Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Hisao MATSUNAGA Last modified date:2020.05.27

Professor / Hydrogen Utilization Engineering / Department of Mechanical Engineering / Faculty of Engineering


Papers
1. Yuhei Ogawa, Osamu Takakuwa, Saburo Okazaki, Koichi Okita, Yusuke Funakoshi, Hisao Matsunaga, Saburo Matsuoka, Pronounced transition of crack initiation and propagation modes in the hydrogen-related failure of a Ni-based superalloy 718 under internal and external hydrogen conditions, Corrosion Science, 10.1016/j.corsci.2019.108186, 161, 2019.12, The role of hydrogen in tensile ductility loss and on the fracture behaviours of Ni-based superalloy 718 was investigated via tensile tests under hydrogen-charged conditions (internal hydrogen) or in gaseous hydrogen environments (external hydrogen), in combination with post-mortem analyses of fractured samples using electron microscopy techniques. Whereas intergranular fracture was responsible for material degradation under external hydrogen, the failure modes under internal hydrogen conditions were primarily dominated by cracking along slip planes or twin boundaries. The mechanisms of crack initiation and propagation are extensively discussed in terms of hydrogen distribution, intrinsic deformation character of the material and hydrogen-modified dislocation behavior..
2. Åman Mari, Kentaro Wada, Hisao Matsunaga, Heikki Remes, Gary Marquis, The influence of interacting small defects on the fatigue limits of a pure iron and a bearing steel, International Journal of Fatigue, 10.1016/j.ijfatigue.2020.105560, 135, 2020.06, This study investigates the effect of interacting small cracks on the fatigue limits of two types of pure iron of varying strengths and of a bearing steel. The experimental results revealed that although the fatigue limits were essentially controlled by the mechanics of interacting cracks, the non-propagating crack features and the severity of crack coalescence varied greatly among the different materials. In addition, it is demonstrated that the material-independent, analytical, interaction-criterion alone is not sufficient to estimate interaction effects in reality. This research shows that the material effect can be considered in terms of hardness and non-propagating crack size..
3. Saburo Okazaki, Osamu Takakuwa, Yuhei Ogawa, Koichi Okita, Yusuke Funakoshi, Junichiro Yamabe, Saburo Matsuoka, Hisao Matsunaga , Effect of defects and hydrogen on the fatigue limit of Ni-based superalloy 718
, Procedia Structural Integrity , https://doi.org/10.1016/j.prostr.2019.12.034, 19, 312-319, 2019.12.
4. Tanaka Yuya, Matsunaga Hisao, Endo Masahiro, Moriyama Shigeaki , Micro-scale frictional behavior of a bearing steel (JIS SUJ2) in cyclic sliding motion
, Procedia Structural Integrity , https://doi.org/10.1016/j.prostr.2019.12.035, 19, 320-327, 2019.12.
5. Junichiro Yamabe, Kentaro Wada, Tohru Awane, Hisao Matsunaga, Hydrogen distribution of hydrogen-charged nickel analyzed via hardness test and secondary ion mass spectrometry, International Journal of Hydrogen Energy , https://doi.org/10.1016/j.ijhydene.2020.01.117, 45, 15, 9188-9199, 2020.03.
6. Naoaki Nagaishi, Saburo Okazaki, Yuhei Ogawa, Hisao Matsunaga, Dynamic improvement of fatigue strength via local phase transformation in a circumferentially-notched austenitic stainless steel under fully-reversed loading condition, Scripta Materialia, 10.1016/j.scriptamat.2019.09.014, 176, 126-130, 2020.02, The fatigue limit of a circumferentially-notched austenitic stainless steel exhibited peculiar improvement under fully-reversed loading (R =−1), as compared with that under tension-tension loading (R = 0.1), behavior considered to be unconventional in smooth specimens of similar materials. This was attributed to the different cyclic stress-strain responses at the notch-root, where it was almost elastic at R = 0.1, whereas an elasto-plastic response continued up to later stage of the fatigue process at R =−1. Such cyclic plasticity enhanced martensitic transformation locally and resulted in hardening, thereby restricting fatigue crack initiation from the notch-root..
7. Kentaro Wada, Junichiro Yamabe, Hisao Matsunaga, Visualization of trapped hydrogen along grain boundaries and its quantitative contribution to hydrogen-induced intergranular fracture in pure nickel, Materialia, 10.1016/j.mtla.2019.100478, 8, 2019.12, The phenomenon of hydrogen-trapping and its quantitative contribution to hydrogen-induced intergranular (IG) fracture were studied using a combination of thermal desorption analysis, secondary ion mass spectrometry and slow strain rate tensile tests. Hydrogen was trapped along grain boundaries (GBs) with a binding energy of ≈20 kJ/mol, accompanied by IG sulfur. The true fracture stress and fracture surface morphology were strongly dependent on the concentration of trapped hydrogen, leading to the conclusion that the hydrogen-induced IG fracture of pure Ni is controlled by the concentration of hydrogen trapped along GBs, and not by the concentration of lattice hydrogen..
8. Kentaro Wada, Junichiro Yamabe, Yuhei Ogawa, Osamu Takakuwa, Takashi Iijima, Hisao Matsunaga, Comparative study of hydrogen-induced intergranular fracture behavior in Ni and Cu–Ni alloy at ambient and cryogenic temperatures, Materials Science and Engineering A, 10.1016/j.msea.2019.138349, 766, 2019.10, In order to clarify the contribution of dislocation‒hydrogen interaction on the hydrogen embrittlement (HE) of pure Ni and of Cu‒55 wt% Ni binary alloy, slow strain rate tensile (SSRT) tests were conducted at room temperature (RT) and at 77 K on hydrogen-precharged specimens. Regarding the SSRT test at RT, hydrogen increased the flow stress and induced intergranular fracture in both pure Ni and Cu–Ni alloy. Furthermore, based on scanning transmission electron microscopy investigations, it was suggested that the evolution of dislocation structures had been enhanced by hydrogen, but only in the case of pure Ni. At 77 K, the ductility of pure Ni was degraded by hydrogen, whereas that of Cu–Ni alloy was not. The difference in temperature dependence of the dislocation‒hydrogen interaction between pure Ni and Cu–Ni alloy was discussed, based on the previously proposed HE mechanisms..
9. Jean Gabriel Sezgin, Osamu Takakuwa, Hisao Matsunaga, Junichiro Yamabe, Simulation of the effect of internal pressure on the integrity of hydrogen pre-charged BCC and FCC steels in SSRT test conditions, Engineering Fracture Mechanics, 10.1016/j.engfracmech.2019.106505, 216, 2019.07, Three effects of hydrogen have been reported on an austenitic stainless steel (Type-316L), a Cr-Mo steel (JIS-SCM435) and a carbon steel (JIS-SGP) during slow strain rate tensile (SSRT) tests performed in air on H-charged, smooth round-bar specimens. Two H-charging conditions were considered: exposure to 100-MPa hydrogen gas (270 °C, 200 h for Type-316L), and immersion in a NH4SCN solution (40 °C, 48 h for other steels). Modifications of the micro-void coalescence (MVC) mechanism were observed for each steel: decrease of dimple size (Type-316L), increase of dimple size (JIS-SGP), and formation of quasi-cleavage (QC) surfaces (JIS-SCM435). To clarify the contribution of the hydrogen-induced cracking (HIC) mechanism to these failures, the pressure build-up in preexisting cavities and its impact on the material strength was simulated by finite difference method (FDM) and finite element method (FEM). The failure criterion was defined based upon the elastoplastic fracture mechanics parameter: J-integral. For Type-316L, no effect of internal pressure on the fracture was expected. For JIS-SCM435 and JIS-SGP, although an effect of internal pressure exists, its relatively low value cannot lead to failure. SSRT tests were performed on Type-316L under the following conditions: (I) non-charged in vacuum; (II) H-charged in vacuum; (III) H-charged in 115 MPa nitrogen gas; (IV) non-charged in 115 MPa nitrogen gas. The experimental results successfully supported the simulation-based conclusions..
10. Naoaki Nagaishi, Michio Yoshikawa, Saburo Okazaki, Junichiro Yamabe, Fusahito Yoshida, Hisao Matsunaga, Evaluation of fatigue life and fatigue limit of circumferentially-notched Type 304 stainless steel in air and hydrogen gas based on crack-growth property and cyclic stress-strain response, Engineering Fracture Mechanics, 10.1016/j.engfracmech.2019.05.005, 215, 164-177, 2019.06, Fatigue tests were performed using circumferentially-notched, round bar specimens with a stress concentration factor, Kt, of 6.6 for Type 304, metastable, austenitic stainless steel. The tests were carried out in ambient air and in 0.7 MPa hydrogen gas at room temperature. In a relatively higher stress amplitude regime (i.e., the amplitude resulting in Nf < 105), the hydrogen gas environment caused a marked degradation in fatigue life. In contrast, in a relatively lower stress amplitude regime (i.e., the amplitude resulting in Nf > 105), it appeared that fatigue life did not differ between air and hydrogen gas. It was also confirmed that the fatigue limit appeared not have been degraded in the hydrogen environment though there was a slight difference between the data obtained in two environments. The fatigue life curve and fatigue limit were predicted by assuming that the notch was equivalent to a circumferential crack. Consequently, there was a significant disparity between the prediction and the experimental results. As a result of microscopic observations of the fracture process in combination with elastic-plastic finite element analyses, these discrepancies were attributed to (i) complex cyclic plastic deformation behavior under large- and small-scale yielding conditions within the vicinity of the notch root, (ii) the retardation of crack initiation in the finite life regime, and (iii) the absence of non-propagating cracks at the fatigue limit, all of which are typical characteristics of metastable austenitic stainless steel..
11. Kevinsanny, Saburo Okazaki, Osamu Takakuwa, Yuhei Ogawa, Koichi Okita, Yusuke Funakoshi, Junichiro Yamabe, Saburo Matsuoka, Hisao Matsunaga, Effect of defects on the fatigue limit of Ni-based superalloy 718 with different grain sizes, Fatigue and Fracture of Engineering Materials and Structures, 10.1111/ffe.12989, 42, 5, 1203-1213, 2019.05, Tension-compression fatigue tests were performed on two types of Ni-based superalloy 718 with different microstructures in which small artificial defects of various sizes and shapes were introduced. The susceptibility of the fatigue strength to the defects varied significantly with the microstructure morphology, ie, a smaller grain size made the alloy more susceptible to defects. The fatigue limit as a small-crack threshold was successfully predicted using the √area parameter model. The evaluation of the fatigue limit was classified into the following three stages depending on the defect size: (a) harmless defect regime, (b) small-crack regime, and (c) large-crack regime. Such a classification enabled comprehensive evaluation of the fatigue limit in a wide range of defect size, considering (a) defect size over a range of small crack to large crack and (b) characteristics of matrix represented by grain size and hardness..
12. Domas Birenis, Yuhei Ogawa, Hisao Matsunaga, Osamu Takakuwa, Junichiro Yamabe, Øystein Prytz, Annett Thøgersen, Hydrogen-assisted crack propagation in α-iron during elasto-plastic fracture toughness tests, Materials Science and Engineering A, https://doi.org/10.1016/j.msea.2019.04.084, 756, 396-404, 2019.05, Elasto-plastic fracture toughness tests of a commercially pure iron were performed in air and in hydrogen gas at two different pressures. Some unique characteristics of hydrogen-enhanced cracking were exhibited at both the macroscopic and microscopic length scales, based on the observation of fracture surface, fracture plane, plasticity distribution and dislocation structure. The possible mechanisms responsible for the hydrogen-induced degradation of fracture toughness are discussed..
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14. Sho Hashimoto, Hiroki Komata, Saburo Okazaki, Hisao Matsunaga, Quantitative evaluation of the flaking strength of rolling bearings with small defects as a crack problem, International Journal of Fatigue, 10.1016/j.ijfatigue.2018.10.003, 119, 195-203, 2019.02, Rolling contact fatigue (RCF) tests were conducted on rolling bearings with drilled holes at the mid-point of the raceway. Flaking limit was determined by the shear-mode threshold of a crack that emanated at the edge of drilled hole. To quantify the RCF strength according to fracture mechanics principles, Mode II stress intensity factor (SIF) range of the crack was derived. Taking a small crack effect on the shear-mode fatigue crack into account, RCF strength was successfully evaluated as a crack problem, irrespective of the diameters and depths of the hole. The values of the threshold SIF range obtained by RCF tests were in good agreement with those obtained in the torsional fatigue tests under static compression..
15. Osamu Takakuwa, Yuhei Ogawa, Junichiro Yamabe, Hisao Matsunaga, Hydrogen-induced ductility loss of precipitation-strengthened Fe-Ni-Cr-based superalloy, Materials Science and Engineering A, 10.1016/j.msea.2018.10.040, 739, 335-342, 2019.01, A brittle-like faceted morphology of a precipitation-strengthened Fe-Ni-Cr-based superalloy after charging via exposure to high-pressure hydrogen gas (100 MPa) at elevated temperature (543 K) was interpreted based on multiple electron microscopy observations: scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and electron channeling contrast (ECC) imaging. The observation results revealed that the brittle-like facets were derived from intergranular cracking accompanied by hydrogen-assisted microvoid nucleation at the grain boundaries (GBs). Deformation twinning also played a crucial role in triggering the final grain boundary separation due to local stress concentration at its intersection with the GBs after severe strain hardening; such a process has not yet been considered to explain the hydrogen-induced ductility loss of this type of alloy..
16. Eric Maire, Stanislas Grabon, Jérôme Adrien, Pablo Lorenzino, Yuki Asanuma, Osamu Takakuwa, Hisao Matsunaga, Role of hydrogen-charging on nucleation and growth of ductile damage in austenitic stainless steels, Materials, 10.3390/ma12091426, 12, 9, 2019.01, Hydrogen energy is a possible solution for storage in the future. The resistance of packaging materials such as stainless steels has to be guaranteed for a possible use of these materials as containers for highly pressurized hydrogen. The effect of hydrogen charging on the nucleation and growth of microdamage in two different austenitic stainless steels AISI316 and AISI316L was studied using in situ tensile tests in synchrotron X-ray tomography. Information about damage nucleation, void growth and void shape were obtained. AISI316 was found to be more sensitive to hydrogen compared to AISI316L in terms of ductility loss. It was measured that void nucleation and growth are not affected by hydrogen charging. The effect of hydrogen was however found to change the morphology of nucleated voids from spherical cavities to micro-cracks being oriented perpendicular to the tensile axis..
17. Kentaro Wada, Junichiro Yamabe, Yuhei Ogawa, Osamu Takakuwa, Takashi Iijima, Hisao Matsunaga, Fracture and deformation behavior in slow-strain-rate tensile testing of Cu-Ni alloy with internal hydrogen, ASME 2019 Pressure Vessels and Piping Conference, PVP 2019 Materials and Fabrication, 10.1115/PVP2019-93477, 2019.01, The effect of hydrogen on the deformation and fracture behavior in pure Cu, pure Ni and Cu-Ni alloy was studied via tensile tests of H-charged, smooth and circumferentially-notched specimens at room temperature (RT) and 77 K. Hydrogendiffusion properties were determined by the desorption method. To obtain a uniform hydrogen concentration in the H-charged specimens, specimens were exposed to 100-MPa hydrogen gas at 543 K for 200 h, based on the determined hydrogen diffusivity. In tensile tests of smooth pure Ni and Cu-Ni alloy specimens at RT, common hydrogen effects were detected, namely, an increase in yield and flow stresses-a hardening effect; and a ductility loss that was accompanied by a change in fracture surface from ductile to brittle feature-an embrittling effect. With regard to the embrittling effect, the pure Ni and Cu-Ni alloy showed different fracture-surface morphologies at RT; the pure Ni showed an intergranular (IG) surface and the Cu-Ni alloy surface was flat. However, a number of IG cracks were detected beneath the fracture surfaces on the smooth Cu-Ni alloy. The tensile tests of the H-charged smooth specimens at 77 K yielded an IG surface for the pure Ni and a ductile fracture surface with dimples in the Cu-Ni alloy. In contrast, tensile tests of the Hcharged, notched specimens at RT demonstrated clear IG fractures for the pure Ni and Cu-Ni alloy. These facts indicate that IG cracking was the first step in the embrittling process for the pure Ni and Cu-Ni alloy, and IG cracking was accompanied by a large plastic deformation that formed the flat surface (unclear IG surface) for the smooth Cu-Ni alloy. Considering that the HE of both pure Ni and Cu-Ni alloy was related to IG cracking, possible mechanisms were discussed and tensile tests performed at 77 K suggested two possibilities: (I) interaction between hydrogen-moving dislocation is more important in the HE process of the Cu-Ni alloy compared to the pure Ni; (II) hydrogen transportation towards grain boundaries are required to cause the IG fracture in the Cu-Ni alloy..
18. Osamu Takakuwa, Yuhei Ogawa, Saburo Okazaki, Hisao Matsunaga, Saburo Matsuoka, Temperature dependence of fatigue crack growth in low-carbon steel under gaseous hydrogen, ASME 2019 Pressure Vessels and Piping Conference, PVP 2019 Materials and Fabrication, 10.1115/PVP2019-93451, 2019.01, In order to elucidate the temperature dependence of hydrogen-assisted fatigue crack growth (HAFCG), the fatigue crack growth (FCG) test was performed on low-carbon steel JISSM490B according to ASTM E647 using compact tension (CT) specimen under 0.7 MPa (≈ 0.1 ksi) hydrogen-gas at room temperature (RT: 298 K (≈ 77 °F)) and 423 K (≈ 302 °F) at stress intensity factor range of ΔK = 30 MPa m1/2 (≈ 27 ksi in1/2). Electron backscatter diffraction (EBSD) observation was performed on the mid-thick section of CT specimen in order to investigate change in plasticity around the crack wake in gaseous hydrogen environment and how it changes due to temperature elevation. The obtained results showed the higher temperature, the lower intense of HAFCG as reported in our previous article. Plasticity around the crack wake became less in gaseous hydrogen environment, especially tested at 298 K. The propensity of the results obtained at higher temperature (423 K) can be separated into two cases: (i) intense plasticity occurs like tested in air, (ii) crack propagates straighter accompanying less plasticity like tested in gaseous hydrogen environment at 298 K. This implies macroscopic FCG rate is determined by combination of microscopic FCG rate in the case (i) and case (ii)..
19. Saburo Matsuoka, Takashi Iijima, Satoko Yoshida, Junichiro Yamabe, Hisao Matsunaga, Various strength properties of aluminum alloys in high-pressure hydrogen gas environment, ASME 2019 Pressure Vessels and Piping Conference, PVP 2019 Materials and Fabrication, 10.1115/PVP2019-93478, 2019.01, Three types of strength tests, slow strain rate tensile (SSRT), fatigue life, and fatigue crack growth (FCG) tests, were performed using six types of aluminum alloys, 5083-O, 6061-T6, 6066-T6, 7N01-T5, 7N01-T6, and 7075-T6, in air and 115 MPa hydrogen gas at room temperature. All the strength properties of every material were not deteriorated in 115 MPa hydrogen gas. In all the materials, FCG rates were lower in 115 MPa hydrogen gas than in air. This was considered to be due to a lack of water-or oxygen-adsorbed film at crack tip in hydrogen gas. In 5083-O, 6061-T6 and 6066-T6, relative reduction in area (RRA) were remarkably higher in 115 MPa hydrogen gas than in air. These differences were attributed to a hydrostatic pressure produced in 115 MPa hydrogen gas. In contrast, in 7N01-T5, 7N01-T6 and 7075-T6, the values of RRA in 115 MPa hydrogen gas were nearly the same as those in air. Observation of fractured specimens inferred that the degree of such a hydrogen-induced improvement was determined by the fracture mode (e.g. cupand-cone or shear fracture), which is dominated by the microstructure morphology..
20. Yuhei Ogawa, Saburo Okazaki, Osamu Takakuwa, Hisao Matsunaga, The roles of internal and external hydrogen in the deformation and fracture processes at the fatigue crack tip zone of metastable austenitic stainless steels, Scripta Materialia, 10.1016/j.scriptamat.2018.08.003, 157, 95-99, 2018.12, Fatigue crack growth (FCG) tests were performed with two types of metastable austenitic stainless steels having different austenite phase stabilities under hydrogen-precharged conditions (internal hydrogen) and in gaseous hydrogen environments (external hydrogen). The materials showed a peculiarly slower FCG rate with internal hydrogen than with external hydrogen even though the hydrogen concentration was much higher under the internal hydrogen conditions. The results are interpreted in terms of hydrogen-modified plastic deformation character comprising inhibited cross-slipping or enhanced deformation twinning in combination with the sequence of hydrogen penetration and strain-induced α′ martensite formation in the local region surrounding the fatigue crack tip..
21. Yuhei Ogawa, Hisao Matsunaga, Junichiro Yamabe, Michio Yoshikawa, Saburo Matsuoka, Fatigue limit of carbon and Cr–Mo steels as a small fatigue crack threshold in high-pressure hydrogen gas, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2018.09.026, 43, 43, 20133-20142, 2018.10, The fatigue limit properties of a carbon steel and a low-alloy Cr–Mo steel were investigated via fully-reversed tension-compression tests, using smooth specimens in air and in 115-MPa hydrogen gas. With respect to the Cr–Mo steel, specimens with sharp notches were also tested in order to investigate the threshold behavior of small cracks. The obtained S–N data inferred that the fatigue limit was not negatively affected by hydrogen in either of the steels. Observation of fatigue cracks in the unbroken specimens revealed that non-propagating cracks can exist even in 115-MPa hydrogen gas, and that the crack growth threshold is not degraded by hydrogen. The experimental results provide justification for the fatigue limit design of components that are to be exposed to high-pressure hydrogen gas..
22. Saburo Matsuoka, Osamu Takakuwa, Saburo Okazaki, Michio Yoshikawa, Junichiro Yamabe, Hisao Matsunaga, Peculiar temperature dependence of hydrogen-enhanced fatigue crack growth of low-carbon steel in gaseous hydrogen, Scripta Materialia, 10.1016/j.scriptamat.2018.05.035, 154, 101-105, 2018.09, [URL].
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24. Yuhei Ogawa, Domas Birenis, Hisao Matsunaga, Osamu Takakuwa, Junichiro Yamabe, Øystein Prytz, Annett Thøgersen, The role of intergranular fracture on hydrogen-assisted fatigue crack propagation in pure iron at a low stress intensity range, Materials Science and Engineering: A, 10.1016/j.msea.2018.07.014, Available online 6 July 2018, 2018.07, [URL].
25. Hiroshi Nishiguchi, Yuta Matsuda, Takayuki Fukuda, Kenji Higashida, Junichiro Yamabe, Hisao Matsunaga, Hydrogen-entry properties of torsional prestrained carbon steels, Zairyo/Journal of the Society of Materials Science, Japan, 10.2472/jsms.67.723, 67, 7, 723-729, 2018.07, Hydrogen-entry properties of torsional prestrained ferritic-pearlitic low-carbon JIS-S10C, JIS-S25C and JIS-S45C steels were investigated. A round bar specimen was prestrained by torsion test and then charged with hydrogen by cathodic charging or immersion charging. The torsion test enabled to introduce a large plastic deformation to the specimen without necking, which led to much higher level of hydrogen content, CH, than tensile test. CH was increased with an increase in torsional prestrain at the specimen outer surface, εpre,s. In the prestrain range, εpre,s < 30%, there was little influence of pearlite on CH. By contrast, when εpre,s > 40%, there was a marked influence of pearlite on CH in JIS-S10C and JIS-S25C, whereas, CH in JIS-S45C was lower than that of JIS-S25C despite the fact that fraction of pearlite in JIS-S45C was much higher than that in JIS-S25C. It was presumed that such a complex hydrogen-entry property was determined by the competition between (I) the increase in dislocation density near the boundaries between ferrite and pearlite and (II) the inhibition against the increase in dislocation density by a stress redistribution in pearlite grains. The torsional strain at final rapture was the largest in JIS-S10C, which accordingly conduced to the largest hydrogen content in the broken specimen. The series of experimental results manifested that the torsion test enables the investigation of strength properties as well as the hydrogen-entry properties for BCC steels under an extremely large hydrogen content (~30 mass ppm)..
26. Jean-Gabriel Sezgin, Hallvard G. Fjær, Hisao Matsunaga, Junichiro Yamabe, Vigdis Olden, Hydrogen Trapping in X70 Structural Pipeline Steel and Weldments, Proceedings of the Twenty-eighth (2018) International Ocean and Polar Engineering Conference, 2018.06.
27. Domas Birenis, Yuhei Ogawa, Hisao Matsunaga, Osamu Takakuwa, Junichiro Yamabe, Øystein Prytz, Annett Thøgersen, Interpretation of hydrogen-assisted fatigue crack propagation in BCC iron based on dislocation structure evolution around the crack wake, Acta Materialia, 10.1016/j.actamat.2018.06.041, 156, 245-253, 2018.06, [URL].
28. Domas Birenis, Yuhei Ogawa, Hisao Matsunaga, Osamu Takakuwa, Junichiro Yamabe, Øystein Prytz, Annett Thøgersen, Hydrogen-assisted fatigue crack propagation in a pure BCC iron. Part II
Accelerated regime manifested by quasi-cleavage fracture at relatively high stress intensity range values, 12th International Fatigue Congress, FATIGUE 2018 MATEC Web of Conferences, 10.1051/matecconf/201816503010, 165, 2018.05, Hydrogen effect on fatigue performance at relatively high values of stress intensity factor range, ΔK, of pure BCC iron has been studied with a combination of various electron microscopy techniques. Hydrogen-assisted fatigue crack growth rate is manifested by a change of fracture features at the fracture surface from ductile transgranular in air to quasi-cleavage in hydrogen gas. Grain reference orientation deviation (GROD) analysis has shown a dramatic suppression of plastic deformation around the crack wake in samples fatigued in hydrogen. These results were verified by preparing site-specific specimens from different fracture features by using Focused Ion Beam (FIB) technique and observing them with Transmission Electron Microscope (TEM). The FIB lamella taken from the sample fatigued in air was decorated with dislocation cell structure indicating high amount of plasticity, while the lamella taken from the quasi-cleavage surface of the sample fatigued in hydrogen revealed a distribution of dislocation tangles which corresponds to smaller plastic strain amplitude involved at the point of fracture. These results show that a combination of critical hydrogen concentration and critical stress during fatigue crack growth at high ΔK values triggers cleavage-like fracture due to reduction of cohesive force between matrix atoms..
29. Yuhei Ogawa, Domas Birenis, Hisao Matsunaga, Osamu Takakuwa, Junichiro Yamabe, Øystein Prytz, Annett Thøgersen, Hydrogen-assisted fatigue crack propagation in a pure BCC iron. Part I
Intergranular crack propagation at relatively low stress intensities, 12th International Fatigue Congress, FATIGUE 2018 MATEC Web of Conferences, 10.1051/matecconf/201816503011, 165, 2018.05, The role of hydrogen on intergranular (IG) fracture in hydrogen-assisted fatigue crack growth (HAFCG) of a pure iron at low stress intensity was discussed in terms of the microscopic deformation structures near crack propagation paths. The main cause of IG fracture was assumed to be the hydrogen-enhanced dislocation structure evolution and subsequent microvoids formation along the grain boundaries. Additionally, the impact of such IG cracking on the macroscopic FCG rate was evaluated according to the dependency of IG fracture propensity on the hydrogen gas pressure. It was first demonstrated that the increased hydrogen pressure results in the larger area fraction of IG and corresponding faster FCG rate. Moreover, gaseous hydrogen environment also had a positive influence on the FCG rate due to the absence of oxygen and water vapor. The macroscopic crack propagation rate was controlled by the competition process of said positive and negative effects..
30. Kentaro Wada, Soma Yoshimura, Tomoko Yamamoto, Yoshihiro Ohkomori, Hisao Matsunaga, Shear-mode Crack Initiation Behavior in the Martensitic and Bainitic Microstructures, 12th International Fatigue Congress, FATIGUE 2018 MATEC Web of Conferences, 165, 04009, 2018.05.
31. Jean Gabriel Sezgin, Osamu Takakuwa, Hisao Matsunaga, Junichiro Yamabe, Assessment of the contribution of internal pressure to the structural damage in a hydrogen-charged Type 316L austenitic stainless steel during slow strain rate tensile test, 22nd European Conference on Fracture, ECF 2018 Procedia Structural Integrity, 10.1016/j.prostr.2018.12.340, 13, 1615-1619, 2018.01, The aim of this study is to provide a quantification of the internal pressure contribution to the SSRT properties of H-charged Type-316L steel tested in air at room temperature. Considering pre-existing penny-shaped voids, the transient pressure build-up has been simulated as well as its impact on the void growth by preforming J
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calculations. Several void distributions (size and spacing) have been considered. Simulations have concluded that there was no impact of the internal pressure on the void growth, regardless the void distribution since the effective pressure was on the order of 1 MPa during the SSRT test. Even if fast hydrogen diffusion related to dislocation pipe-diffusion has been assessed as a conservative case, the impact on void growth was barely imperceptible (or significantly low). The effect of internal pressure has been experimentally verified via the following conditions: (I) non-charged in vacuum; (II) H-charged in vacuum; (III) H-charged in 115-MPa nitrogen gas; (IV) non-charged in 115-MPa nitrogen gas. As a result, the relative reduction in area (RRA) was 0.84 for (II), 0.88 for (III), and 1.01 for (IV), respectively. The difference in void morphology of the H-charged specimens did not depend on the presence of external pressure. These experimental results demonstrate that the internal pressure had no effect on the tensile ductility and void morphology of the H-charged specimen..
32. Yuhei Ogawa, Dain Kim, Hisao Matsunaga, Saburo Matsuoka, Evaluation of the compatibility of high-strength aluminum alloy 7075-T6 to high-pressure gaseous hydrogen environments, ASME 2018 Pressure Vessels and Piping Conference, PVP 2018 Materials and Fabrication, 2018.01, To develop safer and more cost-effective high-pressure hydrogen tanks used in fuel cell vehicles (FCVs), the metallic materials with the following three key properties, i.e. lightweight, high strength and excellent resistance to hydrogen embrittlement should be explored. In this study, the compatibility of high-strength, precipitation-hardened aluminum alloy 7075-T6 was evaluated according to the four types of mechanical testing including slow-strain rate tensile (SSRT), fatigue life, fatigue crack growth (FCG) and fracture toughness tests in high-pressure gaseous hydrogen environments (95 ~ 115 MPa) at room temperature. Even though numerous publications have previously reported significant degradation of the mechanical properties of 7075-T6 in some hydrogenating environments, such as moist atmosphere, the understanding with regards to the performance of this alloy in high-pressure gaseous hydrogen environments is still lacking. In SSRT tests, the alloy showed no degradation of tensile strength and ductility. Furthermore, fatigue life, fatigue crack growth and fracture toughness properties were also not degraded in hydrogen gas. Namely, it was first demonstrated that the material has big potential to be used for hydrogen storage tanks for FCVs, according to its excellent resistance to high-pressure gaseous hydrogen..
33. Naoaki Nagaishi, Hisao Matsunaga, Michio Yoshikawa, Junichiro Yamabe, Saburo Okazaki, Saburo Matsuoka, Fatigue life properties of circumferentially-notched bar of austenitic stainless steel with various concentration factors, ASME 2018 Pressure Vessels and Piping Conference, PVP 2018 Materials and Fabrication, 2018.01, Fatigue tests were performed using three types of round-bar specimens of Type 304, meta-stable, austenitic stainless steel. The specimens had circumferential notch with stress concentration factors, Kt, of 2, 3 or 6.6. Load controlled fatigue tests were conducted at stress ratio, R, of 0.1 and −1 in ambient air at room temperature. At R of 0.1, fatigue life was decreased with an increase in the stress concentration factor. Conversely, at R of −1, the stress concentration factor had little influence on the fatigue life. To understand the mechanism of the stress ratio effect, local deformation behavior at and beneath the notch root during the fatigue test was computed by means of finite element analysis considering that the plastic constitutive model describes the cyclic stress-strain response..
34. Chris San Marchi, Hisao Matsunaga, Hideo Kobayashi, Junichiro Yamabe, Stefan Zickler, Martina Schwarz, Saburo Matsuoka, Global harmonization of fatigue life testing in gaseous hydrogen, ASME 2018 Pressure Vessels and Piping Conference, PVP 2018 Materials and Fabrication, 2018.01, Methods to qualify materials for hydrogen service are needed in the global marketplace to enable sustainable, low-carbon energy technologies, such as hydrogen fuel cell electric vehicles. Existing requirements for qualifying materials are not adequate to support growth of hydrogen technology as well as being inconsistent with the growing literature on the effects of hydrogen on fracture and fatigue. This report documents an internationally coordinated effort to develop a test method for qualifying materials for high-pressure hydrogen fuel system onboard fuel cell electric vehicles. In particular, consistency of fatigue life testing strategies is discussed. Fatigue life tests were conducted at three different institutes in high-pressure gaseous hydrogen (90 MPa) at low temperature (233K) to confirm consistency across distinct testing platforms. The testing campaign includes testing of both smooth and notched axial fatigue specimens at various combinations of pressure and temperature. Collectively these testing results provide insight to the sensitivity of fatigue life testing to important testing parameters such as pressure, temperature and the presence of stress concentrations..
35. Jean Gabriel Sezgin, Hallvard G. Fjær, Hisao Matsunaga, Junichiro Yamabe, Vigdis Oldeng, Hydrogen trapping in X70 structural pipeline steel and weldments, 28th International Ocean and Polar Engineering Conference, ISOPE 2018 Proceedings of the 28th International Ocean and Polar Engineering Conference, ISOPE 2018, 228-235, 2018.01, Diffusion measurements and thermal desorption measurements have been performed on a X70 pipeline steel, in as received and normalized and quenched condition, after being hydrogen charged for 200 h at 100 MPa hydrogen gas pressure and 85℃. Numerical simulations based on the assumption of thermodynamic equilibrium were performed, aiming to compare the trapping energies when fitting to the TDS spectra. TDS experiments revealed a reversible trap site with activation energy of 26.2 kJ.mol
-1
. Irreversible trap sites with an activation energy of >100 kJ.mol-
1
were observed from both as-received and heat-treated condition. In contrast, a reversible trap site with an activation energy of 49.2 kJ.mol
-1
was observed only from the heat-treated condition. The numerical modelling based on the assumption of equilibrium between hydrogen in traps and hydrogen in lattice is seen to provide a good fit to the experimental data..
36. Domas Birenis, Yuhei Ogawa, Hisao Matsunaga, Osamu Takakuwa, Øystein Prytz, Junichiro Yamabe, Annett Thøgersen, Hydrogen-assisted fatigue crack propagation in a commercially pure BCC iron, ASME 2018 Pressure Vessels and Piping Conference, PVP 2018 Materials and Fabrication, 2018.01, Hydrogen effect on fatigue performance of commercially pure BCC iron has been studied with a combination of various electron microscopy techniques. The fatigue crack growth (FCG) in gaseous hydrogen was found to consist of two regimes corresponding to a slightly accelerated regime at relatively low stress intensity factor range, ΔK, (Stage I) and the highly accelerated regime at relatively high ΔK (Stage II). These regimes were manifested by the intergranular and quasi-cleavage types of fractures respectively. Scanning electron microscopy (SEM) observations demonstrated an increase in plastic deformation around the crack wake in the Stage I, but considerably lower amount of plasticity around the crack path in the Stage II. Transmission electron microscopy (TEM) results identified dislocation cell structure immediately beneath the fracture surface of the Stage I sample, and dislocation tangles in the Stage II sample corresponding to fracture at high and low plastic strain amplitudes respectively..
37. Saburo Okazaki, Hisao Matsunaga, Masami Nakamura, Saburo Matsuoka, Shigeru Hamada, Influence of hydrogen on tensile and fatigue life properties of 304/308 austenitic stainless steel butt welded joints, ASME 2018 Pressure Vessels and Piping Conference, PVP 2018 Materials and Fabrication, 2018.01, To investigate the influence of hydrogen on the tensile and fatigue life properties of welded joints of 304/308 austenitic stainless steels, slow strain rate tensile (SSRT) tests and fatigue life tests were conducted in laboratory air using hydrogen exposed specimens. The specimens were fabricated from welded plates, and to elucidate the role of weld structure on hydrogen-induced degradation, the welded joint was solution-treated. In the SSRT tests of the as-welded (AW) joint, a non-exposed specimen failed at the base metal (BM), whereas a hydrogen-exposed specimen failed near the weld toe. In the case of the solution-treated-welded (STW) joint, the non-exposed specimen failed at the part of solution treated weld metal, whereas an H-exposed specimen failed near the weld toe. As a result, internal hydrogen significantly degraded the elongation of the AW joint. In the fatigue test, all the specimens failed near the weld toe. Internal hydrogen degraded the fatigue life considerably. However, the pre-charging led to little, if any, reduction in the fatigue limit. Similarly to the AW joint, hydrogen gas exposure notably degraded the fatigue life of the STW joint and led to little reduction in the fatigue limit. To investigate the relationship between the hydrogen-induced degradation and strain-induced martensitic transformation during fatigue testing, the volume fraction of ferrite in the broken specimens was measured by a ferrite scope. The volume fraction of martensitic transformation increased with an increase in the stress amplitude. These experimental results implied that the hydrogen-induced fatigue life degradation in the welded joint was closely related to the martensitic transformation during the fatigue process. The mechanisms of both the degradation in fatigue life and non-degradation in fatigue limit will be discussed further..
38. Hajime Fukumoto, Yoru Wada, Hisao Matsunaga, Takeru Sano, Hiroshi Kobayashi, Introduction of technical document in Japan for safe use of ground storage vessels made of low alloy steels for hydrogen refueling stations, ASME 2018 Pressure Vessels and Piping Conference, PVP 2018 Codes and Standards, 10.1115/PVP201884099, 2018.01, As is well known, low alloy steels are widely used as materials for high pressure vessels because of their high tensile strength and reasonable price, but also show severe hydrogen embrittlement. Therefore, in 2016, the authors introduced a scenario for the safe use of low alloy steels in highly pressurized hydrogen gas as a "Guideline" at ASME PVP 2016 [1]. Following discussions with stakeholders and experts in recent years, we published Technical Document (TD) as an industrial standard prior to regulation, on the safe use of ground storage vessels made of low alloy steels in Hydrogen Refueling Stations (HRSs) based on performance requirements. This article presents an outline of the TD describing the required types of testing as performance requirements for confirming the good hydrogen compatibility of low alloy steels, such as controlling tensile strength in an appropriate range, confirming leak-before-break, determining the life of ground storage vessels by fatigue testing and determining the inspection term by fatigue crack growth analysis using the fatigue crack growth rate in highly pressurized hydrogen..
39. Hideo Kobayashi, Hiroshi Kobayashi, Takeru Sano, Takashi Maeda, Hiroaki Tamura, Ayumu Ishizuka, Mitsuo Kimura, Nobuhiro Yoshikawa, Takashi Iijima, Junichiro Yamabe, Saburo Matsuoka, Hisao Matsunaga, Methods of material testing in high-pressure hydrogen environment and evaluation of hydrogen compatibility of metallic materials – Current status in Japan, ASME 2018 Pressure Vessels and Piping Conference, PVP 2018 Materials and Fabrication, 2018.01, In Japan, with regards to the widespread commercialization of 70 MPa-class hydrogen refueling stations and fuel cell vehicles, two national projects have been promoted on both the infrastructure and the automobile sides. These projects have been promoted to establish the criteria for determining hydrogen compatibility of materials and to expand the usable materials for high-pressure hydrogen environment. For these projects, establishing test methods to evaluate the hydrogen compatibility of materials is one of the most important tasks. This paper describes the status of common standardization of testing methods. Two projects share a common database for the testing results, which is currently put to practical use..
40. Osamu Takakuwa, Michio Yoshikawa, Saburo Matsuoka, Junichiro Yamabe, Saburo Okazaki, Hisao Matsunaga, Temperature dependence of fatigue crack growth in low-alloy steel under gaseous hydrogen, ASME 2018 Pressure Vessels and Piping Conference, PVP 2018 Materials and Fabrication, 2018.01, In order to elucidate the temperature dependence of hydrogen-enhanced fatigue crack growth (FCG), the FCG test was performed on low-alloy Cr-Mo steel JIS-SCM435 according to ASTM E647 using compact tension (CT) specimen under 0.1 - 95 MPa hydrogen-gas at temperature ranging from room temperature (298 K) to 423 K. The obtained results were interpreted according to trap site occupancy under thermal equilibrium state. The FCG was significantly accelerated at RT under hydrogen-gas, that its maximum acceleration rate of the FCG was 15 at the pressure of 95 MPa at the temperature of 298 K. The hydrogen-enhanced FCG was mitigated due to temperature elevation for all pressure conditions. The trap site with binding energy of 44 kJ/mol dominated the temperature dependence of hydrogen-enhanced FCG, corresponding approximately to binding energy of dislocation core. The trap site (dislocation) occupancy is decreased with the temperature elevation, resulting in the mitigation of the FCG acceleration. On the basis of the obtained results, when the occupancy becomes higher at lower temperature, e.g. 298 K, hydrogen-enhanced FCG becomes more pronounced. The lower occupancy at higher temperature does the opposite..
41. Kentaro Wada, Adeyinka Abass, Saburo Okazaki, Yoshihiro Fukushima, Hisao Matsunaga, Kaneaki Tsuzaki, Fatigue Crack Threshold of Bearing Steel at a Very Low Stress Ratio, Procedia Structural Integrity, https://doi.org/10.1016/j.prostr.2017.11.104, 7, 391-398, 2017.12.
42. Yuhei Ogawa, Domas Birenis, Hisao Matsunaga, Annett Thøgersen, Øystein Prytz, Osamu Takakuwa, Junichiro Yamabe, Multi-scale observation of hydrogen-induced, localized plastic deformation in fatigue-crack propagation in a pure iron, Scripta Materialia, https://doi.org/10.1016/j.scriptamat.2017.06.037, 140, pp. 13-17, 2017.11, [URL].
43. Osamu Takakuwa, Junichiro Yamabe, Hisao Matsunaga, Yoshiyuki Furuya, Saburo Matsuoka, Comprehensive Understanding of Ductility Loss Mechanisms in Various Steels with External and Internal Hydrogen, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, 10.1007/s11661-017-4323-3, 48A, 11, 5717-5732, 2017.11, [URL].
44. Yuhei Ogawa, Hisao Matsunaga, Junichiro Yamabe, Michio Yoshikawa, Matsuoka Saburo, Unified evaluation of hydrogen-induced crack growth in fatigue tests and fracture toughness tests of a carbon steel, International Journal of Fatigue, https://doi.org/10.1016/j.ijfatigue.2017.06.006, 103, pp. 223-233, 2017.10, [URL].
45. Junichiro Yamabe, Michio Yoshikawa, Hisao MATSUNAGA, Matsuoka Saburo, Hydrogen trapping and fatigue crack growth property of low-carbon steel in hydrogen-gas environment, International Journal of Fatigue, 102, pp. 202-213, 2017.09, [URL].
46. Sho Hashimoto, Hiroki Komata, Hisao Matsunaga, Quantative Evaluation of the Flaking Strength of Rolling Bearings with Small Defects:(Part 1: FEM Analyses of the Stress Intensity Factor, Kll, under Rolling Contact), Procedia Structural Integrity, 7, 453-459, 2017.08.
47. Hisao Matsunaga, Sho Hashimoto, Hiroki Komata, , Quantative Evaluation of the Flaking Strength of Rolling Bearings with Small Defects:(Part 2: Evaluation of the Flaking Strength of Rolling Bearings with Small Drilled Holes, based on the Stress Intensity Factor), Procedia Structural Integrity, 7, 460-467, 2017.08.
48. Hisao Matsunaga, Takakuwa Osamu, Junichiro Yamabe, Matsuoka Saburo, Hydrogen-enhanced fatigue crack growth in steels and its frequency dependence, Philosophical Transactions of the Royal Society A, 10.1098/rsta.2016.0412, 375, 2098, 2017.07, [URL].
49. Osamu Takakuwa, Junichiro Yamabe, Hisao Matsunaga, Yoshiyuki Furuya, Saburo Matsuoka, Recent Progress on Interpretation of Tensile Ductility Loss for Various Austenitic Stainless Steels With External and Internal Hydrogen, ASME 2017 Pressure Vessels and Piping Conference, 10.1115/PVP2017-65671, 2017.07.
50. Yuhei Ogawa, Junichiro Yamabe, Hisao Matsunaga, Saburo Matsuoka, Excellent Resistance to Hydrogen Embrittlement of High-Strength Copper-Based Alloy, ASME 2017 Pressure Vessels and Piping Conference, 2017.07.
51. Saburo Okazaki, Hisao Matsunaga, Shigeru Hamada, Masami Nakamura, Hisatake Itoga, Saburo Matsuoka, A Case Study of a Cooling Pipe for a Pre-Cooler Used in a 70MPa Hydrogen Station, ASME 2017 Pressure Vessels and Piping Conference, 2017.07.
52. Naoaki Nagaishi, Michio Yoshikawa, Saburo Okazaki, Hisao Matsunaga, Junichiro Yamabe, Saburo Matsuoka, Fatigue Life Properties of Circumferentially- Notched, Type 304 Austenitic Stainless Steel in Hydrogen Gas, ASME 2017 Pressure Vessels and Piping Conference, 2017.07.
53. Yuhei Ogawa, Junichiro Yamabe, Hisao Matsunaga, Matsuoka Saburo, Material performance of age-hardened beryllium–copper alloy, CDA-C17200, in a high-pressure, gaseous hydrogen environment, International Journal of Hydrogen Energy, https://doi.org/10.1016/j.ijhydene.2017.04.270, 42, 26, 16887-16900, 2017.06, [URL].
54. Junichiro Yamabe, Takakuwa Osamu, Hisao Matsunaga, Hisatake Itoga, Matsuoka Saburo, Hydrogen diffusivity and tensile-ductility loss of solution-treated austenitic stainless steels with external and internal hydrogen, International Journal of Hydrogen Energy, https://doi.org/10.1016/j.ijhydene.2017.04.055, 42, 18, pp. 13289-13299, 2017.05, [URL].
55. Saburo Okazaki, Kentaro Wada, Hisao Matsunaga, Masahiro Endo, The influence of static crack-opening stress on the threshold level for shear-mode fatigue crack growth in bearing steels, Engineering Fracture Mechanics, 174, pp. 127-138, 2017.04, [URL].
56. , [URL].
57. Mari Aman, Saburo Okazaki, Hisao Matsunaga, Gary Marquis, Heikki Remes, Interaction effect of adjacent small defects on the fatigue limit of a medium carbon steel, Fatigue & Fracture of Engineering Materials & Structures, 10.1111/ffe.12482, 40, pp. 130-144, 2017.01, [URL].
58. Matsuoka Saburo, Junichiro Yamabe, Hisao MATSUNAGA, Hydrogen-induced ductility loss of austenitic stainless steels for slow strain rate tensile testing in high-pressure hydrogen gas, Solid State Phenomena, 258, pp. 259-264, 2016.12.
59. Junichiro Yamabe, Daiki Takagoshi, Hisao Matsunaga, Matsuoka Saburo, Takahiro Ishikawa, Takenori Ichigi, High-strength copper-based alloy with excellent resistance to hydrogen embrittlement, International Journal of Hydrogen Energy, https://doi.org/10.1016/j.ijhydene.2016.05.156, 41, 33, pp. 15089-15094, 2016.09, [URL].
60. Setsuo Takaki, Shigenobu Nanba, Kazunari Imakawa, MACADRE ARNAUD PAUL ALAIN, Junichiro Yamabe, Hisao Matsunaga, Matsuoka Saburo, Determination of hydrogen compatibility for solution-treated austenitic stainless steels based on a newly proposed nickel-equivalent equation, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2016.06.193, 41, 33, pp. 15095-15100, 2016.07, [URL].
61. Hisao MATSUNAGA, Takuya Nakashima, Kosei Yamada, Takashi Matsuo, Junichiro Yamabe, Saburo MATSUOKA, Effect of Test Frequency on Hydrogen-enhanced Fatigue Crack Growth in Type 304 Stainless Steel and Ductile Cast Iron, American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP(2016), 2016.07.
62. Yuhei Ogawa, Hisao MATSUNAGA, Michio Yoshikawa, Junichiro Yamabe, Saburo MATSUOKA, Fatigue life properties and anomalous macroscopic fatigue fracture surfaces of low carbon steel JIS-SM490B in high-pressure hydrogen gas environment, American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP(2016), 2016.07.
63. Saburo MATSUOKA, Junichiro Yamabe, Hisao MATSUNAGA, Mechanism of Hydrogen-Assisted Surface Crack Growth of Austenitic Stainless Steels in Slow Strain Rate Tensile Test, American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP(2016), 2016.07.
64. Junichiro Yamabe, Michio Yoshikawa, Hisao MATSUNAGA, Matsuoka Saburo, Effects of hydrogen pressure, test frequency and test temperature on fatigue crack growth properties of low-carbon steel in gaseous hydrogen, Structural Integrity Procedia, 2, pp. 525-532, 2016.07.
65. Masahiro Endo, Saburo Okazaki, Hisao Matsunaga, Shigeaki Moriyama, Kiyotaka Munaoka, Keiji Yanase, A New Fatigue Testing Machine for Investigating the Behavior of Small Shear-Mode Fatigue Cracks, Experimental Techniques, 10.1111/ext.12140, 40, pp. 1065-1073, 2016.06, [URL].
66. Junichiro Yamabe, Michio Yoshikawa, Hisao Matsunaga, Matsuoka Saburo, Effects of hydrogen pressure, test frequency and test temperature on fatigue crack growth properties of low-carbon steel in gaseous hydrogen, Structural Integrity Procedia, 2016.06.
67. Kaneaki Tsuzaki, Koki Fukuda, Motomichi Koyama, Hisao Matsunaga, Hexagonal close-packed Martensite-related Fatigue Crack Growth under the Influence of Hydrogen: Example of Fe–15Mn–10Cr–8Ni–4Si Austenitic Alloy, Scripta Materialia, 1016/j.scriptamat.2015.10.016, Vol. 113, pp. 6-9, 2016.03, [URL].
68. Saburo Matsuoka, Junichiro Yamabe, Hisao Matsunaga, Criteria for determining hydrogen compatibility and the mechanisms for hydrogen-assisted, surface crack growth in austenitic stainless steels, Engineering Fracture Mechanics, 10.1016/j.engfracmech.2015.12.023, Vol. 153, pp. 103-127, 2016.01, [URL].
69. , [URL].
70. Hisao Matsunaga, Chengqi Sun, Youshi Hong, Yukitaka Murakami, Dominant Factors for Very-High-Cycle Fatigue of High-Strength Steels and a New Design Method for Components, Fatigue & Fracture of Engineering Materials & Structures, 10.1111/ffe.12331, Vol. 38, pp. 1274-1284, 2015.11, [URL].
71. Pablo Lorenzino, Saburo Okazaki, Hisao MATSUNAGA, Yukitaka Murakami, Effect of small defect orientation on fatigue limit of carbon steels, Fatigue & Fracture of Engineering Materials & Structures, Vol. 38, pp. 1076-1086, 2015.09, [URL].
72. Yamabe Junichiro, Hisao MATSUNAGA, Yoshiyuki Furuya, Saburo MATSUOKA, ON THE MATERIAL QUALIFICATION AND STRENGTH DESIGN FOR HYDROGEN SERVICE, American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP, 2015.07.
73. Hisatake ITOGA, Hisao MATSUNAGA, Yamabe Junichiro, Saburo MATSUOKA, EFFECTS OF EXTERNAL AND INTERNAL HYDROGEN ON TENSILE PROPERTIES OF AUSTENITIC STAINLESS STEELS CONTAINING ADDITIVE ELEMENTS, American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP, 2015.07.
74. Hisao MATSUNAGA, Ryota Kondo, Yamabe Junichiro, Michio Yoshikawa, Hisatake ITOGA, Saburo MATSUOKA, HYDROGEN-ASSISTED CRACKING OF CR-MO STEEL IN SLOW STRAIN RATE TENSILE TEST WITH HIGH-PRESSURE GASEOUS HYDROGEN, American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP, 2015.07.
75. Pablo Lorenzino, Jean-Yves Buffiere, Saburo Okazaki, Yukitaka Murakami, Hisao Matsunaga, Synchrotron 3D characterization of arrested fatigue cracks initiated from small tilted notches in steel, Frattura ed Integrità Strutturale, 10.3221/IGF-ESIS.33.27, Vol. 33, pp. 215-220, 2015.06, [URL].
76. Yamabe Junichiro, Hisatake ITOGA, Torhu Awane, Takashi Matsuo, Hisao MATSUNAGA, Saburo MATSUOKA, Pressure cycle testing of Cr-Mo steel pressure vessels subjected to gaseous hydrogen, Journal of Pressure Vessel Technology, 10.1115/1.4030086, Paper No: PVT-14-1204, (13 pages), 2015.04, [URL].
77. Hisao Matsunaga, Michio Yoshikawa, Ryota Kondo, Junichiro Yamabe, Saburo Matsuoka, Slow strain rate tensile and fatigue properties of Cr–Mo and carbon steels in a 115 MPa hydrogen gas atmosphere, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2015.02.098, Vol. 40, 16, pp. 5739-5748, 2015.03, [URL].
78. Junichiro Yamabe, Hisao Matsunaga, Yoshiyuki Furuya, Shigeru Hamada, Hisatake Itoga, Michio Yoshikawa, Etsuo Takeuchi, Saburo Matsuoka, Qualification of chromium-molybdenum steel based on the safety factor multiplier method in CHMC1-2014, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2014.10.114, Vol. 40, 1, pp. 719-728, 2015.01, [URL].
79. Hisao MATSUNAGA, Chengqi Sun, Youshi Hong, Yukitaka Murakami, Dominant Factors for Very High Cycle Fatigue of High Strength Steels, Proceedings of the Sixth International Conference on Very High Cycle Fatigue (VHCF-6), 2014.10.
80. Saburo OKAZAKI, Hisao MATSUNAGA, Tohru UEDA, Hiroki KOMATA, Masahiro ENDO, A Practical Expression for Evaluating the Small Shear-mode Fatigue Crack Threshold in Bearing Steel, Theoretical and Applied Fracture Mechanics, 10.1016/j.tafmec.2014.07.016, Vol. 73, pp. 161-169, 2014.08, [URL].
81. Hisao MATSUNAGA, Michio Yoshikawa, Hisatake ITOGA, Yamabe Junichiro, Shigeru Hamada, Saburo MATSUOKA, TENSILE- AND FATIGUE-PROPERTIES OF LOW ALLOY STEEL JIS-SCM435 AND CARBON STEEL JIS-SM490B IN 115 MPA HYDROGEN GAS, American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP, 10.1115/PVP2014-28511, 2014.07, [URL].
82. Yamabe Junichiro, Hisatake ITOGA, Torhu Awane, Hisao MATSUNAGA, Shigeru Hamada, Saburo MATSUOKA, FATIGUE-LIFE AND LEAK-BEFORE-BREAK ASSESSMENTS OF CR-MO STEEL PRESSURE VESSELS WITH HIGH-PRESSURE GASEOUS HYDROGEN, American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP, 10.1115/PVP2014-28604, 2014.07, [URL].
83. Hisatake ITOGA, Takashi Matsuo, Akihiro Orita, Hisao MATSUNAGA, Saburo MATSUOKA, Ryuichi Hirotani, SSRT AND FATIGUE CRACK GROWTH PROPERTIES OF HIGH-STRENGTH AUSTENITIC STAINLESS STEELS IN HIGH-PRESSURE HYDROGEN GAS, American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP, 10.1115/PVP2014-28640, 2014.07, [URL].
84. Hisao MATSUNAGA, Hiroki KOMATA, Yamabe Junichiro, Yoshihiro FUKUSHIMA, Saburo MATSUOKA, Effect of Size and Depth of Small Defect on the Rolling Contact Fatigue Strength of Bearing Steel JIS-SUJ2, Procedia Materials Science, 10.1016/j.mspro.2014.06.268, 3, 1663-1668, 2014.06.
85. Pablo Lorenzino, Saburo Okazaki, Hisao MATSUNAGA, Yukitaka MURAKAMI, Effect of orientation of small defects on fatigue limit of steels, MATEC Web of Conferences, 10.1051/matecconf/20141207001, 12, Article number 07001, 2014.06.
86. Hisao MATSUNAGA, Masahiko MAKIZAKI, Darrell F. SOCIE, Keiji YANASE, Masahiro ENDO, Acceleration of fatigue crack growth due to occasional mode II loading in 7075 aluminum alloy, Engineering Fracture Mechanics, 10.1016/j.engfracmech.2014.04.015, Vol. 123, pp. 126-136, 2014.05, [URL], The effect of an occasional mode II loading on the subsequent mode I fatigue crack growth was investigated in a thin-walled 7075-T6511 aluminum alloy tube. Careful observation of crack growth behavior revealed that an occasional mode II loading has two contrasting effects on the subsequent crack growth. First is a retardation effect that is associated with a crack closure development due to the mode II loading. However, this effect was insignificant with respect to the crack growth life as a whole. Second is an acceleration effect that is associated with an accelerated crack growth rate in mode II. It was found that, in a relatively high ΔK regime, mode II crack growth was from one to two orders of magnitude faster than mode I crack growth. This study shows that mode II crack growth should be considered as a predominant factor in evaluating the effect of an occasional mode II loading for a mode I crack in 7075 aluminum alloy..
87. Hisatake ITOGA, Hisao MATSUNAGA, Saburo MATSUOKA, Effect of Hydrogen Gas on the Growth of Small Fatigue Crack in JIS-SCM435, Advanced Materials Research, Vol. 891-892, pp. 942-947, 2014.01.
88. YUKITAKA MURAKAMI, Yamabe Junichiro, Hisao MATSUNAGA, Microscopic Mechanism of Hydrogen Embrittlement in Fatigue and Fracture, Key Engineering Materials, Vol. 592, pp. 3-13, 2014.01.
89. , [URL].
90. Hisao MATSUNAGA, Teruki USUDA, Keiji YANASE, Masahiro ENDO, Ductility Loss in Ductile Cast Iron with Internal Hydrogen, Metallurgical and Materials Transactions A, DOI: 10.1007/s11661-013-2109-9, Vol. 45, pp. 1315-1326, 2013.11, [URL].
91. Hisao MATSUNAGA, Masahiko MAKIZAKI, Keiji YANASE, Finite Element Modeling of Plasticity-induced Crack Closure Due to Occasional Mode II Loading on Mode I Fatigue Crack Growth, Engineering Fracture Mechanics, 111, 38-49, 2013.10, [URL], Plasticity-induced fatigue crack closure associated with occasional mode II loading was simulated for two-dimensional middle-crack tension geometry by using the finite element method. When a single mode II cycle was superposed onto the steady-state mode I crack growth, the range of crack tip opening displacement, ΔCTOD, exhibited the initial drop and subsequent recovery under plane strain condition. On the other hand, under plane stress condition, ΔCTOD exhibited the initial jump and drop right after the single mode II loading, and then it showed the recovery. The present results indicate that occasional mode II loading can cause a small retardation for mode I crack growth due to the enhanced plasticity-induced closure..
92. Yukitaka MURAKAMI, Hisao MATSUNAGA, Arezou ABYAZI, Yoshihiro FUKUSHIMA, Defect Size Dependence on Threshold Stress Intensity for High-strength Steel with Internal Hydrogen, Fatigue & Fracture of Engineering Materials & Structures, 10.1111/ffe.12077, Vol. 36, 850, 2013.09, [URL].
93. , [URL].
94. Teruki USUDA, Kenshin MATSUNO, Hisao MATSUNAGA, Keiji YANASE, Masahiro ENDO, Hydrogen-induced Ductility Loss in Cast Irons, Materials Science Forum, 10.4028/www.scientific.net/MSF.750.264, 750, 260-263, 2013.02.
95. Masahiko MAKIZAKI, Hisao MATSUNAGA, Keiji YANASE, Masahiro ENDO, Effect of Occasional Shear Loading on Fatigue Crack Growth in 7075 Aluminum Alloy, Materials Science Forum, 10.4028/www.scientific.net/MSF.750.264, 750, 264-267, 2013.02, Effect of occasional mode II loading on subsequent mode I fatigue crack growth behavior was investigated by using a thin-walled tube made of 7075-T6511 aluminum alloy. Careful observation of crack growth behavior revealed that the occasional mode II loading has two contradictory effects for crack growth behavior. The first is a retardation effect that is associated with the plastic deformation near crack tip. However, this effect is negligibly small for the crack growth life as a whole. The second is an acceleration effect caused by mode II fatigue crack growth itself. It was found that under relatively high ΔK level, the mode II crack growth was about an order magnitude faster than mode I crack growth. Therefore, to properly evaluate the effect of occasional shear loading in the 7075 alloy, the mode II crack growth should be taken into account..
96. Saburo OKAZAKI, Atsushi KUSABA, Hisao MATSUNAGA, Masahiro ENDO, Investigation for small shear-mode fatigue cracks in bearing steels, Materials Science Forum, 10.4028/www.scientific.net/MSF.750.264, 750, 236-239, 2013.02.
97. K.Matsuno, H.Matsunaga, M.Endo, and K.Yanase, Effect of hydrogen on uniaxial tensile behaviors of a ductile cast iron, International Journal of Modern Physics: Conference Series, 10.1142/S2010194512003522, 6, 407-412, 2012.06.
98. Naoya Shomura, Keiji Yanase, Hisao Matsunaga, Masahiro Endo, Effects of Crack Size and Crack Face Interference on Shear Fatigue Crack Growth in a Bearing Steel, Advanced Materials Research, 10.4028/www.scientific.net/AMR.275.15, 275, 15-18, 2011.07.
99. Toshiya Shingo, Keiji Yanase, Hisao Matsunaga, Masahiro Endo, An Analysis of Fatigue Strength of Notched Components, Advanced Materials Research, 10.4028/www.scientific.net/AMR.275.43, 275, 43-46, 2011.07.
100. Hisao MATSUNAGA, Hiroshi NODA, Visualization of Hydrogen Diffusion in a Hydrogen-Enhanced Fatigue Crack Growth in Type 304 Stainless Steel, Metallurgical and Materials Transactions A, 10.1007/s11661-011-0661-8, 42, 2696-2705, 2011.03, [URL].
101. Hisao Matsunaga, Kenshin Matsuno, Katsuya Hayashida, Effect of Hydrogen on Tensile Properties of a Ductile Cast Iron, Proceedings of TMS 2011 Annual Meeting, 2011.03.
102. Naoya Shomura, Daisuke Koyanagi, Hisao Matsunaga, Masahiro Endo, Interference of Crack Faces and Shear-Mode Fatigue Crack Threshold in a Bearing Steel , Multiscaling of Synthetic and Natural Systems with Self-Adoptive Capability (Proc. of Mesomechanics 2010), 153-156, 2010.06.
103. Hisao Matsunaga, Effect of Interference of Crack Faces on Shear-mode Threshold for Small Fatigue Cracks in a Bearing steel, Proceedings of 9th International Conference on Multiaxial Fatigue and Fracture (ICMFF9), 2010.06.
104. Hiromasa TAKAHASHI, Shigeaki MORIYAMA, Haruhiko FURUTA, Hisao MATSUNAGA, Yuki SAKAMOTO, Toshihiro KIKUTA, Three Lateral Osteotomy Designs for Bilateral Sagittal Split Osteotomy: Biomechanical Evaluation with Three-dimensional Finite Element Analysis, Head & Face Medicine, 6:4 , 2010.03.
105. Arthur J. McEvily, Hisao Matsunaga, On Fatigue Striations, Scientia Iranica, Transaction B: Mechanical Engineering, 17, pp.75-82, 2010.02.
106. Hisao MATSUNAGA, Naoya SHOMURA, Satoshi MURAMOTO, Masahiro ENDO, Shear Mode Threshold for a Small Fatigue Crack in a Bearing Steel, Fatigue & Fracture of Engineering Materials & Structures, 10.1111/j.1460-2695.2010.01495.x, 34, 72-82, 2010.01, [URL].
107. Daisuke Koyanagi, Naoya Shomura, Masahiro Endo, Hisao Matsunaga, Shigeaki Moriyama, Near-threshold Fatigue Behaviors of Small Shear Cracks in Bearing Steel, Proceedings of 4th International Conference on Experimental Mechanics 2009 (ICEM2009), 2009.11.
108. Katsuya Hayashida, Hisao Matsunaga, Masahiro Endo, Hydrogen Emission in Fatigue Process of Hydrogen-charged Austenitic Stainless Steels, Proceedings of 4th International Conference on Experimental Mechanics 2009 (ICEM2009), doi:10.1117/12.852121, 2009.11.
109. Arthur J. McEvily, Masahiro Endo, Keiji Yamashita, Sotomi Ishihara, Hisao Matsunaga, Fatigue Notch Sensitivity and the Notch Size Effect , International Journal of Fatigue, 30, 12, 2087-2093, 2008.12.
110. Arthur J. McEvily, Takashi Nakamura, Hiroyuki Oguma, Keiji Yamashita, Hisao Matsunaga, Masahiro Endo, On the Mechanism of Very High Cycle Fatigue in Ti–6Al–4V , Scripta Materialia, 59, 1207-1209, 2008.11.
111. Hisao Matsunaga, Satoshi Muramoto, Masahiro Endo, Threshold of Shear-mode Fatigue Crack Growth in Bearing Steel, Proceedings of 17th European Conference on Fracture (ECF17), 2008.09.
112. Satoshi Muramoto, Hisao Matsunaga, Shigeaki Moriyama, Masahiro Endo, Crack Size Dependency of Shear-mode Fatigue Crack Threshold in Bearing Steel, Key Engineering Materials, 10.4028/www.scientific.net/KEM.385-387.449, 385-387, 449-452, 2008.07.
113. Arthur J. McEvily, Sotomi Ishihara, Masahiro Endo, Hiroshi Sakai, Hisao Matsunaga, On one- and Two-parameter Analyses of Short Fatigue Crack Growth, International Journal of Fatigue, 29, 2237-2245, 2007.12.
114. A. J. McEvily, M. Endo, S. Cho, J. Kasivitamnuay, H. Matsunaga, Fatigue Striations and Fissures in 2024-T3 Aluminum Alloy, Materials Science Forum, 10.4028/www.scientific.net/MSF.567-568.397, 567-568, 397-400, 2007.12, A study has been made of the striations and fissures developed in the aluminum alloy 2024-T3 during fatigue crack growth. Fissures were found to form on inclined facets. They were uniformly spaced as the result of a shielding process. Striation spacings were in accord with da/dN values at the higher levels of K investigated, but at low K levels striation spacings were larger than the corresponding da/dN values. The percentage of the fracture surface containing striations varied with the K level, ranging from less than 1 % at low K levels to 80 % at higher K levels. The reason for the discrepancy between the spacing of striations and the corresponding da/dN values is discussed..
115. Daisuke Cho, Hisao Matsunaga, Shear-type Fatigue Crack Growth in SAE52100 Steel, Key Engineering Materials, 10.4028/www.scientific.net/KEM.353-358.287, 353-358, 287-290, 2007.09.
116. Hiroshi NODA, Hisao MATSUNAGA, Fatigue Crack Growth Acceleration Due to Hydrogen in Type 304 Stainless Steel, Key Engineering Materials, 10.4028/www.scientific.net/KEM.345-346.319, 345-346, 319-322, 2007.09.
117. Hiroshi Noda, Hisao Matsunaga, Hydrogen Emission and Martensitic Transformation in the Vicinity of Fatigue Cracks in Hydrogen-charged Type 304 Stainless Steel, Proceedings of International Conference on Advanced Technology in Experimental Mechanics '07 (ATEM'07), 2007.09.
118. Hisao Matsunaga, Daisuke Cho, Satoshi Muramoto, Shear-Mode Fatigue Crack Growth in Bearing Steel, Proceedings of 8th International Conference on Multiaxial Fatigue and Fracture (ICMFF8), 2007.06.
119. Yukitaka Murakami, Hisao Matsunaga, The effect of hydrogen on fatigue properties of steels used for fuel cell system, International Journal of Fatigue, 28, 1509-1520, 2006.11.
120. Masahiro Endo, Arthur J. McEvily, Hisao Matsunaga, Dietmar Eifler, The Growth of Short Cracks from Defects under Multi-Axial Loaing, Proceedings of the 16th European Conference of Fracture, ECF16, 2006.07.
121. Yukitaka Murakami, Junji Nagata, Hisao Matsunaga, Factors Affecting Ultralong Life Fatigue and Design Method for Components, Proceedings of the 9th International Congress on Fatigue, Fatigue 2006, 2006.05.
122. Yukitaka Murakami, Hisao Matsunaga, Effect of Hydrogen on High Cycle Fatigue Properties of Stainless Steels Used for Fuel Cell System, Proceedings of the 3rd International Conference on Very High Cycle Fatigue (VHCF-3), 322-333, 2004.09.
123. Hisao MATSUNAGA, Yukitaka MURAKAMI, Masanobu KUBOTA, Joon-Hyun LEE, Fatigue Strength of Ti-6Al-4V Alloys Containing Small Artificial Defects, Materials Science Research International, 9, 4, 263-269, Vol.9, No.4, pp.263-269, 2003.12.
124. Effect of FOD on Fatigue Strength of Ti-6Al-4V Alloy.
125. Hisao MATSUNAGA, Ryuichi EZAKI and Yukitaka MURAKAMI, THE EFFECT OF HYDROGEN ON THE HIGH CYCLE FATIGUE STRENGTH OF TI-6AL-4V, The Eighth International Fatigue Congress, Fatigue 2002, Vol.4, pp.2525-2532, 2002.06.
126. Hisao Matsunaga, Yukitaka Murakami, Effect of Small Defects on Fatigue Strength of Ti-6Al-4V Alloy, APCFS & ATEM'01, Vol.1, pp366-371, 2001.10.
127. Hisao Matsunaga, Owe Mårs, Bengt Johannesson, Yukitaka Murakami, Statistical Distribution of Powder Sizes and Fatigue Strength of Powder Metal, Proceedings of The Seventh International Fatigue Congress, Fatigue ’99, 3/4, 1817-1822, 1999.06.
128. Masahiro Endo, Takumi Saito, Shigeaki Moriyama, Saburo Okazaki, Hisao MATSUNAGA, FRICTION AND WEAR PROPERTIES OF HEAT-TREATED Cr-Mo STEEL DURING RECIPROCATING SLIDING CONTACT WITH SMALL RELATIVE MOTION, Proceedings of 4th International Conference on Fracture Fatigue and Wear Wear, FFW 2015, 3, 215-220.