九州大学-研究者情報 [髙桑脩 (准教授) 工学研究院機械工学部門]

髙桑脩（たかくわおさむ）

データ更新日：2024.04.22

准教授　／　工学研究院機械工学部門

学会発表等

1.	髙桑脩, 水素脆性による力学特性の低下とその分析法, 安全・安心な社会を築く先進材料・非破壊計測技術シンポジウム, 2024.03.
2.	小川祐平, 野口耕平, 髙桑脩, Ni基超合金718における水素脆性き裂の発生クライテリア, 日本鉄鋼協会第187回春季講演大会, 2024.03.
3.	髙桑脩, 小川祐平, 転位－水素相互作用の熱活性化過程に着目した低炭素鋼の水素助長疲労き裂進展メカニズム, 日本鉄鋼協会第186回秋季講演大会, 2023.09.
4.	小川祐平, 西田会希, 髙桑脩, 津﨑兼彰, Fe-Ni-Crオーステナイト鋼における水素誘起変形双晶の連続EBSD観察, 日本鉄鋼協会第186回秋季講演大会, 2023.09.
5.	森山潤一朗, 髙桑脩, 山口正剛, 小川祐平, 津﨑兼彰, 第一原理計算を用いたFe-Cr-Niオーステナイト合金中への水素固溶特性の検討：平均および局所水素濃度に与えるCr・Ni原子の影響, 日本鉄鋼協会第186回秋季講演大会, 2023.09.
6.	岩野竜也, 髙桑脩, 平山恭介, 戸田裕之, シンクロトロン放射光によるオーステナイト鋼のひずみ誘起マルテンサイト変態の3次元その場観察, 日本鉄鋼協会第186回秋季講演大会, 2023.09.
7.	Yuhei OGAWA, Osamu TAKAKUWA, Fatigue crack propagation in ferritic iron under pressurized gaseous hydrogen, FEMS EUROMAT23, 2023.09.
8.	Junichiro MORIYAMA, Osamu TAKAKUWA, Masatake YAMAGUCHI, Yuhei OGAWA, Kaneaki TSUZAKI, First-principles study on the hydrogen absorption energy in Fe-Cr-Ni austenitic systems: Effect of Cr and Ni content, FEMS EUROMAT23, 2023.09.
9.	Tatsuya IWANO, Osamu TAKAKUWA, Kyosuke HIRAYAMA, Hiroyuki TODA, 3D in situ observation for strain-induced martensitic transformation in austenitic steel by synchrotron X-ray, FEMS EUROMAT23, 2023.09.
10.	Osamu TAKAKUWA, Yuhei OGAWA, Hydrogen-accelerated/decelerated fatigue crack propagation in Ni-based superalloy 718, 5th International Conference on Structural Integrity (ICSI 2023), 2023.08.
11.	Yuhei OGAWA, Osamu TAKAKUWA, Hydrogen-assisted fatigue crack propagation in ferritic iron: An overview of macroscale behavior and microscale mechanisms, 5th International Conference on Structural Integrity (ICSI 2023), 2023.08.
12.	Junichiro MORIYAMA, Osamu TAKAKUWA, Masatake YAMAGUCHI, Yuhei OGAWA, Kaneaki TSUZAKI, First-principles study on the hydrogen absorption energy in Fe-Cr-Ni austenitic systems: Effect of Cr and Ni content, 5th International Conference on Structural Integrity (ICSI 2023), 2023.08.
13.	髙桑脩, 小川祐平, 内部水素による析出強化型Ni基超合金718の疲労き裂進展加速／減速現象, 日本材料学会第8回マルチスケール材料力学シンポジウム, 2023.05.
14.	森山潤一朗，髙桑脩, 山口正剛，小川祐平，津﨑兼彰, 第一原理計算を用いたFe-Cr-Niオーステナイト合金への水素固溶特性の検討：水素溶解エネルギーと局所濃度分布に対するCr原子の役割, 日本材料学会第8回マルチスケール材料力学シンポジウム, 2023.05.
15.	岩野竜也，髙桑脩, 平山恭介，戸田裕之, シンクロトロン放射光によるオーステナイト鋼におけるひずみ誘起マルテンサイト変態のその場観察, 日本材料学会第8回マルチスケール材料力学シンポジウム, 2023.05.
16.	髙桑脩, 竹中修平, Ni基超合金718の水素誘起き裂進展下限界：粒界析出物δ相の影響, 日本鉄鋼協会第185回春季講演大会, 2023.03.
17.	岩野竜也，髙桑脩，平山恭介，戸田裕之, シンクロトロン放射光によるオーステナイト鋼のひずみ誘起マルテンサイト変態の3次元その場観察, 日本鉄鋼協会第185回春季講演大会, 2023.03.
18.	小川祐平，野口耕平，髙桑脩, Ni基超合金Alloy718の水素ガス環境脆化：支配要因とメカニズム, 日本鉄鋼協会第185回春季講演大会, 2023.03.
19.	Osamu Takakuwa, Yuhei Ogawa, Hydrogen-accelerated / decelerated fatigue crack propagation in Nickel-based superalloy 718, International Symposium on Hydrogen Embrittlement in Nickel-based Superalloys, 2022.12.
20.	Yuhei Ogawa, Osamu Takakuwa, Gaseous hydrogen-assisted failure in Ni-based alloy 718 during tensile test: phenomenological understanding and mechanisms, International Symposium on Hydrogen Embrittlement in Nickel-based Superalloys, 2022.12.
21.	小川祐平，髙桑脩, 津﨑兼彰, オーステナイト鋼における水素による固溶強化の元素濃度・試験温度依存性, 日本鉄鋼協会第184回春季講演大会, 2022.09.
22.	森山潤一郎，髙桑脩, 第一原理計算に基づくFe-Cr-Ni合金の水素占有率予測モデルの構築とその評価, 日本鉄鋼協会第184回春季講演大会, 2022.09.
23.	竹中修平, 髙桑脩, Ni基超合金718のき裂進展下限界値に及ぼす固溶水素の影響, 日本鉄鋼協会第183回春季講演大会, 2022.03.
24.	森山潤一郎, 髙桑脩, 山口正剛, 小川祐平, 津﨑兼彰, Fe-Cr-Ni原子構造の水素溶解エネルギーに及ぼすNiおよびCrの影響に関する第一原理計算, 日本鉄鋼協会第183回春季講演大会, 2022.03.
25.	髙桑脩, 宮田龍之介, 小川祐平, Ni基超合金の水素誘起疲労き裂進展加速／減速現象, 日本鉄鋼協会第183回春季講演大会, 2022.03.
26.	岩田圭一郎, 中村眞実, 岡﨑三郎, 松原和輝, 髙桑脩, 小川祐平, 松永久生, き裂先端部の塑性域寸法に及ぼす高圧水素ガス環境の影響 —低合金鋼 SCM435 における単一過大荷重負荷後の疲労き裂遅延現象にもとづく考察—, 日本機械学会M&M材料力学カンファレンス2021, 2021.09.
27.	石井悠太郎, 髙桑脩, 水素ガス環境下における炭素鋼の疲労き裂進展温度依存性／負荷周波数依存性, 日本機械学会M&M材料力学カンファレンス2021, 2021.09.
28.	岩田圭一郎, 中村眞実, 岡﨑三郎, 松原和輝, 髙桑脩, 小川祐平, 松永久生, 高圧水素ガス中における低合金鋼SCM435の単一過大荷重負荷後の疲労き裂進展挙動, 日本機械学会九州支部第74期総会・講演会, 2021.03.
29.	野口耕平, 小川祐平, 髙桑脩, 松永久生, 水素チャージしたNi基超合金718の引張特性に及ぼす試験温度の影響,, 日本機械学会九州支部第74期総会・講演会, 2021.03.
30.	西田会希, 小川祐平, 松永久生, 髙桑脩, 津﨑兼彰, 水素固溶に伴うオーステナイト鋼の強度・延性向上効果に対するCr・Ni量の影響, 日本鉄鋼協会第181回春季講演大会, 2021.03.
31.	小川祐平, 細井日向, 津﨑兼彰, 髙桑脩, 松永久生, 鉄鋼の高強度・高延性化元素としての水素の新たな一面：Fe-Cr-Ni基合金での一例, 日本鉄鋼協会第181回春季講演大会, 2021.03.
32.	竹中修平, 髙桑脩, 析出硬化型Ni基超合金Alloy718 のき裂進展下限界に及ぼす固溶水素の影響, 日本機械学会M&M材料力学カンファレンス2021, 2021.03.
33.	髙桑脩, 温度依存性に着目したbcc鋼の水素助長疲労き裂進展加速メカニズム, ESISM第11回プラストンに基づく変形現象研究会, 2021.01.
34.	小川祐平, 髙桑脩, 松永久生, BCC鉄中における水素助長疲労き裂進展の巨視的挙動と微視的メカニズム, MRM (Materials Research Meeting) Forum 2020, 2020.12.
35.	Osamu TAKAKUWA, Investigation of material compatibility to high-pressure hydrogen-gas, International Conference on Flow Dynamics 2020, 2020.10.
36.	岩田圭一郎, 中村眞実, 岡﨑三郎, 小川祐平, 髙桑脩, 松永久生, 松原和輝, 高圧水素ガス中における低合金鋼SCM435の疲労き裂進展特性に対する単一過大荷重の影響, 日本鉄鋼協会第180回秋季講演大会, 2020.09.
37.	野口耕平, 小川祐平, 髙桑脩, 松永久生, Ni基超合金718の引張特性に及ぼす内部・外部水素の影響とその温度依存性, 日本鉄鋼協会第180回秋季講演大会, 2020.09.
38.	小川祐平, 細井日向, 津﨑兼彰, 髙桑脩, 松永久生, 水素チャージに伴うオーステナイト系ステンレス鋼310Sの高強度・高延性化とそのメカニズム, 日本鉄鋼協会第179回春季講演大会, 2020.03.
39.	髙桑脩, 小川祐平, 岡崎三郎, 松永久生, 温度依存性に着目した炭素鋼の水素助長疲労き裂進展加速メカニズム, 日本鉄鋼協会第179回春季講演大会, 2020.03.
40.	Osamu TAKAKUWA, Yuhei OGAWA, Hisao MATSUNAGA, Temperature dependence of hydrogen-assisted fatigue crack growth of ferrite-pearlite steel in gaseous environment, Joint Research Symposium -Hydrogen-Material Interactions-, 2020.01.
41.	髙桑脩, 松永久生, 西村貴郎, 國立悦生, 宮本宜幸, レーザー溶接部における新たな疲労き裂進展試験法の開発と溶接部の強度特性に及ぼす水素の影響, 溶接構造シンポジウム2019, 2019.12.
42.	和田健太郎, 山辺純一郎, 小川祐平, 髙桑脩, 飯島高志, 松永久生, 純ニッケルおよび銅ニッケル合金の引張破壊に及ぼす内部水素の影響と温度依存性, 日本機械学会M&M材料力学カンファレンス2019, 2019.11.
43.	細井日向, 髙桑脩, 小川祐平, 松永久生, 固溶水素による析出強化型Fe基超合金A286の延性低下メカニズム, 日本機械学会M&M材料力学カンファレンス2019, 2019.11.
44.	宮田龍之介, 髙桑脩, 小川祐平, 松永久生, Ni基超合金718における特異な水素誘起き裂進展挙動, 日本機械学会九州支部沖縄講演会, 2019.11.
45.	細井日向, 髙桑脩, 小川祐平, 松永久生, 内部水素による析出強化型Fe基超合金A286の延性低下メカニズム, 第9回構造物の安全性・信頼性に関する国内シンポジウムJCOSSAR2019, 2019.10.
46.	松永久生, 小川祐平, 髙桑脩, BCC鋼の水素環境での疲労き裂進展特性, 日本鉄鋼協会第178回秋季講演大会, 2019.09.
47.	小川祐平, 髙桑脩, 岡崎三郎, 沖田耕一, 船越裕亮, 松永久生, 松岡三郎, 内部水素および外部水素環境下におけるNi基超合金Alloy718の水素脆性破壊挙動, 日本鉄鋼協会第178回秋季講演大会, 2019.09.
48.	小川祐平, 髙桑脩, 松永久生, 高圧水素環境下におけるBCC鋼の水素誘起疲労き裂進展加速メカニズム－モデル材料純鉄における変形組織への水素の影響－, 日本機械学会M&M若手シンポジウム2019, 2019.08.
49.	髙桑脩, 小川祐平, 松永久生, 高圧水素環境下におけるBCC鋼の水素誘起疲労き裂進展加速メカニズム－汎用鋼における水素脆化の温度依存性－, 日本機械学会M&M若手シンポジウム2019, 2019.08.
50.	Hisao MATSUNAGA, Osamu TAKAKUWA, Junichiro YAMABE, Recent Progress in the Study on Strength Properties of Metallic Materials in High-Pressure Hydrogen Environments, The 8th World Hydrogen Technologies Convention (WHTC2019), 2019.06.
51.	Peculiar Temperature Dependence of Hydrogen-Assisted Fatigue Crack Growth of Low-Carbon Steel in Gaseous Hydrogen, Osamu TAKAKUWA, Yuhei OGAWA, Junichiro YAMABE, Hisao MATSUNAGA, Japan-Korea-China Joint Workshop on Hydrogen Materials 2019, 2019.04.
52.	髙桑脩, 橋口雄大, 松永久生, 西村貴郎, 國立悦生, 宮本宜幸, 異種材料レーザ溶接部の疲労き裂進展下限界特性に及ぼす水素ガス環境の影響, 溶接学会2019年度溶接疲労強度研究委員会, 2019.04.
53.	髙桑脩, 小川祐平, 松永久生, 水素環境によるオーステナイト系ステンレス鋼の疲労き裂進展加速と延性低下, 日本鉄鋼協会2019年度「水素脆化の基本要因と実用課題」フォーラム, 2019.04.
54.	細井日向,髙桑脩, 小川祐平, 松永久生, 析出強化型Fe基超合金A286の引張変形および破壊挙動に及ぼす固溶水素の効果, 日本鉄鋼協会第177回春季講演大会, 2019.03.
55.	小川祐平, 木村由比子, 松永久生, 髙桑脩, 山辺純一郎, BCC鉄中の水素誘起疲労き裂進展の微視的機構とき裂進展加速挙動に及ぼす固溶炭素の影響, 日本鉄鋼協会第177回春季講演大会, 2019.03.
56.	Hisao MATSUNAGA, Osamu TAKAKUWA, Junichiro YAMABE, Recent Activities for Hydrogen Compatibility of Materials Used in Hydrogen Stations in Japan, International Workshop on Standards and Codes for Hydrogen Infrastructure Safety, 2018.11.
57.	松永久生，髙桑脩，佐藤慎巳，岡崎三郎，中村眞実, 九州大学・水素材料先端科学研究センター金属材料研究部門の取組み, 溶接学会第244回溶接法研究委員会, 2018.11.
58.	髙桑脩, 岡﨑三郎, 山辺純一郎, 松永久生, 松岡三郎, 高圧水素ガス中におけるオーステナイト系ステンレス鋼の強度特性, 溶接学会平成30年度秋季全国大会, 2018.09.
59.	松永久生, 髙桑脩, 山辺純一郎, 松岡三郎, 高圧水素ガス中における材料強度試験, 溶接学会平成30年度秋季全国大会, 2018.09.
60.	小川祐平, Domas BIRENIS, 松永久生, 髙桑脩, 山辺純一郎, 水素ガス環境中における純鉄の疲労き裂進展特性とその微視的メカニズム, 溶接学会平成30年度秋季全国大会, 2018.09.
61.	中村眞実, 岡﨑三郎, 松永久生, 髙桑脩, 松岡三郎, 高圧水素ガス中におけるオーステナイト系ステンレス鋼溶接金属317LのSSRT特性, 溶接学会平成30年度秋季全国大会, 2018.09.
62.	岡﨑三郎, 中村眞実, 松永久生, 髙桑脩, 松岡三郎, オーステナイト系ステンレス鋼突合せ溶接継手の疲労強度特性に及ぼす内部水素の影響, 溶接学会平成30年度秋季全国大会, 2018.09.
63.	髙桑脩, 岡﨑三郎, 山辺純一郎, 松永久生, 松岡三郎, 高圧水素ガス中におけるオーステナイト系ステンレス鋼の強度特性, 溶接学会平成30年度秋季全国大会, 2018.09.
64.	髙桑脩，小川祐平，山辺純一郎，松永久生, 鉄基超合金A286の水素誘起破壊メカニズム, 日本鉄鋼協会第176回秋季講演大会, 2018.09.
65.	小川祐平, Domas BIRENIS, 松永久生, 髙桑脩, 山辺純一郎, 水素ガス環境中疲労き裂進展過程におけるBCC鉄中の粒界破壊メカニズム, 日本鉄鋼協会第176回秋季講演大会, 2018.09.
66.	小川祐平, Domas BIRENIS, 髙桑脩, 山辺純一郎, 松永久生, 高圧水素ガス中におけるBCC鋼の疲労き裂進展加速メカニズム, 日本鉄鋼協会2018年度「水素脆化の基本要因と特性評価」研究会, 2018.09.
67.	松永久生, 髙桑脩, 小川祐平, 山辺純一郎, 松岡三郎, 水素ガス環境中での疲労き裂進展の加速におけるき裂先端の水素濃度分布と転位水素占有率の重要性, 日本高圧力技術協会HPI技術セミナー「水素社会の実現に向けた学識と実践の融合」, 2018.06.
68.	Domas Birenis, Yuhei Ogawa, Hisao Matsunaga, Osamu Takakuwa, Junichiro Yamabe, Øystein Prytz, Annett Thøgersen, Hydrogen-assisted fatigue crack propagation in a pure BCC iron. Part II Accelerated regime manifested by quasi-cleavage fracture at relatively high stress intensity range values, 12th International Fatigue Congress, FATIGUE 2018, 2018.05, [URL], Hydrogen effect on fatigue performance at relatively high values of stress intensity factor range, ΔK, of pure BCC iron has been studied with a combination of various electron microscopy techniques. Hydrogen-assisted fatigue crack growth rate is manifested by a change of fracture features at the fracture surface from ductile transgranular in air to quasi-cleavage in hydrogen gas. Grain reference orientation deviation (GROD) analysis has shown a dramatic suppression of plastic deformation around the crack wake in samples fatigued in hydrogen. These results were verified by preparing site-specific specimens from different fracture features by using Focused Ion Beam (FIB) technique and observing them with Transmission Electron Microscope (TEM). The FIB lamella taken from the sample fatigued in air was decorated with dislocation cell structure indicating high amount of plasticity, while the lamella taken from the quasi-cleavage surface of the sample fatigued in hydrogen revealed a distribution of dislocation tangles which corresponds to smaller plastic strain amplitude involved at the point of fracture. These results show that a combination of critical hydrogen concentration and critical stress during fatigue crack growth at high ΔK values triggers cleavage-like fracture due to reduction of cohesive force between matrix atoms..
69.	Yuhei Ogawa, Domas Birenis, Hisao Matsunaga, Osamu Takakuwa, Junichiro Yamabe, Øystein Prytz, Annett Thøgersen, Hydrogen-assisted fatigue crack propagation in a pure BCC iron. Part I Intergranular crack propagation at relatively low stress intensities, 12th International Fatigue Congress, FATIGUE 2018, 2018.05, [URL], The role of hydrogen on intergranular (IG) fracture in hydrogen-assisted fatigue crack growth (HAFCG) of a pure iron at low stress intensity was discussed in terms of the microscopic deformation structures near crack propagation paths. The main cause of IG fracture was assumed to be the hydrogen-enhanced dislocation structure evolution and subsequent microvoids formation along the grain boundaries. Additionally, the impact of such IG cracking on the macroscopic FCG rate was evaluated according to the dependency of IG fracture propensity on the hydrogen gas pressure. It was first demonstrated that the increased hydrogen pressure results in the larger area fraction of IG and corresponding faster FCG rate. Moreover, gaseous hydrogen environment also had a positive influence on the FCG rate due to the absence of oxygen and water vapor. The macroscopic crack propagation rate was controlled by the competition process of said positive and negative effects..
70.	Osamu TAKAKUWA, Yuhei OGAWA, Junichiro YAMABE, Hisao MATSUNAGA, Hydrogen-Assisted Fracture in Pre-Charged Precipitation-Hardened Iron-Based Superalloy A286, Korea-China-Japan Joint Workshop on Hydrogen Materials 2018, 2018.04.
71.	髙桑脩, 岡﨑三郎, 山辺純一郎, 松永久生, 松岡三郎, 水素ガス環境下における低炭素鋼SM490Bの疲労き裂進展の温度依存性, 日本鉄鋼協会第175回春季講演大会, 2018.03.
72.	小川祐平, 岡﨑三郎, 髙桑脩, 松永久生, 準安定オーステナイト系ステンレス鋼中の疲労き裂進展加速に対する内部水素と外部水素の役割, 日本鉄鋼協会第175回春季講演大会, 2018.03.
73.	小川祐平, Domas BIRENIS, 松永久生, 髙桑脩, 山辺純一郎, き裂先端の変形組織に基づいた純鉄中の水素助長疲労き裂進展加速機構に関する検討, 日本機械学会九州支部第71期総会・講演会, 2018.03.
74.	ケビンサニー, 岡﨑三郎, 髙桑脩, 山辺純一郎, 松永久生, 松岡三郎, 竹腰正雄, 砂川英生, 小林悌宇, 沖田耕一, Ni基超合金718の疲労限度特性に及ぼす微小欠陥の影響, 日本機械学会九州支部第71期総会・講演会, 2018.03.
75.	Osamu TAKAKUWA, Junichiro YAMABE, Hisao MATSUNAGA, Saburo MATSUOKA, Compatibility of Type 304 Stainless Steel to High-Pressure Hydrogen Gas, HYDROGENIUS, I2CNER & HydroMate Joint Research Symposium 2018, 2018.02.
76.	Yuhei OGAWA, Domas BIRENIS, Hisao MATSUNAGA, Osamu TAKAKUWA, Junichiro YAMABE, Interpretation of Hydrogen-Assisted Fatigue Crack Propagation in a Pure BCC Iron Based on Crack Tip Plasticity Evolution, HYDROGENIUS, I2CNER & HydroMate Joint Research Symposium 2018, 2018.02.
77.	Jean Gabriel Sezgin, Osamu Takakuwa, Hisao Matsunaga, Junichiro Yamabe, Assessment of the contribution of internal pressure to the structural damage in a hydrogen-charged Type 316L austenitic stainless steel during slow strain rate tensile test, 22nd European Conference on Fracture, ECF 2018, 2018.01, [URL], The aim of this study is to provide a quantification of the internal pressure contribution to the SSRT properties of H-charged Type-316L steel tested in air at room temperature. Considering pre-existing penny-shaped voids, the transient pressure build-up has been simulated as well as its impact on the void growth by preforming J _Ic calculations. Several void distributions (size and spacing) have been considered. Simulations have concluded that there was no impact of the internal pressure on the void growth, regardless the void distribution since the effective pressure was on the order of 1 MPa during the SSRT test. Even if fast hydrogen diffusion related to dislocation pipe-diffusion has been assessed as a conservative case, the impact on void growth was barely imperceptible (or significantly low). The effect of internal pressure has been experimentally verified via the following conditions: (I) non-charged in vacuum; (II) H-charged in vacuum; (III) H-charged in 115-MPa nitrogen gas; (IV) non-charged in 115-MPa nitrogen gas. As a result, the relative reduction in area (RRA) was 0.84 for (II), 0.88 for (III), and 1.01 for (IV), respectively. The difference in void morphology of the H-charged specimens did not depend on the presence of external pressure. These experimental results demonstrate that the internal pressure had no effect on the tensile ductility and void morphology of the H-charged specimen..
78.	Domas Birenis, Yuhei Ogawa, Hisao Matsunaga, Osamu Takakuwa, Øystein Prytz, Junichiro Yamabe, Annett Thøgersen, Hydrogen-assisted fatigue crack propagation in a commercially pure BCC iron, ASME 2018 Pressure Vessels and Piping Conference, PVP 2018, 2018.01, Hydrogen effect on fatigue performance of commercially pure BCC iron has been studied with a combination of various electron microscopy techniques. The fatigue crack growth (FCG) in gaseous hydrogen was found to consist of two regimes corresponding to a slightly accelerated regime at relatively low stress intensity factor range, ΔK, (Stage I) and the highly accelerated regime at relatively high ΔK (Stage II). These regimes were manifested by the intergranular and quasi-cleavage types of fractures respectively. Scanning electron microscopy (SEM) observations demonstrated an increase in plastic deformation around the crack wake in the Stage I, but considerably lower amount of plasticity around the crack path in the Stage II. Transmission electron microscopy (TEM) results identified dislocation cell structure immediately beneath the fracture surface of the Stage I sample, and dislocation tangles in the Stage II sample corresponding to fracture at high and low plastic strain amplitudes respectively..
79.	Osamu Takakuwa, Michio Yoshikawa, Saburo Matsuoka, Junichiro Yamabe, Saburo Okazaki, Hisao Matsunaga, Temperature dependence of fatigue crack growth in low-alloy steel under gaseous hydrogen, ASME 2018 Pressure Vessels and Piping Conference, PVP 2018, 2018.01, In order to elucidate the temperature dependence of hydrogen-enhanced fatigue crack growth (FCG), the FCG test was performed on low-alloy Cr-Mo steel JIS-SCM435 according to ASTM E647 using compact tension (CT) specimen under 0.1 - 95 MPa hydrogen-gas at temperature ranging from room temperature (298 K) to 423 K. The obtained results were interpreted according to trap site occupancy under thermal equilibrium state. The FCG was significantly accelerated at RT under hydrogen-gas, that its maximum acceleration rate of the FCG was 15 at the pressure of 95 MPa at the temperature of 298 K. The hydrogen-enhanced FCG was mitigated due to temperature elevation for all pressure conditions. The trap site with binding energy of 44 kJ/mol dominated the temperature dependence of hydrogen-enhanced FCG, corresponding approximately to binding energy of dislocation core. The trap site (dislocation) occupancy is decreased with the temperature elevation, resulting in the mitigation of the FCG acceleration. On the basis of the obtained results, when the occupancy becomes higher at lower temperature, e.g. 298 K, hydrogen-enhanced FCG becomes more pronounced. The lower occupancy at higher temperature does the opposite..
80.	松永久生, 高越大輝, 髙桑脩, 山辺純一郎, 松岡三郎, 山田紘樹, 宇山英幸, 軸受鋼SUJ2の水素侵入特性に及ぼす表面処理の影響, 日本鉄鋼協会2017年度「水素脆化の基本要因と特性評価」研究会, 2017.12.
81.	小川祐平, Domas BIRENIS, 松永久生, 髙桑脩, 山辺純一郎, 水素ガス中における純鉄の疲労き裂進展加速機構に関する微視的検討, 日本材料学会九州支部第4回学術講演会, 2017.11.
82.	坂田優太, 髙桑脩, 岡﨑三郎, 山辺純一郎, 松岡三郎, 松永久生, 竹腰正雄, 砂川英生, 小林悌宇, 沖田耕一, Ni基超合金718の疲労寿命限度特性に及ぼす内部水素の影響, 日本材料学会九州支部第4回学術講演会, 2017.11.
83.	髙桑脩, 小川祐平, 山辺純一郎, 松永久生, 鉄基超合金A286の破壊形態に及ぼす内部水素の影響, 日本機械学会M&M2017材料力学カンファレンス, 2017.09.
84.	髙桑脩, 山辺純一郎, 松永久生, 古谷佳之, 松岡三郎, 外部水素と内部水素に着目した低合金鋼および炭素鋼の破壊形態の検証, 日本鉄鋼協会第174回秋季講演大会, 2017.09.
85.	小川祐平, Domas BIRENIS, 松永久生, 髙桑脩, 山辺純一郎, マルチスケール観察手法を用いた純鉄の水素助長疲労き裂進展機構に関する検討, 日本鉄鋼協会第174回秋季講演大会, 2017.09.
86.	髙桑脩, 松永久生, 山辺純一郎, 高圧水素ガス環境へのSUS304の適合性評価, 日本鉄鋼協会「水素脆化の基本要因と特性評価」研究会, 2017.08.
87.	髙桑脩, 山辺純一郎, 松永久生, 古谷佳之, 松岡三郎, 外部水素と内部水素に着目したオーステナイト系ステンレス鋼のSSRT破壊形態の分類, 日本鉄鋼協会第173回春季講演大会, 2017.03.
88.	髙桑脩, 山辺純一郎, 松永久生, 古谷佳之, 松岡三郎, 外部水素と内部水素に着目したオーステナイト系ステンレス鋼の引張特性に及ぼす水素の影響, 東京オリンピックで水素社会を実証するための技術課題に関する研究分科会, 2017.02.
89.	Junichiro Yamabe, Osamu Takakuwa, Tohru Awane, Saburo Matsuoka, Hydrogen-assisted degradation of high-strength stainless steel with a newly developed aluminum-based coating in high-pressure hydrogen gas environment, ASME 2017 Pressure Vessels and Piping Conference, PVP 2017, 2017.01, [URL], The paper presents the hydrogen-entry, tensile, and fatigue properties of a precipitation-hardened martensitic stainless steel, JIS-SUS630, with a newly developed coating, whose thickness ranges from 10 to 20 μm. The newly developed coating consists of alumina, aluminum, and ferroaluminum, and has an excellent resistance to hydrogen entry in 100-MPa hydrogen gas at 270°C. The hydrogen entry in the coated specimen occurred under a diffusion-controlled process and the effective hydrogen diffusivity was approximately one thousandth of that of the base steel. Although the hydrogen diffusivity of JIS-SUS630 was two orders of magnitude larger than that of JIS-SUS304, the effective hydrogen diffusivity of the coated JIS-SUS630 was nearly equal to that of the coated SUS304. In our previous study with secondary-mass ion spectroscopy (SIMS), the coating's excellent resistance to hydrogen entry was attributed to interfacial hydrogen trapping between the aluminum and ferroaluminum layers. The experimental result obtained in this study suggested that the excellent resistance to hydrogen entry demonstrated by the developed coating can be attributed to the reduction in the permeation area induced by the interfacial trapping of hydrogen. The tensile tests of a smooth, round-bar specimen and fatigue tests of a circumferentially notched specimen with exposure to 100-MPa hydrogen gas at 270°C were performed in air at room temperature (RT). The test results showed that the tensile and fatigue properties of the coated specimens were not degraded by hydrogen exposure, whereas those for the non-coated specimens were significantly degraded. Hydrogen-pressure cycle tests of the coated, tubular specimens with an inner notch were also carried out with 95-MPa hydrogen gas at 85°C, demonstrating that the fatigue life of the tubular specimen was improved by the developed coating..
90.	Osamu Takakuwa, Junichiro Yamabe, Hisao Matsunaga, Yoshiyuki Furuya, Saburo Matsuoka, Recent progress on interpretation of tensile ductility loss for various austenitic stainless steels with external and internal hydrogen, ASME 2017 Pressure Vessels and Piping Conference, PVP 2017, 2017.01, [URL], Slow-strain rate tensile (SSRT) tests on various metals having γ-Fe phase; Type 304 and 316L stainless steels, HP160 high strength stainless steel, and A286 Fe-based super alloy were conducted in external hydrogen and with internal hydrogen. The external hydrogen indicates non-charged specimens tested in high-pressure hydrogen-gas environment, whereas the internal hydrogen indicates hydrogen-charged specimens, with uniform distribution of hydrogen, tested in inert gas. The hydrogen distribution was calculated based on the measured hydrogen diffusivity and solubility. The fracture morphologies were observed by scanning electron microscopy (SEM). For Types 304, 316L, and HP160 the relative reduction in area (RRA of the steels was successfully reproduced by the nickel equivalent, Ni_eq, showing the higher Ni_eq, the lager RRA. Furthermore, at a low Ni_eq, the RRA of the steel with external hydrogen was nearly equal to that with internal hydrogen. In contrast, at a high Ni_eq, the RRA of the steel with internal hydrogen was slightly degraded by hydrogen, RRA ∼ 0.8, whereas that in external hydrogen was not degraded, RRA ∼ 1. For A286, despite a high Ni_eq, the RRA of the alloy with internal hydrogen was significantly degraded by hydrogen, RRA ∼ 0.5. The fracture morphologies were categorized into four types: quasi-cleavage fracture associated with hydrogen-assisted surface cracks; ordinary void formation with no hydrogen effect; small-void formation associated with void sheet enhanced by hydrogen; facet formation induced by hydrogen. These categorized morphologies could be interpreted in terms of hydrogen distribution (internal or external hydrogen), austenitic stability (a low or high Ni_eq), and microstructure (solution or precipitation-hardened treatment)..
91.	36. 髙桑脩, 山辺純一郎, 松永久生, 古谷佳之, 松岡三郎, SSRT特性に及ぼす外部水素と内部水素の影響, 日本鉄鋼協会「水素脆化の基本要因と特性評価」研究会, 2016.11.
92.	Osamu Takakuwa, Yuta Mano, Hitoshi Soyama, Effect of hydrogen on the micro- and macro-strain near the surface of austenitic stainless steel, 2014 International Conference on Materials Science and Engineering Technology, MSET 2014, 2014.01, [URL], The objective of this study is to evaluate the effect of hydrogen on the micro- and macro-strain of austenitic stainless steel using X-ray diffraction. When hydrogen is trapped in lattice sites, it can affect both the micro- and macro-strain. The micro-strain was evaluated through fitting profiles to measured X-ray diffraction profile using a fundamental parameter method. The macro-strain, i.e., the residual stress, was evaluated by a 2D method using a two-dimensional PSPC. The experimental samples were charged with hydrogen by a cathodic charging method. The results revealed that the induced residual stress was equi-biaxial and compressive, and that the micro-strain increased. Both of these varied rapidly with increasing hydrogen charging time. Saturation occurred at a compressive stress of around 130 MPa. On reaching saturation, the hydrogen charging was terminated and desorption of hydrogen began at room temperature. Then, the strains decreased and the compressive stress reverted, ultimately, to a tensile stress of 180 MPa. Martensitic transformation occurred due to hydrogen charging and this had a significant effect on the X-ray diffraction profile..
93.	Osamu Takakuwa, Yuta Mano, Hitoshi Soyama, Effect of indentation load on vickers hardness of austenitic stainless steel after hydrogen charging, ASME 2014 Pressure Vessels and Piping Conference, PVP 2014, 2014.01, [URL], In order to reveal the effect of indentation load on Vickers hardness of austenitic stainless steel after hydrogen charging, the Vickers hardness measurements have been conducted with three different indentation load of 0.49, 1.96 and 9.80 N on the surface of type 316L austenitic stainless steel after hydrogen charging. Relationship between plastic deformation behavior during indentation process and hydrogen absorption behavior was revealed. In the Vickers hardness test, Vickers hardness keeps same value though the indentation load varies. Needless to say, the value did not depend on magnitude of the indentation load before hydrogen charging in the present study. However, the Vickers hardness increased along with hydrogen charging time and, interestingly, the increase in the Vickers hardness due to the presence of hydrogen depends on magnitude of the indentation load. In the load of 0.49 N and 9.80 N, the Vickers hardness has a maximum value of 3.04 and 2.04 GPa which is 1.58 and 1.15 times larger than value of 1.73 and 1.70 GPa before hydrogen charging, respectively. The hydrogen-induced hardening behavior observed by the Vickers hardness tests employing different indentation load would be evaluated by the relationship between the plastic deformation depth and the hydrogen absorption depth..
94.	H. Soyama, Osamu Takakuwa, A. Naito, Effect of nozzle shape for high injection pressure on aggressivity of cavitating jet, 21st International Conference on Water Jetting: Looking to the Future, Learning from the Past, 2012.12, A cavitating jet can be used for cutting and a material testing to evaluate cavitation erosion resistance of materials. In order to use the cavitating jet more efficiently, effect of nozzle shape should be investigated, as aggressivity of the jet was affected by the nozzle shape. In the present paper, erosion rate, intensity of luminescence and acoustic power were measured to evaluate the aggressivity of the jet from various types of the nozzle for high injection pressure. It was found that the aggressivity of the jet was drastically changed by the nozzle shape..
95.	Osamu Takakuwa, Masaaki Nishikawa, Hitoshi Soyama, Suppression of fatigue crack growth in austenite stainless steel by cavitation peening, 9th International Conference on Fracture and Damage Mechanics, FDM 2010, 2011.01, [URL], Cavitation normally causes severe damage in hydraulic machinery such as pumps and turbines by the impact produced by cavitation bubbles collapsing. Although cavitation is known as a factor of erosion, Soyama et al. succeeded in utilizing impacts of cavitation bubble collapsing for surface modification by controlling cavitating jet in the same way as shot peening. The local plastic deformation caused by cavitation impact enhances the fatigue strength of metallic materials, and the surface modification technique utilizing cavitation impact is called "cavitation peening (CP)". It is well known that the peening improves fatigue strength by introducing compressive residual stress on the surface, but little attention has been paid to the behavior of fatigue crack growth of the material which was modified by CP. In the present study, the fatigue behavior of austenite stainless steel with and without CP was evaluated by a plate bending fatigue test, and the results revealed that the compressive residual stress introduced by CP suppresses fatigue crack growth rate by 70 % compared to that without CP..
96.	H. Soyama, N. Yamada, Osamu Takakuwa, Y. Sekine, M. Mikami, Release of micro strain in tool alloy steel by a cavitating jet in air, 19th International Conference on Water Jetting, 2008.12, Cavitation impacts can be utilized to improve material properties such as fatigue strength. In case of such application, cavitation was produced by a cavitating jet. In order to investigate mechanism of surface modification, tool alloy steel was treated by a cavitating jet and the surface was analyzed by using X-ray diffraction methods, i.e., 2D method and a fundamental approach. Residual stress was measured by 2D method and micro strain, which is strain in the grain, was evaluated by a fundamental parameter approach. In the present paper, in order to enhance cavitation impacts, a cavitating jet in air was used for surface treatment of tool alloy steel. It was revealed that a cavitating jet in air can introduce compressive residual stress. It was also shown that micro strain introduced by heat treatment or mechanical finishing was released by a cavitating jet in air..

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