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Masanobu Kubota Last modified date:2024.01.25

Professor / Hydrogen Compatible Materials and Fracture (in Department of Mechanical Engineering, April 2014 - Current), Air Liquide Industrial Chair on Hydrogen Structural Materials and Fracture (in Department of Mechanical Engineering, Oct. 2010 - March 2014)
Advanced Energy Materials Thrust
International Institute for Carbon-Neutral Energy Research


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Homepage
https://kyushu-u.elsevierpure.com/en/persons/masanobu-kubota
 Reseacher Profiling Tool Kyushu University Pure
https://i2cner.kyushu-u.ac.jp/en/teams/materials/
Advanced Energy Materials Thrust, International Institute for Carbon-Neutral Energy (I2CNER), Kyushu University .
http://i2cner.kyushu-u.ac.jp/en/team/team_detail.php?code=2
Hydrogen Materials Compatibility Division, International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University .
Phone
092-802-6720
Academic Degree
Dr. Eng
Country of degree conferring institution (Overseas)
No
Field of Specialization
Strength of engineering materials, Metal fatigue, Fretting fatigue, Hydrogen structural materials
Total Priod of education and research career in the foreign country
00years00months
Outline Activities
I study strength of materials for energy and low-carbon society by experimental approach with many international and interdisciplinary collaborations previously at Hydrogen Materials Compatibility Research Division (until March 2020) and currently Advanced Energy Materials Thrust (from April 2020 - Present), International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University. At the same time, I belong Research Center for Hydrogen Industrial Use and Storage (HYDROGENIUS) as a professor. There, I study fatigue limit in high-pressure hydrogen. Also, I am working at Department of Mechanical Engineering, Kyushu University as a professor. Thanks to the support by Department of Mechanical Engineering, I open a laboratory "Hydrogen Materials Compatibility and Fracture" in the department. I am glad to have time with the students at Department of Mechanical Engineering.

Education: I am (was) in charge of Academic frontier for all undergraduate students, Advanced engineering for international course students, Mechanical engineering experiment for 3rd grade student in Mechanical Engineering course, and Hydrogen energy structural materials for master course students mainly in Mechanical Engineering. Regarding education of student, my goal is as follows. Students can find their own interest in their research. Then, students can pursue science by their original idea and creativity. In my laboratory, the students need to learn computer programing, electric circuit, machining, design and drawing, presentation etc. in addition to strength of materials. For the improvement of my teaching skills, I attend faculty development courses and join Society for Engineering Education, Japan.

Research: Hydrogen embrittlement, which is degradation of material strength due to hydrogen, is the major research interest. Particularly, I put effort into the study on the effect of impurities contained in hydrogen gas on hydrogen embrittlement, degradation of materials strength in high-temperature hydrogen gas. Also, fretting fatigue is one of main research themes. For the study of material strength in the presence of hydrogen, I try to facilitate fusion of the researchers at different fields such as chemistry and thermodynamics. Also, I try to promote fusion of the researchers using different approach such as experiment, modeling and computation. I put emphasis on technology transfer.

(1) Effect of hydrogen on fretting fatigue, fatigue and fracture toughness: To achieve optimization of cost and performance of high-pressure hydrogen containment systems without compromising safety, these studies are being carried out.

(2) Fatigue limit in high-pressure hydrogen gas: We developed a special fatigue testing machine to obtain fatigue limit in high-pressure hydrogen. We are only institute capable for this experiment worldwide.

(3) Degradation of material strength in high-temperature hydrogen: It can be expected that SOFC and SOEC will be extensively used in the near future. These energy and material interconversion devices operate in hydrogen at elevated temperature. Material strength in this extremely aggressive environment should be studied for the safety of those advanced hydrogen technologies.

(4) Fretting fatigue: Fretting fatigue is one of the major factors in the design of machines and structure to prevent catastrophic failure accidents. Mechanism and the method how to evaluate quantitatively are studying with a company.

Social contribution: Chief secretary of Kyushu Branch, The Japan Society of Mechanical Engineers (2021.3 - Present), Steering committee of Kyushu branch of the Japan Society of Materials Science (2008-2015), Editorial committee of journal of Japan Society for Mechanical Engineers (2009-2010), Referee of contributed paper to JSME journal (domestic and international), International symposium (MMYoung and ISFF), Workshops, Board member of the Japan Society of Materials Science (2016-2019)

Technical Program Committee of International Hydrogen Conference 2022 (IHC2022), International cooperation: Local committee (Asia region) of International symposium on fretting fatigue (ISFF 6 - ISFF 10), Planning committee of international symposium for young researchers (M&M div, JSME), ASMP208, VHF-9 and so on.
Research
Research Interests
  • Activation of metallic catalyst by friction
    keyword : Catalyst Carbon monoxide Carbon dioxide Hydrogen Decomposition
    2020.04.
  • Inhibitory effect on hydrogen-assisted degradation of material strength
    keyword : Hydrogen, Fracture, Fatigue, Fretting, Fracture toughness, Impurity
    2014.04.
  • Degradation of material strength in hydrogen at elevated temperature
    keyword : Hydrogen, High temperature, Creep, Fatigue
    2017.04.
  • Fatigue limit in high-pressure hydrogen
    keyword : Hydrogen, Fatigue Limit
    2014.04.
  • study on propagation behavior of small crack in railway wheel materials
    keyword : Small crack, Crack propagation, Threshold, Railway
    2010.04.
  • Development of weld joint for high-pressure hydrogen piping
    keyword : Hydrogen, Welding technique
    2014.04~2017.03.
  • Effect of hydrogen on fracture toughness
    keyword : Hydrogen Fracture toughness
    2010.10~2013.09.
  • Evaluation of fretting fatigue strength of mechanical component received torsion
    keyword : Fretting fatigue, Torsion, Spline, Press Fit
    2008.04Evaluation and improvement of fretting fatigue strength in machine component applied cyclic torsion.
  • Elucidation of mechanism of fretting fatigue strength reduction due to hydrogen
    keyword : Hydrogen, Fretting Fatigue, Mechanism, Reduction of Fretting Fatigue strength, Adhesion, Small cracks
    2007.04Mechanism elucidation of fretting fatigue strength reduction due to hydrogen gas: Fretting fatigue strength decreases in hydrogen gas environment. To clarify the mechanisms, elaborate observations of fretted surface and crack propagation behavior are doing. .
  • Effect of hydrogen gas and absorbed hydrogen on fretting fatigue strength
    keyword : Hydrogen gas, Hydrogen concentration, Fretting fatigue strength
    2003.04The objective of this study is to clarify the effect of hydrogen gas on fretting fatigue strength of the materials used for hydrogen utilization machines and structures. In hydrogen gas environment, fretting fatigue strengths of A286, SUS304 and SUS316L decrease in the long-life region..
  • Study on fretting fatigue in oil-well pipe materials
    keyword : Fretting, Fretting fatigue, Oil-well pipe, Coating, Lubrication
    2016.04.
  • Selection of shape and size of stress-relief groove for improvement of fretting fatigue strenth
    keyword : Fretting fatigue, Stress-relief groove, Improvement of fretting fatigue strength
    2005.04Stress relief groove has been used to improve the fretting fatigue strength of fitted part between mechanical components. However, the applicability of groove has not been fully evaluated and there are insufficient investigations to determine the optimal groove shape. In this study, the evaluation of fretting fatigue strength of specimens which have various shapes of stress relief groove was conducted by fretting fatigue tests and FEM analyses in order to develop an index for the selection of groove shape..
Current and Past Project
  • Establishment of more solid partnership between Norway and Japan through education of PhD students and brain circulation of researchers based on study of hydrogen embrittlement.
  • Education of PhD students are promoted through international collaboration on the research of hydrogen embrittlement.
  • Effect of hydrogen on creep properties and mechanism that hydrogen accelerate creep deformation are studied.
  • Introduction of nitrogen stainless steel and its weld joint is required for high-pressure hydrogen piping. Nitrogen is important alloying element to improve strength and hydrogen compatibility, however, the state of existence may be changed during welding process. This study is aiming at development of weld joint of nitrogen stainless steel which is applicable for high-pressure hydrogen piping. ①Development of welding technique, ②Characterization of microstructure, ③Study on hydrogen compatibility of developed weld joint.
  • ・Study on hydrogen compatibility of engineering steels and alloys
    ・Study on hydrogen compatibility of specific materials to expand allowable pressure range and temperature range
    ・Provision of hydrogen materials data sheets
  • To secure sustainable development of humankind, early realization of low-carbon economy and hydrogen society is necessary. Development of wide range of technologies is indispensable.
  • Comprehensive tie-up between Kyushu University and Hitachi Ltd. Investigations of fatigue strength under high-pressurized hydrogen environment
  • Development of fatigue strength design method for hydrogen utilization machines
  • Development for safe utilization and infrastructure of hydrogen project
  • Integration Technology of Mechanical System for Hydrogen Utilization
Academic Activities
Reports
1. Contact Mechanics and Evaluation of Fretting Fatigue Strength.
2. Contact Mechanics and Evaluation of Fretting Fatigue Strength.
Papers
1. Masanobu Kubota, Ryosuke Komoda, Yuki Nakamura, Improvement of fretting fatigue strength by carbon monoxide and catalyst activation under chemomechanical effects of fretting, Theoretical and Applied Fracture Mechanics, https://doi.org/10.1016/j.tafmec.2022.103460, 121, 103460, 2022.10, It is known that the fretting fatigue strength in hydrogen (H2) gas is lower than that in air. The objective of this study is to mitigate the hydrogen effect during the fretting fatigue test in H2 gas by adding carbon monoxide (CO) to the H2 environment. The expected CO effect was reduction in the hydrogen uptake into the material following deactivation of the catalytic surface where H2 molecules dissociate into H atoms. However, an unexpected result, which was unique in fretting, was obtained. The fretting fatigue test using JIS SUS304 austenitic stainless steel was performed in H2, argon (Ar), 2 vol% CO mixed H2, and 2 vol% CO mixed Ar gases. The fretting fatigue strengths in the CO-mixed gases were significantly improved. For instance, the fretting fatigue life at σa = 240 MPa was 8.8 × 10^5 cycles in the H2 and 10^7 cycles or longer in the CO mixed H2. The cause of the improved fretting fatigue strength was the formation of amorphous carbon between the contacting surfaces during the fretting. The carbon reduced the tangential force coefficient between the contacting surfaces from around 0.6 in the H2 to 0.2 or less in the CO mixed H2. The reduced tangential force resulted in improvement of the fretting fatigue strength. Although the detailed mechanisms of the carbon deposition were unclear, it is plausible that the catalytic action of the metal surface for the CO decomposition into C and O was activated by the effect of fretting, such as removal of the surface oxide layer and other chemomechanical effects. .
2. Andrew Chapman,Elif Ertekin, Masanobu Kubota, Akihide Nagao, Kaila Bertsch, Arnaud Macadre, Toshihiro Tsuchiyama, Takuro Masamura, Setsuo Takaki, Ryosuke Komoda, Mohsen Dadfarnia, Brian Somerday, Alexander Tsekov Staykov, Joichi Sugimura, Yoshinori Sawae, Takehiro Morita, Hiroyoshi Tanaka, Kazuyuki Yagi, Vlad Niste, Prabakaran Saravanan, Shugo Onitsuka, Ki-Seok Yoon, Seiji Ogo, Toshinori Matsushima, Ganbaatar Tumen-Ulzii, Dino Klotz, Dinh Hoa Nguyen, George Harrington, Chihaya Adachi, Hiroshige Matsumoto, Leonard Kwati, Yukina Takahashi, Nuttavut Kosem, Tatsumi Ishihara, Miho Yamauchi, Bidyut Baran Saha, Md. Amirul Islam, Jin Miyawaki, Harish Sivasankaran, Masamichi Kohno, Shigenori Fujikawa, Roman Selyanchyn, Takeshi Tsuji, Yukihiro Higashi, Reiner Kirchheim, and Petros Sofronis, Achieving a Carbon Neutral Future through Advanced Functional Materials and Technologies, Bulletin of The Chemical Society of Japan, https://doi.org/10.1246/bcsj.20210323, 95, 1, 73-103, 2022.01, Current greenhouse gas emissions suggest that keeping global temperature increase below 1.5 degrees, as espoused in the Paris Agreements will be challenging, and to do so, the achievement of carbon neutrality is of utmost importance. It is also clear that no single solution can meet the carbon neutral challenge, so it is essential for scientific research to cover a broad range of technologies and initiatives which will enable the realization of a carbon free energy system. This study details the broad, yet targeted research themes being pioneered within the International Institute for Carbon-Neutral Energy Research (I2CNER). These approaches include hydrogen materials, bio-mimetic catalysts, electrochemistry, thermal energy and absorption, carbon capture, storage and management and refrigerants. Here we outline the state of the art for this suite of technologies and detail how their deployment, alongside prudent energy policy implementation can engender a carbon neutral Japan by 2050. Recognizing that just as no single
technological solution will engender carbon neutrality, no single nation can expect to achieve this goal alone. This study represents a recognition of conducive international policy agendas and is representative of interdisciplinary, international collaboration..
3. Daisuke Takazaki, Toshihiro Tsuchiyama, Ryosuke Komoda, Mohsen Dadfarnia, Brian P. Somerday, Petros Sofronis, Masanobu Kubota , Effect of Hydrogen on Creep Properties of SUS304 Austenitic Stainless Steel, Corrosion, 77, 3, 256-265, 2021.03, The objective of this study is to derive mechanistic insight into the degradation of metals in high-temperature hydrogen in order to enable the safety of evolving hydrogen technologies that operate at elevated temperature. Creep testing was performed in argon and hydrogen gases under absolute pressure of 0.12 MPa at 873 K. The material was JIS SUS304 austenitic stainless steel. Results revealed that the creep life
(time to failure) and creep ductility (strain to failure) of the SUS304 in hydrogen gas and in argon displayed opposite trends. While the creep life (time to failure) of the SUS304 in hydrogen gas was significantly shorter than that in argon, creep ductility (strain to failure) was higher in hydrogen. Associated with the relatively higher creep ductility, evidence of transgranular microvoid coalescence was more prevalent on
fracture surfaces produced in hydrogen compared to those produced in argon. In addition, analysis of the steady-state creep relationships in hydrogen and argon indicated that the same creep mechanism operated in the two environments, which was deduced as dislocation creep. Regarding the mechanisms governing reduced creep life in hydrogen, the effects of decarburization, carbide formation, and the hydrogen-enhanced localized plasticity mechanism were investigated. It was confirmed that these effects were not responsible for the reduced creep life in hydrogen, at least within the creep life range of this study. Alternately, the plausible role of hydrogen was to enhance the vacancy density, which led to magnified lattice diffusion (self-diffusion) and associated dislocation climb. As a consequence, hydrogen accelerated the creep strain rate and shortened the creep life..
4. Ryosuke Komoda, Masanobu Kubota, Aleksandar Tsekov Staykov, Patrick Ginet, Francoise Barbier, Jader Furtado, Inhibitory effect of oxygen on hydrogen-induced fracture of A333 pipe steel, Fatigue and Fracture of Engineering Materials and Structures, 10.1111/ffe.12994, 42, 6, 1387-1401, 2019.06, The effect of oxygen contained in hydrogen gas environment as an impurity on hydrogen environment embrittlement (HEE) of A333 pipe steel was studied through the fracture toughness tests in hydrogen gases. The oxygen contents in the hydrogen gases were 100, 10, and 0.1 vppm. A significant reduction in the J-Δa curve was observed in the hydrogen with 0.1-vppm oxygen. Under given loading conditions, the embrittling effect of hydrogen was completely inhibited by 100 vppm of oxygen. In the case of the hydrogen with 10-vppm oxygen, initially the embrittling effect of hydrogen was fully inhibited, and then subsequently appeared. It was confirmed that 1-vppm oxygen reduced the embrittling effect of hydrogen. The results can be explained by the predictive model of HEE proposed by Somerday et al..
5. Kubota, M., Komoda, R., Furtado, J, The effects of oxygen impurities on fretting fatigue of austenitic stainless steel in hydrogen gas, Proceedings of 2016 Hydrogen Confrerence, Edited by B.P. Somerday and P. Sofronis, ASME, 454-461, 2017.10.
6. 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..
7. 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..
8. Fatigue properties of work-hardened oxygen-free cupper in high-pressure hydrogen.
9. Fundamental Mechanisms Causing Reduction in Fretting Fatigue Strength by Hydrogen
(Effect of Hydrogen on Small Crack Initiation at the Adhered Spot).
10. Fundamental Mechanisms Causing Reduction in Fretting Fatigue Strength by Hydrogen
(Effect of Hydrogen on Small Crack Initiation at the Adhered Spot).
11. "Effects of Multiple Overloads and Hydrogen on High-Cycle Fatigue Strength of Notched Specimen of Austenitic Stainless Steels" in the transactions of the Japan Society for Mechanical Engineers, Ser. A.
12. 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..
13. Mechanism of reductin of fretting fatigue limit in hydrogen gas in SUS304.
14. 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.
15. 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.
16. 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.
17. 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.
18. 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.
19. 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.
20. 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.
21. 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.
22. 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.
23. Fretting Fatigue Properties of SCM435H and SUH660 in Hydrogen Gas Environment by Masanobu KUBOTA, Yasuhiro TANAKA and Yoshiyuki KONDO, Transactions of Japan Society of Mechanical Engineers, Vol .73, No. 736, pp. 1382-1387 (2007.12)
.
24. 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.
25. 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.
26. M. Kubota, N. Noyama, C. Sakae and Y. Kondo, Fretting in Hydrogen gas, Tribology international, 39/10, pp.1241-1247, 2006.10.
27. Effect of hydrogen gas environment on fretting fatigue strength.
28. 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.
29. 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.
30. 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.
31. 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.
32. 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.
Presentations
1. Masanobu Kubota, Daiskuke Takazaki, Ryosuke Komoda, Kentrao Wada, Toshihiro Tsuchiyama, Mohsen Dadfarnia, Brian P Somerday, Petros Sofronis, Creep in High-Temperature Hydrogen, 6th International Conference on Materials and Reliability (ICMR 2022), 2022.12, Virtual zero GHG emission by 2050 is very challenging target. Utilization of high-temperature hydrogen will play a key role in the effort to achieve this ambitious goal. It is known that hydrogen can deteriorate material strength at ambient and sub ambient temperatures (hydrogen embrittlement). On the other hand, there are experimental results and theoretical predictions that no hydrogen embrittlement occurs at high temperature because of weak interaction between hydrogen and defects in the material at high temperature. Nevertheless, reduced creep life in hydrogen at elevated temperature is reported. Regarding the mechanisms that hydrogen affects creep life, it seems that there are no definitive discussions. In this presentation, the result of the creep test of SUS304 austenitic stainless steel and SUY-1 pure iron in hydrogen at 600℃ will be shown. Then, the mechanism of the reduced creep life in hydrogen is discussed based on the examinations of the experimental results and the analysis of an analytical creep deformation model..
2. Masanobu Kubota, Effect of Hydrogen on Creep Properties of Austenitic Stainless Steels and Pure Iron, Third International Forum on Hydrogen Codes, Standards and Safety in United Nations Development Program (UNDP) Hydrogen Industry Conference 2021, 2021.12, To secure the safety of advanced high-temperature hydrogen technologies such as SOFC and SOEC, degradation of material strength in hydrogen at elevated temperature was studied. In the creep test in hydrogen at 873K, the creep life was significantly reduced. .
3. Daisuke Takazaki, Toshihiro Tsuchiyama, Masanobu Kubota, Effect of hydrogen on creep properties of SUS304, HYDROGENIUS, I2CNER, and HydroMate joint research symposium, 2020.01, The objective of this study is to derive mechanistic insight into the degradation of metals in high-temperature hydrogen in order to enable the safety of evolving hydrogen technologies that operate at elevated temperature. Creep testing was carried out in argon and hydrogen gases under absolute pressures of 0.12 MPa at 873 K. The material was JIS SUS304 austenitic stainless steel. Results revealed that the creep life (time-to-failure) and creep ductility (strain-to-failure) displayed opposite trends in hydrogen compared to argon, i.e. creep life was significantly reduced while creep ductility was higher in hydrogen. Associated with the higher creep ductility, evidence of transgranular microvoid coalescence was more prevalent on fracture surfaces produced in hydrogen gas. Regarding the mechanisms governing reduced creep life in hydrogen, the effects of decarburization and carbide formation were investigated. It was confirmed that these effects were minor contributors to the reduced creep life at least within the creep life range of this study. Alternately, it was postulated that hydrogen-stabilized vacancy formation enhanced self-diffusion, leading to accelerated creep strain rate and shortened creep life in hydrogen..
4. Masanobu Kubota, Development of technology and science for materials for high-pressure hydrogen containment system in Japan, Kuwait Symposium on Blue Hydrogen, 2020.12, Steels, stainless steels and other metallic materials are necessary to construct hydrogen chain from hydrogen production to end use via hydrogen storage and transportation. These structural materials for hydrogen service is used under severe conditions in terms of material strength. Because ultra-high pressure (70 MPa for fuel cell vehicles and 82 MPa for hydrogen refueling stations) is used to store and transport hydrogen efficiently (Liquid hydrogen is future option). In addition, hydrogen can degrade material strength (it is called hydrogen embrittlement). Actually, hydrogen embrittlement is difficult problem, because resistance of steel against hydrogen embrittlement is achieved by either alloying of a lot of amount of expensive rare earth metals and lowering material strength. These measures directly increase cost of materials. The materials for hydrogen service should be selected based on scientific knowledge about hydrogen embrittlement while seeing cost of materials. Japan have developed hydrogen technologies with industry and academia based on their strategy road map. The roadmap includes development and research of structural materials. In this presentation, recent history and accomplishments of the national projects of Japan for high-pressure hydrogen materials are introduced. In addition, material science that enables optimization of cost and performance of high-pressure hydrogen containment systems without compromising safety that I2CNER is pursuing is also introduced..
5. 久保田祐信, Effect of Hydrogen on Fatigue Limit, International Forum of Advanced Materials (IFAM) 2019, 2020.09, The objective is to gain a basic understanding of the effect of hydrogen on the fatigue limit. The material was low-alloy steel adjusted to be sensitive to hydrogen embrittlement by heat treatment. A statistical fatigue test was carried out using smooth and deep-notched specimens at a loading frequency of 20 Hz. The environment was laboratory air and hydrogen gas. The pressure of hydrogen gas was 0.1 MPa in gauge pressure. The fatigue limit of the smooth specimen was higher in hydrogen gas than that in air, although the material showed severe hydrogen embrittlement during the SSRT. The fatigue limit of the deep-notched specimen in hydrogen gas was the same as that in air. For the smooth specimen, the fatigue limit was determined by whether or not crack initiated. For the deep-notched specimen, the fatigue limit was determined by whether or not crack propagate. The results can be interpreted as that hydrogen have no significant effect on crack initiation in high-cycle fatigue regime and affected the threshold of crack propagation..
6. Zahra S. Hosseini, Mohsen Dadfarnia, Masanobu Kubota, Akihide Nagao, Brian P. Somerday, Petros Sofronis, Robert O. Ritchie, Mechanistic Model for Fatigue Crack Growth in Hydrogen, TMS2019, 2019.03, Hydrogen accelerated fatigue crack growth is a mode of environmental failure for which a mechanistic model is still lacking. In this work we attempt to develop a fatigue crack propagation model in the Paris regime on the assumption that the underlying mechanism is crack-tip plastic blunting and re-sharpening. In particular, we attempt to predict Paris law behavior by accounting for the material constitutive behavior in response to cyclic loading and using inputs that can be obtained from macroscopic experiments such as the uniaxial cyclic straining. The model is tested against predictions of the response due to overload and varying hydrostatic constraint. Lastly we investigate the role of hydrogen on crack propagation by considering the effect of hydrogen on the hardening response and the kinetics of hydrogen uptake..
7. Effects of coating and lubrication on fretting fatigue properties of oil-well pipe material.
8. The Effect of Carbon Monoxide Inhibitor against the Accelerated Fatigue Crack Growth in Gaseous Hydrogen and its Loading Frequency Dependency.
9. Masanobu Kubota, Xuesong Cui, Ryosuke Komoda, Hiroshi Wakabayashi and Yasuhisa Tanaka, Effects of Hydrogen and Weld Defect on Tensile Properties of SUH660 and SUS316L Different Materials Welding Joints, 2018 3rd International Conference on Design, Materials and Manufacturing (ICDMM 2018), 2019.06, This document explains and demonstrates how to prepare your camera-ready manuscript for Trans Tech Publications. The best is to read these instructions and follow the outline of this text. The text area for your manuscript must be 17 cm wide and 25 cm high (6.7 and 9.8 inches, resp.). Do not place any text outside this area. Use good quality, white paper of approximately 21 x 29 cm or 8 x 11 inches (please do not change the document setting from A4 to letter). Your manuscript will be reduced by approximately 20% by the publisher. Please keep this in mind when designing your figures and tables etc..
10. Effect of material strength on inhibitory effect of carbon monoxide on hydrogen-assisted fracture
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11. Masanobu Kubota, Ryosuke Komoda, Jader Furtado, The effect of hydrogen on fretting fatigue strength of austenitic stainless steels, The 9th National Conference on Pressure Vessel Technology (NCPVT), 2017.11, 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. Fretting fatigue strength of austenitic stainless steels was significantly reduced in hydrogen gas. 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 causes 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 effects of hydrogen and oxygen addition to hydrogen on the fretting fatigue strength. For the fretting fatigue test, a controlled method to add ppm-level oxygen to a hydrogen environment was firstly 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 was significantly lower in hydrogen gas than in air. Fretting removed surface oxide layer. It caused two primary consequences, enhancement of hydrogen entry and local adhesion between contacting surfaces. The adhesion resulted severe cyclic plastic strain at the adhered spot. It facilitated formation of small cracks. In addition, microstructural change from austenite to martensite was also induced by the cyclic plastic strain. The reduced fretting fatigue strength in hydrogen was synergistically caused by chemical, physical and mechanical processes. The fretting fatigue strength in the oxygen/hydrogen mixtures was significantly lower than that in the high-purity hydrogen. Since addition of oxygen to hydrogen environment usually mitigate the effect of hydrogen, the results obtained were opposite. 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 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. As the result that the oxidation behavior was changed, the fretting fatigue strength was reduced by the addition of oxygen..
12. 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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13. 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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14. 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..
15. 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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16. 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..
17. 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..
18. 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..
19. 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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20. Factors affect fretting fatigue propertoes in hydrogn.
21. 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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22. 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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23. Fatigue properties of ultra-fine grain austenitic stainless steel and effect of hydrogen.
24. 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..
25. 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..
26. 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..
27. 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..
28. A study on the damage caused by repetitive open-close movement in a high-pressure hydrogen gas valve.
29. Effects of Multiple Overloads and Hydrogen on High-Cycle Fatigue Strength of Notched Specimen of Austenitic Stainless Steel and Prediction of Reduction of Fatigue Limit
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30. Effects of Notch Root Radius and Stress Ratio on the Behavior of Short Crack at Notch Root.
31. Effect of 10MPa Hydrogen gas environment on high-cycle fatigue properties of carbon steels.
32. "Effect of Hydrogen on Fretting Fatigue Strength of SUS316L Austenitic Stainless Steel" presented at JSME Kyushu branch annual technical meeting 2011 took place in Ito campus, Kyushu University.
33. Effectiveness of combination of press-fit for improvement of fatigue strength of splined shaft.
34. Effect of Hydrogen on Fretting Fatigue in Austenitic Stainless Steels.
35. Improvement of Fretting Fatigue Strength by Hybrid Joint.
36. Mechanism of Reduction of Fretting Fatigue Limit in Hydrogen Gas in SUS304.
37. Optimization of Shape of Stress-relief Groove for Improvement of Fretting Fatigue Strength.
38. Effect of Hydrogen on the Reduction of Fatigue Strength by Multiple Overloading.
39. Mechanism of Reduction of Fretting Fatigue Limit in Hydrogen Gas Environmet.
40. Contact Mechanics and Evaluation of Fretting Fatigue Strength .
41. The effect of hydrogen gas environment on fretting fatigue strength of materials used for hydrogen utilization machines
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42. Fretting and Fatigue.
43. Evaluation of Fretting Fatigue Strength and Fatigue Design Method.
44. The effect of hydrogen gas environment on fretting fatigue strength of materials used for hydrogen utilization machines
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45. Fretting and Fatigue
Masanobu Kubota.
46. Fretting fatigue and Design Method
Masanobu Kubota.
47. Effect and Elucidation of Mechanism of Hydrogen Gas Environment on Fretting Fatigue Strength of Hydrogen Utilization Machines’ materials.
48. Evaluation of Fatigue Strength of Fine Copper Wire for Electric Equipment
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Awards
  • Development of environmental-friendly and energy-saving car air-conditioning compressor using downsized power transmission shaft by hybrid joint structure
  • Mechanism of Reduction of Fretting Fatigue Limit in Hydrogen Gas in SUS304
  • Award for the Best Paper 2007, Japan Society of Materials Science
    Effect of stress relief groove shape on fretting fatigue strength and index for the selection of groove shape
  • Studies on effect of influence factors on fretting fatigue and quantitative evaluation of fretting fatigue strength
Educational
Educational Activities
I consider research plans for students by fully utilizing superb international and interdisciplinary research environment of I2CNER such that the students can play a primary role in international arena in their future. I provide research guidance for doctor, master and undergraduate students. I provide students many opportunities of communication with abroad researchers, researchers at domestic and international companies, debate in English in order to develop broad perspectives. Students need many skills and knowledge of design & drawing, machining, experiment, observation, programming, control of devices, presentation and so on.

A lecture of hydrogen energy structural materials is opened for master course's students. I provide students basic knowledge and information about advanced studies related to the effect of hydrogen on strength of metal materials. I have an experiment for 3rd grade students. The subject is torsion test of mild steel and cast iron. This experiment is important to enhance understanding of classroom lectures such as strength of materials, elastic mechanics and engineering materials. For bachelor students, Advanced Engineering (English) and Academic Frontier (Japanese) are opened. Importance of use of hydrogen energy and materials issues for hydrogen utilization technology are introduced.

Math and linear algebra were held in Kyushu Politechnique College until 2006. A lot of examples related with engineering problems are included in order to build up interest.

As an extensive education activity, I have been served several workshops and seminars concerning fretting fatigue, fatigue and hydrogen-materials interactions. Most of the participants are from manufacturing companies. Based on these activities, I have a lot of collaboration with industry.
Social
Professional and Outreach Activities
Many collaborations with industry in terms of analysis and prevention of failure caused by fatigue, fretting fatigue and hydrogen embrittlement were done. Usually failure accident is hidden by the sense of company secret, but in two cases, publications in scientific journal were made. The results of my research were taken into account in some lawsuits as an expert opinion.

For the contribution to regional industry, some collaborative researches were done with small companies in Kyushu area.

I believe that development of real products is the highest goal of our study (Technology transfer). It is very important in terms of relevance of studies.

I served as a board member, journal editors committee, reviewer, managing committee in academic societies. I try to do my best to further development of academic societies.

I held many seminars for citizens, high-school students and engineers in order to educate importance of fatigue, fretting fatigue and hydrogen embrittlement.
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