Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Masanobu Kubota Last modified date:2018.06.09

Professor / Hydrogen Compatible Materials and Fracture (April 2014 - Current), Air Liquide Industrial Chair on Hydrogen Structural Materials and Fracture (Oct. 2010 - March 2014) / Hydrogen Materials Compatibility Division / International Institute for Carbon-Neutral Energy Research


Papers
1. MasanobuKubota, ArnaudMacadre, KoichiMori and RyoMori, Fatigue Properties of Ultra-Fine Grain Austenitic Stainless Steel and the Effect of Hydrogen, MATEC Web of Conferences, 165, 2018.05, The fatigue properties of ultra-fine grain austenitic steel(UFG16-10), which has a 1 μm average grain size, were studied as part of the project aimed at the development of high-strength low-cost stainless steels for hydrogen service. The fatigue properties of the UFG16-10 werecompared with that of a coarse grain material with the same chemical composition (CG16-10) and two kinds of commercialsteels, JIS SUS316 and JIS SUH660. The fatigue strength of the UFG16-10was 2.8 times higher than that of the CG16-10. The effect of hydrogenon the fatigue limit of the UFG16-10was not significant. However, the fatigue life of the UFG16-10 was reducedby hydrogen in the short life regime. In the fatigue crack growth test, the UFG16-10showed a good crack growth resistance that was equivalent to that of the SUH660 and significantlyhigher than that of the SUS316. However, the crack growth rate was significantly accelerated by hydrogen. The cause of the hydrogen-assisted fatigue crack growth of the UFG16-10was transformation of the microstructure at the crack tip from austenite to strain-induced martensite.This wasalso the cause of the reducedfatigue life of the hydrogen-charged UFG16-10..
2. Ryosuke Komoda, Masanobu Kubota, Aleksandar Staykov, Patrick Ginet, Francoise Barbier, Jader Furtado , Inhibition of hydrogen environment assisted cracking by small amount of oxygen contained in hydrogen gas, Proceedings of the 6th International Conference on Crack Path (CP2018), 2018.08, Fracture toughness tests of a pipe steel were conducted in hydrogen environment. The crosshead speed was 2.0 × 10-5 mm/s. The gas pressure was 0.6 MPa. The temperature was kept at 293 K. Two gas systems were used to investigate the small amount of oxygen on hydrogen environment assisted cracking (HEAC). One is a closed gas system, where hydrogen gas is stored in the gas chamber. In this system, oxygen content in the gas chamber gradually increased with time and reached 1 vppm during the test. Another is an open gas system, where high-purity hydrogen gas is continuously supplied into the gas chamber. In this system, the oxygen content in the gas chamber can be kept at 0.1 vppm. The fracture toughness in the hydrogen with 0.1 vppm oxygen was significantly lower than that in air. The fracture toughness in the hydrogen with the maximum oxygen content of 1 vppm was higher than that in the hydrogen with 0.1 vppm oxygen. 1 vppm oxygen partially inhibited the HEAC. Owing to detailed analysis of the fracture toughness test results, the critical oxygen content to appear the inhibitory effect of oxygen under the test conditions could be estimated as 0.3 vppm..
3. Masanobu Kubota, Xuesong Cui, Ryosuke Komoda, Hiroshi Wakabayashi and Yasuhisa Tanaka , Effects of hydrogen and weld defect on tensile properties of SUH660 and SUS316L welded joints, Proceedings of 3rd International Conference on Design, Materials and Manufacturing (ICDMM2018), 2018.08, The effect of hydrogen on the tensile properties of the SUH660 and SUS316L different materials welded joints was characterized in conjunction with the joint shape and weld defects. The butt welded joint specimen without weld defect fractured at the SUS316L base material, and did not cause hydrogen embrittlement (HE). However, the failure position of the spigot-lap welded joint specimen moved from the SUS316L base material to the weld part when hydrogen charging was applied. This resulted in a significant reduction of the elongation. It was presumed that the HE was induced by the stress concentration due to the weld shape. The weld defect induced HE in both joints. The weld defect was produced by incomplete penetration. It also caused incomplete mixing of the weld metal. Consequently, filler nickel segregated around the weld defect, then HE occurred..
4. Komoda, R., Kubota, M., Staykov, A., Ginet, P., Barbier, F., Furtado, J, Inhibition of hydrogen embrittlement of Cr-Mo steel by the addition of impurities to hydrogen environment and the effect of material strength, Proceedings of International Ocean and Polar Engineering Conference 2018 (ISOPE-2018), 2018.06, The effect of impurities, added to hydrogen environment, on hydrogen embrittlement (HE) was investigated in association with the effect of material strength. Addition of CO and O2 deactivated the HE. O2 prevented the HE with lower concentration than CO. Material with higher strength required larger amount of impurities to prevent the HE. Reduction of hydrogen uptake was the primary result of the addition of the impurities, but a certain amount of hydrogen uptake occurred when the HE was completely inhibited. Discussion regarding essential HE mechanisms for the fracture morphologies was required to interpret the effect of material strength..
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. Komoda, R., Morita, N., Nakashima, F., Kubota, M., Sawada, R., Development of new measurement method applying mems technology for relative slip range during fretting fatigue test in hydrogen, Proceedings of 2016 Hydrogen Confrerence, Edited by B.P. Somerday and P. Sofronis, ASME, 454-461, 2017.10.
7. 髙﨑 大裕, 久保田 祐信, 薦田 亮介, 奥 洋介, 杉野 正明, 牧野 泰三, Effect of contact pressure on fretting fatigue failure of oil-well pipe material, International Journal of Fatigue, https://doi.org/10.1016/j.ijfatigue.2017.03.024, 110, 1, 67-74, 2017.08, In a traditional way of oil-well development, casing pipes were laid into a hole drilled beforehand. Recently, a new technology that drilling and laying of casing pipes are simultaneously done by casing pipes a drill bit is at-tached to the top pipe has been developed. The thread joints connecting pipes receive bending rotating load during drilling, and then fretting fatigue is concerned at the thread joints. Based on the results of the full-scale fatigue test of a thread joint, there were two failure modes. The first one was fatigue failure at the thread corner. The second one is fretting fatigue fail-ure at the middle of the contact part of the threads. Fretting fatigue cracks frequently originate at the contact edge because of severe stress concentration. For this fretting fatigue failure mode, many approaches for quantitative evalua-tion of the fretting fatigue strength have been developed. On the other hand, the fretting fatigue crack dur-ing the full scale test of the thread joint was formed at the middle of the contact part. Similar failure mode can be seen in the fretting fatigue with relatively lower con-tact pressure, but quantitative understanding has not yet been achieved..
8. 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..
9. 奥 洋介, 杉野 正明, Yoshinori Ando, 牧野 泰三, 薦田 亮介, 髙﨑 大裕, 久保田 祐信, Fretting Fatigue on Thread Root of Premium Threaded Connections, Tribology International, http://dx.doi.org/10.1016/j.triboint.2016.10.021, 108, 111-120, 2017.04, Identification of the fatigue failure mode of the premium threaded connection for Oil Country Tubular Goods pipes was conducted via full-scale fatigue tests. A through-wall crack was found at the imperfect thread root of the male embodiment, but the crack initiation site depended on the stress level. At relatively higher stress amplitude region, the crack originated from the thread rounded corner by stress concentration. At relatively lower stress amplitude region, the crack originated at the middle of the thread root because of fretting fatigue. To investigate the fretting fatigue mechanism in the threaded connection, a fundamental fretting fatigue test was conducted. This test achieved the fretting fatigue failure at the middle of the contact surface under large gross slip condition..
10. 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, Proc. the Asian Conference on Experimental Mechanics 2016 (ACEM 2016), 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. The first one was the fatigue failure at the thread corner radius, which has been already quantitatively evaluated. 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..
11. 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..
12. 薦田 亮介, 久保田 祐信, Jader Furtado, Effect of addition of oxygen and water vapor on fretting fatigue properties of an austenitic stainless steel in hydrogen, Tribology International, http://dx.doi.org/10.1016/j.ijhydene.2014.12.129, 40, 16868-16877, 2015.12, JIS SUS304 fretting fatigue test was done in high-purity hydrogen, an oxygenehydrogen mixture and humidified hydrogen. The fretting fatigue strength in hydrogen was drastically changed depending onthe oxygen level. Basedonthe XPS(X-ray photoelectron spectroscopy) analysis of the fretted surface, it was found that the fretting removed the original protection layer of the stainless steel, however, the addition of water vapor or ppm-level of oxygen produced an oxide layer on the fretted surface during the fretting that surpassed the removal effect of the initial oxide layer by fretting. In fact, a strong adhesion between the contacting surfaces occurred and no fretting wear particles were observed in the high-purity hydrogen. On the other hand, oxidized fretting wear particles were found in the oxygen-hydrogen mixture. Based on the geometry of contact used in this study, a severe concentration of the contact pressure arouse at the contact edge. This produces a compressive stress field in the specimen where the crack growth was suppressed. This stress concentration was relieved when fretting wear occurs. Therefore, the change in the fretting fatigue strength in hydrogen by the addition of oxygen is closely related to the change in the wear behavior..
13. 松本 拓哉, 久保田 祐信, 松岡 三郎, Patrick Ginet, Jader Furtado, Francois Barbier, Threshold stress intensity factor for hydrogen-assisted cracking of Cr-Mo steel used as stationary storage buffer of a hydrogen refueling station, Proc. International Conference on Hydrogen Safety (ICHS2015), 2015.10, In order to determine appropriate value for threshold stress intensity factor for hydrogen-assisted cracking, KIH, constant-displacement and rising-load tests were conducted in high-pressure hydrogen gas for JIS-SCM435 low alloy steel (Cr-Mo steel) used as stationary storage buffer of a hydrogen refuelling station with 0.2 % proof strength and ultimate tensile strength equal to 772 MPa and 948 MPa respectively. Thresholds for crack arrest under constant displacement and for crack initiation under rising load were identified. The crack arrest threshold under constant displacement was 44.3 MPa·m1/2 to 44.5 MPa·m1/2 when small-scale yielding and plane-strain criteria were satisfied and the crack initiation threshold under rising load was 33.1 MPa·m1/2 to 41.1 MPa·m1/2 in 115 MPa hydrogen gas. The crack arrest threshold was roughly equivalent to the crack initiation threshold although the crack initiation threshold showed slightly more conservative values. It was considered that both test methods could be suitable to determine appropriate value for KIH for this material..
14. 森 功一, 久保田 祐信, MACADRE ARNAUD PAUL ALAIN, Fatigue properties of ultra-fine grain austenitic stainless steel and effect of hydrogen, Proc. Third Japan-China Joint Fatigue Symposium , 2014.11, The fatigue properties of ultra-fine grain austenitic steel (UFG), which has a 1m average grain size, were studied. The effect of hydrogen was also investigated using hydrogen-charged material. The fatigue strength of the UFG was 2.8 times higher than that of coarse grain material which has an average grain size of 21m. The effect of hydrogen charge on the fatigue strength of the UFG was not significant. The fatigue crack growth resistance of the UFG is remarkably improved compared with that of SUS316. The crack path of the UFG was very straight, while that of the coarse grain materials was meandering and branching. The development of slip bands at the crack tip was extremely reduced in the UFG than in the coarse grain materials. It was presumed that the significant improvement of the fatigue properties of the UFG was achieved by the fact that the ultra-fine grains suppressed the slip deformation at the crack tip, and as a conse-quence, the crack opening displacement might decrease. .
15. 薦田 亮介, 久保田 祐信, 近藤 良之, Jader Furtado, Effect of oxygen addition on fretting fatigue strength in hydrogen of JIS SUS304 stainless steel, Tribology International, http://dx.doi.org/10.1016/j.triboint.2014.02.025, 76, 92-99, 2014.08, The mechanisms that cause a significant reduction in the fretting fatigue strength of SUS304 stainless steel in gaseous hydrogen is discussed focusing on the adhesion between contact surfaces and crack nucleation. The reduction in the fretting fatigue strength in hydrogen was partially mitigated by the prevention of the adhesion by the addition of oxygen. To characterize the effect of hydrogen on the fretting fatigue crack nucleation, fatigue tests carried out in air and in hydrogen, and finite element analyses were conducted. The crack nucleation limit in both tests was significantly lower in hydrogen than in air. The role of hydrogen in the fretting fatigue crack nucleation is another cause of the reduced fretting fatigue strength of SUS304 steel in hydrogen..
16. 薦田 亮介, 吉開 巨都, 久保田 祐信, Jader Furtado, Reduction in Fretting Fatigue Strength of Austenitic Stainless Steels due to Internal Hydrogen, Advanced Materials Research, 891-892, 891-896, 2014.03, Fretting fatigue is one of the major factors in the design of hydrogen equipment. The effect of internal hydrogen on the fretting fatigue strength of austenitic stainless steels was studied. The internal hydrogen reduced the fretting fatigue strength. The reduction in the fretting fatigue strength became more significant with an increase in the hydrogen content. The reason for this reduction is that the internal hydrogen assisted the crack initiation. When the fretting fatigue test of the hydrogen-charged material was carried out in hydrogen gas, the fretting fatigue strength was the lowest. Internal hydrogen and gaseous hydrogen synergistically induced the reduction in the fretting fatigue strength of the austenitic stainless steels. In the gaseous hydrogen, fretting creates adhesion between contacting surfaces where severe plastic deformation occurs. The internal hydrogen is activated at the adhered part by the plastic deformation which results in further reduction of the crack initiation limit..
17. 久保田 祐信, High-Cycle Fatigue Properties of Carbon Steel and Work-Hardened Oxygen Free Copper in High Pressure Hydrogen, Advanced Materials Research, 891-892, 575-580, 2014.03, The high-cycle fatigue properties of 0.35 % carbon steel and work-hardened oxygen-free copper in 10MPa hydrogen were studied. The fatigue limit of the carbon steel in hydrogen was almost the same as that in air. The fatigue strength at 107 cycles of the copper was higher in hydrogen than in air. The fatigue life of both materials is longer in hydrogen than in air. The reason was the delays in the crack initiation and the early propagation of the cracks in hydrogen. For both materials, the detrimental effect on the fatigue strength due to the hydrogen environment was small, however, it was determined that hydrogen participates in the slip deformation. The morphology of the slip bands was specific in hydrogen. In the copper, the slip bands, which are non-viable in air, developed in hydrogen..
18. 青木 辰郎, 池宮 秀也, 久保田 祐信, Yoshiyuki Kondo, EFFECT OF HYDROGEN ON FRACTURE TOUGHNESS OF LOW ALLOY STEELS
, Proceedings of 2012 Hydrogen Conference, 173-181, 2014.02, A fracture toughness test in air under continuous hydrogen charge was performed using four kinds of low alloy steels. The reduction in fracture toughness JIC was characterized in terms of the effect of material, hardness and loading rate. The reduction in JIC was significant when a slower loading rate was used and a harder material was used. However, the 3.5NiCrMoV steel showed relatively less reduction in JIC compared with other materials even when the hardness was higher than that of other materials. The fracture surface was changed from dimpled to quasi-cleavage when the reduction in JIC was significant. .
19. 久保田 祐信, 足立裕太郎, 白石 悠貴, 薦田 亮介, Jader Furtado, EFFECT OF HYDROGEN AND ADDITION OF OXYGEN ON FRETTING FATIGUE PROPERTIES, Proceedings of 2012 Hydrogen Conference, 391-399, 2014.02, The fretting fatigue strength of SUS304 was more significantly reduced in hydrogen than in air. One of the causes was adhesion between the contacting surfaces and formation of many small cracks. In the adhesion mimicked fatigue test, hydrogen assisted in the crack initiation. This is another reason for the reduced fretting fatigue strength in hydrogen. The effect of oxygen addition to hydrogen was also investigated. An increase in the fretting fatigue strength was found in the oxygen-hydrogen mixture. The friction force coefficient was reduced in the oxygen- hydrogen mixture. The critical maximum shear stress range to crack initiation was higher in the oxygen-hydrogen mixture than in only hydrogen. These are the possible reasons for the increase in the fretting fatigue strength in the oxygen-hydrogen mixture..
20. Fatigue properties of work-hardened oxygen-free cupper in high-pressure hydrogen.
21. Fundamental Mechanisms Causing Reduction in Fretting Fatigue Strength by Hydrogen
(Effect of Hydrogen on Small Crack Initiation at the Adhered Spot).
22. Fundamental Mechanisms Causing Reduction in Fretting Fatigue Strength by Hydrogen
(Effect of Hydrogen on Small Crack Initiation at the Adhered Spot).
23. "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.
24. "Effect of Contact Conditions on Growth of Small Crack in Fretting Fatigue" in the transactions of the Japan Society for Mechanical Engineers, Ser. A.
25. 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..
26. Masanobu Kubota, Kyohei Kuwada, YasuhiroTanaka, YoshiyukiKondo, Mechanism ofreductionoffrettingfatiguelimitcausedbyhydrogengas in SUS304austeniticstainlesssteel, Tribology International, 44, 1495-1502, 2011.10.
27. Tatsuro AOKI, Hideya IKEMIYA, Masanobu KUBOTA, and Yoshiyuki KONDO, Fracture Toughness of Low Alloy Steels in Absorbed Hydrogen Condition, 2nd Japan-China Joint Symposium on Fatigue of Engineering Materials and Structures, 65-68, 2011.10.
28. "Effect of Heat Treatment on the Hydrogen Enhanced Fatigue Crack Propagation of Low Carbon Steel S25C" in the journal of the Japan Society of Materials Science.
29. Masanobu Kubota, Toru Sakuma, Junichiro Yamaguchi and Yoshiyuki Kondo, Effects of hydrogen and multiple overloads on the fatigue strength of notched component
, Proceedings of International Conference on Advanced Technology in Experimental Mechanics 2011 (ATEM11), 2011.09.
30. Shunsuke KATAOKA, Hiroaki ONO, Masanobu Kubota and Yoshiyuki KONDO , Mechanism of improving fretting fatigue strength by stress relief groove, Proceedings of International Conference on Advanced Technology in Experimental Mechanics 2011 (ATEM11), 2011.09.
31. Effects of Small Defect and Hydrogen on Fatigue Strength of Weld-Jointed Tube in Austenitic Stainless Steel.
32. Koshiro Mizobe, Yuki Shiraishi, Msanobu Kubota and Yoshiyuki Kondo , EFFECT OF HYDROGEN ON FRETTING FATIGUE STRENGTH OF SUS304 AND SUS316L AUSTENITIC STAINLESS STEELS, Proceedings of the JSME/ASME 2011 International Conference on Materials and Processing (ICM&P2011), 2011.06.
33. Kanetaka MIYAZAWA, Masato MIWA, Akihiro TASHIRO, Tatsuro AOKI, Msanobu KUBOTA and Yoshiyuki KONDO , INPROVEMENT OF TORSIONAL FRETTING FATIGUE STRENGTH OF SPLINED SHAFT USED FOR CAR AIR CONDITIONING COMPRESSORS BY HYBRID JOINT, Proceedings of the JSME/ASME 2011 International Conference on Materials and Processing (ICM&P2011), 2011.06.
34. Effect of Loading Rate and Tempering Temperature on Fracture Toughness of Hydrogen-Charged Low Alloy Steel SCM440 .
35. Koshiro Mizobe, Masanobu Kubota and Yoshiyuki Kondo, Behavior of short fatigue crack at notch root, Key Engineering Materials, 10.4028/www.scientific.net/KEM.465.515, 465, 515-518, 2011.01, It has been recognized that the threshold stress intensity factor range ΔKth of a short crack is lower than that of a long crack. The short crack behavior in plain specimen has been studied by many researchers. However, the behavior of a short crack at the root of a long notch is not yet clear. The crack closure behavior is considered to be affected by the constraint at notch root and it is dependent on the length and the root radius of notch. In this study, fatigue tests on specimens with short pre-crack at long notch were done and the difference in crack closure behavior was studied. As a result, short crack effect appeared in any notch root radius. In a sharp notch, the crack opening point easily reached its stable condition after a small amount of crack extension. On the contrary in a dull notch, the opening point was lower than the stable condition and consequently short crack effect lasted in relatively wide range of crack extension. The small crack effect of notched specimen was discussed based on crack closure behavior..
36. Yoshiyuki Kondo, Koshiro Mizobe, Masanobu Kubota, Effects of Hydrogen Concentration, Specimen Thickness and Loading Frequency on the Hydrogen Enhanced Crack Propagation of Low Alloy Steel, Key Engineering Materials, 10.4028/www.scientific.net/KEM.465.519, 465, 519-522, 2011.01, Crack propagation of SCM440H low alloy steel under varying load is enhanced by absorbed hydrogen. Substantial acceleration of crack propagation rate up to 1000 times was observed compared with that of uncharged material. The role of factors affecting enhanced acceleration was investigated by changing hydrogen concentration absorbed in metal, specimen thickness and loading frequency. Results are as follows. (1) 0.2 mass ppm diffusible hydrogen in metal was enough to cause enhanced acceleration. The predominant fracture mode showing acceleration was quasi cleavage. (2) In the case of thin specimen thinner than 0.8mm, the tri-axiality of stress is weak, and the enhanced crack propagation did not appear. However, the introduction of side-groove to 0.8mm specimen in order to increase the tri-axiality resulted in enhanced acceleration. (3) Lower loading frequency resulted in higher crack propagation rate in cycle domain. The crack propagation rate in time domain was almost constant irrespective of loading frequency. Enough concentration of hydrogen, tri-axiality and low loading frequency resulted in enhanced acceleration of fatigue crack propagation..
37. Masanobu KUBOTA, Toru SAKUMA, Junichiro YAMAGUCHI and Yoshiyuki KONDO, Effect of Hydrogen Absorption on the Fatigue Strength Reduction caused by Multiple Overloads in Notched Component, Journal of Solid Mechanics and Materials Engineering, 2010.11.
38. Effects of hydrogen concentration, specimen thickness, loading frequency and temperature on the hydrogen enhanced crack propagation of low alloy steel.
39. Yoshiyuki Kondo, Masanobu Kubota and Koshiro Mizobe, Mechanistic Role of Hydrogen on the Enhanced Crack Propagation of Low Alloy Steel SCM440H, Proceedings of the 18th European Conference on fracture (ECF18), 2010.08.
40. Yoshiyuki Kondo, Masanobu Kubota and Katsuya Shimada, Hydrogen Enhanced Crack Propagation of SCM440H Low-alloy Steel under Long-term Varying Load, Engineering Fracture Mechanics, 2010.07.
41. Koshiro MIZOBE, Masanobu KUBOTA, and Yoshiyuki KONDO, Behavior of Short Fatigue Crack at Notch Root, Proceedings of the Sixth International Conference on Materials Structure & Micromechanics of Fracture (MSMF-6), Brno, Czech, 2010.06.
42. Yoshiyuki KONDO, Masanobu KUBOTA and Koshiro MIZOBE, Effects of Hydrogen Concentration, Specimen Thickness, Loading Frequency and Temperature on the Hydrogen Enhanced Crack Propagation of Low Alloy Steel, Proceedings of the Sixth International Conference on Materials Structure & Micromechanics of Fracture (MSMF-6), Brno, Czech, 2010.06.
43. Yuta UEDA, Masanobu KUBOTA and Yoshiyuki KONDO, Effect of Absorbed and Environmental Hydrogen on Short Fatigue Crack Propagation near Threshold in Low Alloy Steel, Journal of solid mechanics and material engineering, 10.1299/jmmp.4.830, 4, 6, 830-839, 2010.06.
44. Mechanism of reductin of fretting fatigue limit in hydrogen gas in SUS304.
45. 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.
46. Effect of absorbed hydrogen and environmental hydrogen on short fatigu ecrack propagation near thershold in low alloy steel.
47. Study on crack opening displacement and hydrogen enhanced crack propagation of low alloy steel.
48. Yoshiyuki Kondo, Masanobu Kubota and Katsuya Shimada, Hydrogen Eenhanced Crack Propagation of SCM440H Low Alloy Steel under Long-term Varying Load, Engineering Fracture Mechanics, Avairable online, 2010.05.
49. 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.
50. 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.
51. 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.
52. Yoshiyuki KONDO, Tomoe Sudo and Masanobu KUBOTA, Critical Crack Size that Causes Retardation of Short Fatigue Crack by Single Overload, Fatigue and Fracture of Engineering Materials and Structures, 32, 10, 856-864, 2009.10.
53. Yoshiyuki KONDO, Takuya OGAWA and Masanobu KUBOTA, Applied Stress Estimation from the Fatigue Fracture Surface in the Near Threshold Region of Fatigue Crack Propagation, Journal of Solid Mechanics and Materials Engineering, Vol.2, No.4, pp.537-548, 2009.10.
54. Yoshiyuki KONDO, Hikaru EDA and Masanobu KUBOTA, Effect of Small Notch and Absorbed Hydrogen on the Fatigue Fracture in Two-step Stress Test within Fatigue Limit Diagram, Fatigue and Fracture of Engineering Materials and Structures, 32, 9, 736-743, 2009.09.
55. 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.
56. 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.
57. Masanobu KUBOTA, Jun-ichiro YAMAGUCHI and Yoshiyuki KONDO, Fatigue Strength Reduction of Notched Component in Hydrogen Gas after Multiple Overloading, European Conference on Fracture 17, Distributed by CD-ROM, 2009.09.
58. Yoshiyuki KONDO, Masanobu KUBOTA and Hikaru EDA, Effect of Notch Shape and Absorbed Hydrogen on the Fatigue Fracture below Fatigue Limit, European Conference on Fracture 17, Distributed by CD-ROM, 2009.09.
59. Tomoe SUDO, Masanobu KUBOTA and Yoshiyuki KONDO, Single Overload Effect in Short Crack, European Conference on Fracture 17, Distributed by CD-ROM, 2009.09.
60. Y. Kondo, H. Eda, M. Kubota, Effect of small notch and absorbed hydrogen on the fatigue fracture in two-step stress test within fatigue limit diagram, Fatigue and fracture of engineering materials, Vol. 32, pp.736-743, 2009.07.
61. Crack Propagation Behavior of SCM440H Low Alloy Steel Enhanced by Hydrogen under Long-term Varying Load and Static Load.
62. Yoshiyuki KONDO, Hikaru EDA and Masanobu KUBOTA, Fatigue Failure under Varying Loading within Fatigue Limit Diagram, Materials Science Forum, Vol.567-568, pp.1-8, 2008.10.
63. Keiko SHISHME, Masanobu KUBOTA and Yoshiyuki KONDO, Effect of Absorbed Hydrogen on the Near Threshold Fatigue Crack Growth Behavior of Short Crack, Materials Science Forum, Vol.567-568, pp.409-412, 2008.10.
64. Effect of Notch Shape and Absorbed Hydrogen on the Fatigue Fracture below Fatigue Limit.
65. Effect of Absorbed Hydrogen on the Near Threshold Fatigue Crack Growth Behavior of Short Crack
(Examination on Low Alloy Steel, Carbon Steel and A286 Alloy).
66. Effect of Load Variation on the Transition of Crack Path in Delayed Failure of 12Cr Steel.
67. Applicability of Applied Stress Estimation Method Based on the Micro Hardness of Fatigue Fracture Surface of Stainless Steel without Striations.
68. 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.
69. 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.
70. 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.
71. 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)
.
72. Effect of Absorbed Hydrogen on Torsional Fatigue Behavior of Stainless Steels (Examination by Continuous Cathodic Polarization), Transactions of Japan Society of Mechanical Engineers, Vol. 73, No. 736, pp.1351-1357 (2007.12).
73. Effect of stress relief groove shape on fretting fatigue strength and index for the selection of groove shape
by Yoshiyuki KONDO, Shunsuke KATAOKA, Masanobu KUBOTA and Chu SAKAE, Journal of the Society of Materials Science "Zairyo", Vol.56, No.12, pp.1156-1162 (2007.12). .
74. 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.
75. 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.
76. Yoshiyuki Kondo, Ogawa Takuya, Masanobu Kubota, Estimation of applied stress in the near threshold region of fatigue crack propagation utilizing high frequency current impedance and hardness measurement, Proceedings of ATEM07, Dstributed by CD-ROM, 2007.09.
77. Kekio Shishime, Masanobu Kubota, Yoshiyuki Kondo, Effect of absorbed hydrogen on the near threshold fatigue crack growth behavior of short crack, Proceedings of MSMF-5, Brno, Czech, 2007.06.
78. Yoshiyuki Kondo, Hikaru Eda, Masanobu Kubota, Fatigue Failure under Varying Loading within Fatigue Limit Diagram, Proceedings of MSMF-5, Bruno,Czech, 2007.06.
79. Masanobu Kubota, Yasuhiro Tanaka, Kyohei Kuwada, Yoshiyuki Kondo, Hydrogen Gas Effect on Fretting Fatigue Properties of Materials Used in Hydrogen Utilization Machines, Proceedings of 5th International Symposium on Fretting Fatigue (ISFF5), Session 6, No. 4, 2007.04.
80. Yoshiyuki Kondo, Chu Sakae, Masanobu Kubota, Syaka Nagamatsu, Fatigue Strength of Small-Notched Specimens under Variable Amplitude Loading within Fatigue Limit Diagram, Fatigue and Fracture of Engineering Materials and Structures, Vol. 30, pp.301-310, 2007.04.
81. Shunsuke Kataoka, Masanobu Kubota, Chu Sakae, Yoshiyuki Kondo, EFFECT OF STRESS RELIEF GROOVE SHAPE ON FRETTING FATIGUE STRENGTH, Asian Pasific Conference on Fracture and Strength (APCFS2006), PP.123, 2006.11.
82. Y. Kondo, C. Sakae, M. Kubota, S. Nagamatsu, Fatigue strength of small-notched specimens under variable amplitude loading within the fatigue limit diagram, Fatigue and Fracture of Engineering Materials and Structures, Vol.30, pp.301-310, 2006.10.
83. M. Kubota, N. Noyama, C. Sakae and Y. Kondo, Fretting in Hydrogen gas, Tribology international, 39/10, pp.1241-1247, 2006.10.
84. Evaluation of Fatigue Crack Propagation Property on the Wheelseat of Normalized Axles for Narrow Gauge Line Vehicle.
85. Y. KONDO, C. SAKAE, M. KUBOTA and H. KITAHARA, Fretting Fatigue under Variable Amplitude Loading below Fretting Fatigue Limit, Fatigue and Fracture of Engineering Materials and Structures, 29, pp.183-189, 2006.01.
86. Effect of hydrogen gas environment on fretting fatigue strength.
87. Effect of crack length, stress ratio and hydrogen on fatigue crack propagation threshold of high-strength steel.
88. Y. KONDO, C. SAKAE, M. KUBOTA and K. YANAGIHARA, Non-propagating Crack Behavior at Giga-cycle Fretting Fatigue Limit, Fatigue and Fracture of Engineering Materials and Structures, 10.1111/j.1460-2695.2005.00896.x, 28, 6, 501-506, Vol.28, pp.501-506, 2005.01.
89. Y. KONDO, C. SAKAE, M. KUBOTA and M. KASHIWAGI, Interpretation of Material Hardness, Stress Ratio and Crack Size Effects on the ΔKth of Small Cracks Based on Crack Closure Measurement, Journal of ASTM International, Vol.2, No.4, Paper ID JAI 11990, 2005.01.
90. 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.
91. Hisao MATSUNAGA, Yukitaka MURAKAMI, Masanobu KUBOTA, Joon-Hyun LEE, Fatigue Strength of Ti-6Al-4V Alloys Containing Small Artificial Defects, Material Science Research International, 9, 4, 263-269, Vol.9, No.4, pp.263-269, 2003.04.
92. 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.
93. Y. Kondo, C. Sakae, M. Kubota and T. Kudou, The Effect of Material Hardness and Mean Stress on the Fatigue Limit of Material Containing Small Defect, Fatigue and Fracture of Engineering Materials and Structures, 10.1046/j.1460-2695.2003.00656.x, 26, 8, 675-682, 26, pp.675-682, 2003.01.
94. 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.
95. Sang-Woo Choi, Joon-Hyun Lee, M. Kubota and Y. Murakami, The characteristics of Ultrasonic Signals for Detecting Micro-Defects in Ti-6Al-4V Alloy, Journal of the Korean Society for Nondestructive Testing, Vol. 21, No. 6 (in Korean), 2001.12.
96. K Hirakawa and M Kubota, On the fatigue design method for high-speed railway axles, Journal of Rail and Rapid Transit, 10.1243/0954409011531413, 215, 2, 73-82, Vol. 215, Part F2, pp. 73-82, 2001.01.
97. Yasuo OCHI, Masanobu Kubota, Ryouichi SHIBATA,
Initiation and Propagation Behavior of Small Fatigue Cracks in HIP-Treated Aluminum Alloy: AC4CH,
Proceedings of Small Fatigue Cracks: Mechanics, Mechanisms and Applications,
pp. 215-221, 1999 (Hawaii, USA)..
98. 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.
99. K. Hirakawa and M. Kubota, On The Fatigue Design Method for High Speed Railway Axles, Proc. of 12th International Wheelset Congress, 10.1243/0954409011531413, 215, 2, 73-82, pp. 477-482, 1998.09.
100. Y. Ochi and M. Kubota, Effects of Matrix-Structures on Low Cycle Fatigue Properties in Ductile Cast Irons, Proc. of Low Cycle Fatigue and Elasto-Plastic Behviour of Materials, pp.339-344, 1998.09.
101. 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.
102. K. Hirakawa, K. Toyama and M. Kubota, The Analysis and Prevention of Failure in Railway Axles, International Journal of Fatigue, 10.1016/S0142-1123(97)00096-0, 20, 2, 135-144, Vol. 20, No. 2, pp. 135-144, 1998.02.
103. T. Okamoto, M. Kubota and K. Hirakawa, Non-Destructive Inspection of Fretting Fatigue Cracks, Proc. of International Conference on Materials and Mechanics '97 (ICM&M '97), pp.379-384, 1997.07.
104. K. Hirakawa, K. Toyama and M. Kubota, The Analysis and Prevention of Failure in Railway Axles, Proc. JSME International Symposium on Product Liability and Failure Prevention, 10.1016/S0142-1123(97)00096-0, 20, 2, 135-144, pp. 47-59, 1996.10.
105. M. Kubota, Y. Ochi, S. Okazaki, A. Ishi and T. Hattori, High Cycle Fatigue Properties of HIP-Treated FDI Material, Proc. of Asian Pacific Conference for Fracture and Strength ’96(APCFS ‘96), pp.881-886, 1996.07.
106. Microscopic Observation of Initiation and Propagation Behavior of Small Crack on HIP-Treated AC4CH in High Cycle Fatigue,
M. Kubota, Y. Ochi, A. Ishii and R. Shibata,
Journal of Material Testing Research Association of Japan,
Vol.46, No. 1, pp.42-47 (Jan. 1996).
107. M. Kubota, Y. Ochi, A. Ishii and R. Shibata, Improvement of High Cycle Fatigue Strength in Advanced Cast Aluminum Alloys by HIP Treatment, Proc. of International Symposium on Advanced Technology in Experimental Mechanics ’95(ATEM ’95), pp.171-176, 1995.11.
108. Effect of Microstructures on Low-Cycle Fatigue Properties and Surface Crack Propagation Behavior in Ductile Cast Irons
Trans. JSME, Ser. A,
Vol. 60, No. 571, pp.619-625 (March 1994).
109. Improvement of High Cycle Fatigue Properties by HIP Treatment for Cast Alminum Alloy,
Trans. JSME, Ser. A,
Vol. 61, No. 591, pp.2342-2348 (July 1995).