九州大学 研究者情報
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久保田 祐信(くぼた まさのぶ) データ更新日:2018.03.15

教授 /  カーボンニュートラル・エネルギー国際研究所 水素適合材料研究部門 水素適合材料・破壊学(2014.4 - Current), エア・リキード水素構造材料・破壊学(2010.10 - 2014.3)


主な研究テーマ
高圧水素配管用溶接継手の開発
キーワード:水素,溶接
2014.04~2017.03.
高圧水素中の疲労限度
キーワード:水素,疲労限度
2014.04~2018.03.
高温水素環境における材料強度劣化に関する研究
キーワード:水素,高温,クリープ,疲労
2017.04~2019.03.
水素助長破壊に対する水素ガス中不純物の影響
キーワード:水素,破壊,疲労,フレッティング,不純物
2014.04~2018.03.
鉄道用車輪材料の微小き裂進展挙動に関する研究
キーワード:微小き裂,き裂進展,下限界,鉄道
2010.04.
破壊靭性に及ぼす水素の影響
キーワード:水素 破壊靭性
2010.10~2013.09.
ねじりを受ける部品のフレッティング疲労強度評価
キーワード:フレッティング疲労,ねじり,スプライン,はめ合い
2008.04.
水素環境中フレッティング疲労の強度低下メカニズム解明
キーワード:水素,フレッティング疲労,機構,強度低下,凝着,微小き裂
2007.04.
水素ガスならびに材料中水素がフレッティング疲労強度に及ぼす影響
キーワード:水素ガス,水素濃度,フレッティング疲労強度
2003.04.
耐フレッティング疲労設計としての応力緩和溝形状選定に関する研究
キーワード:フレッティング疲労,応力緩和溝,疲労強度向上
2005.04.
従事しているプロジェクト研究
NEDO 水素利用技術研究開発事業/水素ステーション安全基盤整備に関する研究開発/高圧水素ガス用高窒素高強度ステンレス鋼配管の溶接継手に関する研究開発
2014.04~2017.02, 代表者:松本拓哉, 株式会社エア・リキード・ラボラトリーズ, 株式会社エア・リキード・ラボラトリーズ
高圧水素ガス配管用に高窒素ステンレス鋼の使用と溶接継手の導入が期待されている.窒素は材料強度と耐水素脆化特性を向上させる重要な元素であるが,溶接熱によって窒素放出または窒素の存在状態変化が生じることが懸念される.本事業は,大きく分けて以下の3つの研究開発項目からなり,これらの研究開発成果を活用することで高圧水素ガス配管への高窒素高強度ステンレス鋼溶接継手導入を目指す.① 高窒素高強度ステンレス鋼配管の溶接技術開発,② 溶接金属の金属組織評価,③ 溶接部の水素脆化評価.
NEDO 水素利用技術研究開発事業/FCV及び水素供給インフラの国内規制適正化、国際基準調和等に関する研究開発/FCV及び水素ステーション関連機器向け使用可能鋼材の拡大及び複合容器の基準整備等に関する研究開発/水素ステーション用既存金属材料の鋼種拡大に関する研究開発
2013.04~2018.02, 代表者:中野和久, 一般財団法人 石油エネルギー技術センター, 一般財団法人 石油エネルギー技術センター
・汎用材の水素環境下での利用に関する研究開発を行い、データベース構築及び技術基準の整備に資する資料を作成する。
・超高圧、広温度範囲の材料設計のための検討を行ない、データベース構築及び技術基準の整備に資する資料を作成する。
.
WPI  九州大学カーボンニュートラル・エネルギー国際研究所
2010.12, 代表者:ペトロス・ソフロニス, イリノイ大学, 日本
人類の持続的発展のために低炭素社会・水素社会への早期移行を目指して,広範な技術の開発・確立を行う..
水素先端科学基礎研究事業
2006.04~2012.03, 代表者:村上敬宜, 九州大学大学院, NEDO(日本)
水素を安全・簡便に利用するための指針を産業界に提供し、基盤整備を行う..
九州大学-日立グループ包括提携 高圧水素環境下における材料問題の検討(2)
2006.10~2008.03, 代表者:近藤 良之, 九州大学, 九州大学
水素ガス環境下の疲労強度について研究を行った..
福岡水素戦略会議 研究助成
2005.10, 代表者:近藤良之, 九州大学, 九州大学(日本)
高圧水素ガス環境で使用される機械部品について,耐水素疲労設計法を構築する..
NEDO水素社会構築共通基盤整備事業
2003.04, 代表者:野口博司, 九州大学, JRCM(日本)
水素社会の基盤構築のため,水素による金属材料劣化を調査し,部品の安全性を確立する.水素環境中で使用される材料に対する標準,例示基準作成..
21世紀COE 水素利用機械システムの統合技術
2002.04, 代表者:村上敬宜, 九州大学大学院 工学研究院, 九州大学大学院 工学研究院
研究教育拠点形成のために,「統合技術会議」と呼ばれる会議を設置する.その統括下に「安全評価技術」「水素利用技術」「水素供給技術」に関わる3つの流動・融合型コラボラトリー(コラボ)を設け,他分野や産業界,また海外からの研究参加を積極的に導入するプロジェクト研究と統合技術教育を行う..
研究業績
主要著書
主要原著論文
1. 久保田 祐信, 片岡 俊介, 髙﨑 大裕, 近藤 良之, A Quantitative Approach to Evaluate Fretting Fatigue Limit Using a Pre-Cracked Specimen, Tribology International, http://dx.doi.org/10.1016/j.triboint.2016.10.017, 108, 48-56, 2017.04, A pre-cracked specimen, which has a 70-μm-deep crack, was used for the fretting fatigue test to understand the reasons for the change in the fretting fatigue limit due to changes in the contact pressure, position of the precrack, and foot length of the contact pad. The threshold stress intensity factor range to crack propagation of the pre-crack, ΔKth, was obtained by the crack growth test. The stress intensity factor range of the pre-crack under fretting conditions was then evaluated by a finite element analysis to estimate the fretting fatigue limit of the pre-crack specimen. The effects of these variables on the fretting fatigue limit were quantitatively explained by the results of the FEM and ΔKth of the short crack..
2. 久保田 祐信, 薦田 亮介, Jader Furtado, Fretting fatigue in hydrogen and the effect of oxygen impurity, Proc. the Asian Conference on Experimental Mechanics 2016 (ACEM 2016), 2016.11, Fretting is a coupled problem of fatigue and frictional contact. It brings unique phenomena that enhance the hydrogen-induced degradation of fatigue strength. Therefore, the role of hydrogen in the fretting fatigue is seriously considered by both manufacturers and users of hydrogen equipment. The fretting fatigue limit in hydrogen was significantly lower than that in air, whereas the fatigue limit of the conventional fatigue test was the same for the both tests. The results clearly demonstrate that the fretting had some specific effects that enhance hydrogen-induced degradation of fatigue strength..
3. 久保田 祐信, 薦田 亮介, 水素雰囲気におけるフレッチング疲労 , トライボロジスト, 60, 10, 651-657, 2015.10, フレッチング疲労に及ぼす水素の影響はかなり古くから調べられている様子であるが,研究の数は少なく,また燃料電池技術を核とした水素エネルギー利用に即した研究が必要である.ここでは,著者らの研究を中心に,オーステナイト系ステンレス鋼の低圧の水素ガス中フレッチング疲労,水素チャージ材の大気中フレッチング疲労などについて強度特性と機構を解説する..
4. 河上紘大, 副島孝, 久保田 祐信, 高圧水素中における無酸素銅加工硬化材の疲労特性, 銅と銅合金, 52, 1, 245-250, 2013.08, The effects of hydrogen on the high-cycle fatigue properties of a work-hardened oxygen-free copper (OFC) was investigated. The fatigue strength in 10MPa hydrogen was increased compared to that in air. The cause of the increased fatigue strength in the hydrogen was the delay of crack initiation and the decrease of crack growth rate due to the absence of oxygen and water vapor. In this sense, hydrogen embrittlement didn’t occur in this material. However, hydrogen significantly enhanced the development of slip bands. The morphology of slip bands during the fatigue test in hydrogen was definitely different from that observed in air. Based on the detailed observation of the slip bands, it is presumed that the possible cause of the enhanced slip deformation during the fatigue in hydrogen is enhanced localized plastic deformation (HELP)..
5. 松本 拓哉, 伊藤賀久岳, 平林 佐那, 久保田 祐信, 松岡 三郎, 0.7MPa 水素ガス中における炭素鋼鋼板SM490B の弾塑性破壊靭性に及ぼす変位速度の影響, 日本機械学会論文集(A 編), 79, 804, 1210-1225, 2013.08, The elastic-plastic fracture toughness, JIc, of SM490B carbon steel plate was investigated in air and 0.7 MPa
hydrogen gas. JIc tests were conducted in accordance with the JSME standard, JSME S001 (1981). JIc was much smaller
in hydrogen at a displacement velocity of V = 2 × 10–3 mm/s (JIc = 10.0 kJ/m2) than in air at V = 2 × 10–3 mm/s (JIc =
248.6 kJ/m2). JIc in air does not satisfy the validity requirement. In hydrogen, surprisingly, a further decrease in V did not
decrease JIc, but increased it. JIc in hydrogen at V = 2 × 10–5 mm/s was 60.9 kJ/m2. The large and small values of JIc in air
and hydrogen corresponded to the fracture morphology. In air at V = 2 × 10–3 mm/s, a critical stretched zone, SZWc, was
formed at the tip of the fatigue pre-crack, followed by dimples. In hydrogen at V = 2 × 10–3 mm/s, quasi-cleavage instead
of SZWc and dimples were formed at the pre-crack tip. In hydrogen at V = 2 × 10–5 mm/s, SZWc was formed at the precrack
tip, followed by dimples again. This elastic-plastic fracture toughness behavior was analyzed assuming HESFCG
(hydrogen-enhanced successive fatigue crack growth), which is proposed by the authors to explain the acceleration of
fatigue crack growth rate in the presence of hydrogen. The elastic plastic fracture toughness test shown in 0.7 MPa
hydrogen gas at V = 2 × 10–3 mm/s is the same as that shown in a fatigue crack growth test in 0.7 MPa hydrogen gas at a
number of cycles of n = 1 and stress ratio of R = 0; and thus JIc in 0.7 MPa hydrogen gas at V = 2 × 10–3 mm/s is not the
real elastic-plastic fracture toughness. We conclude that the real elastic-plastic fracture toughness in 0.7 MPa hydrogen
gas can be determined by fracture toughness testing in 0.7 MPa hydrogen gas at V = 2 × 10–5 mm/s..
6. 薦田亮介, 久保田 祐信, 近藤 良之, Jader Furtado, 水素ガス中フレッティング疲労における疲労強度低下の基本的機構(凝着部に発生する微小き裂の発生条件に及ぼす水素の影響), 79, 801, 536-545, 2013.05, The authors have reported a significant reduction in fretting fatigue strength of austenitic stainless steels due to
hydrogen. One of the causes of the reduced fretting fatigue strength in hydrogen is adhesion between contacting
surfaces and following formation of small cracks which emanate from the adhered spots. The objective of this study is
to understand the effect of hydrogen on the initiation of the small cracks under fretting fatigue conditions. Since the
adhesion between contacting surfaces during fretting in hydrogen is very localized, a small contact length was used in
this test in order to facilitate understanding by avoiding such localization. The fretting fatigue test of an austenitic
stainless steel SUS304 was performed in air and 0.13MPa hydrogen. In the fretting fatigue test, hydrogen participates in
the initiation of the fretting fatigue crack. It can be presumed that high strain at the contact edge activates hydrogen
assisted fracture in terms of dislocation mobility. Adhesion mimic test, in which a small contact area was welded, was
also performed. As the result, the crack initiation limit evaluated by the maximum range of shear stress was
significantly lower in hydrogen than in air. Hydrogen assists small crack initiation under fretting fatigue conditions.
This is one of the possible causes of the significant reduction of fretting fatigue strength in hydrogen..
7. 久保田祐信,佐久間亨,山口純一郎,近藤良之, オーステナイト系ステンレス鋼の切欠き材の高サイクル疲労強度に及ぼす過大応力と水素の影響, 日本機械学会論文集(A 編), 77, 782, 1747-1759, 2012.10, SUS304,SUS316L鋼の切欠き材に水素チャージを施し,0.6MPa水素ガス環境中でN=200回の繰返し過大応力負荷後に高サイクル疲労試験を実施し,過大応力負荷と水素が高サイクル疲労強度低下に及ぼす影響を検討した.高サイクル疲労強度は過大応力負荷によって低下した.その原因は過大応力により発生した微小き裂である.SUS304では水素の影響により疲労強度低下が助長されたが,SUS316Lでは水素の影響は見られなかった.切欠き底の微小き裂進展挙動を評価し,さらにKthとき裂長さの関係を用いて,任意の負荷条件,切欠き先端半径に対して影響を予測する方法を提案した..
8. Kanetaka MIYAZAWA, Masato MIWA, Akihiro TASHIRO, Tatsuro AOKI Masanobu KUBOTA and Yoshiyuki KONDO, Improvement of Torsional Fretting Fatigue Strength of Splined Shaft Used for Car Air Conditioning Compressors by Hybrid Joint, Journal of Solid Mechanics and Materials Engineering, 10.1299/jmmp.5.753, 5, 12, 753-764, 2011.12, To improve the fatigue strength of the splined shaft used for a car’s air conditioning compressor, press fit was added to the innermost part of the spline. This shaft connection consisting of a spline and press fit is called a "hybrid joint" in this study. A torsional fretting fatigue test was performed focusing on the effect of the amount of interference on the fatigue strength. The fatigue strength of the splined shaft was drastically increased by the hybrid joint. The fatigue strength of the hybrid joint was at most 8 times higher than that of the conventional spline-joint shaft. The fatigue strength as well as the failure mode of the hybrid-jointed specimens were changed depending on the amount of interference. The reason was that the relative slip was significantly reduced with an increase in the amount of interference. The specimen consisted of a shaft, a boss and a bolt. The hybrid joint prevented loosening of the bolt, while loosening of the bolt was found to occur in the conventional spline-joint shaft..
9. 久保田 祐信,田中 康宏,桑田 喬平,近藤 良之, SUS304の水素ガス中フレッティング疲労における疲労限度低下機構, 材料, 59, 6, 439-446, 2010.06.
10. Masanobu Kubota, Tsuyoshi Nishimura, Yoshiyuki Kondo, Effect of hydrogen concetration on fretting fatigue strength, Journal of solid mechanics and material engineering, 10.1299/jmmp.4.816, 4, 6, 816-829, 2010.06.
11. Masanobu KUBOTA, Shunsuke KATAOKA and Yoshiyuki KONDO, Effect of Stress Relief Groove on Fretting Fatigue Strength and Index for the Selection of Optimal Groove Shape, International Journal of fatigue, 31, 3, 439-446, 2010.05.
12. Masanobu KUBOTA, kenj HIRAKAWA, The effect of rubber contact on the fretting fatiguestrength of railway wheel tire, Tribology International, 42, 9, 1352-1359, 2010.05.
13. Masanobu KUBOTA, Yasuhiro TANAKA, Kyohei KUWADA and Yoshiyuki KONDO, Hydrogen Gas Effect on Fretting Fatigue Properties of Materials Used in Hydrogen Utilization Machines, Tribology International, 42, 9, 1352-1359, 2010.05.
14. Masanobu Kubota, Kenji Hirakawa, The effect of rubber contact on the fretting fatigue strength of railway wheel tire, Tribology International, Vol. 42, pp.1389-1398, 2009.09.
15. Masanobu Kubota, Yasuhiro Tanaka, Yoshiyuki Kondo, The effect of hydrogen gas environment on fretting fatigue strength of materials used for hydrogen utilization machines, Tribology International, Vol. 42, pp. 1352-1359, 2009.09.
16. Masanobu KUBOTA, Yasuhiro TANAKA and Yoshiyuki.KONDO, Fretting Fatigue Strength of SCM435H Steel and SUH660 Heat Resistant Steel in Hydrogen Gas Environment, Tribotest, Vol. 14, pp.177-191, 2008.09.
17. Masanobu KUBOTA, Yasuhiro TANAKA, Kyouhei KUWADA and Yoshiyuki KONDO, Mechanism of Reduction of Fretting Fatigue Limit in Hydrogen Gas Environment, Proceedings of the 3rd International Conference on Material and Processing, Distributed by CD-ROM, 2008.09.
18. Masanobu KUBOTA, Shunsuke KATAOKA and Yoshiyuki KONDO, Effect of Stress Relief Groove on Fretting Fatigue Strength and Index for the Selection of Optimal Groove Shape, International Journal of Fatigue, Vol. 31, pp.436-446, 2008.07.
19. 久保田 祐信,田中 康博,近藤 良之, SCM435H及びSUH660のフレッティング疲労特性に及ぼす水素ガス環境の影響, 日本機械学会論文集, Vol.73, No. 736, 1382-1387, 2007.12.
20. Shunsuke Kataoka, Chu Sakae, Masanobu Kubota, Yoshiyuki Kondo, Effect of Stress Relief Groove Shape on Fretting Fatigue Strength, Key Engineering Materials, Vol.353-358, 2007, pp.856-859, 2007.11.
21. Masanobu Kubota, Shunsuke Kataoka, Yoshiyuki Kondo, Evaluation of optimal shape of stress relief groove for the improvement of fretting fatigue strength , Proceedings of ATEM07, Distributed by CD-ROM, 2007.09.
22. Kenji HIRAKAWA, Masanobu KUBOTA, The effect of rubber contact on the fretting fatigue strength of railway wheel tire, Proceedings of 5th International Symposium on Fretting Fatigue, Session 8, No. 4, 2007.04.
23. M. Kubota, N. Noyama, C. Sakae and Y. Kondo, Fretting in Hydrogen gas, Tribology international, 39/10, pp.1241-1247, 2006.10.
24. 久保田祐信,納山尚樹,笛田宗広,栄 中,近藤良之, フレッティング疲労に及ぼす水素ガス環境の影響, 材料, 第54巻第12号,pp. 1231-1236, 2005.12.
25. Masanobu KUBOTA, Sotaro NIHO, Chu SAKAE and Yoshiyuki KONDO, Effect of Under Stress on Fretting Fatigue Crack Initiation of Press-Fitted Axle, JSME International Journal, 10.1299/jsmea.46.297, 46, 3, 297-302, Vol. 46, No. 3, pp.297-302, 2003.07.
26. Masanobu KUBOTA, Hidenori ODANAKA, Chu SAKAE, Yoshihiro OHKOMORI, and Yoshiyuki KONDO, The Analysis of Fretting Fatigue Failure in Backup Roll and its Prevention, ASTM STP 1425, 10.1520/STP10775S, 1425, 434-445, pp. 434-445, 2003.03.
27. Masanobu Kubota, Sotaro Niho, Chu Sakae and Yoshiyuki Kondo, Effect of Under Stress on Fretting Fatigue Crack Initiation of Press-Fitted Axle, Proc. of JSME/ASME International Conference on Materials and Processing 2002, 10.1299/jsmea.46.297, 46, 3, 297-302, Proc. of JSME/ASME International Conference on Materials and Processing 2002, 2002.10.
28. Masanobu KUBOTA, Kentaro TSUTSUI, Taizo MAKINO, Kenji HIRAKAWA, The Effect of the Contact Conditions and Surface Treatments on the Fretting Fatigue Strength of Medium Carbon Steel, ASTM STP 1367, 10.1520/STP14749S, 1367, 477-490, 2000.01.
29. M. Kubota, T. Ochi, A. Ishii and R. Shibata, Crack Propagation Properties on HIP-Treated Cast Aluminum Alloys, Material Science and Research International, 4, 3, 193-199, Vol. 4, No. 3, pp. 193-199, 1998.09.
主要総説, 論評, 解説, 書評, 報告書等
1. 久保田 祐信, 接触界面力学とフレッティング疲労強度評価, 日本機械学会 講習会「締結・接合部の設計の実際と今後の展開」, 2008.12.
2. 久保田 祐信, 水素利用機器材料の水素ガス環境中フレッティング疲労強度, 圧力技術 Vol.46, No.4, 2008.07.
3. 久保田 祐信, 接触界面力学とフレッティング疲労強度評価, 日本機械学会 講習会「締結・接合部の設計の実際と今後の展開」, 2007.11.
4. 久保田 祐信, フレッティングと疲労, 熱処理技術協会, 2007.09.
主要学会発表等
1. 久保田 祐信, MACADRE ARNAUD PAUL ALAIN, Hydrogen Compatibility of Ultra-Fine Grain Austenitic Stainless Steel, International Colloquium on Environmentally Preferred Advanced Generation Grid evolution global summit "HYDROGEN" (ICEPAG2017), 2017.03, A certain kind of austenitic stainless steel shows a good resistance against hydrogen-induced degradation of material strength. However, basically the yield strength of single austenitic phase materials is not so high. For hydrogen equipment, high strength is very beneficial in terms of cost of the material and performance of the equipment. Therefore, the development of high-strength austenitic stainless steels is strongly desired. Alloying and following precipitation hardening are useful to obtain high strength, but these methods are not always good in terms of material cost. On the other hand, grain refinement is a promising method to improve the mechanical strength of metals. The idea of this study is the combination of austenitic stainless steel and grain refinement in order to obtain both high strength and hydrogen compatibility.
The material was synthesized by a thermo-mechanical treatment invented by Takaki et al [Takaki, 1988]. The grain size was adjusted during reaustenization of the microstructure so that its average size was 1 m. The yield strength was 596 MPa. It was almost twice higher than that of commercial austenitic stainless steels. The improvement of the yield strength by the grain refinement was significant.
Fatigue tests were carried out to obtain the fatigue strength and identify the crack origin. In addition, fatigue crack growth tests were also carried out to obtain the crack growth behavior. The effect of hydrogen on the fatigue properties was evaluated with hydrogen charged material. The reference materials were JIS SUS316 and JIS SUH660. The fatigue limit of the 1 m grain size material was approximately 2.8 times higher than that of the SUS316. The hydrogen charge didn’t affect the fatigue limit, but reduced the fatigue life in the short life region.
The crack origin was a non-metallic inclusion. It was surprising that the size of the inclusion was 2 m. Usually an inclusion acts as the crack origin when the material hardness is higher than HV400 and its size is several tens of m. The hardness of the 1 m grain size material was less than HV300. Therefore, the experimental fact that the crack initiated from a 2 m inclusion was beyond the knowledge about engineering metals.
Generally, the crack growth resistance is deteriorated by grain refinement because the crack path becomes smooth. However, this material showed a good crack growth resistance which was equivalent to the SUH660. It was found that the crack tip opening displacement (CTOD) during crack growth was distinctively smaller compared to those of the reference materials. Furthermore, the plastic zone size at the crack tip was also considerably smaller than those of the reference materials. According to classic crack growth mechanisms, the CTOD is proportional to the plastic zone size and the CTOD governs the crack growth rate. Therefore, a possible mechanism for the good crack growth resistance is the barrier of the grain boundary of the small grains against the dislocation motion and the following suppression of plastic deformation at the crack tip.
The hydrogen charge caused an acceleration of the crack growth, and this result is consistent with the reduced fatigue life of the hydrogen charged material. The reason for the acceleration of the crack growth was the transformation of microstructure from austenite to strain-induced martensite during crack growth. The grain refinement significantly improved the both static and fatigue strength. However, there is room for improvement in hydrogen compatibility.
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2. 久保田 祐信, 薦田 亮介, Jader Furtado, Fretting fatigue in hydrogen and the effect of oxygen impurity, The 15th Asian Coference on Experimental Mechanics (ACEM2016), 2016.11, Fretting is a coupled problem of fatigue and frictional contact. It brings unique phenomena that enhance the hydrogen-induced degradation of fatigue strength. Therefore, the role of hydrogen in the fretting fatigue is seriously considered by both manufacturers and users of hydrogen equipment. Figure 1 shows the result of the conventional fatigue test and the fretting fatigue test of SUS304 austenitic stainless steel in 0.1 MPa hydrogen gas and air. The fretting fatigue limit in hydrogen was significantly lower than that in air, whereas the fatigue limit of the conventional fatigue test was the same for the both tests. The esults clearly demonstrate that the fretting had some specific effects that enhance hydrogen-induced degradation of fatigue strength.
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3. 髙﨑 大裕, 久保田 祐信, 薦田 亮介, 吉田 修一, 奥 洋介, 牧野 泰三, 杉野 正明, Effect of Contact Pressure on Fretting Fatigue Failure of Oil-Well Pipe Material
, The 15th Asian Coference on Experimental Mechanics (ACEM2016), 2016.11, Fretting fatigue is a combination of fatigue and a kind of wear. Since the fretting fatigue strength is significantly lower than plain fatigue strength, fretting fatigue is one of the most important factors in the design of components. In resent oil-well development, drilling casing technology becomes popular. As shown in Fig. 1, the thread joint between pipes might suffer from fretting fatigue. In the results of full-scale fatigue test of thread joint, there were two failure modes [1]. The first one was the fatigue failure at the thread corner radius, which has been already quantitatively evaluated [2]. The second one is the fretting fatigue failure at the inner contact surface, which has not been studied yet. The objective of this study is to clarify the mechanism of the fretting fatigue failure at the inner contact surface. For this purpose, a fretting fatigue test with different contact pressure was carried out..
4. 久保田 祐信, Akihide Nagao, University of Illinois at Urbana Champaign, Harvard University, University of Illinois at Urbana Champaign, University of Thessaly, Sandia National Laboratories, Livermore, SOFRONIS PETROS, Constitutive equations of hydrogen-enhanced plasticity for quantitative understanding of the mechanisms of hydrogen-assisted fracture, 2016 International Hydrogen Conference, 2016.09, Although the phenomenon of hydrogen-induced degradation of metals and alloys is well documented, there remains a paucity of information with regard to 3-D constitutive material model in the presence of hydrogen. Such constitutive material models that account for the hydrogen effects on the microplasticity of crystals are central to the challenges for material performance prognosis under in-service conditions. Once such a constitutive model is developed and tested under monotonic and cyclic loading conditions, it can be used in a general purpose finite element code to investigate such issues as the role of maximum stress in promoting accelerated fatigue crack growth in the presence of hydrogen.
The objective of this work is the development of a single crystal plasticity model that accounts for the hydrogen effect on dislocation activity along individual slip systems and the interactions between slip systems under varied crystal orientations and loading triaxialities. Toward this objective, a concerted experimental and simulation effort has been mounted by an international team of researchers from the academia, industry, and national laboratories.
In the experimental part of this study, a special tensile test fixture has been designed to carry out uniaxial tension, which can accommodate rotation of the tensile axis and allow for tension free from bending moments. The shape of the specimen has been chosen using computational plasticity so as to minimize stress concentration effects close to the specimen grips. To monitor the response of specific crystal orientations the specimen is mounted and stressed in a way that slip proceeds sequentially from a given single system to multiple slip systems as the load increases. A non-contact strain measurement system is employed in order to avoid imposing any deformation constraints on the specimen. The material used for experiments in this study is single crystal nickel, which has a FCC structure. The computational part of the study involves the development of a single crystal plasticity model accounting for the hydrogen effects on slip along individual systems and their interactions. At the preliminary stages of this investigation, the model of Bassani and Wu has been adopted and modified to account for the hydrogen effects.
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5. 久保田 祐信, 薦田 亮介, Jader Furtado, The effect of oxygen impurities on fretting fatigue of austenitic stainless steel in hydrogen gas, 2016 International Hydrogen Conference, 2016.09, Fretting fatigue is a form of contact fatigue, which frequently occurs on the mating surfaces of joined structures subjected to a fatigue load, which could be one of the major concerns in the design of machines and structures due to the significant reduction in the fatigue strength. For the fretting fatigue in hydrogen, a significant reduction in the fretting fatigue strength has been reported in austenitic stainless steels. Since hydrogen could influence both the fatigue and the phenomena occurring at the contacting surfaces such as friction, fretting wear, oxidation, etc., the mechanisms that cause the reduction in the fretting fatigue properties are very complicated. When considering the service conditions of hydrogen-containment systems, some amount of impurities in the hydrogen should be accepted. The objective of this study is to clarify the effect of oxygen added to hydrogen on the fretting fatigue strength of an austenitic stainless steel. For the fretting fatigue test, a controlled method to add ppm-level oxygen to a hydrogen environment was established. The fretting fatigue tests were carried out in high-purity hydrogen (0.088 vol. ppm O2) and in oxygen/hydrogen mixtures with 5, 35 and 100 vol. ppm O2 concentrations. The material was JIS SUS304 austenitic stainless steel. The fretting fatigue strength in the oxygen/hydrogen mixtures was significantly lower than that in the high-purity hydrogen. The fretting fatigue strength in the oxygen/hydrogen mixtures slightly changed depending on the oxygen level. Based on the X-ray photoelectron spectroscopy analysis of the fretted surface, it was found that the oxide layer of the stainless steel was removed by the fretting in the high-purity hydrogen. The removal of the oxide layer could contribute strong adhesion between contacting surfaces. On the other hand, an oxide layer was produced on the fretted surface in the oxygen/hydrogen mixture by overcoming the removal action of the fretting. It resulted weakening of the adhesion between contacting surfaces, and larger slip between contacting surfaces was produced. As the result, stress conditions at the contact part were changed. Therefore, the change in the oxidation behavior is closely related to the reduction of the fretting fatigue strength by the addition of oxygen..
6. 久保田 祐信, 片岡 俊介, 近藤 良之, A quantitative approach to evaluate fretting fatigue limit using a pre-cracked specimen, 8th International Symposium on Fretting Fatigue (ISFF8), 2016.04, As the general feature of fretting fatigue, non-propagating cracks are frequently found in the unbroken specimens or structural members of machines. Based on this fact, the fretting fatigue limit can be evaluated by the critical stress to crack propagation of a small crack under fretting conditions. In this context, a pre-cracked specimen was prepared for the fretting fatigue test. In the fretting fatigue test using a pre-cracked specimen, the fretting fatigue limit decreased, then increased with an increase in the contact pressure. The threshold stress intensity factor to crack propagation of the small crack, ΔKth, was obtained by the crack growth test. The stress intensity factor range of the pre-crack under fretting conditions, ΔK, was evaluated by a finite element analysis. It was clarified that the change in the fretting fatigue limit with a change in the contact pressure is quantitatively explained by comparison of ΔK to ΔKth. Based on this result, the effect of the position of the pre-crack on the fretting fatigue limit was also both experimentally and analytically investigated..
7. 久保田 祐信, Fretting Fatigue in Hydrogen and the Effect of Impurity Addition to Hydrogen on Fretting Fatigue Properties, 3rd World Cngress on Petrochemistry and Chemical Engineering (Petrochemistry 2015), 2015.12, Hydrogen is necessary to establish a sustainable and environmentally-friendly society. However, hydrogen could degrade materials strength. Therefore, one of the key issues to deploy high-pressure hydrogen containment systems is how to optimize the cost, performance and safety of those systems. For this issue, many studies on hydrogen-affected fracture are under way in order to identify fundamental mechanisms, develop predictive performance models, develop next generation materials, reduce regulations, develop design methods, identify appropriate material testing standards in high-pressure hydrogen environment, and so on.
Fretting fatigue is a kind of fatigue at the contact part between mechanical components. As can be expected from the fact that fretting is sometimes termed as fretting corrosion, it involves some chemical reactions, which might have a great impact on fatigue properties. Since hydrogen could influence both fatigue and the phenomena occurring at the contact surface such as friction, wear, oxidation, etc., the effects of hydrogen on fretting fatigue are very complicated. In fact, fretting fatigue strength of austenitic stainless steels is significantly lower in hydrogen than in air. As a result, the industries related to hydrogen-containment systems are deeply concerned about fretting fatigue in hydrogen. Figure 1 shows an example of fretting found in a high-pressure hydrogen containment system, which occurred at the contact part between 100MPa hydrogen packing and its holder.
When considering service conditions of hydrogen-containment systems, some amount of impurities in hydrogen should be accepted. For example, the purity of hydrogen for PEM fuel cell is designated by ISO standard as 99.99%. On the other hand, positive use of impurities is expected based on the report in which the addition of small amounts of oxygen to hydrogen inhibited hydrogen-affected fracture. The objective of this study is to clarify the effect of oxygen and water vapor added to hydrogen on fretting fatigue strength of an austenitic stainless steel.
For the fretting fatigue test, a controlled method for the addition of ppm-level oxygen to hydrogen environment was established. Fretting fatigue tests in hydrogen containing 0.088, 5, 35 and 100 volume-ppm oxygen were carried out using the test apparatus shown in Fig. 2. The fretting fatigue strength in the oxygen-hydrogen mixture was different depending on the oxygen level as shown in Fig. 3. In the fretting fatigue test in hydrogen with humidification, it was found that the humidification of hydrogen significantly reduced the fretting fatigue strength.
Based on the XPS (X-ray photoelectron spectroscopy) analysis of the fretted surface (Fig. 4), it was found that the fretting removed the original protection layer of the stainless steel, however, the addition of water vapor or ppm-level of oxygen produced an oxide layer on the fretted surface during the fretting that surpassed the removal effect of the initial oxide layer by fretting. In fact, a strong adhesion between the contacting surfaces occurred and no fretting wear particles were observed in the high-purity hydrogen. On the other hand, oxidized fretting wear particles were found in the oxygen-hydrogen mixture.
In addition, the reasons for the change in the fretting fatigue strength in hydrogen due to the addition of impurities were examined from the view point of the change in mechanical stress conditions.
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8. 久保田 祐信, 森 功一, MACADRE ARNAUD PAUL ALAIN, Study on Hydrogen Compatibility in Fatigue of Ultra-Fine Grain Austenitic Stainless Steel, European Congress and Exhibition on Advanced Mterials and Processes 20415 (EUROMAT 2015), 2015.09, This study is aiming to develop higher yield strength austenitic steels without compromising performance in hydrogen by a method of grain refinement. Austenitic stainless steels are superior in hydrogen compatibility than ferritic and martensitic steels. However, austenitic steels have the drawback of relatively low proof strength. It causes increase of thickness of tubes, and it results increase cost and decrease of flow rate.
The material was prepared by thermo-mechanical treatment using reversion from strain-induced martensite to austenite, which has been developed by Takaki et al [1]. Two materials, which have 1m and 21m of average grain size, were prepared. The microstructure is shown in Fig.1. The yield strength was 596MPa for the material with 1m grain size and the proof strength was 156MPa for the material with 21m grain size.
Fatigue test of hydrogen charged and uncharged materials was done with a stress ratio of -1 at a loading frequency of 15Hz in air. Crack growth tests were also performed. The fatigue limit of the 1m grain size material was significantly higher than that of the 21m grain size material. But the fatigue life in the short life region was significantly reduced by hydrogen charge.
It seems that there is no precedent, the crack growth resistance of the ultra-fine grain material was good compared to that of commercial austenitic stainless steels. However, the hydrogen charge accelerated crack growth. This was consistent with the reduction of fatigue life. Based on the observation of morphology of crack, slip bands and crack opening displacement, a possible toughening mechanism, which is inherent in ultra-fine grain austenitic stainless steel was considered..
9. 久保田 祐信, 薦田 亮介, Jader Furtado, Basic Study on The Effect of Hydrogen on Fretting Fatigue, Society of Tribologists and Lubrication Engineers (STLE), 2014 Annual Meeting at Disney Contemporary Resort, 2014.05, The effect of hydrogen on the fretting fatigue strength of SUS304 austenitic stainless steels and the mechanisms were studied. The fretting fatigue strength is significantly lower in hydrogen gas than in air. The fretting fatigue strength is decreased by hydrogen charge. Addition of oxygen partially increased the fretting fatigue strength in gaseous hydrogen. Adhesion between the contacting surfaces is one of the causes of the reduced fretting fatigue strength in hydrogen. The adhesion causes increase in stress, severe plastic deformation and microstructure change.Initiation limit of fretting fatigue cracks was reduced by hydrogen. This is also one of the causes of the reduced fretting fatigue strength in hydrogen.
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10. 久保田 祐信, Jader Furtado, 薦田 亮介, 水素中フレッティング疲労に及ぼす諸因子の影響, 日本材料学会 第316回疲労部門委員会(破壊力学部門委員会 合同部門委員会) , 2014.05, フレッティング疲労に影響を及ぼす因子は数多くあるが,水素中では表面粗さ,水蒸気,微量酸素などが特有の現象を引き起こす.水素中では接触面間の凝着が発生し,その部分に多数の微小き裂が発生するために疲労強度が低下する.凝着には雰囲気が強く影響を及ぼすために,微量酸素,水蒸気の影響により疲労強度が変化する.凝着がフレッティング疲労強度を低下させることを証明するために,大気中でも水素中と似た凝着を発生させる方法を開発した.凝着以外の低下原因として,水素による微小き裂の発生限度の低下,微視組織変化などがあることを見いだした..
11. 久保田 祐信, Jader Furtado, 薦田 亮介, 吉開 巨都, Fretting fatigue properties under the effect of hydrogen and the mechanisms that cause the reduction in fretting fatigue strength, Joint HYDROGENIUS & I²CNER International Workshop on Hydrogen-Materials Interactions, 2014.01, The effect of hydrogen on the fretting fatigue strength of austenitic stainless steels and the mechanisms were studied.
The fretting fatigue strength is significantly lower in hydrogen gas than in air.
The fretting fatigue strength is decreased by hydrogen charge.
Adhesion between the contacting surfaces is one of the causes of the reduced fretting fatigue strength in hydrogen in terms of stress concentration, severe plastic deformation and microstructure change.
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12. 久保田 祐信, High-cycle fatigue properties of work-hardened copper in 10MPa hydrogen gas, Joint HYDROGENIUS & I²CNER International Workshop on Hydrogen-Materials Interactions, 2014.01, High-cycle fatigue properties of work-hardened oxygen-free copper in 10MPa hydrogen gas were studied.
(1) The fatigue limit in hydrogen increased compared to that in air.
(2) The increased fatigue strength was caused by the delay of the crack growth.
(3) Hydrogen participated in the slip deformation. Hydrogen activates dislocations which are immobile in air.
(4) Crack initiation and development of slip bands occurred at lower stress amplitude in hydrogen than in air. The possible mechanism is HELP.
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13. 森功一, 久保田 祐信, MACADRE ARNAUD PAUL ALAIN, 超微細粒オーステナイト系ステンレス鋼の疲労特性と水素の影響, 日本機械学会2013 年度年次大会, 2013.09, Austenitic stainless steel is used as a hydrogen compatible material. However, it has the disadvantage of a low yield strength.
In this study, the tensile and fatigue properties of an ultra-fine grain austenitic stainless steel were investigated. The effect of
hydrogen was also characterized. The fine-grained material shows a significant improvement in the proof strength as well as
the fatigue strength. In addition the deterioration due to hydrogen was minor..
14. Jader Furtado, 薦田亮介, 久保田 祐信, Fretting fatigue properties under the effect of hydrogen and the mechanisms that cause the reduction in fretting fatigue strength, 13th International Conference on Fracture (ICF-13), 2013.06, Fretting fatigue, which is a composite phenomenon of metal fatigue and friction, is one of the major factors in the design of mechanical components as it significantly reduces fatigue strength. Since hydrogen can influence both fatigue and friction, fretting fatigue is one of the important concerns in designing hydrogen equipment. The authors carried out the fretting fatigue tests on austenitic stainless steels in order to characterize the effect of hydrogen and to explain the mechanism responsible for hydrogen embrittlement. In this study, the significant reduction in fretting fatigue strength due to hydrogen is shown including other factors influencing the fretting fatigue strength such as surface roughness, hydrogen content and the addition of oxygen. The cause of the reduction in the fretting fatigue strength in hydrogen is local adhesion between the contacting surfaces and subsequent formation of many small cracks. Furthermore, hydrogen enhances crack initiation under fretting fatigue conditions. Transformation of the microstructure from austenite to martensite is another possible reason. A hydrogen charge also reduces the fretting fatigue strength. The cause is the reduction in the crack growth threshold, Kth, due to hydrogen..
15. 宮澤金敬, 三輪昌人, 近藤 良之, 久保田 祐信, DEVELOPMENT OF THE HYBRID JOINT AND TORSIONAL FRETTING FATIGUE STRENGTH IMPROVEMENT IN THE POWER TRANSMISSION SHAFT, Seventh International Symposium on Fretting Fatigue, 2013.04, Downsizing and reduction of the weight of components is a critical issue for automotive parts manufacturers in the face of strong demand for a reduction of the environmental burden caused by automobiles. Improving the efficiency of the car air conditioning compressor significantly contributes to improved fuel efficiency, but requires downsizing of the compressor’s power transmission shaft. At the same time, the fatigue strength of shaft has to be improved in order to transmit a given level of power through a smaller component. Currently, the spline used for the compressor transmission shaft is the part most prone to fretting fatigue, so an investigation was carried out revealing that the fretting fatigue strength of the downsized spline was insufficient to meet design requirements. Therefore, a new type of joint, a hybrid joint, was developed that combined the press-fit and spline. The structure of the hybrid joint is shown in Fig. 1. The hybrid joint prevented fretting fatigue failure of the downsized spline, resulting in a significant improvement in fatigue strength. In order to use the hybrid joint in the actual product, factors with a bearing on its fatigue strength, particularly the contact pressure and the contact length in the press-fit part, were studied. Contact pressure is one of the major factors influencing fretting fatigue strength of the press-fit part. Since the diameter of the shaft used in this study is relatively small, the contact pressure significantly changes by the degree of interference, which is the difference between shaft diameter and inner diameter of boss..
16. 久保田 祐信, 薦田亮介, 足立裕太郎, 近藤 良之, Jader Furtado, EFFECT OF HYDROGEN AND IMPURITIES ON FRETTING FATIGUE PROPERTIES
, Seventh International Symposium on Fretting Fatigue, 2013.04, The authors have reported that the reduction in fatigue strength due to fretting can be significantly enhanced in hydrogen. In this study, the mechanisms enhancing hydrogen embrittlement by fretting were investigated. Impurities in hydrogen can be considered as an influencing factor on the fretting fatigue strength in hydrogen. The effect of oxygen addition was also studied..
17. 薦田亮介, 久保田 祐信, 近藤 良之, Jader Furtado, THE MECHANISM CAUSING REDUCTION IN FRETTING FATIGUE STRENGTH DUE TO HYDROGEN, Seventh International Symposium on Fretting Fatigue, 2013.04, Hydrogen is the most promising candidate as a new energy carrier in the very near future. Fretting fatigue in hydrogen containment equipment should be considered in order to ensure safety. The authors have reported a significant reduction in the fretting fatigue strength due to hydrogen [1]. One of the causes of the reduced fretting fatigue strength in hydrogen is small cracks that emanate from a locally adhered spot between contacting surfaces. The objective of this study is to establish a quantitative understanding of the effect of hydrogen on the initiation of the small cracks under fretting fatigue conditions..
18. Ryosuke Komoda, Yoshiyuki Kondo, Masanobu Kubota, Study on the reduction mechanism of fretting fatigue strength in hydrogen gas, Joint HYDROGENIUS and I2CNER International Workshop on Hydrogen-Materials Interactions, 2012.02.
19. Masanobu Kubota, Yoshiyuki Kondo, Saburo Matsuoka & Yukitaka Murakami , Effect of Hydrogen on Fatigue Crack Initiation, Small Crack Growth and Long Crack Growth, Joint HYDROGENIUS and I2CNER International Workshop on Hydrogen-Materials Interactions, 2012.02.
20. 足立 裕太郎,近藤 良之,久保田 祐信, 水素用高圧バルブの繰返し開閉による損傷に関する研究, 日本機械学会材料力学部門 M&M2011カンファレンス, 2011.07.
21. 久保田 祐信,佐久間 亨,山口 純一郎,近藤 良之, オーステナイト系ステンレス鋼切欠き材の高サイクル疲労強度に及ぼす過大応力と水素の影響と疲労限度低下の予測
, 日本機械学会材料力学部門 M&M2011カンファレンス, 2011.07.
22. 瀬尾 明光,久保田 祐信,近藤 良之, 切欠き底の微小き裂の挙動に及ぼす切欠き半径と応力比の影響, 日本機械学会材料力学部門 M&M2011カンファレンス, 2011.07.
23. Kanetaka MIYAZAWA and Masato MIWA, Akihiro TASHIRO, Tatsuro AOKI, Manobu Kubota and Yoshiyuki Kondo , INPROVEMENT OF TORSIONAL FRETTING FATIGUE STRENGTH OF SPLINED SHAFT USED FOR CAR AIR CONDITIONING COMPRESSORS BY HYBRID JOINT, the JSME/ASME 2011 International Conference on Materials and Processing (ICM&P2011), 2011.06.
24. Koshiro Mizobe, Yuki Shiraishi, Manobu Kubota and Yoshiyuki Kondo , EFFECT OF HYDROGEN ON FRETTING FATIGUE STRENGTH OF SUS304 AND SUS316L AUSTENITIC STAINLESS STEELS, the JSME/ASME 2011 International Conference on Materials and Processing (ICM&P2011), 2011.06.
25. 石崎敬之,久保田祐信,近藤良之, 炭素鋼の高サイクル疲労特性におよぼす10MPa水素ガス環境の影響, 日本材料学会 第60期学術講演会, 2011.05.
26. 溝部 浩志郎,久保田 祐信,近藤 良之, オーステナイト系ステンレス鋼SUS316Lのフレッティング疲労強度に及ぼす水素の影響, 機械学会九州支部 第64期総会・講演会, 2011.03.
27. 青木 辰郎, 宮澤 金敬, 三輪 昌人, 近藤 良之, 久保田 祐信, スプライン軸の疲労強度向上に対する圧入併用の効果, 日本機械学会第18回機械材料・材料加工技術講演会(M&P2010), 2010.11.
28. 白石 悠貴,久保田 祐信,近藤 良之, オーステナイト系ステンレス鋼のフレッティング疲労に及ぼす水素の影響, 日本機械学会第18回機械材料・材料加工技術講演会(M&P2010), 2010.11.
29. 宮澤 金敬,三輪 昌人,田代 晃浩,近藤 良之,久保田 祐信 , ハイブリッド締結によるスプライン軸のフレッティング疲労強度向上, 日本機械学会2010年度年次大会, 2010.09.
30. Masanobu Kubota, Yasuhiro Tanaka, Kyohei Kuwada, Yoshiyuki Kondo, Mechanism of fretting fatigue limit reduction in hydrogen gas in SUS304
, The 6th International Symposium on Fretting Fatigue, 2010.04.
31. Masanobu Kubota, Toru Sakuma, Junichiro Yamaguchi, Yoshiyuki Kondo, Effect of Hydrogen Absorption on the Fatigue Strength Reduction caused by Multiple Overloads in Notched Component , JSME M&M Symposium for Young Researchers, 2010.03.
32. Masanobu Kubota, Tsuyoshi Nishimura, Yoshiyuki Kondo, EFFECT OF HYDROGEN CONCENTRATION ON FRETTING FATIGUE STRENGTH
, Asian Pacific Conference for Materials and Mechanics 2009, 2009.11.
33. 久保田祐信,田中康博,桑田喬平,近藤良之, SUS304鋼の水素ガス中におけるフレッティング疲労限度低下機構の検討, 日本機械学会 第17回機械材料・材料加工技術講演会(M&P2009), 2009.11.
34. 坂本惇司,近藤良之,久保田祐信, フレッティング疲労強度向上のための応力逃がし溝形状の最適化, 日本機械学会 2009年度年次大会, 2009.09.
35. 佐久間亨,久保田祐信,近藤良之, 過大荷重による疲労強度低下に及ぼす水素の影響, 日本材料学会 第58期学術講演会, 2009.05.
36. Masanobu Kubota, Yasuhiro Tanaka, Kyohei Kuwada, yoshiyuki Kondo, Mechanism of Reduction of Fretting Fatigue Limit in Hydrogen Gas Environmet, 3rd International Conference on Material and Processing ICM&P2008, 2008.10.
37. 久保田 祐信, 接触界面力学とフレッティング疲労強度評価, 日本機械学会 機械材料・材料加工部門 講習会 締結・接合部の設計の実際と今後の展開, 2007.11.
38. 久保田 祐信,近藤 良之, 水素利用機器用材料の水素ガス環境中フレッティング疲労強度, 日本鉄鋼協会・第154回秋季講演大会, 2007.09.
39. Masanobu Kubota , Shunsuke Kataoka, Yoshiyuki Kondo, Evaluation of optimal shape of stress relief groove for the improvement of fretting fatigue strength
, International Conference on Advanced Technology in Experimental Mechanics 2007 ―(ATEM'07), 2007.09.
40. 久保田 祐信, フレッティングと疲労, 熱処理技術セミナー, 2007.09.
41. 久保田 祐信, フレッティング疲労強度と設計技術, 日本機械学会 2007年度年次大会, 2007.09.
42. 久保田 祐信,近藤 良之, 水素利用機器用材料の水素ガス環境中フレッティング疲労強度, 日本鉄鋼協会 第154回秋期講演大会 討論会「水素エネルギー関連構造材料の特性評価と研究開発の現状」, 2007.09.
43. 久保田 祐信, フレッティングと疲労, 平成19年度 第2回熱処理技術セミナー, 2007.09.
44. Masanobu Kubota, Shunsuke Kataoka, Yoshiyuki Kondo, Evaluation of optimal shape of stress relief groove for the improvement of fretting fatigue strength
, International Conference on Advanced Technology in Experimental Mechanics 2007, ATEM07, 2007.09.
45. 久保田 祐信, フレッティング疲労強度と設計技術, 日本機械学会2007年度年次大会ワークショップ「締結・接合部の事故例と教訓」, 2007.09.
46. Kenji Hirakawa, Masanobu Kubota, The effect of rubber contact on the fretting fatigue strength of railway wheel tyre
, 5th International symposium on Fretting Fatigue, 2007.04, The cause of the derailment of ICE train which occurred in 1998 at Eschede was the fatigue failure of a wheel tyre. Figure 1 shows the structure of the rubber sprung wheel. It was discussed that fretting fatigue between the rubber block and inner side of the tire affected the initiation of incipient crack. To clarify the effect of rubber contact on the fatigue strength of the tyre, the authors made fretting fatigue experiments under rubber contact conditions.
At first, fundamental fretting fatigue test was made using a servo-hydraulic fatigue machine. The specimen consisted of a 15mm diameter bar with two parallel flats where rubbers contacted. The specimen is made of medium carbon steel. Using bridge type fretting pads, which hold rubbers to contact with the flat parts of specimen, fretting testing was made. Two cylindrical rubbers, which were taken from the rubber block of a resilient wheel. Contact pressure was 24MPa at the first set-up of testing, which was the similar value of the related wheel assembling pressure calculated by FEM method. Two kind of the fatigue stress amplitude were applied to the specimens. The one was 90MPa, which is the fretting fatigue strength of this carbon steel fretted with steel. The second amplitude was 200MPa, which is twice a large as the fretting fatigue strength. No damage by the contact of rubber was obtained.
Secondly, three-dimensional elastic stress analysis on a rubber-sprung single-ring railway wheel was made using a general-purpose Finite Element Method (ABACUS program). Figure 2 shows the FEM model. Since the rubber is a super-elastic material, Mooney-Revlin Model was used in the calculation. It was found that the wheel tyre is subjected to a cyclic stress in one revolution of the wheel and the maximum stress occurs at the centre of inner surface of the tyre where the fatigue crack initiated.
Finally, fatigue tests of full size wheel-set were made as shown in Fig. 3 to confirm the fatigue resistance of the wheel at high load levels for up to 20millions of cycles of loading. After 20 millions of cycles of 280kN, which is 3.5time higher load than the static wheel load, no fretting damage could be observed.
It was concluded that the no effect of rubber contact on the fretting fatigue strength of a rubber-sprung single-ring railway wheel was observed..
47. Masanobu Kubota, Yasuhiro Tanaka, Kyohei Kuwada and Yoshiyuki Kondo, Effect of Hydrogen Gas Environment and its Mechanism on Fretting Fatigue Strength of Materials for Hydrogen Utilization Machines, 5th International Symposium on Fretting Fatigue, 2007.04.
48. 田中 康博,久保田 祐信,近藤 良之, 機械構造用材料のフレッティング疲労強度に及ぼす水素ガス環境の影響とその機構解明の検討, 日本機械学会九州支部第60期総会・講演会, 2007.03.
49. 久保田 祐信, 電気配線用微細銅線の疲労強度評価, 日本材料学会 マイクロマテリアル部門委員会, 2006.12.
50. M. Kubota , N. Noyama , C. Sakae , Y. Kondo, Fretting fatigue strength in hydrogen gas environment, Fatigue 2006, 2006.05.
特許出願・取得
特許出願件数  1件
特許登録件数  0件
学会活動
所属学会名
日本工学教育協会
九州工学教育協会
日本鉄道技術協会(2007退会)
軽金属学会(2007退会)
日本材料学会
日本機械学会
学協会役員等への就任
2016.09~2018.08, 産業技術総合研究所, 応力発光技術コンソーシアム 委員.
2016.04~2018.03, 日本材料学会, 理事.
2015.05~2016.09, 日本機械学会, 年次大会 実行委員.
2014.03~2014.03, 日本材料学会, 平成26年度役員推薦委員会 委員.
2017.03~2018.02, 日本機械学会 機械材料・材料加工部門, 運営委員.
2016.03~2017.02, 日本機械学会 機械材料・材料加工部門, 第1技術委員会(年次大会担当) 委員長.
2015.03~2016.02, 日本機械学会 機械材料・材料加工部門, 第1技術委員会(年次大会担当) 副委員長.
2013.08~2014.03, 日本機械学会, JSME新学術誌アソシエイトエディタ.
2014.02~2014.03, 日本材料学会, 第63期役員候補推薦委員会委員.
2013.03~2013.03, 日本材料学会, 平成25年度役員推薦委員会.
2012.04~2014.03, 日本溶接協会, 中立委員.
2013.04~2014.03, 日本材料学会九州支部, 常議員.
2013.04~2014.03, 日本材料学会九州支部, 幹事.
2012.04~2013.03, 日本機械学会, 編集委員(journal of Solid Mechanics and Materials Engineering).
2012.04~2013.03, 日本材料学会九州支部, 常議員.
2012.04~2013.03, 日本材料学会九州支部, 幹事.
2012.03~2012.03, 日本材料学会, 平成24年度役員推薦委員会.
2011.04~2012.03, 日本機械学会, 材料力学部門 第3技術委員会.
2011.04~2013.03, 日本材料学会, 代議員.
2011.04~2012.03, 日本機械学会, 機械材料・材料加工部門 第7技術委員会(ジャーナル関係)委員.
2011.04~2012.03, 日本機械学会, 編集委員.
2010.04~2012.03, 日本材料学会九州支部, 幹事.
2009.05~2010.03, 日本材料学会 疲労部門委員会・信頼性工学部門委員会 金属材料疲労信頼性データ集積評価委員会, 委員.
2009.05~2010.11, 日本機械学会, 幹事.
2009.03~2009.03, 日本材料学会, 平成20年度論文賞受賞候補業績審査委員.
2009.04~2010.03, 日本機械学会 材料力学部門, 第4技術委員.
2009.04~2011.03, 日本機械学会, 会誌編集委員.
2009.04~2010.03, 日本機械学会, 論文校閲委員.
2009.04~2010.03, 日本材料学会九州支部, 常議員.
2008.12~2010.03, 日本材料学会九州支部, 評議員.
2008.12~2009.03, 日本材料学会九州支部, 功労賞選考委員.
2008.03~2008.09, 日本機械学会, 日本機械学会基準S015 フレッティング疲労試験方法 改正原案作成委員会 委員.
2008.04~2009.03, 日本機械学会, 論文校閲委員.
2008.04~2009.03, 日本材料学会九州支部, 幹事.
学会大会・会議・シンポジウム等における役割
2016.12.16~2016.12.16, 日本材料学会 疲労部門委員会 第328回疲労部門委員会研究討論会(Study on Hydrogen-Induced Degradation of Materials Strength, Computational and Experimental Approaches), オーガナイザー.
2016.12.09~2016.12.10, 日本材料学会九州支部 第3回学術講演会(A会場 第3セッション), 座長(Chairmanship).
2015.12.21~2015.12.21, 福岡水素エネルギー戦略会議 平成27年度  高圧水素下における機械要素研究分科会, 座長(Chairmanship).
2015.09.16~2015.09.16, 日本機械学会 2015年度年次大会 機械材料・材料加工部門一般セッション(5), 座長(Chairmanship).
2015.05.22~2015.05.24, 日本材料学会 第64期通常総会・学術講演会 一般セッション「建築材料」, 座長(Chairmanship).
2015.03.13~2015.03.13, 日本機械学会九州支部 第68期総会講演会 材料力学(2), 座長(Chairmanship).
2014.12.16~2014.12.16, 福岡水素エネルギー戦略会議 平成26年度  高圧水素下における機械要素研究分科会, 座長(Chairmanship).
2014.03.12~2014.03.13, 日本機械学会 九州支部 第67期総会・講演会, 座長(Chairmanship).
2014.03.02~2014.03.07, 11th International Fatigue Congress (Fatigue 2014) : Damage Evaluation and Fatigue Design, 座長(Chairmanship).
2013.11.29~2013.11.29, 福岡水素エネルギー戦略会議 平成25年度  高圧水素下における機械要素研究分科会, 座長(Chairmanship).
2013.10.11~2013.10.14, 日本機械学会 材料力学部門 M&M2013材料力学カンファレンス (OS-17 締結・接合のプロセスと接合部・界面の信頼性), 座長(Chairmanship).
2013.09.27~2013.09.28, 日本機械学会九州支部 鹿児島講演会(OS3 構造材料の環境強度と劣化・損傷Ⅱ), 座長(Chairmanship).
2013.05.17~2013.05.19, 日本材料学会 第62期通常総会・講演会(一般セッション 金属Ⅱ), 座長(Chairmanship).
2013.03.13~2013.03.13, 日本機械学会 九州支部第66期講演会, 座長(Chairmanship).
2012.02.22~2012.02.22, 福岡水素エネルギー戦略会議 平成24年度  高圧水素下における機械要素研究分科会, 座長(Chairmanship).
2012.01.20~2012.01.20, 福岡水素エネルギー戦略会議 平成23年度第4回研究分科会 ~ 高圧水素下における機械要素研究分科会 / 高圧水素貯蔵・輸送研究分科会 ~, 座長(Chairmanship).
2011.11.05~2011.11.05, 日本材料学会九州支部 特別講演会 Professor Eifler, 司会(Moderator).
2011.10.13~2011.10.13, I2CNER 8th Institute Interest Seminer Series, 座長(Chairmanship).
2011.09.19~2011.09.21, International Conference on Advanced Technology in Experimental Mechanics 2011 (ATEM11), 座長(Chairmanship).
2011.07.16~2011.07.18, 日本機械学会材料力学部門 材料力学カンファレンス2011(M&M2011) GS4, 座長(Chairmanship).
2011.07.16~2011.07.18, 日本機械学会材料力学部門 材料力学カンファレンス2011(M&M2011) OS8-3, 座長(Chairmanship).
2011.07.16~2011.07.18, 日本機械学会材料力学部門 材料力学カンファレンス2011(M&M2011) OS8-1, 座長(Chairmanship).
2011.03.17~2011.03.17, 日本機械学会九州支部第64期総会・講演会, 座長(Chairmanship).
2011.03.16~2011.03.16, 日本機械学会九州支部第65期総会・講演会, 座長(Chairmanship).
2010.09.05~2010.09.08, 日本機械学会2010度年次大会, 座長(Chairmanship).
2010.03.02~2010.03.03, JSME M&M Symposium for Young Researchers, 座長(Chairmanship).
2009.11.13~2009.11.16, Asian Pacific Conference for Materials and Mechanics 2009, 座長(Chairmanship).
2009.09.16~2009.09.18, 日本機械学会 材料力学部門 材料力学カンファレンスM&M2008, 座長(Chairmanship).
2009.08.03~2009.08.07, 日本機械学会 2008年度年次大会, 座長(Chairmanship).
2009.03.18~2009.03.18, 日本機械学会九州支部 第62期講演会, 座長(Chairmanship).
2008.05.23~2008.05.24, 日本材料学会 第57期学術講演会, 座長(Chairmanship).
2008.03.19~2008.03.19, 日本機械学会九州支部 第61期講演会, 座長(Chairmanship).
2007.10.20~2007.10.20, 日本機械学会 九州支部・中国四国支部合同 沖縄講演会, 座長(Chairmanship).
2007.09, 日本機械学会2007年度年次大会 OS J-09-2 締結・接合部の力学・プロセスと信頼性(接着・接合,溶接), 座長(Chairmanship).
2007.04, 5th International Symposium on Fretting Fatigue, 座長(Chairmanship).
2007.03, 日本機械学会九州支部第60期総会・講演会, 座長(Chairmanship).
2006.12, 締結・接合・接着部のCAE用モデリング及び評価技術の構築」分科会,日本機械学会,材料加工部門,フレッティング 第一回ワーキンググループ, 司会(Moderator).
2006.03, 日本機械学会 九州支部 第59期総会講演会, 座長(Chairmanship).
2005.09, 日本機械学会 2005年度年次大会, 座長(Chairmanship).
2005.03, 日本機械学会九州支部 第58期講演会, 座長(Chairmanship).
2004.09, 日本機械学会 2004年度年次大会, 座長(Chairmanship).
2004.09, 日本機械学会 2004年年次大会, 座長(Chairmanship).
2004.05, 日本材料学会 第53期学術講演会, 座長(Chairmanship).
2004.03, 日本機械学会 九州支部 第57期講演会, 座長(Chairmanship).
2002.10, JSME/ASME International Conference on Materials and Processing 2002, 座長(Chairmanship).
2001.08, 日本機械学会 2001年度年次大会, 座長(Chairmanship).
2016.09.11~2016.09.14, 日本機械学会 2016年度年次大会, 機械材料・材料加工部門 第1技術委員会(年次大会担当) 委員長.
2016.09.11~2016.09.14, 日本機械学会 2016年度年次大会, 機械材料・材料加工部門 第1技術委員会(年次大会担当) 副委員長.
2016.09.11~2016.09.14, 日本機械学会 2016年度年次大会, 実行委員.
2016.04.17~2016.04.20, 8th International Symposium on Fretting Fatigue, International committee.
2012.04.08~2012.04.11, 7th International Symposium on Fretting Fatigue, International committee.
2015.03.05~2015.08.13, Fourth Asian Symposium on Materials and Processing (ASMP2015), Scientific and Program Committee.
2011.07.15~2011.07.18, 日本機械学会 M&M2011材料力学カンファレンス, 実行委員,産学連携フォーラム担当,セッションオーガナイザー3件.
2011.06.13~2011.06.17, the 4th JSME/ASME 2011 International Conference on Materials and Processing (ICM&P), Session organizer, session chair.
2010.10.09~2010.10.11, 日本機械学会 M&M2010材料力学カンファレンス, セッション・オーガナイザー.
2010.09.05~2010.09.08, 日本機械学会 2010年度年次大会, セッション・オーガナイザー.
2010.04.19~2010.04.21, 6th International Symposium on Fretting Fatigue, International committee.
2010.03.02~2010.03.03, 2010 M&M International Symposium for Young Researcher, Local Organizing Committee.
2007.04.21~2007.04.23, 5the International Symposium on Fretting Fatigue, International comitee, Japan.
2006.12, 締結・接合・接着部のCAE用モデリング及び評価技術の構築」分科会,日本機械学会材料加工部門,フレッティング 第一回ワーキンググループ, 主催者.
2005.11, 日本機械学会 M&M2005材料力学カンファレンス, 実行委員.
2005.09, 日本機械学会 2005年度年次大会, セッション・オーガナイザー S21 金属材料の疲労特性と破壊機構.
2004.05, 4 th International Sympsium on Fretting Fatigue, International Committee, Japan and Australia.
学会誌・雑誌・著書の編集への参加状況
2009.04~2011.03, 日本機械学会誌, 国内, 編集委員.
学術論文等の審査
年度 外国語雑誌査読論文数 日本語雑誌査読論文数 国際会議録査読論文数 国内会議録査読論文数 合計
2016年度   13 
2015年度   14 
2014年度     10 
2013年度    
2011年度 10      11 
2010年度
2009年度   16 
2008年度 14 
2007年度
2006年度
2002年度
2001年度
1999年度
受賞
平成23年度 技術賞, 日本材料学会, 2012.05.
日本機械学会 機械材料・材料加工部門 一般表彰 優秀講演論文賞, 日本機械学会 機械材料・材料加工部門, 2010.09.
日本材料学会論文賞, 日本材料学会, 2008.05.
日本機械学会賞(論文), 日本機械学会, 2007.04.
学術奨励賞, 日本材料学会, 2006.05.
優秀研究発表賞, 日本材料学会, 2005.03.
Young Researcher Award, The 4th International Symposium on the 21st Century COE Program Nagaoka University of Technology & The 5th International Symposium on Eco-Materials Processing & Design, 2004.01.
優秀講演論文賞, 日本機械学会 機械材料・加工部門, 2001.10.
研究資金
科学研究費補助金の採択状況(文部科学省、日本学術振興会)
2010年度~2012年度, 基盤研究(C), 代表, 部品接触部の水素による疲労限度低下の下限予測手法の確立.
2006年度~2008年度, 基盤研究(B), 分担, 多量に水素侵入した水素利用機器材料のフレッティング疲労強度低下予測法の確立.
2005年度~2007年度, 萌芽研究, 分担, ストライエーションが観察されない疲労破面の応力推定法.
2005年度~2006年度, 奨励研究(B), 代表, 水素環境中の疲労き裂進展挙動に及ぼす温度上昇による拡散係数増加の影響.
2002年度~2003年度, 奨励研究(A), 代表, 電子機器微細配線の高サイクル疲労強度評価と耐久性向上に関する研究.
2000年度~2001年度, 奨励研究(A), 代表, 水浸法によるはめ合い内部のフレッチング疲労き裂進展挙動の観察と進展性評価.
2000年度~2002年度, 基盤研究(A), 分担, 高速鉄道車軸・車輪の信頼性・耐久性向上技術の開発に向けての総合的研究.
日本学術振興会への採択状況(科学研究費補助金以外)
2000年度~2002年度, 日韓科学協力事業共同研究, 分担, 最新超音波探傷法と破壊力学に基づいた航空機用Ti合金の微小疲労き裂予知モデルの開発.
競争的資金(受託研究を含む)の採択状況
2014年度~2016年度, 新エネルギー・産業技術総合開発機構(NEDO)水素利用技術研究開発事業/水素ステーション安全基盤整備に関する研究開発事業, 分担, 高圧水素ガス用高窒素高強度ステンレス鋼配管の溶接継手に関する研究開発.
2016年度~2016年度, 福岡水素戦略会議 研究助成(調査枠), 分担, 液体水素用金属シールの実用化に向けた開発課題の抽出と性能向上に関する研究開発.
2010年度~2012年度, 福岡水素エネルギー戦略会議 研究開発支援事業, 分担, 弾性変形シール形ステンレス金属パッキンの実用化研究開発.
2005年度~2009年度, 福岡水素戦略会議, 分担, 水素利用機械の耐水素性疲労設計法の構築.
1999年度~1999年度, 分担, 衝撃波を用いたコンクリート構造物の非接触非破壊検査法の開発とその自動化に関する研究.
1998年度~2002年度, 運輸施設整備事業団, 分担, 高速化時代における鉄道車軸の安全性確保と耐久性向上に関する研究.
共同研究、受託研究(競争的資金を除く)の受入状況
2016.10~2017.09, 代表, 異種材溶接継ぎ手の強度特性に及ぼす水素の影響.
2016.06~2017.05, 代表, フレッティング疲労特性と微小疲労き裂進展特性に基づく疲労強度評価法の開発.
2015.06~2016.05, 代表, フレッティング疲労特性および微小疲労き裂進展特性に基づく疲労性能評価法の開発.
2014.12~2017.11, 代表, 鉄鋼材料の水素脆化抑制に及ぼすガス不純物の影響.
2014.06~2015.05, 代表, フレッティング疲労特性および微小疲労き裂進展特性に基づく疲労性能評価法の開発.
2014.04~2015.03, 代表, 140MPa水素用圧力トランスミッタの強度信頼性確保に関する共同研究.
2014.04~2015.03, 分担, 連続炭素繊維シート補強した樹脂材のクリープ強度に及ぼす射出成形因子の影響の基礎研究.
2013.10~2014.03, 代表, Materials Compatibility with Hydrogen at High Pressure and Related Testing Methods.
2013.06~2014.05, 代表, 鉄道輪軸用材料の微小疲労き裂進展特性評価.
2013.04~2014.03, 分担, 連続炭素繊維シート補強した樹脂材のクリープ強度に及ぼす射出成形因子の影響の基礎研究.
2012.04~2013.03, 代表, CFRP材における動力伝達軸受け部のフレッチング疲労強度に及ぼす環境影響について.
2012.04~2013.03, 代表, 車輪転動疲労評価モデルに関する研究.
2011.04~2012.03, 代表, 車輪転動疲労評価モデルに関する研究.
2011.04~2012.03, 代表, コンプレッサーシャフトハイブリッド結合におけるねじりフレッチング疲労強度研究.
2010.04~2011.03, 代表, 車輪転動疲労評価モデルに関する研究.
2009.09~2010.03, 代表, 車輪転動疲労評価モデルに関する研究.
2008.04~2009.04, 分担, 動力伝達部におけるフレッティング疲労強度の適用研究.
2006.11~2008.03, 分担, 高圧水素環境下における材料問題の検討.
寄附金の受入状況
2014年度, OSG財団, 超微細粒オーステナイト鋼の機械加工による微視組織特性の変化と機械加工層が疲労強度に及ぼす影響の解明.
2014年度, 日本鉄鋼協会, 超微細粒オーステナイト鋼の疲労特性評価と結晶粒微細化強化機構に基づく高疲労強度の発現機構解明.
2013年度, Air Liquide, Air Liquide 寄付講座.
2010年度, Air Liquide (France) and Air Liquide Japan, Air Liquide 寄付講座.
2009年度, 日立プラントテクノロジー, 奨学寄付金.
2008年度, 日本伸銅協会, 水素利用機器への適合性評価のための銅系材料の水素ガス環境中フレッティング摩耗試験.
2007年度, 日本伸銅協会, 水素利用機器への適合性評価のための銅系材料の水素ガス環境中フレッティング摩耗試験.
学内資金・基金等への採択状況
2013年度~2013年度, 九州大学・水素エネルギー国際研究センター「産学官地域連携による水素社会実証研究」, 代表, 高圧水素容器材料の水素脆化による急速破壊評価とその防止に関する研究.
2012年度~2012年度, 九州大学・水素エネルギー国際研究センター「産学官地域連携による水素社会実証研究」, 代表, 水素利用機器用材料種の拡大のための高圧水素中・高サイクル疲労データの取得と水素の影響機構の解明.
2011年度~2011年度, 九州大学・水素エネルギー国際研究センター「産学官地域連携による水素社会実証研究」, 分担, 水素ガス中フレッティング疲労の疲労限度低下メカニズムにおける接触面間の凝着の寄与の解明.
2010年度~2010年度, 平成22年度 水素エネルギー国際研究センター特別経費「産学官地域連携による水素社会実証研究」海外調査旅費
, 代表, SUS304における水素ガス中フレッティング疲労強度低下機構.
2010年度~2010年度, 九州大学・水素エネルギー国際研究センター「水素社会実証研究」, 分担, 水素用高圧バルブ漏洩の原因究明と対策.
2010年度~2010年度, 組織的な若手研究者等海外派遣プログラム, 代表, 切欠き部材における過大応力の繰返しによる疲労強度低下に及ぼす水素吸蔵の影響.
2008年度~2008年度, 21COE・国際会議参加旅費, 代表, 5th International Symposium on Fretting Fatigueへの参加・渡航費用.

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