore, the creep behavior including each conditions have the same behavior. Using these curves and shift factors, we can calculate the creep behavior, and be able to estimate the creep behavior with the effect of arbitrary time, temperature, crystallinity and fiber contents. ©2010 Society for Experimental Mechanics Inc.
  Springer New York LLC, English, International conference proceedings
  DOI：https://doi.org/10.1007/978-1-4419-9794-4_25
  DOI ID：10.1007/978-1-4419-9794-4_25, ISSN：2191-5652, SCOPUS ID：79960304602
• AE Monitoring of Damage Accumulation in Transparent Conductive Oxide Film under the Mechanical Strain　　　　　　　　　　　　　　　
  WAKAYAMA Shuichi; TAKAGI Nobuyuki; SAKAI Takenobu; MIYASAKA Tsutomu; IKEGAMI Masashi
  J Solid Mech Mater Eng (Web), Volume：5, Number：12, First page：774-779 (J-STAGE), Last page：779, 2011
  In this study, tensile tests of the transparent conductive oxide (TCO) deposited on the polyethylene naphthalate (PEN) films (TCO + PEN films) used in dye-sensitized solar cells (DSCs) were carried out. In order to discriminate the AE signals in TCO from PEN films, PEN film specimens (TCO was removed by 17.5% hydrochloric acid) were also prepared. It was found from the tensile tests that many AE signals were detected in TCO + PEN films, while AE activity in PEN films was much lower. On the other hand, the electric resistance of TCO was also measured during tensile tests. The remarkable increase in AE event rate was recognized at the strain of ∼0.63%, while the electric resistance increased rapidly at the strain of 0.68%. These results demonstrated that the critical damage in TCO was detected by the measurement of AE signals more sensitively than the electric resistance measurement. To identify AE sources, in-situ observation of specimen during tensile test with AE measurement was carried out. During tensile test, cracks transverse to the loading direction in the TCO were found at the strain of 0.67%, and then saturated at the strain of ∼9%. Cracks parallel to the loading direction in TCO were initiated at the strain of 9.63%. On the other hand, the remarkable increase in AE event rate was recognized at the strain of ∼0.7%. It reached a peak at the strain of ∼2%, and then decreased, and increased again at the strain of ∼10%. It was then concluded that AE behavior corresponds to the cracking behavior in TCO. Consequently, it was suggested that AE technique could be a powerful technique for evaluating the damage accumulation process in DSCs.
  The Japan Society of Mechanical Engineers, English
  DOI：https://doi.org/10.1299/jmmp.5.774
  DOI ID：10.1299/jmmp.5.774, ISSN：1880-9871, J-Global ID：201202222804110860, CiNii Articles ID：130002072387
• Mechanical Properties of CNF Reinforced Ceramic Composites Sintered with SPS Technique　　　　　　　　　　　　　　　
  UMINO Kosuke; WAKAYAMA Shuichi; SAKAI Takenobu; UMEHARA Yuka; AKATSU Takashi
  J Solid Mech Mater Eng (Web), Volume：5, Number：12, First page：866-872 (J-STAGE), Last page：872, 2011
  Alumina matrix composites reinforced by carbon nanofibers (CNFs) of 0, 5, 10, 20 vol% were fabricated using a spark plasma sintering (SPS) technique. In this study, to disperse CNFs uniformly in ceramic matrix, an electrostatic adsorption technique was used to fabricate the mixed powder. The open porosity of the specimen increased and the mechanical properties decreased with the increase in CNF content. It might be resulted from the insufficient interfacial shear strength and CNFs worked as flaws in composites. In order to improve the interfacial shear strength, SiC particles were added into the interfacial phase between CNF and matrix so that the thermal mismatch and bonding between CNF and matrix were controlled. Consequently, it was demonstrated that mechanical properties were enhanced and the pull-out length decreased for the specimens with SiC addition. It was then suggested that the interfacial shear strength was successfully improved due to SiC addition.
  The Japan Society of Mechanical Engineers, English
  DOI：https://doi.org/10.1299/jmmp.5.866
  DOI ID：10.1299/jmmp.5.866, ISSN：1880-9871, J-Global ID：201202278506345907, CiNii Articles ID：130002072395
• Effect of Powder Contents on Viscoelastic Behavior of Glass Powder Filled Epoxy Resin　　　　　　　　　　　　　　　
  Takenobu SAKAI; Koichi OKABE; Satoru YONEYAMA
  Volume：11, First page：187, Last page：191, 2011, [Reviewed]
• Effect of Viscoelastic Behavior on Electroconductivity of Recycled Activated Carbon Composites　　　　　　　　　　　　　　　
  Takenobu Sakai; Tomohiko Gushiken; Jun Koyanagi; Rolando Rios-Soberanis; Tomoki Masuko; Satoshi Matsushima; Satoshi Kobayashi; Satoru Yoneyama
  ADVANCES IN EXPERIMENTAL MECHANICS VIII, Volume：70, First page：231, Last page：+, 2011, [Reviewed]
  In the Waterworks Bureau, the activated carbon has been used for filtering water. After the life service of activated carbon, it is normally disposed. This work focuses on the processing of a composite material in order to recycle these wasted carbon particles. These activated carbons were used for the filler of composite materials, and a composite with carbon contents of 10% similar to 60% was manufactured and characterized. They exhibited electroconductive behavior because of the carbon particles used as fillers. The electroconductivity have an intimate relationship with the strain of the material. However, because of the composite viscoelasticity, the electroconductivity presented changes by their stress relaxation behavior with the same strain. In this study, it was revealed the relationship between the viscoelasticity and the electroconductivity of recycled activated carbon composites.
  TRANS TECH PUBLICATIONS LTD, English, International conference proceedings
  DOI：https://doi.org/10.4028/www.scientific.net/.231
  DOI ID：10.4028/www.scientific.net/.231, ISSN：1660-9336, Web of Science ID：WOS:000303372700037
• Effect of crystallinity and fiber volume fraction on creep behavior of glass fiber reinforced polyamide　　　　　　　　　　　　　　　
  Takenobu Sakai; Yuto Hirai; Satoshi Somiya
  Society for Experimental Mechanics - SEM Annual Conference and Exposition on Experimental and Applied Mechanics 2010, Volume：1, First page：821, Last page：826, 2010
  Thermoplastic Polyamide (PA) is known as Nylon®, and its FRP are one of the engineering plastics. It is very important for them to reveal accurately the visco-elastic behavior. Furthermore, PA is a crystalline polymer, and it is necessary to consider the effect of crystallization on mechanical properties. The purpose of this study was to make clear the effect of crystallization and fiber volume fraction on creep behavior of PA and its composites. The creep test was performed using the materials which adjusted crystallinity on each fiber volume fraction. As a result, these materials conformed to Arrhenius type of time-temperature superposition principle, and these effects on creep behavior had the time retardation effect. To compare the creep behavior on these effects, we made the grand master curves for crystallinity and fiber volume fraction. Obtained two grand master curves were compared each other, the shapes of these curves are similarly, and we can superposed them. It is therefore, the creep behavior including each conditions have the same behavior. Using these curves and shift factors, we can calculate the creep behavior, and be able to estimate the creep behavior with the effect of arbitrary time, temperature, crystallinity and fiber contents. © 2010 Society for Experimental Mechanics Inc.
  English, International conference proceedings
  SCOPUS ID：78049450684
• Estimation method of creep behavior on PC under multi-stage load　　　　　　　　　　　　　　　
  坂井 建宣; 隅原 晋平; 宗宮 詮
  Materials system., Volume：28, First page：9, Last page：14, 2010, [Reviewed]
  Japanese
  ISSN：0286-6013, CiNii Articles ID：40017038701, CiNii Books ID：AN00027831
• 炭素繊維強化熱可塑性ポリイミドのクリープ挙動に及ぼすフィジカルエージングの影響　　　　　　　　　　　　　　　
  坂井 建宣; 野溝 寿一; 宗宮 詮
  Volume：10, Number：4, First page：401, Last page：406, 2010, [Reviewed]
• Analysis of creep behavior in thermoplastic based on visco-elastic theory　　　　　　　　　　　　　　　
  Takenobu Sakai; Satoshi Somiya
  Society for Experimental Mechanics - SEM Annual Conference and Exposition on Experimental and Applied Mechanics 2009, Volume：2, First page：1411, Last page：1419, 2009
  Although plastics with high mechanical properties are widely used in the fields including the aircraft and space industries, various types of FRP have been developed to improve the mechanical properties. Even though those plastics and FRPs are superior in the high-temperature mechanical properties, they are visco-elastically deformed by using at high temperature for a long time. It is, therefore, expected to elucidate the characteristics of visco-elastic phenomena of those materials in detail and improve the estimation technique of long-term life based on this elucidation result for enhancing the reliability of the materials and aiming at the high degree of utilization. Although many researches concerning the creep behavior of FRPs have been made, few researches have been made so far for investigating the linear visco-elastic behavior. And it is known that not only the linear visco-elastic behavior is occurred on the plastics, but also non-linear visco-elastic behavior. In this study, the non-linear visco-elastic behavior of plastics and the FRPs was investigated by making an experiment of the bending creep deformation of Polycarbonate (PC) and Polyacetal (Polyoxymethylene, POM). Moreover, the effects of the fiber volume fraction on the creep characteristics were investigated with glass fiber reinforced polycarbonate (GFRPC). After that, the creep analysis was made with containing these effects on the equation of linear visco-elastic theory. ©2009 Society for Experimental Mechanics Inc.
  English, International conference proceedings
  SCOPUS ID：73449093526
• Effect of Thermal History on the Creep Behavior of Polycarbonate　　　　　　　　　　　　　　　
  SAKAI Takenobu; SOMIYA Satoshi
  J Solid Mech Mater Eng (Web), Volume：3, Number：11, First page：1193-1201 (J-STAGE), Last page：1201, 2009
  Thermoplastic resin is often used to form molded material without post-curing or aging treatments. Creep and physical aging occur simultaneously in such material, and these effects are dependent on the time and temperature. The effects of physical aging after molding are also dependent on the thermal history of the material, and this has a large influence on the mechanical properties, especially creep. It is therefore necessary to control the progress of physical aging when designing materials. In this study, we examined the creep deformation of polycarbonate to determine the thermal history as the effect of physical aging on the creep behavior. The physical aging effects had a distinct time and temperature dependency that also affected the density of the material. Our findings showed that it was possible to calculate the effect of the thermal history on physical aging using only the relationship between physical aging and density.
  The Japan Society of Mechanical Engineers, English
  DOI：https://doi.org/10.1299/jmmp.3.1193
  DOI ID：10.1299/jmmp.3.1193, ISSN：1880-9871, J-Global ID：200902242961748360, CiNii Articles ID：130000127279
• Time-temperature dependence behavior of physical aging on creep behavior of PC　　　　　　　　　　　　　　　
  Takenobu Sakai; Satoshi Somiya
  Proceedings of the SEM Annual Conference and Exposition on Experimental and Applied Mechanics 2007, Volume：1, First page：531, Last page：537, 2007
  Thermoplastic resin and its FRTP were practically used without post cure treatment and aging treatment which is called "molded material". For such materials, it is known that creep behavior and physical aging occur simultaneously. And the effect of physical aging has the time and temperature dependency. The effect was occurred on the materials after molded, and the effect saved on the materials as the thermal history. This history has big influence on mechanical properties especially creep properties. Therefore, it is necessary to stay in control of the progress of the physical aging. In this report, the creep deformation of Polycarbonate (PC) was researched to grasp the effect of physical aging on creep behavior. It was clearly that the effect had the time and temperature dependency by two shift factors, and it had the same tendency as density. Using these relationships between the shift factors and density, it must be able to calculate the effect of thermal history as physical aging since the materials were molded by density.
  English, International conference proceedings
  SCOPUS ID：36148999517
• 2539 Study on bending creep behavior of Shape Memory Polymer (DiARY) of Polyurethane Series　　　　　　　　　　　　　　　
  TAO Takayuki; SAKAI Takenobu; SOMIYA Satoshi
  The proceedings of the JSME annual meeting, Volume：2007, First page：279, Last page：280, 2007
  Shape Memory polymer (SMP) is known to have visco-elastic behavior. Shape recovery is considered to occur due to this visco-elastic behavior. On the other hand, creep and creep recovery may also occur that is known as one of visco-elastic behavior. It is important to understand creep and creep recovery behavior, because it effects on material's shape memory and shape recovery characteristics. This research examined the creep and creep recovery behavior by three point bending creep test. As a result, time and temperature dependence was confirmed, and also master curve can be drawn by superposing the creep compliance curves. Moreover, estimation of creep and creep recovery can be possible by master curve, shift factor and Boltzmann's superposition principle.
  The Japan Society of Mechanical Engineers, Japanese
  DOI：https://doi.org/10.1299/jsmemecjo.2007.6.0_279
  DOI ID：10.1299/jsmemecjo.2007.6.0_279, CiNii Articles ID：110007084743, CiNii Books ID：AA11461871
• Viscoelasticity of Shape Memory Polymer: Polyurethane series DiARY　　　　　　　　　　　　　　　
  SAKAI Takenobu; TAO Takayuki; SOMIYA Satoshi
  J Solid Mech Mater Eng (Web), Volume：1, Number：4, First page：480-489 (J-STAGE), Last page：489, 2007
  This study examined the creep behavior of DiARY^®, a shape-memory polymer (SMP), and the factors influencing the creep behavior. The creep test using the short term method obtained the master curve for the creep compliance, and confirmed the time-temperature superposition principle. Using this method, physical aging has little effect on the results of the creep test. To examine the effects of physical aging, we performed the creep test without using this method, which showed that physical aging alters the energy of activation of DiARY and the time-physical age time dependency at a specific temperature. The aging master curves were obtained as very smooth curves. In addition, the aging shift factors were attained when creating the aging master curves. The effect of physical aging depended on the time and temperature, confirming the time-physical aging time superposition principle, and achieved the effect of physical aging described as the aging shift rate. Using the master curve, time-temperature shift factor, and aging shift rate, it was possible to estimate the creep deformation, including the effect of physical aging on creep behavior.
  The Japan Society of Mechanical Engineers, English
  DOI：https://doi.org/10.1299/jmmp.1.480
  DOI ID：10.1299/jmmp.1.480, ISSN：1880-9871, J-Global ID：200902251784719710, CiNii Articles ID：130000078625
• ガラス繊維強化ポリカーボネートのクリープ挙動に及ぼすフィジカルエージングの影響　　　　　　　　　　　　　　　
  坂井 建宣; 宗宮 詮
  Volume：56, Number：5, First page：399, Last page：405, 2007, [Reviewed]
• Estimating creep deformation of glass-fiber-reinforced polycarbonate　　　　　　　　　　　　　　　
  Takenobu Sakai; Satoshi Somiya
  MECHANICS OF TIME-DEPENDENT MATERIALS, Volume：10, Number：3, First page：185, Last page：199, Sep. 2006, [Reviewed]
  Thermoplastic resin and fiber-reinforced thermo-plastics (FRTPs) were used without post-cure treatment as "molded material." For such materials, creep behavior and physical aging occur simultaneously. This study examined the creep behavior of polycarbonate (PC) and glass-fiber-reinforced polycarbonate (GFRPC) injection moldings, including the effect of physical aging and fiber content, and determined that the time-temperature superposition principle could be applied to the creep behavior for different fiber contents. The effects of physical aging on creep behavior were evaluated quantitatively on pure resin and with various fiber contents without heat treatment. We found that the effect of physical aging could be evaluated with the proposed factor, "aging shift rate." To discuss the linearity of viscoelasticity in FRTPs, this study used two shift factors: time and modulus shift factors. The fiber content affected creep behavior by both retarding and restraining it through changing the elastic modulus. This was shown by generating a grand master curve of creep compliance, which included the effects of time, temperature, and fiber content. Using the grand master curve of creep compliance and shift factors, it was possible to estimate the creep deformation of molded materials under varying conditions and fiber contents. The estimated creep deformation gave a very good fit to the experimental creep deformation.
  SPRINGER, English, Scientific journal
  DOI：https://doi.org/10.1007/s11043-006-9017-y
  DOI ID：10.1007/s11043-006-9017-y, ISSN：1385-2000, Web of Science ID：WOS:000243768700002
• Estimation of creep deformation applying phased stress on GFRPC　　　　　　　　　　　　　　　
  Takenobu Sakai; Satoshi Somiya
  Proceedings of the 2006 SEM Annual Conference and Exposition on Experimental and Applied Mechanics 2006, Volume：2, First page：964, Last page：970, 2006
  Thermoplastic resin and its FRTP were practically used without post cure treatment and aging treatment which is called "molded material". For such materials, it is known that creep behavior and physical aging occur simultaneously. On the other hand, the creep test is usually carried out under a constant stress. Furthermore, it is known that nonlinear behavior appears under the phased stresses on creep behavior. In previous reports, the creep deformation of Polycarbonate (PC) and Glass fiber reinforced polycarbonate (GFRPC) was researched to estimate the creep deformation on the molded materials under the phased stresses. Using these results, the creep deformation under phased stresses was estimated with time-temperature superposition principle and the principle of superposition on each creep behavior. Using this estimation method, it was able to estimate the creep deformation of molded materials in arbitrary condition, time, temperature, fiber contents, and stress. Therefore, the results of estimation of creep deformation were very fit to the experimental creep deformation. Furthermore, this estimation method of creep behavior made it possible to estimate the creep behavior on pragmatic conditions.
  English, International conference proceedings
  SCOPUS ID：33750336182
• 2707 Study on creep behaviour of Shape Memory Polymer (DiARY) of Polyurethane Series　　　　　　　　　　　　　　　
  TAO Takayuki; SAKAI Takenobu; SOMIYA Satoshi
  The proceedings of the JSME annual meeting, Volume：2006, First page：143, Last page：144, 2006
  Shape Memory polymer (SMP) is known to have visco-elastic behaviour. Shape recovery is considered to occur due to this visco-elastic behaviour. On the other hand, creep behaviour may also occur that is known as one of visco-elastic behaviour. It is important to understand creep behaviour, because it effects on material's reliability. This research examined the creep behaviour using the SMP, and creep behaviour and influencing factor were investigated by three point bending creep test. As a result, time and temperature dependence was confirmed, and also physical aging has a large effects on creep behaviour. To be more precise, creep deflection was suppressed with increasing of physical aging treatment time. In physical aging time for 1000min, master curve can be drawn by superposing the creep compliance curves, and SMP conformed to Arrhenius type of time-temperature superposition principle.
  The Japan Society of Mechanical Engineers, Japanese
  DOI：https://doi.org/10.1299/jsmemecjo.2006.1.0_143
  DOI ID：10.1299/jsmemecjo.2006.1.0_143, CiNii Articles ID：110006634323, CiNii Books ID：AA11461871

• TiコーティングがFRPの物性に与える影響　　　　　　　　　　　　　　　
  小熊 広之; 白石 知久; 森田 寛之; 坂本 大輔; 坂井 建宣
  Volume：66, Number：9, First page：395, Last page：400, Sep. 2020, [Reviewed], [Last]
  Introduction scientific journal
• 変形挙動予測によるプラスチックの寿命予測　　　　　　　　　　　　　　　
  坂井 建宣
  Volume：2019, Number：10, Oct. 2019, [Lead, Last, Corresponding]
  Introduction scientific journal
• 複合材料の寿命評価－時間－温度換算則－　　　　　　　　　　　　　　　
  坂井 建宣
  Volume：65, Number：8, First page：335, Last page：338, Aug. 2019, [Reviewed], [Lead, Last, Corresponding]
  Introduction scientific journal
• Preparation and characteristic evaluation of silica-agglomerate electret with ultra-thin PTFE layer for ultrasonic sensor
  Kensuke Kageyama; Takeru Orikasa; Ahmad Zarif Afiq Bin Jamaludin; Takenobu Sakai
  IEEJ Transactions on Sensors and Micromachines, Volume：138, First page：441, Last page：447, 01 Jan. 2018
  © 2018 The Institute of Electrical Engineers of Japan. Influence of formation of silica agglomerates on a ultra-thin fluororesin electret on the characteristics of the charge-retention and the aero-ultrasonic sensor was investigated. The ultra-thin PTFE layer (thickness was 2.8 μm) was obtained by spin-coating and silica agglomerates were formed by spraying droplets of colloidal silica. The formation of PTFE/silica agglomerate composite layer on PTFE layer resulted the larger and more flat agglomerates than the formation of single layer of silica agglomerates on the PTFE layer. The measurement of the charge retention of the obtained electrets after 24 h at RT and at 250°C revealed that the formation of PTFE/silica-agglomerate composite layer on the ultra-thin PTFE layer enhanced the charge retention. Furthermore, the electret condenser sensor (ECS) fabricated using the silica-agglomerate electret on the ultra-thin PTFE layer exhibited the excellent sensitivity and high resonance frequency compared with conventional ECS with PFA layer (thickness was 12.5 μm).
  DOI：https://doi.org/10.1541/ieejsmas.138.441
  DOI ID：10.1541/ieejsmas.138.441, ISSN：1341-8939, SCOPUS ID：85052660116
• Effect of temperature and strain rate on damage accumulation behavior of unidirectional CFRP　　　　　　　　　　　　　　　
  Takenobu Sakai; Satoru Abe; Kensuke Kageyama
  33rd Technical Conference of the American Society for Composites 2018, Volume：1, First page：439, Last page：444, 01 Jan. 2018
  © Copyright© (2018) by DEStech Publications, Inc. All rights reserved. Carbon Fiber reinforced plastics (CFRP) is consisted with the carbon fiber and matrix resin. It has reported to consider that the matrix resin's properties also depends on CFRP's mechanical properties in the recent research. Matrix resin's considerable mechanical property is viscoelasticity that depends on time and temperature. In this study, we focused on the effect of temperature and strain rate on the damage accumulation behavior of unidirectional CFRP laminate, and tensile tests with acoustic emission technique were carried out at three different temperature with three different strain rate. As the results of tensile tests, lower temperature and higher strain rate showed higher tensile strength, that is, it is understood that tensile strength depended on the matrix's viscoelastic properties. Crack initiation behavior, which was defined at the point of rapid increase in cumulative AE energy, was depended on the temperature and strain rate. To understand the details of AE information, the frequency analysis was done. In the frequency analysis, the resonant frequency of AE sensors effects on the frequency properties of the detected signals, so we tried to erase the effect of sensors by deconvolution of AE sensor's frequency properties from detected signals. As the results of deconvolution, we could distinguished the failure modes as matrix cracking, fiber/matrix interfacial debonding and fiber breaking. Using these results, matrix cracking, fiber/matrix interfacial debonding were effected by temperature and strain rate, however, fiber breaking was not affected. Consequently, the crack accumulation behavior of each failure mode depended on the temperature and strain rate as the same tendency of matrix's viscoelastic properties.
  SCOPUS ID：85059307841
• Biomechanical contribution of elastin on wound skin of hairless mice　　　　　　　　　　　　　　　
  Takenobu Sakai; Miho Katsuragi; Kenske Kageyama; Ei Yamamoto
  2017 IEEE 6th Global Conference on Consumer Electronics, GCCE 2017, Volume：2017-, First page：1, Last page：2, 19 Dec. 2017, [Reviewed]
  Dynamic mechanical analysis (DMA) was carried out to understand the effect of the application of elastin on wound skin of hairless mice. Wound group, placebo group, and elastin group were selected to evaluate that effect. As the results of DMA testing, the wound and the placebo groups showed lower storage and loss moduli than the elastin group. On the result of loss tangent, there is a small difference between these groups, and the elastin group showed the lowest value. Consequently, the application of elastin on the wounded skin showed the possibility for recovery the skins.
  Institute of Electrical and Electronics Engineers Inc., English
  DOI：https://doi.org/10.1109/GCCE.2017.8229323
  DOI ID：10.1109/GCCE.2017.8229323, SCOPUS ID：85045770977
• Acoustic Emission Technique Applied in Textiles Mechanical Characterization　　　　　　　　　　　　　　　
  Carlos Rolando Rios-Soberanis; Jose Rodriguez-Laviada; Emilio Perez-Pacheco; Takenobu Sakai; Shuichi Wakayama
  2016 THE 3RD INTERNATIONAL CONFERENCE ON MECHATRONICS AND MECHANICAL ENGINEERING (ICMME 2016), Volume：95, First page：1, Last page：4, 2017, [Reviewed]
  The common textile architecture/geometry are woven, braided, knitted, stitch boded, and Z-pinned. Fibres in textile form exhibit good out-of-plane properties and good fatigue and impact resistance, additionally, they have better dimensional stability and conformability. Besides the nature of the textile, the architecture has a great role in the mechanical behaviour and mechanisms of damage in textiles, therefore damage mechanisms and mechanical performance in structural applications textiles have been a major concern. Mechanical damage occurs to a large extent during the service lifetime consequently it is vital to understand the material mechanical behaviour by identifying its mechanisms of failure such as onset of damage, crack generation and propagation. In this work, textiles of different architecture were used to manufacture epoxy based composites in order to study failure events under tensile load by using acoustic emission technique which is a powerful characterization tool due to its link between AE data and fracture mechanics, which makes this relation a very useful from the engineering point of view.
  E D P SCIENCES, English
  DOI：https://doi.org/10.1051/matecconf/20179507016
  DOI ID：10.1051/matecconf/20179507016, ISSN：2261-236X, Web of Science ID：WOS:000406705800076
• Measurement Technique for Dynamic Biomechanical Properties in Musculoskeletal Tissues : Dynamic Mechanical Analysis and Acoustic Emission Technique　　　　　　　　　　　　　　　
  松岡 史都; 若山 修一; 坂井 建宣
  実験力学 : Journal of JSEM : Journal of the Japan Society for Experimental Mechanics, Volume：16, Number：4, First page：289, Last page：294, Dec. 2016
  日本実験力学会, Japanese
  ISSN：1346-4930, CiNii Articles ID：40021071551, CiNii Books ID：AA11822914
• Fabrication and characterization of Silica-aggregate electret with improved wettability of the PFA and the colloidal silica
  呉 シンク; 蔭山 健介; 坂井 建宣
  Volume：33, First page：1, Last page：6, 02 Oct. 2016
  Institute of Electrical Engineers of Japan, Japanese
  CiNii Articles ID：40021215456
• OS1405 Development of diagnosis system of knee osteoarthritis by articular sound　　　　　　　　　　　　　　　
  NAKAMURA Hiroaki; HASE Kazunori; HAYASHI Yuichiro; OTA Susumu; SAKAI Takenobu
  Volume：2016, Number：22, First page："OS1405, Last page：1"-"OS1405-2", 10 Mar. 2016
  An articular sound arising from knee joint is known to be useful for diagnosis of knee osteoarthritis. However, measurement and evaluation method have been unsolved and it has not been implemented yet. This study aims to establish a simple, highly accurate and available in clinical diagnosis system of knee osteoarthritis using articular sound. The articular sound was measured by stethoscopes attached on the shank and the continuous wavelet transform was used for data processing. The discriminant formula was determined using discriminant analysis with parameters from the measurement data and then receiver operating characteristic (ROC) curve was obtained. As a result, the discriminant formula having the sensitivity of 0.778 and specificity of 0.792 was found.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110010050168, CiNii Books ID：AA11902161
• OS1001-322 Relationship between Viscoelastic Characterization Factor and Viscoelastic Testing of Polypropylene　　　　　　　　　　　　　　　
  SAKAI Takenobu
  Volume：2015, First page："OS1001, Last page：322-1"-"OS1001-322-3", 21 Nov. 2015
  By the linear viscoelastic theory in the textbook of viscoelasticity, the viscoelastic parameters obtained by different viscoelastic tests can be interconversion. However, this interconversion is based on that theory, the interconversion of the experimental data have not seen yet. In this study, the viscoelastic tests were carried out with different environment and same test conditions. And also we carried out the viscoelastic tests with the same testing apparatus and using the same materials. The results showed the difference in the environment on the viscoelastic tests, the silicon oil environment more progressed the creep behavior than the air environment. This is because that the silicon oil's thermal conductivity is one fourth of the air, and the heat generated with the deformation could not escape from the surface of the materials. In addition, the static bending tests were carried out with different strain rate and stress rate at elevated temperature. The results of static bending tests were converted to the creep compliances, then the results were compared with master curve of short term creep tests and 1 month long term creep tests. The results shows the good agreement between the master curve and long term creep tests. However the creep compliances obtained by static bending tests showed the different creep behaviors.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110010053538, CiNii Books ID：AA12322087
• 214 Mechanical study with AE Technique for Fracture Mechanism in Transparent Conductive Film under Tensile Loading　　　　　　　　　　　　　　　
  Matsueda Takahiro; Hosoyamada Koji; Yuzawa Ryo; Wakayama Shuichi; Sakai Takenobu; Ikegami Masashi; Miyasaka Tsutomu
  Materials and processing conference, Volume：2015, Number：23, First page："214, Last page：1"-"214-4", 14 Nov. 2015
  Tensile test of Indium Tin Oxide (ITO) deposited on polyerhylene naphthalate (PEN) films used in solar cells were carried out. It was found from tensile tests that many AE signals were detected in ITO films. On the other hand, the electric resistance of ITO + PEN film was also measured later than first AE signal during tensile tests. In order to identify AE sources, in-situ observation of specimen and measurement of electricity resistance were also carried out. It was demonstrated that AE behavior shows good agreement with the cracking behavior in ITO. In addition to it, AE monitoring could be detected damages in ITO under mechanical strain earlier than were measurement of electricity resistance. Consequently, it was suggested that AE technique was extremely effective technique for damage detection and evaluating the damage accumulation process in films used in solar cells.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110010050354, CiNii Books ID：AA11902467
• Dynamic Mechanical Analysis　　　　　　　　　　　　　　　
  坂井 建宣
  実験力学 : Journal of JSEM : Journal of the Japan Society for Experimental Mechanics, Volume：15, Number：3, First page：239, Last page：241, 29 Sep. 2015
  日本実験力学会, Japanese
  ISSN：1346-4930, J-Global ID：201502201504093137, CiNii Articles ID：40020608038, CiNii Books ID：AA11822914
• PS4-8 Detection of Microdamage in Rabbit Patellar Tendon under Impact Tensile Load by Acoustic Emission(PS4: Poster Short Presentation IV,Poster Session)　　　　　　　　　　　　　　　
  Matsuoka Fumito; Wakayama Shuichi; Sakai Takenobu; Yamamoto Ei
  Proceedings of the ... Asian Pacific Conference on Biomechanics : emerging science and technology in biomechanics, Volume：2015, Number：8, First page：288, Last page：288, 16 Sep. 2015
  The Japan Society of Mechanical Engineers, English
  CiNii Articles ID：110010043915, CiNii Books ID：AA12087919
• S0420102 AE Monitoring of Damage Process in Transparent Conductive Film under Tensile Loading　　　　　　　　　　　　　　　
  WAKAYAMA Shuichi; AIZAWA Shutaro; YUZAWA Ryo; SAKAI Takenobu; IKEGAMI Masashi; MIYASAKA Tsutomu
  Mechanical Engineering Congress, Japan, Volume：2015, First page："S0420102, Last page：1"-"S0420102-3", 13 Sep. 2015
  Tensile tests of the transparent conductive films used in DSC (Dye-sensitized solar cell), consisting of ITO (Indium tin oxide) coating and PEN (Polyethylene naphthalate) substrate, were carried out and the damage accumulation process was monitored using acoustic emission technique. Damage initiation in ITO layer was detected earlier by AE technique than the electric resistance measurement during tensile tests. AE generation behavior was consistent with the result of in-situ observation of cracking behavior; initiation and saturation of transverse (perpendicular to tensile direction) cracking followed by the longitudinal (parallel to tensile direction) cracking due to buckling. Utilizing the principle of "fragmentation tests" for composite materials, interfacial shear strength for ITO/PEN interface was evaluated from experimental results for the critical strain at crack saturation and the spacing of saturated cracks. Finally, it was found that the shear strength was degraded by GBL (γ-Butyrolactone) used as electrolyte in DSC.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110010049345, CiNii Books ID：AA12588255
• J0230305 AE Characterization of Accumulation Process of Microdamage in Bovine Cortical Bone　　　　　　　　　　　　　　　
  KANAZAWA Takanobu; WAKAYAMA Shuichi; SAKAI Takenobu
  Mechanical Engineering Congress, Japan, Volume：2015, First page："J0230305, Last page：1"-"J0230305-4", 13 Sep. 2015
  Microdamage of healthy bovine cortical bone specimen and decalcified bone specimen during static compression tests was monitored by acoustic emission (AE) technique. Microdamage accumulation was successively monitored by AE technique. In static compression tests of healthy bone specimen, cracks were propagated due to microdamage accumulation, and cumulative AE events increased before final fracture. In static compression tests of decalcified bone specimen, macrocrack was observed with increasing in cumulative AE energy and cumulative AE events and decreasing in stress before fracture. Maximum stress and Young's modulus between healthy bone specimen and decalcified bone specimen had a significant difference. Those between specimen A (decalcified only specimen inside) and specimen B (decalcified specimen inside and outside) had no significant difference. Microdamage accumulation process of healthy bone specimen and decalcified bone specimen before leading to final fracture was shown by AE technique.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110010048687, CiNii Books ID：AA12588255
• J0230101 AE Monitoring and In-situ Observation Using High-speed Camera of Rupture Process of Rabbit PateUar Tendon under Impact Tensile Load　　　　　　　　　　　　　　　
  MATSUOKA Fumito; WAKAYAMA Shuichi; SAKAI Takenobu; YAMAMOTO Ei
  Mechanical Engineering Congress, Japan, Volume：2015, First page："J0230101, Last page：1"-"J0230101-4", 13 Sep. 2015
  Rabbit patellar tendon-bone complex specimens were subjected to impact tensile load to simulate the sports accident. During the tests, microdamage initiation and accumulation process in tendon was monitored using acoustic emission (AE) technique. In addition, in-situ observation from vertical and horizontal directions using two high-speed cameras was carried out to determine the strain distribution. The stress increased monotonically to the ultimate tensile stress (UTS), which was significantly higher than the static tests. Despite of the extremely short time, a number of AE signals were detected continuously before the UTS. Furthermore, AE signals were emitted in the area where the local strain increased significantly in the strain distribution of the surface. It is then demonstrated that AE technique enables not only the detection of invisible microdamage but the identification of the damage location. It is worth nothing that the amplitudes of detected AE signals were much higher than static tests. Since AE amplitude corresponds to the magnitude of individual microdamage, it is suggested that larger magnitude of individual microdamage is initiated under impact tensile load. Consequently, it is demonstrated that AE technique has a possibility of clarifying the detailed rupture mechanism of tendon or ligament under impact load.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110010048676, CiNii Books ID：AA12588255
• Manufacturing and Evaluation of Tire Powder/PLA Composite for Recycling Wasted Tire　　　　　　　　　　　　　　　
  坂井 建宣; 川井 喬介; 立山 耕平; Rios Soberanis C-R; Rodroguez-Laviada J.; Perez-Pacheco E.; 川田 良暁; 蔭山 健介; 山田 浩之
  Number：15, First page：160, Last page：162, 2015
  Japanese
  ISSN：1346-4922, CiNii Articles ID：40020846819, CiNii Books ID：AA11910104
• Observation of Fiber-Matrix Interfacial Stresses Using Phase-Stepping Photoelasticity　　　　　　　　　　　　　　　
  Takenobu Sakai; Yasunori Iihara; Satoru Yoneyama
  ADVANCEMENT OF OPTICAL METHODS IN EXPERIMENTAL MECHANICS, VOL 3, First page：215, Last page：223, 2015, [Reviewed]
  In this study, the single fiber composite was used to evaluate the stress transfer between a single fiber and a matrix. Single steel fiber was inserted to the epoxy resin, and it was applied the tensile load. Applied load was from 0 N to 177 N, and then the photoelastic images were taken by a digital CCD camera. In the photoelastic analysis, the phase-stepping and phase-unwrapping technique were used to measure the stress difference distribution more accurately. Obtained data were included the 3D information, therefore, we converted the stress difference data, including the 3D information to 2D photoelasticity using the geometrical information. The maximum shear stress was placed on the side surface of the steel fiber near the end of fiber, and the maximum normal stress difference was measured near the surface of the end of the fiber. The results of stress distribution on the interface between the fiber and the resin indicated that the stress concentration was observed in the middle part of the end of the fiber and the side surface near the end of the fiber.
  SPRINGER-VERLAG BERLIN, English
  DOI：https://doi.org/10.1007/978-3-319-06986-9_24
  DOI ID：10.1007/978-3-319-06986-9_24, ISSN：2191-5644, Web of Science ID：WOS:000347773500024
• Time Temperature Superposition Principle　　　　　　　　　　　　　　　
  坂井 建宣
  実験力学 : Journal of JSEM : Journal of the Japan Society for Experimental Mechanics, Volume：14, Number：4, First page：283, Last page：285, 28 Dec. 2014
  日本実験力学会, Japanese
  ISSN：1346-4930, J-Global ID：201502241354952420, CiNii Articles ID：40020347961, CiNii Books ID：AA11822914
• S0420104 Development of Dynamic Evaluation Method on Thermal Shock Fracture Properties of Ceramics　　　　　　　　　　　　　　　
  LI Shiliang; TSUKADA Takamasa; WAKAYAMA Shuichi; SAKAI Takenobu; YOSHIDA Katsumi; AKATSU Takashi
  Mechanical Engineering Congress, Japan, Volume：2014, First page："S0420104, Last page：1"-"S0420104-4", 07 Sep. 2014
  The experimental technique for the investigation of thermal shock fracture of ceramics under various stress ratios was developed. In order to determine the testing configurations, the thermal stress field in specimen was analyzed using FEM. It was found that the ellipse specimen and cooling rod with the specific aspect ratios yield the designated stress ratio which is constant during the test. The corresponding experiments were also carried out. The specimen was heated to 650 ℃ and quenched by means of contacting with a cool copper rod. The transient temperature on the ellipse specimen was measured by IR camera and the thermal stress was calculated by FEM. During thermal shocked fracture AE signals were detected by an AE sensor attached on the bottom of the copper rod. The constant thermal stress ratio was obtained corresponding to the result of FEM calculation. Consequently, the testing configuration, which enables the evaluation of thermal shock fracture behavior under various stress ratio, was developed.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110009945082, CiNii Books ID：AA12588255
• S0420103 Fracture Simulation Based on AE Characterization of Microfracture Process in Ceramics　　　　　　　　　　　　　　　
  WAKAYAMA Shuichi; MIYAGAWA Tomohiro; WAKIMOTO Yosuke; SAKAI Takenobu; IKEDA Junji; MIYAJI Fumiaki
  Mechanical Engineering Congress, Japan, Volume：2014, First page："S0420103, Last page：1"-"S0420103-4", 07 Sep. 2014
  Microfracture process in ceramics was analyzed using Monte-Carlo simulation. It was supposed in the simulation that the microfracture process consists of the maincrack formation resulted from the growth and coalescence of pre-existing microcracks, and the propagation of maincrack to final failure. To determine the crack growth parameters for simulation, microfracture process in alumina ceramics was characterized by acoustic emission technique, and the critical stress for maincrack formation and final strength were determined and compared with the results of simulation. The Monte-Carlo simulation assuming the 3 microcracks array with random size was adapted to the fracture analysis during the proof test with various proof stresses and holding times as well as residual strength measurements. The time-to-maincrack formation, yields and residual strength were calculated and it was found that they showed good agreement with the several experimental results. Consequently, the proof test with the wide range of proof stresses and holding times were examined and their influence on the yields, residual strength and lifetime was discussed.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110009945081, CiNii Books ID：AA12588255
• OS1719 Time-Temperature Dependency on Shape Recovery Property of Shape Memory Polymer　　　　　　　　　　　　　　　
  SAKAI Takenobu; TAO Takayuki; SOMIYA Satoshi
  Volume：2014, First page："OS1719, Last page：1"-"OS1719-2", 19 Jul. 2014
  As one of advanced functional materials, Shape Memory Polymer was studied on the shape recovery property, the shape fix property, and so on. However, it is difficult to comprehend the simple shape recovery behavior, because the viscoelastic and shape recover behaviors will occur simultaneously. Viscoelastic behavior is based on the entanglement effect on their polymeric chain, and the shape recovery behavior is based on the cross-link behavior. It is, therefore, necessary to divide these effects for understanding the viscoelastic and shape recovery behavior. The goal of this paper is to understand the viscoelastic and the simple shape recovery behavior, which depends on the cross-link, of the shape memory polymers.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110009939688, CiNii Books ID：AA12322087
• OS0511 Observation of Deformation Behavior of Adjacent Crystal Grains with Speckle Interferometry　　　　　　　　　　　　　　　
  ARIKAWA Shuichi; SAKAI Takenobu; OGASAWARA Ryosuke; YONEYAMA Satoru
  Volume：2014, First page："OS0511, Last page：1"-"OS0511-2", 19 Jul. 2014
  Deformation behavior of adjacent crystal grains of a metal is observed using speckle interferometry. Coarse grained aluminum specimens which have two crystal grains in the observation region are made by a thermo-mechanical treatment for the observation by speckle interferometry. Grain boundaries are arranged 0°, 45° and 90° for the loading direction. Crystal orientations are measured by electron backscatter diffraction. Tensile tests are performed and the in-plane and the out-of-plane deformation behaviors of the specimen surfaces are observed using speckle interferometry. As the results, strain maps of ε_x, ε_y, and γ_, are obtained and heterogenous deformation behaviors in each crystal grain can be observed. Various values of yield stresses and strains of each crystal grain in each specimen are obtained. The values depend on Schmidt factor obtained from the crystal orientation analysis. A tendency of the variation to decrease with decreasing the angles of the grain boundaries is obtained. Therefore, the experimental investigation of deformations of adjacent crystal grains is made possible by speckle interferometry.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110009939492, CiNii Books ID：AA12322087
• 10210 A basic study on diagnosis method of knee osteoarthritis by articular sound　　　　　　　　　　　　　　　
  TOZAWA Yusuke; HASE Kazunori; OTA Susumu; SAKAI Takenobu
  Volume：2014, Number：20, First page："10210, Last page：1"-"10210-2", 14 Mar. 2014
  The articular sound arising from the knee joint is useful for the diagnosis of knee osteoarthritis. However, measurement and evaluation methods are unsolved, so that a standard diagnosis technique has not been established at present. This study aims to establish of the diagnostic method by the articular sound. The articular sound was measured by four stethoscopes attached to the knee joint. The location and status of the disease from the articular sound were quantitatively evaluated by introducing a signal processing techniques such as AIC (akaike's information criterion) and continuous wavelet transform. As a result, the sound frequency to be produced by knee osteoarthritis patient tended to be higher than that by healthy person.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110009949289, CiNii Books ID：AA11902161
• Bending Fracture Behavior of Wasted Activated Carbon Reinforced Polypropylene　　　　　　　　　　　　　　　
  坂井 建宣; 具志堅 智彦; Soberanis C-R Rios
  Number：14, First page：247, Last page：249, 2014
  Japanese
  ISSN：1346-4922, CiNii Articles ID：40020212692, CiNii Books ID：AA11910104
• ウェアラブルな心音・呼吸音評価装置の開発　　　　　　　　　　　　　　　
  坂井 建宣
  Volume：33, First page：153, Last page：157, 2014
  Japanese
  CiNii Articles ID：40020772224, CiNii Books ID：AN10192980
• 413 Lifetime Prediction of Ceramics by Simulation Considering Interaction of Microcrack　　　　　　　　　　　　　　　
  WAKAYAMA Shuichi; WAKIMOTO Yosuke; SAKAI Takenobu; IKEDA Junji; MIYAJI Fumiaki
  Materials and processing conference, Volume：2013, Number：21, First page："413, Last page：1"-"413-3", 08 Nov. 2013
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110009935909, CiNii Books ID：AA11902467
• 127 Mechanical Properties of Wasted Tire Powder Composites　　　　　　　　　　　　　　　
  SAKAI Takenobu; WAKAYAMA Shuichi; Rolando Soberanis C-R; Rodroguez-Laviada J.; Perez-Pacheco E.
  Materials and processing conference, Volume：2013, Number：21, First page："127, Last page：1"-"127-3", 08 Nov. 2013
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110009935814, CiNii Books ID：AA11902467
• OS0707 Viscoelastic and Damage Accumulation Behavior on Compressive Deformation of Bovine Cortical Bone　　　　　　　　　　　　　　　
  SAKAI Takenobu; YOSHIYA Eri; YASUI Keita; WAKAYAMA Shuichi
  Volume：2013, First page："OS0707, Last page：1"-"OS0707-3", 12 Oct. 2013
  Recently, the osteoporosis victims increase in the senior people. Therefore, the danger of the stress fracture due to the decrease in bone strength is pointed out. Especially, the damage accumulation behavior of the bone in the cyclic load becomes a problem for the fatigue of the bone. Moreover, it is necessary to consider the viscoelastic property for the prediction of the fatigue behavior, because the bone is a viscoelastic material. In this study, our objective is to estimate the fatigue behavior that considers the viscoelasticity behavior and the damage accumulation behavior as damage mechanics. The viscoelastic properties were revealed with the strain rate tests, and we calculated the 3-mode Maxwell parameters with these results. The damage accumulation behaviors were measured with the Acoustic Emission method. Using these results, we could estimate the fatigue behavior of cortical bone with the viscoelastic parameter and cumulative AE energy.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110009936609, CiNii Books ID：AA12322087
• S042013 Dynamic Evaluation of Crack Propagation Behavior on Si_3N_4 by Controlling Microstructure　　　　　　　　　　　　　　　
  SAKAI Takenobu; KAMETANI Go; WAKAYAMA Shuichi; YOSHIDA Katsumi
  Mechanical Engineering Congress, Japan, Volume：2013, First page："S042013, Last page：1"-"S042013-3", 08 Sep. 2013
  The microdamage in silicon nitride during thermal shock fracture was monitored by acoustic emission (AE) technique. Disc-on-Rod test was used to evaluate thermal shock fracture process. Cylinders with different microstructures were fabricated by sintering at different temperatures. In the Disc-on-Rod test, a pre-crack introduced specimen was heated, and only the center of circular specimen was quenched. Crack growth behavior under thermal shock loading can be monitored by using AE technique. The crack extension length was measured by the Digital Microscope. The crack growth resistance was calculated using Virtual Crack Closure Method and the FEM software. The crack growth resistance curves showed the rising R-curve behaviors for each material; therefore, it is assumed that the materials showed toughening mechanisms during the Disc-on Rod tests. As sintering temperature increased, crack growth resistance increased under the thermal shock loading.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110009933997, CiNii Books ID：AA12588255
• 21208 Evaluation of Damage of Flexible Solar Cells under External Load using Acoustic Emission Method　　　　　　　　　　　　　　　
  TAZAWA Hiroyuki; SAKAI Takenobu; WAKAYAMA Shuichi
  Volume：2013, Number：19, First page：549, Last page：550, 14 Mar. 2013
  In this study, the tensile test has been carried out to the flexible solar cells, and there failure processes have been characterized by the acoustic emission (AE) technique and the lock-in thermography. At the same time, the dark I-V curve has been measured during the test, and the leak current at-2 V has been used as a measure of degradation. The cumulative AE energy and the leak current began to increase at the strain of 〜0.8% and 〜1.2%, respectively. Accordingly the AE technique can detect mechanical damages earlier than the leak current increases. It is demonstrated by the lock-in thermography that the mechanical damages at holes contribute to performance degradation.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110009954666, CiNii Books ID：AA11902161
• 10513 Characterization of Damage Process of Rabbit patella Tendon by Acoustic Emission Technique under Simulated In Vivo Environment　　　　　　　　　　　　　　　
  SUZUKI Satomi; SAKAI Takenobu; WAKAYAMA Shuichi; YAMAMOTO Ei
  Volume：2013, Number：19, First page：87, Last page：88, 14 Mar. 2013
  AE monitoring of damage process of rabbit patellar tendon under static tensile load was carried out. Considering strong viscoelasticity of tendon, load was applied at various loading rate (10, 1, 0.1 mm/min) until the complete rupture in physiological saline at 37°C. The displacement of the specimen was monitored by a digital video camera, and acquired images were used for determining the displacement distribution in tendon by the digital image correlation (DIC) technique. It was found that the average failure stress increased as loading rate increased, and the differences in maximum stress were considered to be statistically significant. AE signals were detected before the maximum load and AE source locations corresponded to the locally elongated area, which indicates that fascicle failure takes place before the maximum load. Consequently, the fundamental insights for the damage monitoring technique which are indispensable for the optimization of programs of sports training or rehabilitation are obtained.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110009954435, CiNii Books ID：AA11902161
• 20312 Evaluation of Crack Growth Resistance of Silicon Nitride under Thermal Shock Fracture by Acoustic Emission Technique　　　　　　　　　　　　　　　
  KAMETANI Go; SAKAI Takenobu; WAKAYAMA Shuichi; YOSHIDA Katsumi
  Volume：2013, Number：19, First page：277, Last page：278, 14 Mar. 2013
  The microdamage in silicon nitride during thermal shock fracture was monitored by acoustic emission (AE) technique. Disc-on-Rod test, which was developed by the authors, was used to evaluate thermal shock fracture process. Specimens were composed of β-Si_3N_4 with acicular structure. Cylinders with different microstructures were fabricated by sintering at different temperatures. A pre-crack was introduced using knoop indentation. In the Disc-on-Rod test, specimen was uniformly heated to 850 ℃, and only the center of circular specimen was quenched. After contacting, crack propagated in an unstable manner, at the same time, one relatively high amplitude AE signal was detected. Subsequently, stable crack propagation was observed, and several relatively low amplitude AE signals were generated corresponding to crack propagation. As sintering temperature increased, crack growth resistance decreased under the both thermal shock and mechanical loading. Furthermore, crack growth resistance sunder thermal shock loading were higher than those under mechanical loading.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110009954530, CiNii Books ID：AA11902161
• J022024 Characterization of damage process of the rabbit patellar tendon using acoustic emission under various strain rate　　　　　　　　　　　　　　　
  SUZUKI Satomi; SAKAI Takenobu; WAKAYAMA Shuichi; YAMAMOTO Ei
  Mechanical Engineering Congress, Japan, Volume：2012, First page："J022024, Last page：1"-"J022024-3", 09 Sep. 2012
  AE monitoring of damage process of rabbit patellar tendon under static tensile load was carried out. Considering strong viscoelasticity of tendon, load was applied at various loading rate (10, 1, 0.1 mm/min) until the complete rupture in physiological saline at 37℃. The displacement of the specimen was monitored by a digital video camera, and acquired images were used for determining the displacement distribution in tendon by the digital image correlation (DIC) technique. It was found that AE signals were detected before the maximum load and AE source locations corresponded to the locally elongated area, which indicates that fascicle failure takes place before the maximum load. The average failure stress increased as loading rate increased, and the differences in average failure stress were considered to be statistically significant. Consequently, the fundamental insights for the damage monitoring technique which are indispensable for the optimization of programs of sports training or rehabilitation are obtained.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110009993276, CiNii Books ID：AA12588255
• S042021 AE Detection of Microdamages and Long Term Reliability Assessment of ATZ Composite Ceramics for Artificial Joints　　　　　　　　　　　　　　　
  SAKAI Takenobu; KAZAMA Gaku; WAKAYAMA Shuichi; IKEDA Junji; MIYAJI Fumiaki
  Mechanical Engineering Congress, Japan, Volume：2012, First page："S042021, Last page：1"-"S042021-3", 09 Sep. 2012
  The microdamages in ATZ composite ceramics during 4-point bending test were monitored by acoustic emission (AE) technique, and the rapid increase in cumulative AE energy prior to the final fracture was observed, which could be related with the maincrack formation as the origin of final fracture. The critical stress for maincrack formation σ_c was determined as the stress at rapid increasing point of AE signals. The stress increased with decreasing in Alumina weight fraction without 0% By increasing in ZrO_2, the growth grain size of Al_2O_3 was restrained and the flaw size turned smaller, since σ_c depends on the dispersion in the size and the distribution of initial failure.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110009993393, CiNii Books ID：AA12588255
• Note from the Guest Editor　　　　　　　　　　　　　　　
  SAKAI Takenobu
  実験力学 : journal of JSEM, Volume：12, Number：2, First page：70, Last page：70, 25 Jun. 2012
  Japanese
  ISSN：1346-4930, CiNii Articles ID：10030800702, CiNii Books ID：AA11822914
• 首都大学東京大学院 理工学研究科 機械工学専攻材料力学研究室　　　　　　　　　　　　　　　
  坂井 建宣; 若山 修一
  Volume：12, Number：1, First page：55, Last page：55, 28 Mar. 2012
  Japanese
  ISSN：1346-4930, CiNii Articles ID：10030556144, CiNii Books ID：AA11822914
• 第18回国際複合材料会議報告　　　　　　　　　　　　　　　
  荻原 慎二; 横関 智弘; 本田 真也; 小林 訓史; 黄木 景二; 胡 寧; 中村 理恵; 松崎 亮介; 上田 政人; 島村 佳伸; 中田 政之; 北條 正樹; 合田 公一; 斉藤 博嗣; 坂井 建宣; 中谷 隼人; 廣瀬 康夫; 河井 昌道; 水口 周; 小山 昌志; 野田 淳二; 佐々木 元; 倉敷 哲生; 尾崎 毅志; 加藤 久弥; 武田 真一; 吉村 彰記; 石田 雄一; 小柳 潤; 平野 義鎭; 仲井 朝美
  Volume：38, Number：2, First page：67, Last page：84, 15 Mar. 2012
  Japanese
  ISSN：0385-2563, CiNii Articles ID：10030825480, CiNii Books ID：AN00196748
• Relationship between Electric Conductivity and Viscoelasticity of Used Activated Carbon Composites　　　　　　　　　　　　　　　
  坂井 建宣; 具志堅 智彦; 増子 知樹
  Number：12, First page：161, Last page：164, 2012
  Japanese
  ISSN：1346-4922, CiNii Articles ID：40019492486, CiNii Books ID：AA11910104
• 511 Effect of Molding condition on the compressive properties of PLA-PBAT blend materials　　　　　　　　　　　　　　　
  GUSHIKEN Tomohiko; OMIYA Masaki; SAKAI Takenobu
  Volume：61, First page：121, Last page：122, 2012
  Japanese
  CiNii Articles ID：110009484906, CiNii Books ID：AA11881527
• The Future Image of the Society for Experimental Mechanics : Future of Materials Engineering in JSEM　　　　　　　　　　　　　　　
  SAKAI Takenobu
  実験力学 : journal of JSEM, Volume：11, Number：4, First page：340, Last page：340, 28 Dec. 2011
  Japanese
  ISSN：1346-4930, CiNii Articles ID：10030287004, CiNii Books ID：AA11822914
• A110 AE Characterization of Fatigue Damage in Cortical Bone　　　　　　　　　　　　　　　
  YASUI Keita; SAKAI Takenobu; WAKAYAMA Shuichi
  Proceedings of the ... JSME Conference on Frontiers in Bioengineering, Volume：2011, Number：22, First page：19, Last page：20, 06 Oct. 2011
  The Japan Society of Mechanical Engineers, Japanese
  ISSN：1348-2939, CiNii Articles ID：110009663310, CiNii Books ID：AA11902434
• A114 Characterization of Damage Process of Tendon by Acoustic Emission Technique　　　　　　　　　　　　　　　
  SUZUKI Satomi; SAKAI Takenobu; WAKAYAMA Shuichi; YAMAMOTO Ei
  Proceedings of the ... JSME Conference on Frontiers in Bioengineering, Volume：2011, Number：22, First page：27, Last page：28, 06 Oct. 2011
  The Japan Society of Mechanical Engineers, Japanese
  ISSN：1348-2939, CiNii Articles ID：110009663314, CiNii Books ID：AA11902434
• S042034 Fabrication of Discontinuous Fiber Reinforced Ceramic Composites and Characterization of Mechanical Properties　　　　　　　　　　　　　　　
  UMINO Kosuke; AKIYAMA Yusuke; WAKAYAMA Shuichi; SAKAI Takenobu; UMEHARA Yuka; AKATSU Takashi
  Mechanical Engineering Congress, Japan, Volume：2011, First page："S042034, Last page：1"-"S042034-4", 11 Sep. 2011
  40 vol% SiC whisker reinforced alumina matrix composites (SiCw/Al_2O_3) were fabricated using a spark plasma sintering (SPS) technique. In this study, to decrease the thermal mismatch between SiCw and Al_2O_3, SiC particle (SiCp) was added into Al203 matrix (SiCw/SiCp/Al_2O_3). The relative density of the fabricated specimens was more than 99%, so that the sufficient densification was accomplished. Then, the mechanical properties and fracture morphology were examined. It was found that the mechanical properties of composites were increased from the monolithic Al203 and SiCw/Al_2O_3 composites. SEM observation of fracture surface after bending test showed that the amount of pull-out SiCw and the pull-out length in SiCw/SiCp/Al_2O_3 composites was larger than SiCw/Al_2O_3 composites. Therefore, the interfacial shear strength was successfully reduced due to SiCp addition. Consequently, it was suggested that the improvement of mechanical properties of SiCw/SiCp/Al_2O_3 composites may be accomplished by optimizing the interfacial shear strength due to SiCp addition.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110009759847, CiNii Books ID：AA12588255
• S042024 AE Monitoring of Damage Accumulation Process during Tensile Tests of Transparent Conductive Oxide Films　　　　　　　　　　　　　　　
  TAKAGI Nobuyuki; WAKAYAMA Shuichi; SAKAI Takenobu; IKEGAMI Masashi; MIYASAKA Tsutomu
  Mechanical Engineering Congress, Japan, Volume：2011, First page："S042024, Last page：1"-"S042024-5", 11 Sep. 2011
  In this study, tensile tests of indium tin oxide (ITO) deposited on polyethylene naphthalate (PEN) films (ITO + PEN films) used in dye-sensitized solar cells (DSCs) were carried out. ITO + PEN films are fabricated at 150℃. Therefore, to clarify the influence of heat treatment on mechanical properties of ITO + PEN, the specimens with heat treatment were prepared. In order to discriminate AE signals in ITO from PEN films, PEN film specimens (ITO was removed by 17.5% hydrochloric acid) were also prepared. It was found from tensile tests that many AE signals were detected in ITO + PEN films, while few AE signals were detected in PEN films. On the other hand, the electric resistance of ITO was also measured during tensile tests. These results suggested that the critical damage in ITO was detected by the AE measurement more sensitively than the electric resistance. To identify AE sources, in-situ observation of specimen during tensile test with AE measurement was carried out. It was emphasized that AE behavior shows good agreement with the cracking behavior in ITO. Damages in ITO under mechanical strain were successfully monitored by AE technique in the present study. Consequently, it was suggested that AE technique could be a powerful technique for evaluating the damage accumulation process in DSCs.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110009759843, CiNii Books ID：AA12588255
• 119206 Research about Relationship between Deformation and Electric Resistance on Used Activated Carbon Reinforced Polypropylene　　　　　　　　　　　　　　　
  SAKAI Takenobu; GUSHIKEN Tomohiko; MASUKO Tomoki; MATSUSHIMA Satoshi; KOBAYASHI Satoshi; YONEYAMA Satoru
  Volume：2011, Number：17, First page：95, Last page：96, 17 Mar. 2011
  In the Waterworks Bureau, the activated carbon was used for filtering the water. After use the activated carbon, they were disposed. In this work, we tried to make that composite to recycle these carbons. These wasted activated carbons were used for the filler of composite materials, and we got the composite with the carbon contents of 10%〜60%. To evaluate of mechanical behavior of these composites, tensile test and stress relaxation test were carried out. The results show the powder contents dependency on tensile strength and Young's modulus. As seen in the results of stress relaxation test, the effect of powder contents on stress relaxation was revealed. To evaluate the electric property, the electric resistance was measured by 4-terminal method during tensile test and stress relaxation test. By the measurement of electric resistance, these composites can be used as smart materials.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110009663766, CiNii Books ID：AA11902161
• 220304 Evaluation of the Mechanical Damage Accumulation in Transparent Conductive Oxide Film using Acoustic Emission　　　　　　　　　　　　　　　
  TAKAGI Nobuyuki; WAKAYAMA Shuichi; MIZUTANI Akihiro; SAKAI Takenobu; MIYASAKA Tsutomu; IKEGAMI Masashi
  Volume：2011, Number：17, First page：567, Last page：568, 17 Mar. 2011
  In this study, tensile tests of transparent conductive oxide (TCO) deposited on polyerhylene naphthalate (PEN) films (TCO + PEN films) used in dye-sensitized solar cells (DSCs) were carried out. In order to discriminate AE signals in TCO from PEN films, PEN film specimens (TCO was removed by 17.5% acidum hydrechloricum) were also prepared. It was found from tensile tests that many AE signals were detected in TCO + PEN films, while few AE signals were detected in PEN films. On the other hand, the electric resistance of TCO was also measured during tensile tests. These results suggested that the critical damage in TCO was detected by the measurement of AE signals more sensitively than the electric resistance measurement. To identify AE sources, in-situ observation of specimen during tensile test with AE measurement was carried out. It was emphasized that AE behavior shows good agreement with the cracking behavior in TCO. Damages in TCO under mechanical strain were successfully monitored by AE technique in the present study. Consequently, it was suggested that AE technique could be a powerful technique for evaluating the damage accumulation process in DSCs.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110009664001, CiNii Books ID：AA11902161
• 8E-01 Characterization of Fatigue Damage of Cortical Bone by Acoustic Emission Technique at Different Frequency under Simulated In Vivo Environment　　　　　　　　　　　　　　　
  YASUI Keita; WAKAYAMA Shuichi; SAKAI Takenobu
  Volume：2010, Number：23, First page：77, Last page：78, 07 Jan. 2011
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110008744030, CiNii Books ID：AA11903175
• Relationship between the lamination constitution and the creep behavior of non-crimp fabric　　　　　　　　　　　　　　　
  坂井 建宣; Soberanis C. R. Rios; 若山 修一
  Proceedings of JSEM, Number：11, First page：450, Last page：454, 2011
  Japanese
  ISSN：1346-4922, CiNii Articles ID：40019017304, CiNii Books ID：AA11910104
• Notes from the Guest Editor　　　　　　　　　　　　　　　
  SAKAI Takenobu
  実験力学 : journal of JSEM, Volume：10, Number：4, First page：386, Last page：386, 25 Dec. 2010
  Japanese
  ISSN：1346-4930, CiNii Articles ID：10027692944, CiNii Books ID：AA11822914
• 111 Fracture Behavior of High Content Carbon Nanofiber Reinforced Alumina Composites Using Electrostatic Adsorption　　　　　　　　　　　　　　　
  UMINO Kosuke; WAKAYAMA Syuichi; AKATSU Takashi; SAKAI Takenobu; UMEHARA Yuka
  Materials and processing conference, Volume：2010, Number：18, First page："111, Last page：1"-"111-4", 27 Nov. 2010
  In this study, carbon nanofiber (CNF) reinforced Al_2O_3 composites were fabricated. To fabricate uniformly-dispersed CNF/Al_2O_3 powder, electrostatic adsorption, which could increase the surface potential of CNFs, was applied. Al203 sol was then adsorbed onto the surface of CNFs uniformly. The mixed powder was sintered by spark plasma sintering under the pressure of 50 MPa at 1600℃ in Ar atmosphere. Fracture behavior of the specimen was evaluated by bending test, indentation test and fracture-surface observation. The results showed that the bending strength of specimen was lower than monolithic Al_2O_3. It might be because there were many pores and the interface between CNF and Al_2O_3 were relatively weak. However, a large number of pull-out and bridging of CNFs were observed by the fracture surface observation with a scanning electron microscope. This suggests that CNFs could improve the fracture toughness of the CNF reinforced Al_2O_3 composites.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110008742944, CiNii Books ID：AA11902467
• フィジカルエージング　　　　　　　　　　　　　　　
  坂井 建宣
  Volume：10, Number：1, First page：120, Last page：121, 25 Mar. 2010
  Japanese
  ISSN：1346-4930, CiNii Articles ID：10026406397, CiNii Books ID：AA11822914
• よくわかる学術用語 フィジカルエージング
  坂井建宣
  実験力学, Volume：10, Number：1, First page：120, Last page：121, 25 Mar. 2010
  Japanese
  ISSN：1346-4930, J-Global ID：201002230071759367
• 2009 International Conference of Experimental Mechanics in Singapore 参加報告 : 2009 Asian Conference of Experimental Mechanics　　　　　　　　　　　　　　　
  坂井 建宣
  Volume：10, Number：1, First page：124, Last page：124, 25 Mar. 2010
  Japanese
  ISSN：1346-4930, CiNii Articles ID：10026406405, CiNii Books ID：AA11822914
• Evaluation of visco-elasticity on bone cement added the biocompatibility monomer　　　　　　　　　　　　　　　
  坂井 建宣; 若山 修一; Rios-Soberanis C. R.
  Proceedings of JSEM, Number：10, First page：41, Last page：45, 2010
  Japanese
  ISSN：1346-4922, CiNii Articles ID：40017284647, CiNii Books ID：AA11910104
• Creep Analysis of Polyacetal with Effect of Crystal State　　　　　　　　　　　　　　　
  SAKAI Takenobu; UENO Soichiro; YAMADA Koichi; SOMIYA Satoshi
  Journal of JSEM, Volume：9, Number：4, First page：388, Last page：394, 25 Dec. 2009
  Japanese
  ISSN：1346-4930, CiNii Articles ID：10026406130, CiNii Books ID：AA11822914
• OS0516 Effect of tensile deformation on the crystallinity of biodegradable polymer　　　　　　　　　　　　　　　
  SAKAI Takenobu; NAKASONE Yuji
  Volume：2009, First page：607, Last page：608, 24 Jul. 2009
  The crystal condition of the poly lactic acid that was a crystalline polymer was changed (degree of crystallization etc.), and the tensile test was done. Then the influence of crystal condition on the mechanical attribute was examined. Therefore, heat-treatment was first given to the material based on the melting point and the crystallization temperature of the material requested from differential scanning calorimetry (DSC), and the material that changed the degree of crystallization was made. Next, when the change in the degree of crystallization in the extensional deformation was confirmed because the crystallinity dependence was seen in the extensional deformation as a result of doing the tensile test and having examined it, it was understood that the degree of crystallization had changed by the extensional deformation.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110008065013, CiNii Books ID：AA12322087
• PS25 Evaluation of Compressive Properties of PLA/PBAT Polymer Blends　　　　　　　　　　　　　　　
  YAMAMURA Toshitaka; OMIYA Masaki; SAKAI Takenobu; VIOT Philippe
  Volume：2009, First page：485, Last page：487, 24 Jul. 2009
  Biodegradable polymers, Polylactide(PLA) have a potential to be engineering plastics because of energy and environmental reasons. Conventional polymers are made from the petroleum, but PLA is made from the starch whose source is plants. Thus, PLA is carbon-neutral because the carbon of the starch is from carbon dioxide in the air. PLA is brittle. So, it limits the use of PLA. To improve this brittleness, PLA have been blended with other flexible polymers. In this study, we use Poly butylene adipate-co-terephthalate(PBAT) as the blending polymer. PBAT is fully biodegradable and flexible, though its Young's modulus and tensile strength are inferior to PLA, breaking strain is much higher than PLA PBAT distributes evenly in the PLA matrix. By now, PLA and blended PLA were conducted static tensile tests, but not done compressive tests. So, we evaluated properties in the static and dynamic compressive tests. In result, addition 40 wt % PBAT to PLA, Young's modulus and yielding stress decrease, but maximum strain and the strain energy at crack initiation get larger. In addition, Young's modulus and yielding stress of neat PLA and blended PLA increase with the strain rate rising.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110008064965, CiNii Books ID：AA12322087
• Analysis of creep behavior in thermoplastic and its composites based on linear visco-elastic theory　　　　　　　　　　　　　　　
  坂井 建宣; 宗宮 詮
  Proceedings of JSEM, Number：9, First page：220, Last page：225, 2009
  Japanese
  ISSN：1346-4922, CiNii Articles ID：40016842731, CiNii Books ID：AA11910104
• Evaluation of compressive properties of PLA/PBAT polymer blends　　　　　　　　　　　　　　　
  山村 俊貴; 大宮 正毅; 坂井 建宣
  Proceedings of JSEM, Number：9, First page：151, Last page：156, 2009
  Japanese
  ISSN：1346-4922, CiNii Articles ID：40016842717, CiNii Books ID：AA11910104
• ポリカーボネートのクリープ挙動に及ぼす熱履歴の影響とその測定　　　　　　　　　　　　　　　
  坂井建宣
  First page：137, Last page：142, 2009
  CiNii Articles ID：80020343962
• OS0618 Effect of crystal state on mechanical properties of a crystalline polymer　　　　　　　　　　　　　　　
  Sakai Takenobu; Nakasone Yuji
  Volume：2008, First page："OS0618, Last page：1"-"OS0618-2", 16 Sep. 2008
  結晶性高分子であるポリアセタールの結晶状態(結晶化度など)を変化させて、引張試験および硬さ試験等を行い、力学的特性に及ぼす結晶状態の影響を調べた。そのため、まず、示差走査熱量測定(DSC)から求めた供試材の融点および結晶化温度に基づいて、供試材に熱処理を施し、結晶化度を変化させた供試材を作製した。次に、引張試験を行い、結晶化処理を施した材料と受入材の引張挙動の相違を調べた。また、予ひずみを与えた材料について硬さ試験を行い、硬さに及ぼす予ひずみの影響を調べ、結晶化度の変化が結晶性高分子材料の引張強度特性に及ぼす影響を明らかにした。
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110008697364, CiNii Books ID：AA12322087
• Effect of crystal state on creep behavior of polyacetal　　　　　　　　　　　　　　　
  坂井 建宣; 上野 宗一郎; 山田 幸市
  Proceedings of JSEM, Number：8, First page：267, Last page：270, 2008
  Japanese
  ISSN：1346-4922, CiNii Articles ID：40016856061, CiNii Books ID：AA11910104
• 2007 SEM Annual Conference & Exposition on Experimental and Applied Mechanics　　　　　　　　　　　　　　　
  坂井 建宣
  実験力学 : journal of JSEM, Volume：7, Number：3, First page：297, Last page：297, 25 Sep. 2007
  Japanese
  ISSN：1346-4930, CiNii Articles ID：10019954481, CiNii Books ID：AA11822914
• OS15-3-1 Estimation Corresponding to Temperature Change of Creep Behavior on Glass Fiber Reinforced-Polycarbonate　　　　　　　　　　　　　　　
  Sakai Takenobu; Somiya Satoshi
  Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics, Volume：2007, Number：6, First page："OS15, Last page：3-1-1"-"OS15-3-1-5", 12 Sep. 2007
  Thermoplastic resin was practically used without post cure treatment and physical aging treatment which is called "molded material". For such materials, it is known that creep behavior and physical aging occur simultaneously. And the effect of physical aging has the time and temperature dependency. The effect was occurred on the materials after molded, and the effect saved on the materials as the thermal history. This history has big influence on mechanical properties, especially creep properties. Therefore, it is necessary to understand the progress of the physical aging. In this report, the creep deformation of polycarbonate (PC) was researched to grasp the effect of physical aging on creep behavior. Two types of materials were prepared. One was "molded material", and another was pre-physical aged material. It was confirmed that the effect had the time and temperature dependency, and it had been able to apply the time-pre-aging time superposition principle and time-pre-aging temperature superposition principle of physical aging on creep behavior. The estimation corresponding to temperature change of creep deformation became possible using this superposition principle. The estimation result of the creep deformation of glass fiber reinforced polycarbonate (GFRPC) with temperature change during a creep test had the tendency similar to the experimental data. Therefore, it should be able to estimate the creep behavior with arbitrary thermal history since the materials reached to the saturated state of physical aging.
  The Japan Society of Mechanical Engineers, English
  CiNii Articles ID：110009969382, CiNii Books ID：AA11902310
• E-18 Visco-Elasticity of Shape Memory Polymer : Polyurethane series(Session: Contact strength/Mechanical)　　　　　　　　　　　　　　　
  Sakai Takenobu; Tao Takayuki; Somiya Satoshi
  ASMP : proceedings of Asian Symposium on Materials and Processing, Volume：2006, First page：110, Last page：110, 08 Nov. 2006
  In this research, the creep behavior of shape memory polymer (SMP) was researched. On this material, master curve of creep compliance was obtained, and time-temperature superposition principle was confirmed. The effect of physical aging on creep behavior was researched, too. The effect of physical aging on creep behavior was described on the aging shift factors, and the effect was depended on the change of time and temperature. From this result, time-physical aged time superposition principle was confirmed. Using the master curve and the shift factors of time, temperature and physical aging, it makes to be able to estimate the creep deformation including the effect of physical aging on creep behavior.
  The Japan Society of Mechanical Engineers, English
  CiNii Articles ID：110006781508, CiNii Books ID：AA12251091
• Material Design Method on Creep Behavior of Glass Fiber Reinforced-Polycarbonate　　　　　　　　　　　　　　　
  SAKAI Takenobu; KUSUMOTO Koji; SOMIYA Satoshi
  Volume：2003, First page：71, Last page：72, 01 May 2003
  Japanese
  CiNii Articles ID：10010717047, CiNii Books ID：AA11644747
• Effects of creep tempering on mechanical properties of diesel engine spring　　　　　　　　　　　　　　　
  金子 堅司; 小島 正敏; 坂井 建宣
  Volume：2002, First page：5, Last page：6, 10 Oct. 2002
  A creep tempering is done in production process of a spring designed for a fuel-injection nozzle of diesel engine. It is because that creep deformation occurs during use at high temperature and mechanical properties may change. But, conditions (temperature, time) in the creep tempering depend on empirical data that are not necessarily reasonable. In this study, effects of creep tempering on mechanical properties and residual stress of spring are investigated experimentally and theoretically. It is found that shear residual stress increases and spring constant does not so change after creep tempering process. Calculation methods of both shear residual stress and shear creep constitutive expressions of spring are proposed.
  The Japan Society of Mechanical Engineers, Japanese
  CiNii Articles ID：110002480844, CiNii Books ID：AN00360626

• 高分子の残留応力対策　　　　　　　　　　　　　　　
  [Joint work]
  2016
• 動的粘弾性チャートの解釈事例集　　　　　　　　　　　　　　　
  [Joint work]
  2016
• よくわかる実験技術・学術用語 第２版　　　　　　　　　　　　　　　
  [Joint work]
  2010

• Effect of temperature and strain rate on damage accumulation behavior of unidirectional CFRP　　　　　　　　　　　　　　　
  Takenobu Sakai; Satoru Abe; Kensuke Kageyama
  33rd Technical Conference of the American Society for Composites 2018, Jan. 2018
  Jan. 2018 - Jan. 2018
  © Copyright© (2018) by DEStech Publications, Inc. All rights reserved. Carbon Fiber reinforced plastics (CFRP) is consisted with the carbon fiber and matrix resin. It has reported to consider that the matrix resin's properties also depends on CFRP's mechanical properties in the recent research. Matrix resin's considerable mechanical property is viscoelasticity that depends on time and temperature. In this study, we focused on the effect of temperature and strain rate on the damage accumulation behavior of unidirectional CFRP laminate, and tensile tests with acoustic emission technique were carried out at three different temperature with three different strain rate. As the results of tensile tests, lower temperature and higher strain rate showed higher tensile strength, that is, it is understood that tensile strength depended on the matrix's viscoelastic properties. Crack initiation behavior, which was defined at the point of rapid increase in cumulative AE energy, was depended on the temperature and strain rate. To understand the details of AE information, the frequency analysis was done. In the frequency analysis, the resonant frequency of AE sensors effects on the frequency properties of the detected signals, so we tried to erase the effect of sensors by deconvolution of AE sensor's frequency properties from detected signals. As the results of deconvolution, we could distinguished the failure modes as matrix cracking, fiber/matrix interfacial debonding and fiber breaking. Using these results, matrix cracking, fiber/matrix interfacial debonding were effected by temperature and strain rate, however, fiber breaking was not affected. Consequently, the crack accumulation behavior of each failure mode depended on the temperature and strain rate as the same tendency of matrix's viscoelastic properties.
• Preparation and characteristic evaluation of silica-agglomerate electret with ultra-thin PTFE layer for ultrasonic sensor　　　　　　　　　　　　　　　
  Kensuke Kageyama; Takeru Orikasa; Ahmad Zarif Afiq Bin Jamaludin; Takenobu Sakai
  IEEJ Transactions on Sensors and Micromachines, Jan. 2018
  Jan. 2018 - Jan. 2018
  © 2018 The Institute of Electrical Engineers of Japan. Influence of formation of silica agglomerates on a ultra-thin fluororesin electret on the characteristics of the charge-retention and the aero-ultrasonic sensor was investigated. The ultra-thin PTFE layer (thickness was 2.8 μm) was obtained by spin-coating and silica agglomerates were formed by spraying droplets of colloidal silica. The formation of PTFE/silica agglomerate composite layer on PTFE layer resulted the larger and more flat agglomerates than the formation of single layer of silica agglomerates on the PTFE layer. The measurement of the charge retention of the obtained electrets after 24 h at RT and at 250°C revealed that the formation of PTFE/silica-agglomerate composite layer on the ultra-thin PTFE layer enhanced the charge retention. Furthermore, the electret condenser sensor (ECS) fabricated using the silica-agglomerate electret on the ultra-thin PTFE layer exhibited the excellent sensitivity and high resonance frequency compared with conventional ECS with PFA layer (thickness was 12.5 μm).
• CFRP の損傷蓄積挙動に及ぼすひずみ速度の影響　　　　　　　　　　　　　　　
  坂井建宣; 安部聡; 上田政人; 小林訓史; 荻原慎二; 若山修一; 蔭山健介
  Oct. 2016
  Oct. 2016 - Oct. 2016, Japanese
• OS1405 Development of diagnosis system of knee osteoarthritis by articular sound　　　　　　　　　　　　　　　
  NAKAMURA Hiroaki; HASE Kazunori; HAYASHI Yuichiro; OTA Susumu; SAKAI Takenobu
  日本機械学会関東支部総会講演会講演論文集, Mar. 2016, 一般社団法人日本機械学会
  Mar. 2016 - Mar. 2016, Japanese
  An articular sound arising from knee joint is known to be useful for diagnosis of knee osteoarthritis. However, measurement and evaluation method have been unsolved and it has not been implemented yet. This study aims to establish a simple, highly accurate and available in clinical diagnosis system of knee osteoarthritis using articular sound. The articular sound was measured by stethoscopes attached on the shank and the continuous wavelet transform was used for data processing. The discriminant formula was determined using discriminant analysis with parameters from the measurement data and then receiver operating characteristic (ROC) curve was obtained. As a result, the discriminant formula having the sensitivity of 0.778 and specificity of 0.792 was found.
• An experimental-numerical hybrid approach to analysis of fiber-matrix interfacial stresses　　　　　　　　　　　　　　　
  Takenobu Sakai; Yasunori Iihara; Satoru Yoneyama
  Conference Proceedings of the Society for Experimental Mechanics Series, 2016, Springer New York LLC
  2016 - 2016, English
  In this study, the single fiber composite was used to evaluate the stress transfer between a single fiber and a matrix. Single steel fiber was inserted to the epoxy resin, and it was applied the tensile load. Applied load was from 0 N to 177 N, and then the photoelastic images were taken by a digital CCD camera. On the photoelastic analysis, the stress separation was carried out using an experimental-numerical hybrid method. The boundary conditions for a local finite element model, that is, the tractions along boundaries are inversely determined from photoelastic fringes. After determining the boundary conditions for the local finite element model, the stresses can be obtained by finite element direct analysis. Using this input data and the finite element model of analysis region, not only the stress but also the strain distributions were obtained. Consequently, by using the photoelasticity data and geometric data for input data of finite element analysis, accurate data was obtained by the hybrid method for stress separation.
• ポリプロピレンの粘弾性特性係数と粘弾性試験の関係　　　　　　　　　　　　　　　
  坂井建宣
  日本機械学会M&M材料力学カンファレンス(CD-ROM), Nov. 2015
  Nov. 2015 - Nov. 2015, Japanese
• 214 Mechanical study with AE Technique for Fracture Mechanism in Transparent Conductive Film under Tensile Loading　　　　　　　　　　　　　　　
  Matsueda Takahiro; Hosoyamada Koji; Yuzawa Ryo; Wakayama Shuichi; Sakai Takenobu; Ikegami Masashi; Miyasaka Tsutomu
  Materials and processing conference, Nov. 2015, 一般社団法人日本機械学会
  Nov. 2015 - Nov. 2015, Japanese
  Tensile test of Indium Tin Oxide (ITO) deposited on polyerhylene naphthalate (PEN) films used in solar cells were carried out. It was found from tensile tests that many AE signals were detected in ITO films. On the other hand, the electric resistance of ITO + PEN film was also measured later than first AE signal during tensile tests. In order to identify AE sources, in-situ observation of specimen and measurement of electricity resistance were also carried out. It was demonstrated that AE behavior shows good agreement with the cracking behavior in ITO. In addition to it, AE monitoring could be detected damages in ITO under mechanical strain earlier than were measurement of electricity resistance. Consequently, it was suggested that AE technique was extremely effective technique for damage detection and evaluating the damage accumulation process in films used in solar cells.
• J0230101 AE Monitoring and In-situ Observation Using High-speed Camera of Rupture Process of Rabbit PateUar Tendon under Impact Tensile Load　　　　　　　　　　　　　　　
  MATSUOKA Fumito; WAKAYAMA Shuichi; SAKAI Takenobu; YAMAMOTO Ei
  Mechanical Engineering Congress, Japan, Sep. 2015, 一般社団法人日本機械学会
  Sep. 2015 - Sep. 2015, Japanese
  Rabbit patellar tendon-bone complex specimens were subjected to impact tensile load to simulate the sports accident. During the tests, microdamage initiation and accumulation process in tendon was monitored using acoustic emission (AE) technique. In addition, in-situ observation from vertical and horizontal directions using two high-speed cameras was carried out to determine the strain distribution. The stress increased monotonically to the ultimate tensile stress (UTS), which was significantly higher than the static tests. Despite of the extremely short time, a number of AE signals were detected continuously before the UTS. Furthermore, AE signals were emitted in the area where the local strain increased significantly in the strain distribution of the surface. It is then demonstrated that AE technique enables not only the detection of invisible microdamage but the identification of the damage location. It is worth nothing that the amplitudes of detected AE signals were much higher than static tests. Since AE amplitude corresponds to the magnitude of individual microdamage, it is suggested that larger magnitude of individual microdamage is initiated under impact tensile load. Consequently, it is demonstrated that AE technique has a possibility of clarifying the detailed rupture mechanism of tendon or ligament under impact load.
• J0230305 AE Characterization of Accumulation Process of Microdamage in Bovine Cortical Bone　　　　　　　　　　　　　　　
  KANAZAWA Takanobu; WAKAYAMA Shuichi; SAKAI Takenobu
  Mechanical Engineering Congress, Japan, Sep. 2015, 一般社団法人日本機械学会
  Sep. 2015 - Sep. 2015, Japanese
  Microdamage of healthy bovine cortical bone specimen and decalcified bone specimen during static compression tests was monitored by acoustic emission (AE) technique. Microdamage accumulation was successively monitored by AE technique. In static compression tests of healthy bone specimen, cracks were propagated due to microdamage accumulation, and cumulative AE events increased before final fracture. In static compression tests of decalcified bone specimen, macrocrack was observed with increasing in cumulative AE energy and cumulative AE events and decreasing in stress before fracture. Maximum stress and Young's modulus between healthy bone specimen and decalcified bone specimen had a significant difference. Those between specimen A (decalcified only specimen inside) and specimen B (decalcified specimen inside and outside) had no significant difference. Microdamage accumulation process of healthy bone specimen and decalcified bone specimen before leading to final fracture was shown by AE technique.
• S0420102 AE Monitoring of Damage Process in Transparent Conductive Film under Tensile Loading　　　　　　　　　　　　　　　
  WAKAYAMA Shuichi; AIZAWA Shutaro; YUZAWA Ryo; SAKAI Takenobu; IKEGAMI Masashi; MIYASAKA Tsutomu
  Mechanical Engineering Congress, Japan, Sep. 2015, 一般社団法人日本機械学会
  Sep. 2015 - Sep. 2015, Japanese
  Tensile tests of the transparent conductive films used in DSC (Dye-sensitized solar cell), consisting of ITO (Indium tin oxide) coating and PEN (Polyethylene naphthalate) substrate, were carried out and the damage accumulation process was monitored using acoustic emission technique. Damage initiation in ITO layer was detected earlier by AE technique than the electric resistance measurement during tensile tests. AE generation behavior was consistent with the result of in-situ observation of cracking behavior; initiation and saturation of transverse (perpendicular to tensile direction) cracking followed by the longitudinal (parallel to tensile direction) cracking due to buckling. Utilizing the principle of "fragmentation tests" for composite materials, interfacial shear strength for ITO/PEN interface was evaluated from experimental results for the critical strain at crack saturation and the spacing of saturated cracks. Finally, it was found that the shear strength was degraded by GBL (γ-Butyrolactone) used as electrolyte in DSC.
• 衝撃引張負荷下の家兎膝蓋腱の断裂過程のAEモニタリングと高速度カメラによるその場観察　　　　　　　　　　　　　　　
  松岡史都; 若山修一; 坂井建宣; 山本衛
  日本機械学会年次大会講演論文集(CD-ROM), Sep. 2015
  Sep. 2015 - Sep. 2015, Japanese
• 引張負荷下の透明導電膜における損傷蓄積過程のAEモニタリング　　　　　　　　　　　　　　　
  若山修一; 會澤修太郎; 湯澤亮; 坂井建宣; 池上和志; 宮坂力
  日本機械学会年次大会講演論文集(CD-ROM), Sep. 2015
  Sep. 2015 - Sep. 2015, Japanese
• 脱灰処理を施したウシ皮質骨の微視損傷蓄積過程のAE評価　　　　　　　　　　　　　　　
  金澤孝悦; 若山修一; 坂井建宣
  日本機械学会年次大会講演論文集(CD-ROM), Sep. 2015
  Sep. 2015 - Sep. 2015, Japanese
• 周波数解析による変形性膝関節症の診断　　　　　　　　　　　　　　　
  坂井建宣; 児玉勝也; 川田良暁; 蔭山健介; 戸沢優介; 長谷和徳; 若山修一; 安藤聡子; 中村拓也; 太田進
  応力・ひずみ測定と強度評価シンポジウム講演論文集, Jan. 2015
  Jan. 2015 - Jan. 2015, Japanese
• OS1001-322 Relationship between Viscoelastic Characterization Factor and Viscoelastic Testing of Polypropylene　　　　　　　　　　　　　　　
  SAKAI Takenobu
  The Proceedings of the Materials and Mechanics Conference, 2015, The Japan Society of Mechanical Engineers
  2015 - 2015, Japanese
  By the linear viscoelastic theory in the textbook of viscoelasticity, the viscoelastic parameters obtained by different viscoelastic tests can be interconversion. However, this interconversion is based on that theory, the interconversion of the experimental data have not seen yet. In this study, the viscoelastic tests were carried out with different environment and same test conditions. And also we carried out the viscoelastic tests with the same testing apparatus and using the same materials. The results showed the difference in the environment on the viscoelastic tests, the silicon oil environment more progressed the creep behavior than the air environment. This is because that the silicon oil's thermal conductivity is one fourth of the air, and the heat generated with the deformation could not escape from the surface of the materials. In addition, the static bending tests were carried out with different strain rate and stress rate at elevated temperature. The results of static bending tests were converted to the creep compliances, then the results were compared with master curve of short term creep tests and 1 month long term creep tests. The results shows the good agreement between the master curve and long term creep tests. However the creep compliances obtained by static bending tests showed the different creep behaviors.
• Manufacturing and Evaluation of Tire Powder/PLA Composite for Recycling Wasted Tire　　　　　　　　　　　　　　　
  坂井 建宣; 川井 喬介; 立山 耕平; Rios Soberanis C-R; Rodroguez-Laviada J; Perez-Pacheco E; 川田 良暁; 蔭山 健介; 山田 浩之
  日本実験力学会講演論文集 : 年次講演会 = Proceedings of JSEM : annual Conference on Experimental Mechanics, 2015, 日本実験力学会
  2015 - 2015, Japanese
• AE法を用いた引張負荷下の透明導電膜における破壊機構の力学的検討　　　　　　　　　　　　　　　
  松枝剛広; 細山田晃治; 會澤修太郎; 湯澤亮; 若山修一; 坂井建宣; 池上和司; 宮坂力
  日本機械学会機械材料・材料加工技術講演会論文集(CD-ROM), 2015
  2015 - 2015, Japanese
• 炭素繊維強化熱可塑性ポリイミド(AURUM)の曲げクリープにおける時間‐温度依存性　　　　　　　　　　　　　　　
  岡田瑞生; 上田政人; 後藤健; 小林訓史; 坂井建宣; 荒井広明
  宇宙科学技術連合講演会講演集(CD-ROM), 2015
  2015 - 2015, Japanese
• 関節音による変形性膝関節症診断手法に関する基礎的研究―ウェーブレット変換による評価と音源位置推定精度検証―　　　　　　　　　　　　　　　
  戸沢優介; 長谷和徳; 太田進; 安藤聡子; 坂井建宣
  バイオメカニズム学術講演会予稿集, Nov. 2014
  Nov. 2014 - Nov. 2014, Japanese
• S0420103 Fracture Simulation Based on AE Characterization of Microfracture Process in Ceramics　　　　　　　　　　　　　　　
  WAKAYAMA Shuichi; MIYAGAWA Tomohiro; WAKIMOTO Yosuke; SAKAI Takenobu; IKEDA Junji; MIYAJI Fumiaki
  Mechanical Engineering Congress, Japan, Sep. 2014, 一般社団法人日本機械学会
  Sep. 2014 - Sep. 2014, Japanese
  Microfracture process in ceramics was analyzed using Monte-Carlo simulation. It was supposed in the simulation that the microfracture process consists of the maincrack formation resulted from the growth and coalescence of pre-existing microcracks, and the propagation of maincrack to final failure. To determine the crack growth parameters for simulation, microfracture process in alumina ceramics was characterized by acoustic emission technique, and the critical stress for maincrack formation and final strength were determined and compared with the results of simulation. The Monte-Carlo simulation assuming the 3 microcracks array with random size was adapted to the fracture analysis during the proof test with various proof stresses and holding times as well as residual strength measurements. The time-to-maincrack formation, yields and residual strength were calculated and it was found that they showed good agreement with the several experimental results. Consequently, the proof test with the wide range of proof stresses and holding times were examined and their influence on the yields, residual strength and lifetime was discussed.
• S0420104 Development of Dynamic Evaluation Method on Thermal Shock Fracture Properties of Ceramics　　　　　　　　　　　　　　　
  LI Shiliang; TSUKADA Takamasa; WAKAYAMA Shuichi; SAKAI Takenobu; YOSHIDA Katsumi; AKATSU Takashi
  Mechanical Engineering Congress, Japan, Sep. 2014, 一般社団法人日本機械学会
  Sep. 2014 - Sep. 2014, Japanese
  The experimental technique for the investigation of thermal shock fracture of ceramics under various stress ratios was developed. In order to determine the testing configurations, the thermal stress field in specimen was analyzed using FEM. It was found that the ellipse specimen and cooling rod with the specific aspect ratios yield the designated stress ratio which is constant during the test. The corresponding experiments were also carried out. The specimen was heated to 650 ℃ and quenched by means of contacting with a cool copper rod. The transient temperature on the ellipse specimen was measured by IR camera and the thermal stress was calculated by FEM. During thermal shocked fracture AE signals were detected by an AE sensor attached on the bottom of the copper rod. The constant thermal stress ratio was obtained corresponding to the result of FEM calculation. Consequently, the testing configuration, which enables the evaluation of thermal shock fracture behavior under various stress ratio, was developed.
• 使用済活性炭強化ポリプロピレンの曲げ損傷挙動　　　　　　　　　　　　　　　
  坂井建宣; 具志堅智彦; SOBERANIS C‐R Rios; 増子知樹; 松島聡; 小林訓史; 米山聡; 若山修一
  日本実験力学会講演論文集, Aug. 2014
  Aug. 2014 - Aug. 2014, Japanese
• OS1719 Time-Temperature Dependency on Shape Recovery Property of Shape Memory Polymer　　　　　　　　　　　　　　　
  SAKAI Takenobu; TAO Takayuki; SOMIYA Satoshi
  M&M材料力学カンファレンス, Jul. 2014, 一般社団法人日本機械学会
  Jul. 2014 - Jul. 2014, Japanese
  As one of advanced functional materials, Shape Memory Polymer was studied on the shape recovery property, the shape fix property, and so on. However, it is difficult to comprehend the simple shape recovery behavior, because the viscoelastic and shape recover behaviors will occur simultaneously. Viscoelastic behavior is based on the entanglement effect on their polymeric chain, and the shape recovery behavior is based on the cross-link behavior. It is, therefore, necessary to divide these effects for understanding the viscoelastic and shape recovery behavior. The goal of this paper is to understand the viscoelastic and the simple shape recovery behavior, which depends on the cross-link, of the shape memory polymers.
• OS0511 Observation of Deformation Behavior of Adjacent Crystal Grains with Speckle Interferometry　　　　　　　　　　　　　　　
  ARIKAWA Shuichi; SAKAI Takenobu; OGASAWARA Ryosuke; YONEYAMA Satoru
  M&M材料力学カンファレンス, Jul. 2014, 一般社団法人日本機械学会
  Jul. 2014 - Jul. 2014, Japanese
  Deformation behavior of adjacent crystal grains of a metal is observed using speckle interferometry. Coarse grained aluminum specimens which have two crystal grains in the observation region are made by a thermo-mechanical treatment for the observation by speckle interferometry. Grain boundaries are arranged 0°, 45° and 90° for the loading direction. Crystal orientations are measured by electron backscatter diffraction. Tensile tests are performed and the in-plane and the out-of-plane deformation behaviors of the specimen surfaces are observed using speckle interferometry. As the results, strain maps of ε_x, ε_y, and γ_<xy>, are obtained and heterogenous deformation behaviors in each crystal grain can be observed. Various values of yield stresses and strains of each crystal grain in each specimen are obtained. The values depend on Schmidt factor obtained from the crystal orientation analysis. A tendency of the variation to decrease with decreasing the angles of the grain boundaries is obtained. Therefore, the experimental investigation of deformations of adjacent crystal grains is made possible by speckle interferometry.
• 形状記憶ポリマーの回復特性の時間‐温度依存性　　　　　　　　　　　　　　　
  坂井建宣; 田尾隆幸; 宗宮詮
  日本機械学会M&M材料力学カンファレンス(CD-ROM), Jul. 2014
  Jul. 2014 - Jul. 2014, Japanese
• スペックル干渉法による隣接結晶粒の変形挙動観察　　　　　　　　　　　　　　　
  有川秀一; 坂井建宣; 小笠原良助; 米山聡
  日本機械学会M&M材料力学カンファレンス(CD-ROM), Jul. 2014
  Jul. 2014 - Jul. 2014, Japanese
• 変形性膝関節症患者における膝関節音の信号特性について　　　　　　　　　　　　　　　
  太田進; 安藤聡子; 中村拓也; 岡本正吾; 長谷和徳; 戸沢優介; 坂井建宣
  JOSKAS, Jul. 2014
  Jul. 2014 - Jul. 2014, Japanese
• 家兎膝蓋腱における引張損傷のAE評価　　　　　　　　　　　　　　　
  若山修一; 松岡史都; 坂井建宣; 山本衛
  日本非破壊検査協会講演大会講演概要集, Jun. 2014
  Jun. 2014 - Jun. 2014, Japanese
• 10210 A basic study on diagnosis method of knee osteoarthritis by articular sound　　　　　　　　　　　　　　　
  TOZAWA Yusuke; HASE Kazunori; OTA Susumu; SAKAI Takenobu
  日本機械学会関東支部総会講演会講演論文集, Mar. 2014, 一般社団法人日本機械学会
  Mar. 2014 - Mar. 2014, Japanese
  The articular sound arising from the knee joint is useful for the diagnosis of knee osteoarthritis. However, measurement and evaluation methods are unsolved, so that a standard diagnosis technique has not been established at present. This study aims to establish of the diagnostic method by the articular sound. The articular sound was measured by four stethoscopes attached to the knee joint. The location and status of the disease from the articular sound were quantitatively evaluated by introducing a signal processing techniques such as AIC (akaike's information criterion) and continuous wavelet transform. As a result, the sound frequency to be produced by knee osteoarthritis patient tended to be higher than that by healthy person.
• 関節音による変形性膝関節症診断手法に関する基礎的研究　　　　　　　　　　　　　　　
  戸沢優介; 長谷和徳; 太田進; 坂井建宣
  日本機械学会関東支部総会・講演会講演論文集(CD-ROM), Mar. 2014
  Mar. 2014 - Mar. 2014, Japanese
• Bending Fracture Behavior of Wasted Activated Carbon Reinforced Polypropylene　　　　　　　　　　　　　　　
  坂井 建宣; 具志堅 智彦; Soberanis C-R Rios
  日本実験力学会講演論文集, 2014, 日本実験力学会
  2014 - 2014, Japanese
• Mechanical Properties of Wasted Tire Powder Composites　　　　　　　　　　　　　　　
  坂井 建宣; 若山 修一; Soberanis C-R Rolando
  機械材料・材料加工技術講演会 M&P, Nov. 2013, 日本機械学会
  Nov. 2013 - Nov. 2013, Japanese
• Lifetime Prediction of Ceramics by Simulation Considering Interaction of Microcrack　　　　　　　　　　　　　　　
  若山 修一; 脇本 陽介; 坂井 建宣
  機械材料・材料加工技術講演会 M&P, Nov. 2013, 日本機械学会
  Nov. 2013 - Nov. 2013, Japanese
• 127 Mechanical Properties of Wasted Tire Powder Composites　　　　　　　　　　　　　　　
  SAKAI Takenobu; WAKAYAMA Shuichi; Rolando Soberanis C-R; Rodroguez-Laviada J; Perez-Pacheco E
  Materials and processing conference, Nov. 2013, 一般社団法人日本機械学会
  Nov. 2013 - Nov. 2013, Japanese
• 413 Lifetime Prediction of Ceramics by Simulation Considering Interaction of Microcrack　　　　　　　　　　　　　　　
  WAKAYAMA Shuichi; WAKIMOTO Yosuke; SAKAI Takenobu; IKEDA Junji; MIYAJI Fumiaki
  Materials and processing conference, Nov. 2013, 一般社団法人日本機械学会
  Nov. 2013 - Nov. 2013, Japanese
• 微視き裂の相互作用を考慮したシミュレーションによるセラミックスの寿命予測　　　　　　　　　　　　　　　
  若山修一; 脇本陽介; 坂井建宣; 池田潤二; 宮路史明
  日本機械学会機械材料・材料加工技術講演会論文集(CD-ROM), Nov. 2013
  Nov. 2013 - Nov. 2013, Japanese
• 廃タイヤ粉末強化複合材料の機械的特性　　　　　　　　　　　　　　　
  坂井建宣; 若山修一; SOBERANIS C‐R Rolando; RODROGUEZ‐LAVIADA J; PEREZ‐PACHECO E
  日本機械学会機械材料・材料加工技術講演会論文集(CD-ROM), Nov. 2013
  Nov. 2013 - Nov. 2013, Japanese
• OS0707 Viscoelastic and Damage Accumulation Behavior on Compressive Deformation of Bovine Cortical Bone　　　　　　　　　　　　　　　
  SAKAI Takenobu; YOSHIYA Eri; YASUI Keita; WAKAYAMA Shuichi
  M&M材料力学カンファレンス, Oct. 2013, 一般社団法人日本機械学会
  Oct. 2013 - Oct. 2013, Japanese
  Recently, the osteoporosis victims increase in the senior people. Therefore, the danger of the stress fracture due to the decrease in bone strength is pointed out. Especially, the damage accumulation behavior of the bone in the cyclic load becomes a problem for the fatigue of the bone. Moreover, it is necessary to consider the viscoelastic property for the prediction of the fatigue behavior, because the bone is a viscoelastic material. In this study, our objective is to estimate the fatigue behavior that considers the viscoelasticity behavior and the damage accumulation behavior as damage mechanics. The viscoelastic properties were revealed with the strain rate tests, and we calculated the 3-mode Maxwell parameters with these results. The damage accumulation behaviors were measured with the Acoustic Emission method. Using these results, we could estimate the fatigue behavior of cortical bone with the viscoelastic parameter and cumulative AE energy.
• ウシ皮質骨の圧縮変形における粘弾性挙動および損傷蓄積挙動　　　　　　　　　　　　　　　
  坂井建宣; 吉屋英理; 安井慶太; 若山修一
  日本機械学会M&M材料力学カンファレンス(CD-ROM), Oct. 2013
  Oct. 2013 - Oct. 2013, Japanese
• S042013 Dynamic Evaluation of Crack Propagation Behavior on Si_3N_4 by Controlling Microstructure　　　　　　　　　　　　　　　
  SAKAI Takenobu; KAMETANI Go; WAKAYAMA Shuichi; YOSHIDA Katsumi
  Mechanical Engineering Congress, Japan, Sep. 2013, 一般社団法人日本機械学会
  Sep. 2013 - Sep. 2013, Japanese
  The microdamage in silicon nitride during thermal shock fracture was monitored by acoustic emission (AE) technique. Disc-on-Rod test was used to evaluate thermal shock fracture process. Cylinders with different microstructures were fabricated by sintering at different temperatures. In the Disc-on-Rod test, a pre-crack introduced specimen was heated, and only the center of circular specimen was quenched. Crack growth behavior under thermal shock loading can be monitored by using AE technique. The crack extension length was measured by the Digital Microscope. The crack growth resistance was calculated using Virtual Crack Closure Method and the FEM software. The crack growth resistance curves showed the rising R-curve behaviors for each material; therefore, it is assumed that the materials showed toughening mechanisms during the Disc-on Rod tests. As sintering temperature increased, crack growth resistance increased under the thermal shock loading.
• 微視構造を制御した窒化ケイ素のき裂進展挙動の動的評価　　　　　　　　　　　　　　　
  坂井建宣; 亀谷豪; 若山修一; 吉田克己
  日本機械学会年次大会講演論文集(CD-ROM), Sep. 2013
  Sep. 2013 - Sep. 2013, Japanese
• 引張負荷下における家兎膝蓋腱の損傷蓄積過程のAE法による評価　　　　　　　　　　　　　　　
  坂井建宣; 鈴木仁己; 若山修一; 山本衛
  日本非破壊検査協会講演大会講演概要集, Jun. 2013
  Jun. 2013 - Jun. 2013, Japanese
• 10513 Characterization of Damage Process of Rabbit patella Tendon by Acoustic Emission Technique under Simulated In Vivo Environment　　　　　　　　　　　　　　　
  SUZUKI Satomi; SAKAI Takenobu; WAKAYAMA Shuichi; YAMAMOTO Ei
  日本機械学会関東支部総会講演会講演論文集, Mar. 2013, 一般社団法人日本機械学会
  Mar. 2013 - Mar. 2013, Japanese
  AE monitoring of damage process of rabbit patellar tendon under static tensile load was carried out. Considering strong viscoelasticity of tendon, load was applied at various loading rate (10, 1, 0.1 mm/min) until the complete rupture in physiological saline at 37°C. The displacement of the specimen was monitored by a digital video camera, and acquired images were used for determining the displacement distribution in tendon by the digital image correlation (DIC) technique. It was found that the average failure stress increased as loading rate increased, and the differences in maximum stress were considered to be statistically significant. AE signals were detected before the maximum load and AE source locations corresponded to the locally elongated area, which indicates that fascicle failure takes place before the maximum load. Consequently, the fundamental insights for the damage monitoring technique which are indispensable for the optimization of programs of sports training or rehabilitation are obtained.
• 20312 Evaluation of Crack Growth Resistance of Silicon Nitride under Thermal Shock Fracture by Acoustic Emission Technique　　　　　　　　　　　　　　　
  KAMETANI Go; SAKAI Takenobu; WAKAYAMA Shuichi; YOSHIDA Katsumi
  日本機械学会関東支部総会講演会講演論文集, Mar. 2013, 一般社団法人日本機械学会
  Mar. 2013 - Mar. 2013, Japanese
  The microdamage in silicon nitride during thermal shock fracture was monitored by acoustic emission (AE) technique. Disc-on-Rod test, which was developed by the authors, was used to evaluate thermal shock fracture process. Specimens were composed of β-Si_3N_4 with acicular structure. Cylinders with different microstructures were fabricated by sintering at different temperatures. A pre-crack was introduced using knoop indentation. In the Disc-on-Rod test, specimen was uniformly heated to 850 ℃, and only the center of circular specimen was quenched. After contacting, crack propagated in an unstable manner, at the same time, one relatively high amplitude AE signal was detected. Subsequently, stable crack propagation was observed, and several relatively low amplitude AE signals were generated corresponding to crack propagation. As sintering temperature increased, crack growth resistance decreased under the both thermal shock and mechanical loading. Furthermore, crack growth resistance sunder thermal shock loading were higher than those under mechanical loading.
• 21208 Evaluation of Damage of Flexible Solar Cells under External Load using Acoustic Emission Method　　　　　　　　　　　　　　　
  TAZAWA Hiroyuki; SAKAI Takenobu; WAKAYAMA Shuichi
  日本機械学会関東支部総会講演会講演論文集, Mar. 2013, 一般社団法人日本機械学会
  Mar. 2013 - Mar. 2013, Japanese
  In this study, the tensile test has been carried out to the flexible solar cells, and there failure processes have been characterized by the acoustic emission (AE) technique and the lock-in thermography. At the same time, the dark I-V curve has been measured during the test, and the leak current at-2 V has been used as a measure of degradation. The cumulative AE energy and the leak current began to increase at the strain of 〜0.8% and 〜1.2%, respectively. Accordingly the AE technique can detect mechanical damages earlier than the leak current increases. It is demonstrated by the lock-in thermography that the mechanical damages at holes contribute to performance degradation.
• 家兎膝蓋腱の擬似生体環境下における損傷挙動のAE法による評価　　　　　　　　　　　　　　　
  鈴木仁己; 坂井建宣; 若山修一; 山本衛
  日本機械学会関東支部総会講演会講演論文集, Mar. 2013
  Mar. 2013 - Mar. 2013, Japanese
• フレキシブル太陽電池の外力による損傷のAE法およびロックインサーモグラフィを用いた評価　　　　　　　　　　　　　　　
  田澤博幸; 坂井建宣; 若山修一
  日本機械学会関東支部総会講演会講演論文集, Mar. 2013
  Mar. 2013 - Mar. 2013, Japanese
• 窒化ケイ素の熱衝撃破壊におけるき裂進展抵抗のAE法による評価　　　　　　　　　　　　　　　
  亀谷豪; 坂井建宣; 若山修一; 吉田克己
  日本機械学会関東支部総会講演会講演論文集, Mar. 2013
  Mar. 2013 - Mar. 2013, Japanese
• a‐Siフレキシブル太陽電池セルの単軸引張による損傷のAE法とロックインサーモグラフィを用いた評価　　　　　　　　　　　　　　　
  田澤博幸; 坂井建宣; 若山修一
  応用物理学会春季学術講演会講演予稿集(CD-ROM), Mar. 2013
  Mar. 2013 - Mar. 2013, Japanese
• 使用済タイヤ‐PLA複合材料のタイヤ粉砕方法が機械的挙動に及ぼす影響　　　　　　　　　　　　　　　
  坂井建宣; 森清卓也; SOBERANIS C‐R Rdando; 若山修一; 米山聡
  応力・ひずみ測定と強度評価シンポジウム講演論文集, Jan. 2013
  Jan. 2013 - Jan. 2013, Japanese
• 微視損傷蓄積挙動および粘弾性挙動を考慮したウシ皮質骨の圧縮変形評価　　　　　　　　　　　　　　　
  坂井建宣; 吉屋英理; 安井慶太; 若山修一
  アコースティック・エミッション総合コンファレンス論文集, 2013
  2013 - 2013, Japanese
• Effect of crushing method of wasted tire on mechanical behavior on PLA composites　　　　　　　　　　　　　　　
  Takenobu Sakai; Takuya Morikiyo; C. R. Rios-Soberanis; Satoru Yoneyama; Shuichi Wakayama
  Conference Proceedings of the Society for Experimental Mechanics Series, 2013
  2013 - 2013, English
  Poly Lactic Acid (PLA) is one of the Biodegradable Materials which has excellent mechanical properties. However, PLA is not wasted for the structural materials because of its brittleness. For improvement in the brittleness, the wasted tire was chosen as the reinforcement. On the other hand, wasted tires are a huge problem in terms of health and contamination due to bad disposal. There are many mechanisms to deal with this problem but they still have inconveniences. In this study, we made the wasted tire powder reinforced PLA. The wasted tire powder was crushed by two ways. One is frost shattering method, and the other is thermal shock process. The composites based on PLA were made with these two powders. To investigate the effect of crush method of wasted tire, fracture mechanics were investigated. And the viscoelastic behavior was investigated with the Dynamic Mechanical Analysis. And for impact tests, Split Hopkinson Pressure Bar tests were carried out. As the results of static and impact test, thermal shocked powder composites have the good impact resistance. © The Society for Experimental Mechanics, Inc. 2013.
• Mechanical evaluation and damage sequence identification of multiaxial textile reinforced composites　　　　　　　　　　　　　　　
  C. R. Rios-Soberanis; S. Wakayama; T. Sakai; E. Perez-Pacheco; J. Rodriguez-Laviada
  Annual Technical Conference - ANTEC, Conference Proceedings, Jan. 2013
  Jan. 2013 - Jan. 2013
  Mechanical properties and damage pattern of a multiaxial textile reinforced epoxy composite was evaluated by tension and bending test. A non crimp fabric (NCF) of [0°,+45°, 90°, - 45°] stacking sequence was used as reinforcement. Through the identification of the initiation sites and the coalescence of cracks was possible to correlate the damage with the textile geometry and its effect on the mechanical properties. Fractography was used as a tool to identify governing mechanisms and link these to the material internal structure and the textile geometry. Acoustic emission technique was employed to identify the mechanisms of fracture by correlating the signals of mechanical waves produced my damage with fracture stages. Additionally the effect of textile architecture on the composite mechanical properties and damage pattern was correlated with its damage initiation and propagation. Through a combination of experimental work and theoretical studies the mechanisms controlling the mechanical behavior are explained.
• 粒径制御した窒化ケイ素のディスクオンロッド試験による熱衝撃破壊過程の評価　　　　　　　　　　　　　　　
  亀谷豪; 坂井建宣; 若山修一; 吉田克己
  日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM), Sep. 2012
  Sep. 2012 - Sep. 2012, Japanese
• J022024 Characterization of damage process of the rabbit patellar tendon using acoustic emission under various strain rate　　　　　　　　　　　　　　　
  SUZUKI Satomi; SAKAI Takenobu; WAKAYAMA Shuichi; YAMAMOTO Ei
  Mechanical Engineering Congress, Japan, Sep. 2012, 一般社団法人日本機械学会
  Sep. 2012 - Sep. 2012, Japanese
  AE monitoring of damage process of rabbit patellar tendon under static tensile load was carried out. Considering strong viscoelasticity of tendon, load was applied at various loading rate (10, 1, 0.1 mm/min) until the complete rupture in physiological saline at 37℃. The displacement of the specimen was monitored by a digital video camera, and acquired images were used for determining the displacement distribution in tendon by the digital image correlation (DIC) technique. It was found that AE signals were detected before the maximum load and AE source locations corresponded to the locally elongated area, which indicates that fascicle failure takes place before the maximum load. The average failure stress increased as loading rate increased, and the differences in average failure stress were considered to be statistically significant. Consequently, the fundamental insights for the damage monitoring technique which are indispensable for the optimization of programs of sports training or rehabilitation are obtained.
• S042021 AE Detection of Microdamages and Long Term Reliability Assessment of ATZ Composite Ceramics for Artificial Joints　　　　　　　　　　　　　　　
  SAKAI Takenobu; KAZAMA Gaku; WAKAYAMA Shuichi; IKEDA Junji; MIYAJI Fumiaki
  Mechanical Engineering Congress, Japan, Sep. 2012, 一般社団法人日本機械学会
  Sep. 2012 - Sep. 2012, Japanese
  The microdamages in ATZ composite ceramics during 4-point bending test were monitored by acoustic emission (AE) technique, and the rapid increase in cumulative AE energy prior to the final fracture was observed, which could be related with the maincrack formation as the origin of final fracture. The critical stress for maincrack formation σ_c was determined as the stress at rapid increasing point of AE signals. The stress increased with decreasing in Alumina weight fraction without 0% By increasing in ZrO_2, the growth grain size of Al_2O_3 was restrained and the flaw size turned smaller, since σ_c depends on the dispersion in the size and the distribution of initial failure.
• 種々のひずみ速度下における家兎膝蓋腱の損傷過程のAE法による評価　　　　　　　　　　　　　　　
  鈴木仁己; 坂井建宣; 若山修一; 山本衛
  日本機械学会年次大会講演論文集(CD-ROM), Sep. 2012
  Sep. 2012 - Sep. 2012, Japanese
• 人工関節用ATZ複合セラミックスのAE法による微視損傷検出および長期信頼性評価　　　　　　　　　　　　　　　
  坂井建宣; 風間岳; 若山修一; 池田潤二; 宮路史明
  日本機械学会年次大会講演論文集(CD-ROM), Sep. 2012
  Sep. 2012 - Sep. 2012, Japanese
• 使用済活性炭複合材料の導電性と粘弾性特性の関係　　　　　　　　　　　　　　　
  坂井建宣; 具志堅智彦; 増子知樹; 松島聡; 小林諭史; 米山聡; 若山修一
  日本実験力学会講演論文集, Jul. 2012
  Jul. 2012 - Jul. 2012, Japanese
• 511 Effect of Molding condition on the compressive properties of PLA-PBAT blend materials　　　　　　　　　　　　　　　
  GUSHIKEN Tomohiko; OMIYA Masaki; SAKAI Takenobu
  学術講演会講演論文集, May 2012, 社団法人日本材料学会
  May 2012 - May 2012, Japanese
• ポリ乳酸‐PBATブレンド材における成形条件と圧縮特性　　　　　　　　　　　　　　　
  具志堅智彦; 大宮正毅; 坂井建宣
  日本材料学会学術講演会講演論文集, May 2012
  May 2012 - May 2012, Japanese
• 胸部表面の振動解析による心臓運動の可視化　　　　　　　　　　　　　　　
  坂井建宣; 林和輝; 横田康成; 若山修一; 野方文雄
  応力・ひずみ測定と強度評価シンポジウム講演論文集, Jan. 2012
  Jan. 2012 - Jan. 2012, Japanese
• Relationship between Electric Conductivity and Viscoelasticity of Used Activated Carbon Composites　　　　　　　　　　　　　　　
  坂井 建宣; 具志堅 智彦; 増子 知樹
  日本実験力学会講演論文集, 2012, 日本実験力学会
  2012 - 2012, Japanese
• AE Evaluation of Thermal Shock Fracture Process in Silicon Nitride with Controlled Grain Size　　　　　　　　　　　　　　　
  KAMETANI Go; SAKAI Takenobu; WAKAYAMA Shuichi; YOSHIDA Katsumi
  Prog Acoust Emiss, 2012
  2012 - 2012, English
• AE Studies on Effect of Viscoelasticity of Bovine Cortical Bone on Microdamage Accumulation Behavior　　　　　　　　　　　　　　　
  SAKAI Takenobu; MIYAGAWA Tomohiro; YOSHIYA Eri; YASUI Keita; WAKAYAMA Shuichi
  Prog Acoust Emiss, 2012
  2012 - 2012, English
• AE Monitoring of Damage Process of Rabbit Patellar Tendon under Various Strain Rate　　　　　　　　　　　　　　　
  SUZUKI Satomi; SAKAI Takenobu; WAKAYAMA Shuichi; YAMAMOTO Ei
  Prog Acoust Emiss, 2012
  2012 - 2012, English
• Visualization of Heart Motion Based on Micro-vibration of the Chest Surface　　　　　　　　　　　　　　　
  F. Nogata; Y. Yokota; Y. Kawamura; H. Morita; Y. Uno; W. R. Walsh; T. Sakai
  5TH EUROPEAN CONFERENCE OF THE INTERNATIONAL FEDERATION FOR MEDICAL AND BIOLOGICAL ENGINEERING, PTS 1 AND 2, 2012, SPRINGER
  2012 - 2012, English
  A new technique for imaging heart motion to assist in the understanding of heart diseases for both clinical doctors and patients has been developed. The technique is based on the measurement of micro-vibration of the chest surface using 64 sensors (63- acceleration sensor and one ECG) as a multiple-auscultator to show global and simultaneous heart motion. The results showed clear and simultaneous image of heart motion; contraction/expansion of atrioventricular and ventricle, location of four valves. The measurement time was five minutes approximately using a new mount plate with 64-sensor to fix skin of the chest quickly, which allows to clinical use easily. It was also found that heart vibration has four-frequency bands including one band that is inaudible sound using auscultation. It is concluded that the technique could be applied to inspect heart disease in visual and the digital database management of the auscultation examination. We think that it is needed to introduce new digital management for examining and diagnosing heart disease in a traditional auscultation technique.
• Effect of fabric architecture (NCF) on bending and creep test of textile composites　　　　　　　　　　　　　　　
  T. Sakai; S. Wakayama; C. R. Rios-Soberanis; J. Rodriguez-Laviada; E. Pérez-Pacheco
  ICCM International Conferences on Composite Materials, Dec. 2011
  Dec. 2011 - Dec. 2011
• Study on crystallinity dependency of creep deformation on GFRTP of polyoxythlene (POM)　　　　　　　　　　　　　　　
  S. Somiya; K. Yamada; T. Sakai
  Conference Proceedings of the Society for Experimental Mechanics Series, Dec. 2011
  Dec. 2011 - Dec. 2011
  It has clarified that the viscoelastic property of some kind of thermoplastic resin is dependent on crystallinity in until now. Concretely, it was confirmed that "Time-temperature superposition principle" was established on the creep deformation in them. And also, in various FRTP, in making fiber volume fraction to be a factor for creep deformation, it was clarified that "Time-temperature-fiber volume fraction superposition principle" was established. In this paper on the effect of crystal on creep deformation, the crystallinity was made to be a factor, and it clarified that "Time - temperature -crystallinity superposition principle" was established in POM resin and GFRPOM.
• Estimation of fatigue life of cortical bone considering viscoelastic properties and damage mechanics　　　　　　　　　　　　　　　
  Takenobu Sakai; Keita Yasui; Shuichi Wakayama
  Conference Proceedings of the Society for Experimental Mechanics Series, Dec. 2011
  Dec. 2011 - Dec. 2011
  Recently, the Osteoporosis victims increase in the senior citizen. Therefore, the danger of the stress fracture due to the decrease in bone strength is pointed out. Especially, the damage accumulation behavior of the bone in the cyclic load becomes a problem for the fatigue of the bone. Moreover, it is necessary to consider the viscoelastic property for the prediction of the fatigue behavior, because the bone is a viscoelastic material. In this study, our objective is to estimate the fatigue behavior that considers the viscoelasticity behavior and the damage accumulation behavior as damage mechanics. The viscoelastic properties were revealed with the strain rate tests, and we calculated the 3-mode Maxwell parameters with these results. The damage accumulation behaviors were measured with the Acoustic Emission method. Using these results, we could estimate the fatigue behavior of cortical bone with the viscoelastic parameter and cumulative AE energy.
• 窒化ケイ素セラミックスにおける熱衝撃破壊過程のAE法による評価　　　　　　　　　　　　　　　
  亀谷豪; 坂井建宣; 若山修一; 吉田克己
  日本非破壊検査協会講演大会講演概要集, Oct. 2011
  Oct. 2011 - Oct. 2011, Japanese
• A110 AE Characterization of Fatigue Damage in Cortical Bone　　　　　　　　　　　　　　　
  YASUI Keita; SAKAI Takenobu; WAKAYAMA Shuichi
  Proceedings of the ... JSME Conference on Frontiers in Bioengineering, Oct. 2011, 一般社団法人日本機械学会
  Oct. 2011 - Oct. 2011, Japanese
• A114 Characterization of Damage Process of Tendon by Acoustic Emission Technique　　　　　　　　　　　　　　　
  SUZUKI Satomi; SAKAI Takenobu; WAKAYAMA Shuichi; YAMAMOTO Ei
  Proceedings of the ... JSME Conference on Frontiers in Bioengineering, Oct. 2011, 一般社団法人日本機械学会
  Oct. 2011 - Oct. 2011, Japanese
• 皮質骨における疲労損傷のAE法による評価　　　　　　　　　　　　　　　
  安井慶太; 坂井建宣; 若山修一
  日本機械学会バイオフロンティア講演会講演論文集, Oct. 2011
  Oct. 2011 - Oct. 2011, Japanese
• 腱組織の損傷過程のAE法による評価　　　　　　　　　　　　　　　
  鈴木仁己; 坂井建宣; 若山修一; 山本衛
  日本機械学会バイオフロンティア講演会講演論文集, Oct. 2011
  Oct. 2011 - Oct. 2011, Japanese
• S042024 AE Monitoring of Damage Accumulation Process during Tensile Tests of Transparent Conductive Oxide Films　　　　　　　　　　　　　　　
  TAKAGI Nobuyuki; WAKAYAMA Shuichi; SAKAI Takenobu; IKEGAMI Masashi; MIYASAKA Tsutomu
  Mechanical Engineering Congress, Japan, Sep. 2011, 一般社団法人日本機械学会
  Sep. 2011 - Sep. 2011, Japanese
  In this study, tensile tests of indium tin oxide (ITO) deposited on polyethylene naphthalate (PEN) films (ITO + PEN films) used in dye-sensitized solar cells (DSCs) were carried out. ITO + PEN films are fabricated at 150℃. Therefore, to clarify the influence of heat treatment on mechanical properties of ITO + PEN, the specimens with heat treatment were prepared. In order to discriminate AE signals in ITO from PEN films, PEN film specimens (ITO was removed by 17.5% hydrochloric acid) were also prepared. It was found from tensile tests that many AE signals were detected in ITO + PEN films, while few AE signals were detected in PEN films. On the other hand, the electric resistance of ITO was also measured during tensile tests. These results suggested that the critical damage in ITO was detected by the AE measurement more sensitively than the electric resistance. To identify AE sources, in-situ observation of specimen during tensile test with AE measurement was carried out. It was emphasized that AE behavior shows good agreement with the cracking behavior in ITO. Damages in ITO under mechanical strain were successfully monitored by AE technique in the present study. Consequently, it was suggested that AE technique could be a powerful technique for evaluating the damage accumulation process in DSCs.
• S042034 Fabrication of Discontinuous Fiber Reinforced Ceramic Composites and Characterization of Mechanical Properties　　　　　　　　　　　　　　　
  UMINO Kosuke; AKIYAMA Yusuke; WAKAYAMA Shuichi; SAKAI Takenobu; UMEHARA Yuka; AKATSU Takashi
  Mechanical Engineering Congress, Japan, Sep. 2011, 一般社団法人日本機械学会
  Sep. 2011 - Sep. 2011, Japanese
  40 vol% SiC whisker reinforced alumina matrix composites (SiCw/Al_2O_3) were fabricated using a spark plasma sintering (SPS) technique. In this study, to decrease the thermal mismatch between SiCw and Al_2O_3, SiC particle (SiCp) was added into Al203 matrix (SiCw/SiCp/Al_2O_3). The relative density of the fabricated specimens was more than 99%, so that the sufficient densification was accomplished. Then, the mechanical properties and fracture morphology were examined. It was found that the mechanical properties of composites were increased from the monolithic Al203 and SiCw/Al_2O_3 composites. SEM observation of fracture surface after bending test showed that the amount of pull-out SiCw and the pull-out length in SiCw/SiCp/Al_2O_3 composites was larger than SiCw/Al_2O_3 composites. Therefore, the interfacial shear strength was successfully reduced due to SiCp addition. Consequently, it was suggested that the improvement of mechanical properties of SiCw/SiCp/Al_2O_3 composites may be accomplished by optimizing the interfacial shear strength due to SiCp addition.
• 透明導電酸化膜の引張試験における損傷蓄積過程のAEモニタリング　　　　　　　　　　　　　　　
  高木信幸; 若山修一; 坂井建宣; 池上和志; 宮坂力
  日本機械学会年次大会講演論文集(CD-ROM), Sep. 2011
  Sep. 2011 - Sep. 2011, Japanese
• 不連続繊維強化セラミック複合材料の作製および機械的特性の評価　　　　　　　　　　　　　　　
  海野孝祐; 秋山裕介; 若山修一; 坂井建宣; 梅原由佳; 赤津隆
  日本機械学会年次大会講演論文集(CD-ROM), Sep. 2011
  Sep. 2011 - Sep. 2011, Japanese
• NCFの積層構成とクリープ挙動の関係　　　　　　　　　　　　　　　
  坂井建宣; RIOS‐SOBERANIS C. R; 若山修一
  日本実験力学会講演論文集, Aug. 2011
  Aug. 2011 - Aug. 2011, Japanese
• Analysis of damage progression in textile reinforced composite in tension (static and cyclic) mode using acoustic emission　　　　　　　　　　　　　　　
  T. Sakai; S. Wakayama; C. R. Rios-Soberanis; J. Rodriguez-Laviada; E. Pérez-Pacheco
  Annual Technical Conference - ANTEC, Conference Proceedings, Aug. 2011
  Aug. 2011 - Aug. 2011
  A non crimp fabric (NCF) with a stacking sequence of [0°,+45°, 90°,-45°] embedded in epoxy resin matrix was analyzed. Samples for mechanical test were obtained from laminates at different orientations depending on the textile direction at 0°, 45° and 90° in order to identify the failure mechanisms. Tension mode tests (static and cyclic) were carried out to evaluate the evolution of damage using as a main tool the acoustic emission technique that allows monitoring the mechanical behavior of the materials during the test in "real time".
• Effect of crystallinity and fiber volume fraction on creep behavior of glass fiber reinforced polyamide　　　　　　　　　　　　　　　
  Takenobu Sakai; Yuto Hirai; Satoshi Somiya
  Conference Proceedings of the Society for Experimental Mechanics Series, Jul. 2011
  Jul. 2011 - Jul. 2011
  Thermoplastic Polyamide (PA) is known as Nylon®, and its FRP are one of the engineering plastics. It is very important for them to reveal accurately the visco-elastic behavior. Furthermore, PA is a crystalline polymer, and it is necessary to consider the effect of crystallization on mechanical properties. The purpose of this study was to make clear the effect of crystallization and fiber volume fraction on creep behavior of PA and its composites. The creep test was performed using the materials which adjusted crystallinity on each fiber volume fraction. As a result, these materials conformed to Arrhenius type of time-temperature superposition principle, and these effects on creep behavior had the time retardation effect. To compare the creep behavior on these effects, we made the grand master curves for crystallinity and fiber volume fraction. Obtained two grand master curves were compared each other, the shapes of these curves are similarly, and we can superposed them. It is therefore, the creep behavior including each conditions have the same behavior. Using these curves and shift factors, we can calculate the creep behavior, and be able to estimate the creep behavior with the effect of arbitrary time, temperature, crystallinity and fiber contents. ©2010 Society for Experimental Mechanics Inc.
• 胸部振動計測による心臓内部血流の可視化　　　　　　　　　　　　　　　
  坂井建宣; 野方文雄; 横田康成; 若山修一
  日本非破壊検査協会講演大会講演概要集, May 2011
  May 2011 - May 2011, Japanese
• 119206 Research about Relationship between Deformation and Electric Resistance on Used Activated Carbon Reinforced Polypropylene　　　　　　　　　　　　　　　
  SAKAI Takenobu; GUSHIKEN Tomohiko; MASUKO Tomoki; MATSUSHIMA Satoshi; KOBAYASHI Satoshi; YONEYAMA Satoru
  日本機械学会関東支部総会講演会講演論文集, Mar. 2011, 一般社団法人日本機械学会
  Mar. 2011 - Mar. 2011, Japanese
  In the Waterworks Bureau, the activated carbon was used for filtering the water. After use the activated carbon, they were disposed. In this work, we tried to make that composite to recycle these carbons. These wasted activated carbons were used for the filler of composite materials, and we got the composite with the carbon contents of 10%〜60%. To evaluate of mechanical behavior of these composites, tensile test and stress relaxation test were carried out. The results show the powder contents dependency on tensile strength and Young's modulus. As seen in the results of stress relaxation test, the effect of powder contents on stress relaxation was revealed. To evaluate the electric property, the electric resistance was measured by 4-terminal method during tensile test and stress relaxation test. By the measurement of electric resistance, these composites can be used as smart materials.
• 220304 Evaluation of the Mechanical Damage Accumulation in Transparent Conductive Oxide Film using Acoustic Emission　　　　　　　　　　　　　　　
  TAKAGI Nobuyuki; WAKAYAMA Shuichi; MIZUTANI Akihiro; SAKAI Takenobu; MIYASAKA Tsutomu; IKEGAMI Masashi
  日本機械学会関東支部総会講演会講演論文集, Mar. 2011, 一般社団法人日本機械学会
  Mar. 2011 - Mar. 2011, Japanese
  In this study, tensile tests of transparent conductive oxide (TCO) deposited on polyerhylene naphthalate (PEN) films (TCO + PEN films) used in dye-sensitized solar cells (DSCs) were carried out. In order to discriminate AE signals in TCO from PEN films, PEN film specimens (TCO was removed by 17.5% acidum hydrechloricum) were also prepared. It was found from tensile tests that many AE signals were detected in TCO + PEN films, while few AE signals were detected in PEN films. On the other hand, the electric resistance of TCO was also measured during tensile tests. These results suggested that the critical damage in TCO was detected by the measurement of AE signals more sensitively than the electric resistance measurement. To identify AE sources, in-situ observation of specimen during tensile test with AE measurement was carried out. It was emphasized that AE behavior shows good agreement with the cracking behavior in TCO. Damages in TCO under mechanical strain were successfully monitored by AE technique in the present study. Consequently, it was suggested that AE technique could be a powerful technique for evaluating the damage accumulation process in DSCs.
• 透明導電酸化膜における機械的損傷蓄積のAE法を用いた評価　　　　　　　　　　　　　　　
  高木信幸; 若山修一; 水谷彰宏; 坂井建宣; 宮坂力; 池上和志
  日本機械学会関東支部総会講演会講演論文集, Mar. 2011
  Mar. 2011 - Mar. 2011, Japanese
• 使用済活性炭強化ポリプロピレン複合材料の変形特性と導電性に関する研究　　　　　　　　　　　　　　　
  坂井建宣; 具志堅智彦; 増子知樹; 松島聡; 小林諭史; 米山聡
  日本機械学会関東支部総会講演会講演論文集, Mar. 2011
  Mar. 2011 - Mar. 2011, Japanese
• 使用済活性炭強化ポリプロピレン複合材料の変形特性と導電性の関係　　　　　　　　　　　　　　　
  具志堅智彦; 米山聡; 坂井建宣; 小林訓史; SOBERANIS Rolando Rios; 増子知樹; 松島聡
  応力・ひずみ測定と強度評価シンポジウム講演論文集, Jan. 2011
  Jan. 2011 - Jan. 2011, Japanese
• 8E-01 Characterization of Fatigue Damage of Cortical Bone by Acoustic Emission Technique at Different Frequency under Simulated In Vivo Environment　　　　　　　　　　　　　　　
  YASUI Keita; WAKAYAMA Shuichi; SAKAI Takenobu
  バイオエンジニアリング講演会講演論文集, Jan. 2011, 一般社団法人日本機械学会
  Jan. 2011 - Jan. 2011, Japanese
• 擬似生体環境下の異なる周波数における皮質骨の疲労損傷のAE法による評価　　　　　　　　　　　　　　　
  安井慶太; 若山修一; 坂井建宣
  バイオエンジニアリング講演会講演論文集, Jan. 2011
  Jan. 2011 - Jan. 2011, Japanese
• Relationship between the lamination constitution and the creep behavior of non-crimp fabric　　　　　　　　　　　　　　　
  坂井 建宣; Soberanis C. R. Rios; 若山 修一
  Proceedings of JSEM, 2011, 日本実験力学会
  2011 - 2011, Japanese
• 使用済タイヤ粉含有率がポリ乳酸複合材料の損傷に及ぼす影響　　　　　　　　　　　　　　　
  坂井建宣; RIOS‐SOBERANIS C. R; 若山修一
  アコースティック・エミッション総合コンファレンス論文集, 2011
  2011 - 2011, Japanese
• 111 Fracture Behavior of High Content Carbon Nanofiber Reinforced Alumina Composites Using Electrostatic Adsorption　　　　　　　　　　　　　　　
  UMINO Kosuke; WAKAYAMA Syuichi; AKATSU Takashi; SAKAI Takenobu; UMEHARA Yuka
  Materials and processing conference, Nov. 2010, 一般社団法人日本機械学会
  Nov. 2010 - Nov. 2010, Japanese
  In this study, carbon nanofiber (CNF) reinforced Al_2O_3 composites were fabricated. To fabricate uniformly-dispersed CNF/Al_2O_3 powder, electrostatic adsorption, which could increase the surface potential of CNFs, was applied. Al203 sol was then adsorbed onto the surface of CNFs uniformly. The mixed powder was sintered by spark plasma sintering under the pressure of 50 MPa at 1600℃ in Ar atmosphere. Fracture behavior of the specimen was evaluated by bending test, indentation test and fracture-surface observation. The results showed that the bending strength of specimen was lower than monolithic Al_2O_3. It might be because there were many pores and the interface between CNF and Al_2O_3 were relatively weak. However, a large number of pull-out and bridging of CNFs were observed by the fracture surface observation with a scanning electron microscope. This suggests that CNFs could improve the fracture toughness of the CNF reinforced Al_2O_3 composites.
• 静電交互吸着法を利用した高含有率カーボンナノファイバー強化アルミナ複合材料の破壊挙動　　　　　　　　　　　　　　　
  海野孝祐; 若山修一; 赤津隆; 坂井建宣; 梅原由佳
  日本機械学会機械材料・材料加工技術講演会論文集(CD-ROM), Nov. 2010
  Nov. 2010 - Nov. 2010, Japanese
• Effect of crystallinity and fiber volume fraction on creep behavior of glass fiber reinforced polyamide　　　　　　　　　　　　　　　
  Takenobu Sakai; Yuto Hirai; Satoshi Somiya
  Society for Experimental Mechanics - SEM Annual Conference and Exposition on Experimental and Applied Mechanics 2010, Nov. 2010
  Nov. 2010 - Nov. 2010
  Thermoplastic Polyamide (PA) is known as Nylon®, and its FRP are one of the engineering plastics. It is very important for them to reveal accurately the visco-elastic behavior. Furthermore, PA is a crystalline polymer, and it is necessary to consider the effect of crystallization on mechanical properties. The purpose of this study was to make clear the effect of crystallization and fiber volume fraction on creep behavior of PA and its composites. The creep test was performed using the materials which adjusted crystallinity on each fiber volume fraction. As a result, these materials conformed to Arrhenius type of time-temperature superposition principle, and these effects on creep behavior had the time retardation effect. To compare the creep behavior on these effects, we made the grand master curves for crystallinity and fiber volume fraction. Obtained two grand master curves were compared each other, the shapes of these curves are similarly, and we can superposed them. It is therefore, the creep behavior including each conditions have the same behavior. Using these curves and shift factors, we can calculate the creep behavior, and be able to estimate the creep behavior with the effect of arbitrary time, temperature, crystallinity and fiber contents. © 2010 Society for Experimental Mechanics Inc.
• 種々のひずみ速度下における生体骨の疲労損傷のAE法による評価　　　　　　　　　　　　　　　
  安井慶太; 若山修一; 坂井建宣
  日本非破壊検査協会講演大会講演概要集, Oct. 2010
  Oct. 2010 - Oct. 2010, Japanese
• 生体適合性を有するモノマーを添加した骨セメントの粘弾性評価　　　　　　　　　　　　　　　
  坂井建宣; 若山修一; RIOS‐SOBERANIS C. R; CERVANTES‐UC J. M; MAY‐PAT A; FLORES‐GALLARDO S
  日本実験力学会講演論文集, Aug. 2010
  Aug. 2010 - Aug. 2010, Japanese
• Evaluation of visco-elasticity on bone cement added the biocompatibility monomer　　　　　　　　　　　　　　　
  坂井 建宣; 若山 修一; Rios-Soberanis C. R
  Proceedings of JSEM, 2010, 日本実験力学会
  2010 - 2010, Japanese
• EVALUATION OF MECHANICAL BEHAVIOR OF ACTIVATED CARBON COMPOSITES BY 4-POINT FLEXURAL TEST USING ACOUSTIC EMISSION TECHNIQUE　　　　　　　　　　　　　　　
  SAKAI Takenobu; SOBERANIS C‐R Rios; MASUKO Tomoki; MATSUSHIMA Satoshi; KOBAYASHI Satoshi; WAKAYAMA Shuichi
  Prog Acoust Emiss, 2010
  2010 - 2010, English
• Effect of Powder Contents on Stress Relaxation of Glass Powder Reinforced Epoxy　　　　　　　　　　　　　　　
  T. Sakai; K. Okabe; S. Yoneyama
  FOURTH INTERNATIONAL CONFERENCE ON EXPERIMENTAL MECHANICS, 2010, SPIE-INT SOC OPTICAL ENGINEERING
  2010 - 2010, English
  Glass powder reinforced epoxy was used in the fields of plastic sealing of semiconductor devices. In such environment, the materials were exposed in the high temperature, and the stress relaxation behavior must occur in the materials. Therefore, the analysis of stress relaxation behavior was needed. The stress relaxation behaviors of epoxy composites filled with different amounts of glass powder were investigated. Master curves of stress relaxation were obtained, and time-temperature superposition principle was observed on perpetrated epoxy composites. The slopes of time-temperature shift factors were changed depended on the amount of glass powder. It is therefore, we can calculate the time-temperature shift factors by using this relationship. The effect of amounts of glass powder on stress relaxation was investigated, too. Comparing the master curves of stress relaxation with the different amount of glass powder, it is understood that the stress relaxation behaviors of both materials are the same. And it is explained that the effect of glass powder contents on stress relaxation behavior is the effect of reinforcement and heat resistance.
• Analysis of creep behavior in thermoplastic based on visco-elastic theory　　　　　　　　　　　　　　　
  Takenobu Sakai; Satoshi Somiya
  Society for Experimental Mechanics - SEM Annual Conference and Exposition on Experimental and Applied Mechanics 2009, Dec. 2009
  Dec. 2009 - Dec. 2009
  Although plastics with high mechanical properties are widely used in the fields including the aircraft and space industries, various types of FRP have been developed to improve the mechanical properties. Even though those plastics and FRPs are superior in the high-temperature mechanical properties, they are visco-elastically deformed by using at high temperature for a long time. It is, therefore, expected to elucidate the characteristics of visco-elastic phenomena of those materials in detail and improve the estimation technique of long-term life based on this elucidation result for enhancing the reliability of the materials and aiming at the high degree of utilization. Although many researches concerning the creep behavior of FRPs have been made, few researches have been made so far for investigating the linear visco-elastic behavior. And it is known that not only the linear visco-elastic behavior is occurred on the plastics, but also non-linear visco-elastic behavior. In this study, the non-linear visco-elastic behavior of plastics and the FRPs was investigated by making an experiment of the bending creep deformation of Polycarbonate (PC) and Polyacetal (Polyoxymethylene, POM). Moreover, the effects of the fiber volume fraction on the creep characteristics were investigated with glass fiber reinforced polycarbonate (GFRPC). After that, the creep analysis was made with containing these effects on the equation of linear visco-elastic theory. ©2009 Society for Experimental Mechanics Inc.
• ポリ乳酸ブレンド材の圧縮特性評価　　　　　　　　　　　　　　　
  山村俊貴; 大宮正毅; 坂井建宣; VIOT Philippe
  日本実験力学会講演論文集, Aug. 2009
  Aug. 2009 - Aug. 2009, Japanese
• 熱可塑性樹脂およびその複合材料の線形粘弾性理論に基づくクリープ解析　　　　　　　　　　　　　　　
  坂井建宣; 宗宮詮
  日本実験力学会講演論文集, Aug. 2009
  Aug. 2009 - Aug. 2009, Japanese
• PS25 Evaluation of Compressive Properties of PLA/PBAT Polymer Blends　　　　　　　　　　　　　　　
  YAMAMURA Toshitaka; OMIYA Masaki; SAKAI Takenobu; VIOT Philippe
  M&M材料力学カンファレンス, Jul. 2009, 一般社団法人日本機械学会
  Jul. 2009 - Jul. 2009, Japanese
  Biodegradable polymers, Polylactide(PLA) have a potential to be engineering plastics because of energy and environmental reasons. Conventional polymers are made from the petroleum, but PLA is made from the starch whose source is plants. Thus, PLA is carbon-neutral because the carbon of the starch is from carbon dioxide in the air. PLA is brittle. So, it limits the use of PLA. To improve this brittleness, PLA have been blended with other flexible polymers. In this study, we use Poly butylene adipate-co-terephthalate(PBAT) as the blending polymer. PBAT is fully biodegradable and flexible, though its Young's modulus and tensile strength are inferior to PLA, breaking strain is much higher than PLA PBAT distributes evenly in the PLA matrix. By now, PLA and blended PLA were conducted static tensile tests, but not done compressive tests. So, we evaluated properties in the static and dynamic compressive tests. In result, addition 40 wt % PBAT to PLA, Young's modulus and yielding stress decrease, but maximum strain and the strain energy at crack initiation get larger. In addition, Young's modulus and yielding stress of neat PLA and blended PLA increase with the strain rate rising.
• OS0516 Effect of tensile deformation on the crystallinity of biodegradable polymer　　　　　　　　　　　　　　　
  SAKAI Takenobu; NAKASONE Yuji
  M&M材料力学カンファレンス, Jul. 2009, 一般社団法人日本機械学会
  Jul. 2009 - Jul. 2009, Japanese
  The crystal condition of the poly lactic acid that was a crystalline polymer was changed (degree of crystallization etc.), and the tensile test was done. Then the influence of crystal condition on the mechanical attribute was examined. Therefore, heat-treatment was first given to the material based on the melting point and the crystallization temperature of the material requested from differential scanning calorimetry (DSC), and the material that changed the degree of crystallization was made. Next, when the change in the degree of crystallization in the extensional deformation was confirmed because the crystallinity dependence was seen in the extensional deformation as a result of doing the tensile test and having examined it, it was understood that the degree of crystallization had changed by the extensional deformation.
• Evaluation of compressive properties of PLA/PBAT polymer blends　　　　　　　　　　　　　　　
  山村 俊貴; 大宮 正毅; 坂井 建宣
  Proceedings of JSEM, Jul. 2009, 日本実験力学会
  Jul. 2009 - Jul. 2009, Japanese
• Effect of tensile deformation on the crystallinity of biodegradable polymer　　　　　　　　　　　　　　　
  坂井建宣; 中曽根祐司
  日本機械学会M&M材料力学カンファレンス(CD-ROM), Jul. 2009
  Jul. 2009 - Jul. 2009, Japanese
• Analysis of creep behavior in thermoplastic and its composites based on linear visco-elastic theory　　　　　　　　　　　　　　　
  坂井 建宣; 宗宮 詮
  Proceedings of JSEM, 2009, 日本実験力学会
  2009 - 2009, Japanese
• ポリカーボネートのクリープ挙動に及ぼす熱履歴の影響とその測定　　　　　　　　　　　　　　　
  坂井建宣; 宗宮詮
  応力・ひずみ測定と強度評価シンポジウム講演論文集, 2009
  2009 - 2009, Japanese
• Time-temperature and humidity superposition principle on creep of PBS　　　　　　　　　　　　　　　
  Satoshi Somiya; Yujin Lee; Takenobu Sakai
  Society for Experimental Mechanics - 11th International Congress and Exhibition on Experimental and Applied Mechanics 2008, Dec. 2008
  Dec. 2008 - Dec. 2008
  For dissolve the environmental problem, the application of bio-degradable polymer to the engineering field, might be able to dissolve. Polybutylene Succinate (PBS) is a typical engineering plastics and it is well known that this polymer has good mechanical properties as well as a popular engineering such as polycarbonate. But, because the glassy temperature of PBS resin is lower than normal engineering polymers and shows high water absorption, this resin has problem for the practical using as an engineering polymer. In previous report, water absorption phenomenon of PBS at 50°C was measured and the effect of humidity on mechanical properties and creep compliance deformation were researched. For creep behavior, it was confirmed the amount of absorbed water affected creep deformation as same as the change of temperature. The purpose of this research is to make clear the application of "Time-temperature- humidity superposition principle" on PBS resin under some temperature condition from 30°C to 60°C. © 2008 Society for Experimental Mechanics Inc.
• Effect of crystallization on creep behavior of glass fiber reinforced polyacetal　　　　　　　　　　　　　　　
  Takenobu Sakai; Koichi Yamada; Satoshi Somiya
  Society for Experimental Mechanics - 11th International Congress and Exhibition on Experimental and Applied Mechanics 2008, Dec. 2008
  Dec. 2008 - Dec. 2008
  Thermoplastic Polyoxymethylene (Polyacetal / POM) is one of the engineering plastics. It is very important for POM and its FRP to grasp accurately the viscoelastic behavior. Furthermore, POM is a crystalline polymer with very high crystallinity. Therefore, it is necessary to consider the effect of crystallization. The purpose of this study was to make clear the effect of crystallization on bending creep behavior of POM and glass fiber reinforced POM (GFRPOM). It is considered that there are two factors for polymer crystallization. One is crystallinity which is calculated by ratio of crystal and amorphous part, the other is crystal grain size which represents interior morphology. The creep test was performed using the materials which adjusted crystal grain size and crystallinity. As a result, these materials conformed to Arrhenius type of time-temperature superposition principle, and the effect of crystallinity on creep behavior had the time retardation effect. The effect of crystal grain size made the shape of master curves different every crystal grain size. Therefore, the different crystal grain size makes the different creep behavior. Only considering the effect of same crystal grain size, it was able to estimate the long term creep behavior on materials of arbitrary time, temperature and crystallinity. © 2008 Society for Experimental Mechanics Inc.
• OS0618 Effect of crystal state on mechanical properties of a crystalline polymer　　　　　　　　　　　　　　　
  Sakai Takenobu; Nakasone Yuji
  M&M材料力学カンファレンス, Sep. 2008, 一般社団法人日本機械学会
  Sep. 2008 - Sep. 2008, Japanese
  結晶性高分子であるポリアセタールの結晶状態(結晶化度など)を変化させて、引張試験および硬さ試験等を行い、力学的特性に及ぼす結晶状態の影響を調べた。そのため、まず、示差走査熱量測定(DSC)から求めた供試材の融点および結晶化温度に基づいて、供試材に熱処理を施し、結晶化度を変化させた供試材を作製した。次に、引張試験を行い、結晶化処理を施した材料と受入材の引張挙動の相違を調べた。また、予ひずみを与えた材料について硬さ試験を行い、硬さに及ぼす予ひずみの影響を調べ、結晶化度の変化が結晶性高分子材料の引張強度特性に及ぼす影響を明らかにした。
• 結晶性高分子材料の力学的特性に及ぼす結晶状態の影響　　　　　　　　　　　　　　　
  坂井建宣; 中曽根祐司
  日本機械学会M&M材料力学カンファレンス(CD-ROM), Sep. 2008
  Sep. 2008 - Sep. 2008, Japanese
• ポリアセタールのクリープ挙動に及ぼす結晶状態の影響　　　　　　　　　　　　　　　
  坂井建宣; 上野宗一郎; 山田幸市; 宗宮詮
  日本実験力学会講演論文集, Jun. 2008
  Jun. 2008 - Jun. 2008, Japanese
• Effect of crystal state on creep behavior of polyacetal　　　　　　　　　　　　　　　
  坂井 建宣; 上野 宗一郎; 山田 幸市
  Proceedings of JSEM, 2008, 日本実験力学会
  2008 - 2008, Japanese
• Time-temperature dependence behavior of physical aging on creep behavior of PC　　　　　　　　　　　　　　　
  Takenobu Sakai; Satoshi Somiya
  Proceedings of the SEM Annual Conference and Exposition on Experimental and Applied Mechanics 2007, Nov. 2007
  Nov. 2007 - Nov. 2007
  Thermoplastic resin and its FRTP were practically used without post cure treatment and aging treatment which is called "molded material". For such materials, it is known that creep behavior and physical aging occur simultaneously. And the effect of physical aging has the time and temperature dependency. The effect was occurred on the materials after molded, and the effect saved on the materials as the thermal history. This history has big influence on mechanical properties especially creep properties. Therefore, it is necessary to stay in control of the progress of the physical aging. In this report, the creep deformation of Polycarbonate (PC) was researched to grasp the effect of physical aging on creep behavior. It was clearly that the effect had the time and temperature dependency by two shift factors, and it had the same tendency as density. Using these relationships between the shift factors and density, it must be able to calculate the effect of thermal history as physical aging since the materials were molded by density.
• 2539 Study on bending creep behavior of Shape Memory Polymer (DiARY) of Polyurethane Series　　　　　　　　　　　　　　　
  TAO Takayuki; SAKAI Takenobu; SOMIYA Satoshi
  年次大会講演論文集 : JSME annual meeting, Sep. 2007, 一般社団法人日本機械学会
  Sep. 2007 - Sep. 2007, Japanese
  Shape Memory polymer (SMP) is known to have visco-elastic behavior. Shape recovery is considered to occur due to this visco-elastic behavior. On the other hand, creep and creep recovery may also occur that is known as one of visco-elastic behavior. It is important to understand creep and creep recovery behavior, because it effects on material's shape memory and shape recovery characteristics. This research examined the creep and creep recovery behavior by three point bending creep test. As a result, time and temperature dependence was confirmed, and also master curve can be drawn by superposing the creep compliance curves. Moreover, estimation of creep and creep recovery can be possible by master curve, shift factor and Boltzmann's superposition principle.
• Study on bending creep behavior of Shape Memory Polymer (DiARY) of Polyurethane Series　　　　　　　　　　　　　　　
  田尾隆幸; 坂井建宣; 宗宮詮
  日本機械学会年次大会講演論文集, Sep. 2007
  Sep. 2007 - Sep. 2007, Japanese
• Estimation of creep deformation applying phased stress on GFRPC　　　　　　　　　　　　　　　
  Takenobu Sakai; Satoshi Somiya
  Proceedings of the 2006 SEM Annual Conference and Exposition on Experimental and Applied Mechanics 2006, Oct. 2006
  Oct. 2006 - Oct. 2006
  Thermoplastic resin and its FRTP were practically used without post cure treatment and aging treatment which is called "molded material". For such materials, it is known that creep behavior and physical aging occur simultaneously. On the other hand, the creep test is usually carried out under a constant stress. Furthermore, it is known that nonlinear behavior appears under the phased stresses on creep behavior. In previous reports, the creep deformation of Polycarbonate (PC) and Glass fiber reinforced polycarbonate (GFRPC) was researched to estimate the creep deformation on the molded materials under the phased stresses. Using these results, the creep deformation under phased stresses was estimated with time-temperature superposition principle and the principle of superposition on each creep behavior. Using this estimation method, it was able to estimate the creep deformation of molded materials in arbitrary condition, time, temperature, fiber contents, and stress. Therefore, the results of estimation of creep deformation were very fit to the experimental creep deformation. Furthermore, this estimation method of creep behavior made it possible to estimate the creep behavior on pragmatic conditions.
• 2707 Study on creep behaviour of Shape Memory Polymer (DiARY) of Polyurethane Series　　　　　　　　　　　　　　　
  TAO Takayuki; SAKAI Takenobu; SOMIYA Satoshi
  年次大会講演論文集 : JSME annual meeting, Sep. 2006, 一般社団法人日本機械学会
  Sep. 2006 - Sep. 2006, Japanese
  Shape Memory polymer (SMP) is known to have visco-elastic behaviour. Shape recovery is considered to occur due to this visco-elastic behaviour. On the other hand, creep behaviour may also occur that is known as one of visco-elastic behaviour. It is important to understand creep behaviour, because it effects on material's reliability. This research examined the creep behaviour using the SMP, and creep behaviour and influencing factor were investigated by three point bending creep test. As a result, time and temperature dependence was confirmed, and also physical aging has a large effects on creep behaviour. To be more precise, creep deflection was suppressed with increasing of physical aging treatment time. In physical aging time for 1000min, master curve can be drawn by superposing the creep compliance curves, and SMP conformed to Arrhenius type of time-temperature superposition principle.
• Study on creep behaviour of Shape Memory Polymer (DiARY) of Polyurethane Series　　　　　　　　　　　　　　　
  田尾隆幸; 坂井建宣; 宗宮詮
  日本機械学会年次大会講演論文集, Sep. 2006
  Sep. 2006 - Sep. 2006, Japanese
• ガラス繊維強化ポリカーボネートのクリープ挙動予測方法の開発　　　　　　　　　　　　　　　
  坂井建宣; 宗宮詮
  FRPシンポジウム講演論文集, 2006
  2006 - 2006, Japanese
• 繊維強化プラスチックのクリープ挙動に関する材料設計　　　　　　　　　　　　　　　
  坂井建宣; 楠本晃史; 宗宮詮
  FRP CON-EX講演要旨集, Oct. 2003
  Oct. 2003 - Oct. 2003, Japanese
• Material Design Method on Creep Behavior of Glass Fiber Reinforced-Polycarbonate　　　　　　　　　　　　　　　
  SAKAI Takenobu; KUSUMOTO Koji; SOMIYA Satoshi
  日本複合材料学会研究発表講演会予稿集, May 2003
  May 2003 - May 2003, Japanese
• Effects of creep tempering on mechanical properties of diesel engine spring.　　　　　　　　　　　　　　　
  金子堅司; 小島正敏; 坂井建宣
  日本機械学会中国四国支部地方講演会講演論文集, Oct. 2002
  Oct. 2002 - Oct. 2002, Japanese
• Effects of creep tempering on mechanical properties of diesel engine spring　　　　　　　　　　　　　　　
  金子 堅司; 小島 正敏; 坂井 建宣
  講演論文集, Oct. 2002, 一般社団法人日本機械学会
  Oct. 2002 - Oct. 2002, Japanese
  A creep tempering is done in production process of a spring designed for a fuel-injection nozzle of diesel engine. It is because that creep deformation occurs during use at high temperature and mechanical properties may change. But, conditions (temperature, time) in the creep tempering depend on empirical data that are not necessarily reasonable. In this study, effects of creep tempering on mechanical properties and residual stress of spring are investigated experimentally and theoretically. It is found that shear residual stress increases and spring constant does not so change after creep tempering process. Calculation methods of both shear residual stress and shear creep constitutive expressions of spring are proposed.

• Sep. 2024 - Present
  Strength of Materials 1, Saitama University
• Apr. 2015 - Present
  Mechanical Engineering Seminar, Saitama University
• Dec. 2014 - Present
  Adcanced Materials Evaluation and Engineering, Saitama University
• Apr. 2014 - Present
  Experiments of Mechanical Engineering I, Saitama University
• Apr. 2014 - Present
  Polymer Engineering, Saitama University
• Apr. 2019 - Sep. 2023
  Numerical Analysis I, Saitama University
• Apr. 2015 - Sep. 2023
  Engineering Materials II, Saitama University

• 2016
• 2015
• 2014
• 2018
• 2016
• 2015
• 2018

• SOCIETY FOR EXPERIMENTAL MECHANICS
• THE JAPANESE SOCIETY FOR NON-DESTRUCTIVE INSPECTION
• THE SOCIETY OF MATERIALS SCIENCE, JAPAN
• THE JAPAN SOCIETY OF MECHANICAL ENGINEERS
• THE JAPANESE SOCIETY FOR EXPERIMENTAL MECHANICS
• JAPAN SOCIETY FOR COMPOSITE MATERIALS

• Development of multi-layer indentation method connecting micro and macro mechanical properties　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), 01 Apr. 2021 - 31 Mar. 2024
  Grant amount(Total)：17420000, Direct funding：13400000, Indirect funding：4020000
  Grant number：21H01221
• Investigation of classifying conditions of knee osteoarthritis using frequency analysis at the knee joint based on vibroarthrograpy　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Challenging Research (Exploratory), Challenging Research (Exploratory), 28 Jun. 2019 - 31 Mar. 2022
  Seijoh University
  Grant amount(Total)：6240000, Direct funding：4800000, Indirect funding：1440000
  Grant number：19K22783
• 分子構造からみた時間－温度換算則の妥当性とMD解析による長期寿命予測法の開発　　　　　　　　　　　　　　　
  2020 - 2022
  Grant amount(Total)：15210000, Direct funding：11700000, Indirect funding：3510000
  Grant number：19KK0363
  論文ID：49832622
• アコースティック・エミッション法を用いたCGLガスワイピング音の周波数解析　　　　　　　　　　　　　　　
  Apr. 2020 - Mar. 2021
  Principal investigator
• Evaluation of relationship between molecular structure and life time of polymeric materials　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Young Scientists (A), 01 Apr. 2017 - 31 Mar. 2020
  Sakai Takenobu, Saitama University
  Grant amount(Total)：21970000, Direct funding：16900000, Indirect funding：5070000
  In this study, to understand the effect of difference in molecular structure on viscoelastic behavior, tensile and stress relaxation analysis of polyolefin were carried out by molecular dynamic simulation. In the case of tensile analysis, free volume inside of polymers were increased with tensile strain increased. It was clarified that the increase of free volume leads to the occurrence of damage, and they have the strain rate and temperature dependency. In the case of stress relaxation analysis, relaxation speed decreased with the molecular weight of side chain increased. And it was revealed that the stress relaxation behavior shifts the conformation to the stable confirmation such as trans type and reduces kinking.
  Grant number：17H04897
  論文ID：43551308
• 時間－温度換算則を活用した樹脂の寿命予測　　　　　　　　　　　　　　　
  Apr. 2019 - Mar. 2020
  Principal investigator
• 時間－温度換算則を活用した樹脂の寿命予測　　　　　　　　　　　　　　　
  Apr. 2018 - Mar. 2019
  Principal investigator
• Establishment of a checkup method for early knee osteoarthritis using analyses of vibroarthrography from the knee joint　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Grant-in-Aid for Scientific Research (B), 01 Apr. 2015 - 31 Mar. 2018
  Ota Susumu, Seijoh University
  Grant amount(Total)：16380000, Direct funding：12600000, Indirect funding：3780000
  The purpose of this study was to investigate the vibroarthrography (VAG) for classification of patients with knee osteoarthritis. Our findings were 1) the tibia is the most suitable location for classifying knee osteoarthritis based on VAG signals. 2) The features of VAG with knee OA were obtained from a range from 0 to 45 degrees during standing, and the average frequency was around 180 Hz. 3) T2mapping values of knee joint cartilage using MRI were not related to those features of angle and frequency. 4) For the impulse method, the capacity of vibration absorption in knee OA was decreased from 20 to 30 Hz compared to a healthy population.
  Grant number：15H03047
• Acoustic Diagnosis of Bone Fracture Risks Based on the Conception [Bone fatigue fracture is a result of the degradation of bone quality due to microdamage accumulation]　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research, Grant-in-Aid for Challenging Exploratory Research, 01 Apr. 2015 - 31 Mar. 2017
  WAKAYAMA Shuichi, Tokyo Metropolitan University
  Grant amount(Total)：3640000, Direct funding：2800000, Indirect funding：840000
  Osteoporotic model femur specimens were obtained from rats at 13 or 19 weeks after ovariectomization. In order to evaluate the bone mass and bone quality, the measurement of ultrasonic propagation characteristics, X-ray CT photography and dynamic mechanical analysis (DMA) were carried out. Furthermore, 4-point bending tests and static compression tests of control and osteoporotic model femur specimens were performed. During the tests, microdamage accumulation of rat femur was monitored by acoustic emission. Consequently, it was found that the influence of ovariectomization was more significant for proximal rather than diaphysis.
  Grant number：15K12516
• Test plan for 15 years creep test of polymeric materials　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B), Grant-in-Aid for Young Scientists (B), 01 Apr. 2014 - 31 Mar. 2017
  SAKAI Takenobu, Saitama University
  Grant amount(Total)：4030000, Direct funding：3100000, Indirect funding：930000
  Long-term creep tests for over one year were carried out using Polypropylene. Moreover, short-term creep tests, constant strain rate tests and constant loading rate tests were carried out at various temperature. Creep compliance was calculated by using these short-term tests data, and to get master curves of creep compliance, the time-temperature superposition principle was applied to these data. Master curve of the short-term creep tests data were coincide with the long-term creep tests, and it was clear that the W.L.F. equation was suit on the polypropylene. On the results of the master curves from constant strain-rate and loading-rate tests, they were not coincide with the long-term creep tests. It was cleared that the reason of disagreement was the non-linear viscoelastic behavior of polypropylene.
  Grant number：26820013
• CFRP接着層における弱接着状態検出法の開発　　　　　　　　　　　　　　　
  Oct. 2016 - Mar. 2017
  Principal investigator
• 炭素繊維強化複合材料の疲労特性への時間－温度換算則の適用　　　　　　　　　　　　　　　
  Apr. 2015 - Mar. 2016
  Principal investigator
• ウェアラブルな心音・呼吸音評価装置の開発　　　　　　　　　　　　　　　
  Oct. 2014 - Sep. 2015
  Principal investigator
• Fundamental Study on the Clarification of Rupture Mechanism in Tendon and the Characterization of Damage Healing Process using Acoustic Information　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research, Grant-in-Aid for Challenging Exploratory Research, 01 Apr. 2012 - 31 Mar. 2014
  WAKAYAMA Shuichi; YAMAMOTO Ei; SAKAI Takenobu, Tokyo Metropolitan University
  Grant amount(Total)：3900000, Direct funding：3000000, Indirect funding：900000
  The microdamage of rabbit patellar tendon under static tensile load was detected by AE technique. The damage process of intact and injured tendon was successfully monitored. It was found that the higher amplitude AE signals were detected before the maximum stress under the higher loading rate. It was then suggested that larger scale of microdamages, such as bundles of fibers, ruptured simultaneously under the higher loading rate. AE source location was corresponded with the area where the local strain increased. Consequently, the fundamental insights for the damage monitoring technique which are indispensable for the optimization of programs of sports training or rehabilitation are obtained.
  Grant number：24650267
• 時間－温度換算則を活用した樹脂の寿命予測　　　　　　　　　　　　　　　
  Apr. 2013 - Mar. 2014
  Principal investigator
• 使用済タイヤ強化ポリ乳酸の粘弾性特性と衝撃特性　　　　　　　　　　　　　　　
  Apr. 2012 - Mar. 2013
  Principal investigator
• 使用済みタイヤを用いた生分解性プラスチック複合材料の創製　　　　　　　　　　　　　　　
  Apr. 2010 - Mar. 2011
  Principal investigator
• プラスチックの高温耐久性を考慮した構造設計手法の開発　　　　　　　　　　　　　　　
  Apr. 2007 - Mar. 2008
  Principal investigator

• 膝関節症診断システム　　　　　　　　　　　　　　　
  Patent right