| 1. |
高井健一， 松永久生， 小川祐平， 荒河一渡， 藤浪眞紀， 松本龍介， 小山元道， 柴田曉伸， 武富紳也, 水素脆化における潜伏期から破壊までの実態解明における新展開, ふぇらむ（日本鉄鋼協会）, 2023.04. |
| 2. |
Yuhei Ogawa, Dain Kim, Hisao Matsunaga, Saburo Matsuoka, Evaluation of the compatibility of high-strength aluminum alloy 7075-T6 to high-pressure gaseous hydrogen environments, American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP, Vol.6B-2018, 2018.01, Copyright © 2018 ASME. To develop safer and more cost-effective high-pressure hydrogen tanks used in fuel cell vehicles (FCVs), the metallic materials with the following three key properties, i.e. lightweight, high strength and excellent resistance to hydrogen embrittlement should be explored. In this study, the compatibility of high-strength, precipitation-hardened aluminum alloy 7075-T6 was evaluated according to the four types of mechanical testing including slow-strain rate tensile (SSRT), fatigue life, fatigue crack growth (FCG) and fracture toughness tests in high-pressure gaseous hydrogen environments (95 ~ 115 MPa) at room temperature. Even though numerous publications have previously reported significant degradation of the mechanical properties of 7075-T6 in some hydrogenating environments, such as moist atmosphere, the understanding with regards to the performance of this alloy in high-pressure gaseous hydrogen environments is still lacking. In SSRT tests, the alloy showed no degradation of tensile strength and ductility. Furthermore, fatigue life, fatigue crack growth and fracture toughness properties were also not degraded in hydrogen gas. Namely, it was first demonstrated that the material has big potential to be used for hydrogen storage tanks for FCVs, according to its excellent resistance to high-pressure gaseous hydrogen.. |
| 3. |
Yuhei Ogawa, Osamu Takakuwa, Saburo Okazaki, Saburo Matsuoka, Hisao Matsunaga, Change of crack initiation and propagation modes in hydrogenrelated failure of a precipitation-strengthened NI-based superalloy 718 under internal and external hydrogen conditions, American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP, 10.1115/PVP2019-93204, Vol.6B-2019, 2019.01, © 2019 ASME. The influences of internal and external hydrogen on the tensile ductility loss and fracture behaviors of a precipitationhardened Ni-based superalloy 718 were investigated via slow strain rate tensile (SSRT) testing under hydrogen pre-charged conditions (internal hydrogen) or in gaseous hydrogen environments (external hydrogen). Severe degradation of tensile ductility was confirmed both in internal and external hydrogen conditions, and the degree of such degradation became more significant with increasing hydrogen content or hydrogen gas pressures. Moreover, the loss of tensile ductility was more pronounced in internal hydrogen conditions than external hydrogen environments. In association with such degradation of macroscopic tensile ductility, hydrogen also altered fracture mode from ductile microvoid coalescence to some brittle appearances. Whereas typical intergranular fracture combined with a decent fraction of quasi-cleavage fracture appeared on the fracture surface formed in external hydrogen environments, several types of unique faceted characteristics were found on the fracture surfaces in internal hydrogen conditions. The detailed observation of the mid-sectioned lateral surfaces of post-mortem samples successfully revealed that the observed distinctions consisted of the fracture along grain boundaries and {111} crystallographic planes including annealing twin boundaries, besides the frequency of the cracking along twin boundaries evidently increased at higher hydrogen concentration. On the basis of the series of experimental results, the initiation and propagation mechanisms of those hydrogen-induced cracks are discussed in terms of hydrogen distribution, intrinsic deformation character of the material itself as well as the alteration of plastic deformation mode caused by dissolved hydrogen.. |
| 4. |
金崎俊彦, 永田晃市, 松永久生, 村上敬宜, 材料組織の異なるステンレス鋼の疲労強度に及ぼす水素チャージの影響, 日本機械学会論文集A編, 10.1299/kikaia.72.106, Vol.72, No.713, pp.106-113, 2006.01, The effect of hydrogen on fatigue strength of stainless steels was investigated. There were no definite differences in fatigue life of unnotched specimens between hydrogen-charged specimen (2.46.4 ppm) and uncharged specimen (2.2ppm) of SUS 304. High content of hydrogen (10100 ppm) was detected in a very thin surface layer, approximately at 100200 μm from specimen surface of SUS 304 specimens hydrogen-charged for 336672 hours. There were also no definite differences in fatigue life of unnotched specimens between hydrogen-charged specimen (1.85.8 ppm) and uncharged specimen (0.1ppm) of SUS 405. The uncharged specimens of 0.7 C13 Cr steel (0.2 ppm) failed from subsurface non-metallic inclusions in surface layer. ODAs (Optically Dark Area) were not observed due to the tensile residual stress in the surface layer although the specimens failed in the high cycle regime of 10<SUP>7</SUP> cycles. Increasing hydrogen content from 0.2 ppm to 2.42.7 ppm, the fatigue strength and fatigue life were markedly decreased in 0.7 C13 Cr steel.. |
| 5. |
Toshihiko Kanezaki, Koichi Nagata, Hisao Matsunaga, Yukitaka Murakami, Effects of hydrogen charge on fatigue strength of stainless steels, Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A, 10.1299/kikaia.72.106, Vol.72, No.713, pp.106-113, 2006.01, The effect of hydrogen on fatigue strength of stainless steels was investigated. There were no definite differences in fatigue life of unnotched specimens between hydrogen-charged specimen (2.4-6.4ppm) and uncharged specimen (2.2ppm) of SUS 304. High content of hydrogen (10-100 ppm) was detected in a very thin surface layer, approximately at 100-200 (im from specimen surface of SUS 304 specimens hydrogen-charged for 336-672 hours. There were also no definite differences in fatigue life of unnotched specimens between hydrogen-charged specimen (1.8-5.8ppm) and uncharged specimen (0.1 ppm) of SUS 405. The uncharged specimens of 0.7 C-13 Cr steel (0.2 ppm) failed from subsurface non-metallic inclusions in surface layer. ODAs (Optically Dark Area) were not observed due to the tensile residual stress in the surface layer although the specimens failed in the high cycle regime of 107 cycles. Increasing hydrogen content from 0.2 ppm to 2.4-2.7 ppm, the fatigue strength and fatigue life were markedly decreased in 0.7C-13Cr steel.. |
| 6. |
Hisao Matsunaga, Satoshi Muramoto, Masahiro Endo, Threshold of Shear-mode Fatigue Crack Growth in Bearing Steel, Proceedings of 17th European Conference on Fracture (ECF17), Vol.2, pp.CD-ROM-999, 2008.12, Semi-elliptical shear-mode fatigue cracks were studied in SAE52100 bearing steel loaded with fully-reversed cyclic torsion combined with a static axial compressive stress. Non-propagating cracks smaller than 1 mm in length were obtained in the following two ways; (i) decreasing stress amplitude tests using notched specimens, and (ii) constant stress amplitude tests using smooth specimens. The shape and dimensions of the non-propagating cracks were investigated by a successive polishing of the specimen surface, and the threshold stress intensity factor ranges, δK IIth and δK IIIth, were estimated. The threshold values decreased with a decrease in crack size. There was no significant difference between δK IIth and δK IIIth. Wear on the crack surfaces during crack-growth was inferred by a change in microstructure.. |
| 7. |
A. J. McEvily, H. Matsunaga, On Fatigue Striations, SCIENTIA IRANICA TRANSACTION B-MECHANICAL ENGINEERING, Vol.17, No.1, pp.75-82, 2010.01, This paper provides a review of the research that has led to our current understanding of the process of fatigue striation formation. An important question addressed is whether or not at low stress intensity values, fatigue cracks can propagate intermittently in steels and aluminum alloys. It is concluded that there is no valid evidence for propagation, on other than a cycle-by-cycle basis.. |
| 8. |
H. Matsunaga, N. Shomura, S. Muramoto, M. Endo, Shear mode threshold for a small fatigue crack in a bearing steel, FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES, 10.1111/j.1460-2695.2010.01495.x, Vol.34, No.1, pp.72-82, 2011.01, The fatigue behaviour of small, semi-elliptical surface cracks in a bearing steel was investigated under cyclic shear-mode loading in ambient air. Fully reversed torsion was combined with a static axial compressive stress to obtain a stable shear-mode crack growth in the longitudinal direction of cylindrical specimens. Non-propagating cracks less than 1 mm in size were obtained (i) by decreasing the stress amplitude in tests using notched specimens and (ii) by using smooth specimens in constant stress amplitude tests. The threshold stress intensity factor ranges, delta K(IIth) and delta K(IIIth), were estimated from the shape and dimensions of non-propagating cracks. Wear on the crack faces was inferred by debris and also by changes in microstructure in the wake of crack tip. These effects resulted in a significant increase in the threshold value. The threshold value decreased with a decrease in crack size. No significant difference was observed between the values of delta K(IIth) and delta K(IIIth).. |
| 9. |
Yanase Keiji, Endo Masahiro, Matsunaga Hisao, OS12-3-2 Prediction for Fatigue Crack Behavior under Biaxial Loading, Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics, Vol.2011, No.10, pp."OS12-3-2-1", 2011.09. |
| 10. |
H. Matsunaga, C. Sun, Y. Hong, Y. Murakami, Dominant factors for very-high-cycle fatigue of high-strength steels and a new design method for components, Fatigue and Fracture of Engineering Materials and Structures, 10.1111/ffe.12331, Vol.38, No.11, pp.1274-1284, 2015.11, © 2015 Wiley Publishing Ltd. Dominant factors affecting fatigue failure from non-metallic inclusions in the very-high-cycle fatigue (VHCF) regime are reviewed, and the mechanism for the disappearance of the conventional fatigue limit is discussed. Specifically, this paper focuses on the following: (i) the crucial role of internal hydrogen trapped by non-metallic inclusions for the growth of the optically dark area (around the non-metallic inclusion at fracture origin), (ii) the behaviour of the crack growth from a non-metallic inclusion as a small crack and (iii) the statistical aspects of the VHCF strength, in consideration of the maximum inclusion size, using statistics of extremes. In addition, on the basis of the aforementioned findings, a new fatigue design method is proposed for the VHCF regime. The design method gives the allowable stress, σallowable, for a determined design life, NfD, as the lower bound of scatter of fatigue strength, which depends on the amount of components produced.. |
| 11. |
村上 敬宜, 髙城 壽雄, 和田 健太郎, 福島 良博, 松永 久生, 金属疲労S-N曲線の基本構造にもとづく人工微小欠陥材の疲労寿命とそのばらつきの解析, 材料, 10.2472/jsms.70.889, Vol.70, No.12, pp.889-895, 2021.12. |
| 12. |
村上 敬宜, 髙城 壽雄, 和田 健太郎, 福島 良博, 松永 久生, 金属疲労 S-N 曲線の基本構造と疲労寿命のばらつきの本質, 材料, 10.2472/jsms.70.881, 10.2472/jsms.70.889_references_DOI_4DojcQcCs4FTIQXsoXvUhHbYFub, Vol.70, No.12, pp.881-888, 2021.12. |
| 13. |
杉村 丈一, 西村 伸, 松永 久生, 尾上 清明, 産学官連携による水素社会への取り組み—特集 水素特集, フルードパワー = Fluid power, Vol.36, No.2, pp.9-13, 2022.04. |
| 14. |
渡貫 大輔, 堤 雅子, 飛鷹 秀幸, 和田 健太郎, 松永 久生, 欠陥の影響下における転がり軸受の破壊力学に基づく疲労破壊発生基準, No.694, pp.75-90, 2022.01. |
| 15. |
橋本翔，小俣弘樹，松永久生, 転がり軸受のはく離強度に及ぼす微小欠陥寸法の影響（第2報：応力拡大係数に基づくドリル穴を有する転がり軸受のはく離強度の評価）, NSK TECHNICAL JOURNAL, No. 692, 2020.01. |
| 16. |
橋本翔，小俣弘樹，松永久生, 転がり軸受のはく離強度に及ぼす微小欠陥寸法の影響（第1報：転がり接触下のモードⅡ応力拡大係数のFEM解析）, NSK TECHNICAL JOURNAL, No. 692, 2020.01. |
| 17. |
松永久生, 山辺 純一郎, 松岡 三郎, 高圧水素ガス環境中で使用される金属部品の強度設計, 日本機械学会誌（特集：水素社会実現に向けた製品・技術開発）, 2016.04. |
| 18. |
山辺純一郎, 松永久生, 高圧水素分野の材料研究の最近の動向, 機械工学年鑑, 2015.08. |
| 19. |
松永久生, 破壊力学に基づく転がり疲労評価, トライボロジスト, 2010.10. |
| 20. |
松永久生, 金属微小領域の応力評価への適用, 放射光による応力評価（財団法人・高輝度光科学研究センター）, pp.21-27, 2002.11. |
| 21. |
Yukitaka MURAKAMI, Hisao MATSUNAGA, Ryuichi EZAKI, Measurement of residual stress distribution in a micro-indentation on Ti-6Al-4V alloy, SPring-8 User Experiment Report (JASRI), 2003A, p.71, 2003.11. |
| 22. |
Yukitaka MURAKAMI, Hisao MATSUNAGA, Tohru UEDA, Ryuichi EZAKI, Measurement of residual stress distribution in a micro-indentation on Ti-6Al-4V alloy, SPring-8 User Experiment Report (JASRI), 2002B, p.60, 2003.06. |
| 23. |
Yukitaka MURAKAMI, Tohru UEDA, Hisao MATSUNAGA, X-Ray Diffraction of Hydrogen Charged and Uncharged Cr-Mo Steel SCM435, SPring-8 User Experiment Report (JASRI), 2002A, p.31, 2002.10. |
| 24. |
Yukitaka MURAKAMI, Katsuyuki KANENAWA, Hisao MATSUNAGA, Ryuichi EZAKI, Measurement of residual stress distribution in a micro-indentation on Ti-6Al-4V alloy, SPring-8 User Experiment Report (JASRI), 2002A, p.70, 2002.10. |
| 25. |
Yukitaka MURAKAMI, Yoshihiro FUKUSHIMA, Katsuyuki KANENAWA, Hisao MATSUNAGA, Ryuichi EZAKI, Measurement of residual stress distribution in a micro-indentation on Ti-6Al-4V alloy, SPring-8 User Experiment Report (JASRI), 2001B, p.83, 2002.05. |
| 26. |
Yukitaka MURAKAMI, Yoshihiro FUKUSHIMA, Hisao MATSUNAGA, Measurement of residual stress distribution in a micro-indentation on Ti-6Al-4V alloy, SPring-8 User Experiment Report (JASRI), 2001A, p.80, 2001.10. |
