| 1. |
Shigeru HAMADA, Nao SHIRAMIZU, Hiroshi NOGUCHI, Approximation method for arbitrary-shaped stress concentration source; application of physical and mathematical approximations of arbitrary parent–child notch, Theoretical and Applied Fracture Mechanics, 10.1016/j.tafmec.2023.104116, 129, Article number 104221, 2023.12. |
| 2. |
Taeseul Park, Asuka Kitahara, Toshiyuki Ishina, Shigeru Hamada, Hiroshi Noguchi, Proposal of new crack-tip-opening-displacement as a mechanical driving force of elastic-plastic fracture mechanics, Theoretical and Applied Fracture Mechanics, 10.1016/j.tafmec.2023.104116, 128, Article number 104116, 2023.10. |
| 3. |
Li, W.
Hamada, S., Deterministic approach on microstructurally small crack definition based on a crystalline plasticity finite element method incorporating strain localization, Fatigue and Fracture of Engineering Materials and Structures, 10.1111/ffe.14100, 46, 10, 3699-3712, 2023.07. |
| 4. |
Chen, B.
Hamada, S.
Li, W.
Noguchi, H., Crystal plasticity FEM study of material and mechanical effects on damage accumulation mode of fatigue crack propagation, International Journal of Fatigue, 10.1016/j.ijfatigue.2023.107683, 173, 2023.04. |
| 5. |
Zhang, K.
Hamada, S.
Yokoi, T.
Noguchi, H., Significant reduction of fatigue crack non-propagation limit caused by damage accumulation mode fatigue crack propagation in a precipitation-hardened punched steel plate, Materials Science and Engineering A, 10.1016/j.msea.2023.144871, 871, 2023.03. |
| 6. |
Chen, B.
Hamada, S.
Kato, T.
Makino, T.
Noguchi, H., Quantitative fatigue limit prediction of mechanically long crack under mixed modes based on fracture mechanics and fatigue mechanism, International Journal of Fatigue, 10.1016/j.ijfatigue.2022.107371, 167, 2022.11. |
| 7. |
Li, W.
Hamada, S.
Noguchi, H., Material index for strain localization susceptibility in cracked bodies: Examination of single-crystal Cu using crystal plasticity finite element method, Fatigue and Fracture of Engineering Materials and Structures, 10.1111/ffe.13803, 45, 3137-3153, 2022.07. |
| 8. |
Iwakiri, D.
Mizoguchi, T.
Hamada, S.
Noguchi, H., Material indices controlling the threshold stress intensity factor range of arbitrarily long mechanical cracks based on plasticity-induced-crack-closure analyses, Theoretical and Applied Fracture Mechanics, 10.1016/j.tafmec.2022.103500, 121, 2022.07. |
| 9. |
Zhang, K.
Hamada, S.
Shindome, K.
Yokoi, T.
Noguchi, H., Early crack initiation mode during tensile fracture process in a punch-processed precipitation-hardened steel plates and evaluation method to treat the crack as an equivalent pre-crack, Materials Science and Engineering A, 10.1016/j.msea.2022.143534, 850, 2022.07. |
| 10. |
Higuchi, Y. K.
Ishina, T.
Hamada, S.
Matsumoto, T.
Noguchi, H., Consideration on stable crack propagation from cast defect in As-cast AZX912 Mg alloy, Theoretical and Applied Fracture Mechanics, 10.1016/j.tafmec.2022.103427, 120, 2022.06. |
| 11. |
Yu-ki Higuchi,
Toshiyuki Ishina,
Shigeru Hamada,
Toshiharu Matsumoto,
Hiroshi Noguchi, Analysis for Tensile Strength of Multi-phase Alloy Composed of Ductile Matrix and Brittle Reinforcement with Circumferential Notch in As-cast AZX912 Mg Alloy, Theoretical and Applied Fracture Mechanics, 10.1016/j.tafmec.2022.103465, 121, 2022.06. |
| 12. |
Proaño, B.
Miyahara, H.
Morishita, K.
Matsumoto, T.
Sakai, H.
Noguchi, H.
Hamada, S., Annealing effects on fracture process and tensile strength of non-combustible Mg products fabricated by selective laser melting, Theoretical and Applied Fracture Mechanics, 10.1016/j.tafmec.2022.103411, 120, 2022.05. |
| 13. |
Shigeru Hamada,
Yamato Araki,
Hiroshi Noguchi, Digital-image-correlation observation of cyclic plastic strain field during the damage-accumulation mode of fatigue crack propagation under pure cyclic mode II loading for cold-rolled SUS430 steel, Materials Science and Engineering A, 10.1016/j.msea.2022.143246, 845, 2022.05.  |
| 14. |
Li, W.,
Hamada, S.,
Noguchi, H., Interaction analysis between strain concentration and strain localization in cracked body, Fatigue and Fracture of Engineering Materials and Structures, 10.1111/ffe.13668, 45, 5, 1406-1420, 2022.02. |
| 15. |
Suzuki, K.
Hamada, S.
Koyama, M.
Tsuzaki, K.
Noguchi, H., Notch shape dependence of fatigue crack extension in equiatomic CrMnFeCoNi high-entropy alloy, International Journal of Fatigue, 10.1016/j.ijfatigue.2021.106481, 153, 106481, 2021.08. |
| 16. |
Huynh, T. T.
Hamada, S.
Tsuzaki, K.
Noguchi, H., Roles of hydrogen and plastic strain distribution on delayed crack growth in single-crystalline Fe–Si alloy, Materials Science and Engineering A, 10.1016/j.msea.2020.140703, 803, 140703, 2020.12. |
| 17. |
Proaño, B.
Miyahara, H.
Matsumoto, T.
Hamada, S.
Sakai, H.
Ogawa, K.
Suyalatu,
Noguchi, H., Plastic strain distribution throughout the microstructure duality during the fracture process of non-combustible mg products fabricated by selective laser melting, Theoretical and Applied Fracture Mechanics, 10.1016/j.tafmec.2020.102805, 110, 102805, 2020.10. |
| 18. |
Verma, V. K.
Gopalakrishnan, C. K.
Hamada, S.
Yokoi, T.
Noguchi, H., Effect of strain localization on fatigue properties of precipitation-hardened steel with an arbitrarily length crack, International Journal of Fatigue, 10.1016/j.ijfatigue.2020.106017, 143, 106017, 2020.10. |
| 19. |
Shigeru Hamada, Hiroshi Noguchi , Fatigue characteristics of a notched specimen made of commercially-pure titanium, Theoretical and Applied Fracture Mechanics, 10.1016/j.tafmec.2020.102764, 109, 2020.09. |
| 20. |
He Liu, Shigeru Hamada, Motomichi Koyama, Hiroshi Noguchi, Distinguishing geometric and metallurgic hydrogen-embrittlement susceptibilities in pre-cracked structures made of interstitial-free steel under monotonic tension, Theoretical and Applied Fracture Mechanics, 10.1016/j.tafmec.2020.102574, 108, 2020.08, Hydrogen embrittlement (HE) is widely believed to be harmful to engineering structures made of ferritic steel, particularly in the presence of pre-cracks. However, in this study, the ultimate tensile strength (UTS) of shallow pre-cracked cylinder specimens made of interstitial-free (IF) steel, which represents a standard microstructure of ferritic steel, does not always decrease in the hydrogen environment. Namely, the fracture characteristic is sensitive to hydrogen, but UTS is not under specific conditions. This influence of HE contrary to the common-sense understanding is attributed to the following: (1) the crack propagation assisted by hydrogen-enhanced localized plasticity (HELP) is stable before the onset of plastic instability because of exceedingly-high fracture instability toughness; and (2) the plastic strain localization at the pre-crack tip and secondary crack tips resisted the onset of plastic instability. Additionally, this effect calls into question the general applicability of conventional investigation of HE susceptibility that mainly focuses on the variation of fracture characteristic, which is often defaulted to cause changes in mechanical properties. Here, HE susceptibility is deduced to be depended mainly on geometric properties (geometric HE susceptibility) for shallow pre-cracked structures, while that for deep pre-cracked structures depends mainly on material properties (metallurgic HE susceptibility). Subdividing HE susceptibility helps identify conditions under which plastic strain localization caused by HE susceptibility is beneficial for UTS in fail-safe design.. |
| 21. |
He Liu, Shigeru Hamada, Motomichi Koyama, Hiroshi Noguchi, Equivalence between shallow notch and shallow crack in structural failure caused by plastic instability, Theoretical and Applied Fracture Mechanics, 10.1016/j.tafmec.2020.102577, 108, 2020.08, Introducing crack-like notches is essential for investigating the mechanical properties of pre-cracked structures because fatigue pre-cracking occasionally fails to ensure some rigorous investigation conditions. However, the results obtained by previous studies related to crack-like notches under small-scale yielding are invalid for shallow notches with extensive plasticity, particularly when plastic instability instead of unstable crack propagation governs the structural strength. This study focused on the plastic instability occurring under the plane strain condition without the assistance of pre-crack propagation. The boundary condition, geometric configuration, and elastoplastic fields dominating the overall work hardening in notched and cracked cross-sections were considered in finite element analyses. From the perspective of asymptotic and phenomenological analysis, this study proposes that a shallow crack-like notch should satisfy the following requirements: (1) the structural strength should be independent of the notch geometry, except for the notch depth; (2) the elastoplastic fields in the notched cross-section should be broadly convergent to those in the pre-cracked cross-section; (3) the failure mode characterized by damage pattern should be similar. The underlying reason for crack-like notches existing in extensive plasticity is that different elastoplastic field gradients close to the notch root or crack tip may still result in the same overall work hardening in notched and pre-cracked cross-sections. This concept was experimentally verified using interstitial-free steel, which is a typical strain-hardening ferrite steel with excellent ductility and simple metallurgical microstructure. The generality of the identification method and the significance of influential factors for shallow crack-like notches are discussed in this study.. |
| 22. |
Samsol Faizal Anis, Motomichi Koyama, Shigeru Hamada, Hiroshi Noguchi, Influence of dynamic-strain aging due to excess Mg on fatigue crack growth rate scatter in Al6061-T6 alloy, Theoretical and Applied Fracture Mechanics, 10.1016/j.tafmec.2020.102617, 108, 2020.08, Fatigue failure results in high industrial costs, and its mechanism requires close examination; however, current methods are costly and time-consuming due to the need for a large number of test specimens. The purposes of this study are to investigate the influence of dynamic strain aging on fatigue crack growth rate (FCGR) scatter in Al 6061-T6 alloys and to present a new approach to evaluate the scatter of FCGR using a limited number of the test specimen. Rotating bending fatigue tests of 6061-T6-based Al alloys with added Zr and excess Mg were performed under constant amplitude loading using smooth specimens. The scatter behavior of FCGR is investigated by examining the fatigue crack growth on the specimen surface and fractographic observation on the fracture surface. The accounting for the interaction effects of multiple surface cracks and fractographic examination on striation formation from previous findings revealed that excess Mg promoted small scatter in Mode I fatigue crack growth. This study showed that local plastic deformation affected the FCGR scatter of microstructurally-large fatigue cracks. These findings suggest that dynamic strain aging of Mg induces stable Mode I crack growth due to pinning of dislocation movement on slip planes during the crack growth process.. |
| 23. |
He Liu, Shigeru Hamada, Motomichi Koyama, Hiroshi Noguchi, Shallow Crack Effect on Evaluation of Residual Tensile Strength: Harmless and Stable Cracks in Finite-sized Structure Made of Ductile Metals, Theoretical and Applied Fracture Mechanics, 10.1016/j.tafmec.2020.102734, 109, 2020.08. |
| 24. |
Wakita, Yuto; Tachikawa, Yuya; Nakajima, Hironori; Hamada, Shigeru; Ito, Kohei, Visualization and mechanical strength of glass seal in planar type solid oxide fuel cells, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, 10.1016/j.ijhydene.2020.05.153, 45, 41, 21754-21766, 2020.08. |
| 25. |
Shigeru Hamada, Hiroshi Noguchi, Fatigue characteristics of a notched specimen made of commercially-pure titanium, Theoretical and Applied Fracture Mechanics, 10.1016/j.tafmec.2020.102764, 109, 102764, 2020.07. |
| 26. |
Samsol Faizal Anis, Motomichi Koyama, Shigeru Hamada, HiroshiNoguchi, Simplified stress field determination for an inclined crack and interaction between two cracks under tension, Theoretical and Applied Fracture Mechanics, 10.1016/j.tafmec.2020.102561, 107, 102561, 2020.06. |
| 27. |
Tingshu Chen, Motomichi Koyama, Shigeru Hamada, Hiroshi Noguchi, Fundamental criterion Ktrans for failure analysis of hydrogen-assisted cracks in notched specimens of pure Ni, Theoretical and Applied Fracture Mechanics, 10.1016/j.tafmec.2020.102556, 107, 2020.06, The effects of short notches on crack initiation and extension were studied under electrochemical hydrogen charging in pure nickel. In the hydrogen-charged smooth specimen, multiple cracks were initiated on grain boundaries after significant plastic deformation and were subsequently arrested by crack blunting in the interior of neighboring grains. With the assistance of sub-cracks on specimen surface, quasi-cleavage crack propagation occurred soon after, causing the final failure. The introduction of a notch did not change the crack initiation site (grain boundary). However, crack propagation exhibited significant initial notch-length dependence. A 2.5 mm notch caused quasi-cleavage crack propagation without sub-critical cracks (intergranular cracks) initiation and growth, because the notch root acted as a strongly preferential site for crack extension. However, with a smaller notch, sub-critical cracks initiation and growth were necessary to extend intergranular fracture depth and reach a critical crack length to supply adequate plasticity. This plasticity could not be met in the initial stage from the notch root with hydrogen charging. The relation between maximum remote stress and critical crack length among different notch lengths was shown to be a geometry-independent parameter of pure nickel, which can predict tensile strength under various notch configurations.. |
| 28. |
Verma, Virendra Kumar; Koyama, Motomichi; Hamada, Shigeru; Akiyama, Eiji, Effects of hydrogen content that alters damage evolution mechanisms in SUH 660 precipitation-strengthened Fe–Cr–Ni steel, Materials Science and Engineering: A, 10.1016/j.msea.2020.139750, 791, 139750, 2020.06. |
| 29. |
Kai SUZUKI, Motomichi KOYAMA, Shigeru HAMADA, Kaneaki TSUZAKI and Hiroshi NOGUCHI, Planar Slip-driven Fatigue Crack Initiation and Propagation in an Equiatomic CrMnFeCoNi High-entropy Alloy, International Journal of Fatigue, 10.1016/j.ijfatigue.2019.105418, 133, 105418, 2020.04. |
| 30. |
Virendra Kumar Verma, Motomichi Koyama, Shigeru Hamada, Eiji Akiyama, Multiple damage mechanisms facilitated by planar dislocation glide in a commercial-grade precipitation-strengthened Fe–Ni–Cr-based steel, Materials Science and Engineering A, 10.1016/j.msea.2020.139250, 782, 2020.04, The present study addresses the damage evolution mechanism in precipitation-strengthened Fe–Ni–Cr-based steel (SUH 660) at ambient temperature in air. Specifically, damage quantification and associated microstructure characterization were performed. The damage initiation sites were inclusion and grain boundaries impinging dislocation slip. The early stage of damage evolution was observed before necking of the specimen. Subsequent plastic straining caused damage growth along slip planes and coalescence of damage via localized shear in ligaments between damages, for which the behavior was associated with the planar character of the slip. The damage evolution behavior observed in the post-mortem specimen was consistent with fractographic characteristics.. |
| 31. |
Thanh Thuong Huynh, Motomichi Koyama, Yoshimasa Takahashi, Shigeru Hamada, Kaneaki Tsuzaki, Hiroshi Noguchi, Plastic deformation sequence and strain gradient characteristics of hydrogen-induced delayed crack propagation in single-crystalline Fe–Si alloy, Scripta Materialia, 10.1016/j.scriptamat.2019.11.012, 178, 15, 99-103, 2020.03. |
| 32. |
Shigeru Hamada, Kejin Zhang, Motomichi Koyama, Masaharu Ueda, Hiroshi Noguchi, Fatigue crack propagation modes
plastic deformation mode and damage accumulation mode, International Journal of Fracture, 10.1007/s10704-020-00433-7, 222, 1-2, 111-122, 2020.03, To define the fatigue crack propagation mode for the prediction and classification of the experimental results based on its evolution mechanism, successive mesoscopic observations of a fatigue process under pure cyclic mode II loading are performed. Thus, damage accumulation, which is considered to be a vacancy accumulation, is found to be a mechanism. The phenomena occur not at the crack tip but ahead of it. Thus, “plastic deformation mode” and “damage accumulation mode” are the terms proposed to represent the fatigue crack propagation modes instead of “tensile mode” and “shear mode,” respectively. Moreover, as a method to classify both the fatigue crack propagation modes using the experimental results, it is proposed to identify the plastic strain in the wake of the crack tip.. |
| 33. |
He Liu, Shigeru Hamada, Hiroshi Noguchi, Harmless preexisting crack in structures made of hydrogen-embrittlement sensitive materials under monotonic tension, 2020 4th International Conference on Material Science and Technology, ICMST 2020
IOP Conference Series: Materials Science and Engineering, 10.1088/1757-899X/774/1/012098, 774, 1, 2020.03, The interaction of hydrogen with the dislocations in the plastic zone of preexisting cracks (pre-cracks) in engineering components generally degrades the ultimate tensile strength (UTS). Hence, the crack effect coupled with hydrogen-embrittlement (HE) is widely believed to be harmful in engineering applications. However, in this study, the UTS of shallow pre-cracked structures made of interstitial-free (IF) steel, which is a hydrogen-embrittlement sensitive material, may not be wakened in hydrogen environment. Results of cylinder specimens with saturated hydrogen were experimentally and microscope-analytically compared with that of specimens without hydrogen. Then, this anti-common-sense influence of hydrogen was attributed as follows: (1) the crack propagation assisted by hydrogen enhanced localized plasticity (HELP) is stable before the onset of plastic instability because of high fracture instability toughness; and (2) the plastic strain localization at tips of the pre-crack and secondary cracks resists the onset of plastic instability. Additionally, the applicability of such a shallow crack effect coupled with HE presented by this study in engineering applications was discussed.. |
| 34. |
Samsol Faizal Anis, Motomichi Koyama, Shigeru Hamada, Hiroshi Noguchi, Mode I fatigue crack growth induced by strain-aging in precipitation-hardened aluminum alloys, Theoretical and Applied Fracture Mechanics, 10.1016/j.tafmec.2019.102340, 104, 102340, 2019.12. |
| 35. |
Bochuan Li, Motomichi Koyama, Shigeru Hamada, Hiroshi Noguchi, Effect analysis of stress-intensity-factor-range decreasing rate for obtaining threshold stress-intensity-factor-range, Theoretical and Applied Fracture Mechanics, 10.1016/j.tafmec.2019.102377, 104, 2019.12. |
| 36. |
Bryan Proaño, Hirofumi Miyahara, Toshiharu Matsumoto, Shigeru Hamada, Hitoshi Sakai, Kiyoshi Ogawa, Suyalatu, Hiroshi Noguchi, Weakest region analysis of non-combustible Mg products fabricated by selective laser melting, Theoretical and Applied Fracture Mechanics, 10.1016/j.tafmec.2019.102291, 103, 2019.10. |
| 37. |
Virendra Kumar Verma, Shigeru Hamada, Motomichi Koyama, Understanding the damage initiation mechanism of precipitation-strengthened Fe-Ni-Cr based austenitic steel, 10th International Conference of Materials Processing and Characterization, ICMPC 2020
Materials Today: Proceedings, 10.1016/j.matpr.2020.02.637, 26, 3081-3084, 2019, The present study aims at enhancing the understanding of damage evolution mechanism in precipitation-strengthened Fe-Ni-Cr based steel (SUH660). Tensile deformation at room temperature, subsequent damage quantification and microstructural characterization was performed. The primary damage initiation sites were observed at inclusions and spots where dislocation slip impinges grain boundary. Early damage initiation was also observed.. |
| 38. |
Shigeru Hamada, Jiwang Zhang, Kejin Zhang, Motomichi Koyama, Toshihiro Tsuchiyama, Tatsuo Yokoi, Hiroshi Noguchi, Ductile-to-brittle transition in tensile failure due to shear-affected -zone with a stress-concentration source: A comparative study on punched-plate tensile-failure characteristics of precipitation-hardened and dual-phase steels, International Journal of Fracture, 10.1007/s10704-018-0304-9, 2018.08. |
| 39. |
Shigeru HAMADA,
Taro SUEMASU,
Shuto FUKUDOME,
Motomichi KOYAMA,
Masaharu UEDA,
Hiroshi NOGUCHI, Roughness-induced stress shielding effect in fatigue crack propagation under Mode II loading, International Journal of Fatigue, 10.1016/j.ijfatigue.2018.06.029, 116, 245-256, 2018.06. |
| 40. |
Junji Sakamoto, Shigeru Hamada, Hiroshi Noguchi, Effects of the shape of small flaws and damage due to a focused ion beam on the fatigue strength characteristics of annealed medium‑carbon steel, Engineering Failure Analysis, 10.1016/j.engfailanal.2018.02.005, 87, 49-68, 2018.02. |
| 41. |
Shigeru HAMADA, Tsuyoshi MORIYAMA, Hiroshi NOGUCHI, Dependence of Fatigue Limit on Step Height for Stepped 0.45% Carbon Steel with Singular Stress Field, Engineering Fracture Mechanics, 188, 20-35, 2018.01. |
| 42. |
Masataka Aibara, Motomichi Koyama, Shigeru Hamada, Hiroshi Noguchi, Analysis of fatigue crack configuration influence on fatigue life, 22nd European Conference on Fracture, ECF 2018
Procedia Structural Integrity, 10.1016/j.prostr.2018.12.239, 13, 1148-1153, 2018.01, When a crack initiates and grows in a plain specimen under constant cyclic load amplitude, fatigue crack growth behavior is not reproducible. The fatigue crack length l 0 when the scatter of the fatigue crack growth rate converges is reported by observing the crack growth behavior on the specimen surface. The l 0 is reported that it is approximately six times as long as the grain size in carbon steels. However, the crack shape of the inside is not observed and we considered that the three-dimensional irregular fatigue crack front shape affects the fatigue crack growth behavior on the specimen surface. Furthermore, the physical meaning and controlling factors of the l 0 is still uncertain. Therefore, in this study, we propose two factors that affect the local fatigue crack growth rate: local microstructural and mechanical factors. The former causes a variation of the three-dimensional fatigue crack front shape, and the fatigue crack front shape synergistically affects the mechanical condition at the crack tip. Then we investigated the stress intensity factor values along the tip of the crack including a part of the locally grown crack front. And we propose a concept of force caused by a stable growth part which prevents local growth parts from growing.. |
| 43. |
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.. |
| 44. |
Kejin Zhang, Shigeru Hamada, Motomichi Koyama, Tatsuo Yokoi, Hiroshi Noguchi, Influence of shear-affected-zone due to punching on tensile characteristics of steel plate, 22nd European Conference on Fracture, ECF 2018
Procedia Structural Integrity, 10.1016/j.prostr.2018.12.196, 13, 1047-1052, 2018.01, In punched steel plate, "punched specimen" from here onwards, the region near the edge of the punched hole is called the shear-affected-zone (SAZ), where tensile characteristics are compromised due to the punching process. However, the specific characteristics and influence on the tensile characteristics of the SAZ are unknown. Therefore, it is difficult to predict the effects of punching on the specimen. Here, we evaluated two kinds of specimens: punched and "honed." The hole of the honed specimen is formed by drilling and polishing, thus there is no SAZ on the honed specimens. In these specimens, we focused on the initiation and propagation of cracks under tensile loading and set the following objectives: (1) Determine whether any special events occur in the fracture mechanism of the punched vs honed specimens under tensile loading. (2) Find the reasons for any special events that occur. In our investigation, a punched specimen showed brittle fracture even within the static range of the strain rate. By failure surface observation of the punched specimens, we found that under tensile loading, cracks caused by the shear stress aligned with the tensile direction initiate in the SAZ. These cracks are the origin of the final fracture of the punched specimen. We assumed that whether the break is a ductile failure or brittle fracture depends on whether the crack tip becomes blunt. The differences in the fracture behaviors are investigated via detailed fracture surface observation.. |
| 45. |
Temma Sano, Daisuke Sasaki, Motomichi Koyama, Shigeru Hamada, Hiroshi Noguchi, Proposal and verification of novel fatigue crack propagation simulation method by finite element method., 22nd European Conference on Fracture, ECF 2018
Procedia Structural Integrity, 10.1016/j.prostr.2018.12.240, 13, 1154-1158, 2018.01, In this paper, we propose and verify a novel method to simulate crack propagation without propagating a crack by finite element method. We propose this method for elastoplastic analysis coupled with convection-diffusion. In the previous study, we succeeded in performing elastoplastic analysis coupled with convection-diffusion of hydrogen for a material with a crack under tensile loading. This research extends the successful method to fatigue crack propagation. In convection-diffusion analysis, in order to simulate the invasion and release of elements through the free surface, the crack tip is expressed by using a notch with a sufficiently small radius. Therefore, the node release method conventionally used to simulate crack propagation cannot be applied. Hence, instead of crack propagation based on an analytical model, we propose a novel method that can reproduce the influence of the vicinity of the crack tip on a crack. We moved the stress field near the crack tip in the direction opposite to that of crack propagation by an amount corresponding to the crack propagation length. When we extend the previous method to fatigue crack propagation simulation, we must consider the difference in strain due to loading and unloading. This problem was solved by considering the strain due to loading as a displacement. Instead of moving the strain due to loading, we moved the displacement. First, we performed a simple tensile load analysis on the model and output the displacement of all the nodes of the model at maximum load. Then, the displacement was moved in the direction opposite to that of crack propagation. Finally, the stress field was reproduced by forcibly moving all the nodes by the displacement amount. The strain due to unloading was reproduced by removing the displacement. Furthermore, we verified the equivalence of the crack propagation simulation and the proposed method.. |
| 46. |
Taketo Kaida, Motomichi Koyama, Shigeru Hamada, Hiroshi Noguchi, Eisaku Sakurada, Tatsuo Yokoi, Kohsaku Ushioda, Proposal of fractographic analysis method coupled with EBSD and ECCI, 22nd European Conference on Fracture, ECF 2018
Procedia Structural Integrity, 10.1016/j.prostr.2018.12.226, 13, 1076-1081, 2018.01, Fracture surface contains key information to analyze the crack propagation behavior and identify the causes of fracture in post-mortem specimens/structural parts. For instance, fatigue crack propagation rate and the associated ΔK can be estimated from a fractographic feature, i.e., the striation spacings. However, the current fractography-based methods for the estimation of fatigue crack propagation rate and ΔK require the presence of striations. This requirement limits the capacity for the quantitative analysis of the fracture surface. Therefore, further advancement of fatigue fractography is required to facilitate the quantitative assessment of fracture, using post-mortem specimens/structural parts. In this study, we propose fractography coupled with microstructural evolution underneath the fracture surface. Microstructural characterization was performed, using electron backscattering diffraction (EBSD) and electron channeling contrast imaging (ECCI). In this study, we used a Fe-3Al bcc single crystalline alloy. EBSD-based grain reference orientation deviation analysis showed discrete plastic zones appearing along the crack propagation direction, with spacings corresponding to the crack propagation rate. Furthermore, it was confirmed via ECCI that underneath the fracture surface low- and high-ΔK regions showed vein-like and labyrinth structures, respectively. This information is expected to be useful for microstructure-based estimation of fatigue crack propagation rate and ΔK.. |
| 47. |
Shigeru Hamada, Taro Suemasu, Motomichi Koyama, Masaharu Ueda, Hiroshi Noguchi, Re-examination of fatigue crack propagation mechanism under cyclic Mode II loading, 22nd European Conference on Fracture, ECF 2018
Procedia Structural Integrity, 10.1016/j.prostr.2018.12.191, 13, 1026-1031, 2018.01, The essence of rolling contact fatigue is the so-called "Mode II fatigue crack propagation." However, its understanding has not progressed as much as that of Mode I. We think that this cause is the name: "Mode II fatigue crack propagation." Originally, Modes I and II represented the loading modes for still cracks in fracture mechanics, and not the fatigue crack propagation mechanism. There are many cases where the knowledge of fatigue crack propagation under Mode I loading is applied to that under Mode II loading without consideration. Moreover, in the rolling contact fatigue region where the fatigue crack propagates under Mode II loading, a large plastic deformation is caused by the rolling contact load. Therefore, it is necessary for the test method to reproduce the effects of an actual machine to test materials that exhibit large plastic deformation. Therefore, in this study, we aim to classify the fatigue crack propagation phenomena, regardless of Mode I and II loadings, and re-examine the mechanisms. To that end, we developed a novel test method that enables pure Mode II loading. We used a micro-thin film disc as a specimen, making it possible to cut out and test a part subjected to a large plastic deformation from the actual machine. By observations of the crystallographic structure before the fatigue test and the successive observation of fatigue crack propagation behavior, we propose a crack propagation mechanism, namely, damage accumulation type fatigue crack propagation under Mode II loading, which is different from the opening type fatigue crack propagation.. |
| 48. |
Taro Suemasu, Motomichi Koyama, Shigeru Hamada, Masaharu Ueda, Hiroshi Noguchi, The influence of fracture surface contact in fatigue crack propagation of material having texture under Mode II loading, 22nd European Conference on Fracture, ECF 2018
Procedia Structural Integrity, 10.1016/j.prostr.2018.12.229, 13, 1088-1092, 2018.01, In rolling contact fatigue (RCF), cyclic plastic deformation is caused by cyclic rolling contact, the texture develops, and the fatigue crack propagates in the texture under Mode II loading. As fatigue crack propagation under Mode II loading occurs inside the material, direct observation is difficult. Roughness-induced stress shielding (RISS) effect influences the fatigue crack propagation in RCF. However, as it is difficult to observe fatigue cracks in RCF directly, quantitative evaluation of RISS is difficult. Therefore, in this study, quantitative evaluation of RISS was performed by using a test method that enables direct observation of the fatigue crack propagation behavior under Mode II loading. In an actual machine in which RCF occurs, the texture has been generated. Hence, a material having texture was used for the test. From the results of the test, it was observed that the fatigue crack propagated in the same direction as the pre-crack. Therefore, fatigue crack propagation is considered to be successfully reproduced under Mode II loading. From a quantitative calculation result of the reduction rate of the stress intensity factor range owing to the contact between fracture surfaces by using the shape of the obtained fatigue crack shape and the assumed deformation shape, the reduction rate was determined to be very low. Therefore, the influence of RISS on the stress intensity factor range is considerably small, and it is considered that RISS does not exist in fatigue crack propagation under Mode II loading of a material having texture.. |
| 49. |
Test method for threshold of hydrogen-induced crack growth KI,H of SCM435 in 115 MPa hydrogen gas. |
| 50. |
Bochuan LI, Motomichi Koyama, Shigeru HAMADA, Hiroshi Noguchi, Threshold Stress Intensity Factor Range of a Mechanically-long and Microstructually-short Crack Perpendicular to an Interface with Plastic Mismatch, Engineering Fracture Mechanics, 10.1016/j.engfracmech.2017.07.023, 182, 287-302, 2017.08. |
| 51. |
Koki TAZOE, Shigeru HAMADA, Hiroshi NOGUCHI, Fatigue crack growth behavior of JIS SCM440 steel near fatigue threshold in 9-MPa hydrogen gas environment, International Journal of Hydrogen Energy, 42, 13158-13170, 2017.05. |
| 52. |
Naoki FUKUMURA, Bochuan LI, Motomichi Koyama, Tomohiro SUZUKI, Shigeru HAMADA, Kaneaki Tsuzaki, Hiroshi Noguchi, Material Property Controlling Non-propagating Fatigue Crack Length of Mechanically and Physically Short-Crack Based on Dugdale-model Analysis, Theoretical and Applied Fracture Mechanics, 2017.04. |
| 53. |
Shigeru HAMADA, Masaki NAKANISHI, Tsuyoshi MORIYAMA, Hiroshi NOGUCHI, Re-Examination of Correlation between Hardness and Tensile Properties by Numerical Analysis, Experimental Mechanics, 2017.03. |
| 54. |
Saburo Okazaki, Shigeru Hamada, Hisatake Itoga, Hisao Matsunaga, Masami Nakamura, Saburo Matsuoka, A case study of a cooling pipe for a pre-cooler used in a 70-MPa hydrogen station, ASME 2017 Pressure Vessels and Piping Conference, PVP 2017
Materials and Fabrication, 10.1115/PVP2017-65435, 2017.01, A case study was conducted on the cooling pipe of a pre-cooler which had been used in a 70-MPa hydrogen station demonstration project. The cooling pipe consisted of a main pipe, a mechanical joint pipe and a mechanical joint. The main and mechanical joint pipes had been joined using TIG welding. Through chemical composition analysis, microstructure observation and Vickers hardness measurement, it was revealed that the main and mechanical joint pipes had been manufactured from SUS316L and that 316L was the filler metal used for TIG welding. Round-bar specimens were machined out of the main pipe in order to investigate the tensile properties of the base metal. On the other hand, both round-bar specimen without reinforcement and square-bar specimens with reinforcement were fabricated from the weld-joint. Using the three types of specimens, slow strain rate tensile tests were performed in 0.1 MPa nitrogen gas and in 115 MPa hydrogen gas at a temperature of -40 °C. Reduction of area (RA), φ, for the round base-metal specimen, the round weld-joint specimen and the square weldjoint specimen were respectively, 83.5 %, 71.3 % and 81.4 % in nitrogen gas, whereas the related values in hydrogen gas were 60.1 %, 61.3 % and 40.1 %. In other words, the RA for the three types of specimens was smaller in hydrogen gas than in nitrogen gas. Dimples were formed on the fracture surfaces of the three specimen types in nitrogen gas, whereas both dimples and quasi-cleavages were formed in hydrogen gas.. |
| 55. |
Yasuaki HAMANO, Motomichi Koyama, Shigeru HAMADA, Hiroshi Noguchi, Notch Sensitivity of the Fatigue Limit in High-Strength Steel, ISIJ International, 56, 8, 1480-1486, 2016.08. |
| 56. |
Shigeru HAMADA, Shogo KASHIWA, Hiroshi Noguchi, Measurement Local Mechanical Properties Using Multiple Indentations by a Special Conical Indenter and Error Analysis, Journal of Materials Research, 10.1557/jmr.2015.383, 31, 2, 259-273, 2016.02. |
| 57. |
Daisuke SASAKI, Motomichi Koyama, Shigeru HAMADA, Hiroshi Noguchi, Tensile Properties of Precracked Tempered Martensitic Steel Specimens Tested at Ultralow Strain Rates in High-PressureHydrogen Atmosphere, Philosophical Magazine Letters, 10.1080/09500839.2015.1049574, 95, 5, 260-268, 2015.06. |
| 58. |
Na-oki FUKUMURA, Tomohiro SUZUKI, Shigeru HAMADA, Kaneaki Tsuzaki, Hiroshi Noguchi, Mechanical Examination about Crack Length Dependency and Material Dependency of Threshold Stress Intensity Factor Range with Dugdale Model
, Engineering Fracture Mechanics, http://dx.doi.org/10.1016/j.engfracmech.2015.01.003, 135, 168-186, 2015.02. |
| 59. |
Hao WU, Shigeru HAMADA, Yasuji ODA, Hiroshi NOGUCHI, Effect of Internal Hydrogen on Very High Cycle Fatigue of Precipitation-strengthened Steel SUH660, International Journal of Fatigue, http://dx.doi.org/10.1016/j.ijfatigue.2014.07.006, 70, 406-416, 2015.01. |
| 60. |
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, http://dx.doi.org/10.1016/j.ijhydene.2014.10.114, 40, 1, 719-728, 2015.01. |
| 61. |
Shigeru HAMADA, Tomoya FUJISAWA, Motomichi Koyama, Norimitsu KOGA, Nobuo Nakada, Toshihiro Tsuchiyma, Masaharu UEDA, Hiroshi Noguchi, Strain Mapping with High Spatial Resolution across a Wide Observation Range by Digital Image Correlation, Materials Characterization, 10.1016/j.matchar.2014.10.010, 98, 140-146, 2014.12. |
| 62. |
Hao WU, Shigeru hamada, Hiroshi Noguchi, Fatigue strength characteristics evaluation of SUH660 considering small fatigue crack propagation behavior and hardness distribution, International Journal of Fatigue, http://dx.doi.org/10.1016/j.ijfatigue.2013.12.011, 63, 1-11, 2014.03. |
| 63. |
Tomoya FUJISAWA, shigeru hamada, Norimitsu KOGA, Daisuke SASAKI, Toshihiro Tsuchiyma, Nobuo Nakada, Kazuki Takashima, Masaharu Ueda, Hiroshi Noguchi, Proposal of an engineering definition of a fatigue crack initiation unit for evaluating the fatigue limit on the basis of crystallographic analysis in case of pearlitic steel, International Journal of Fracture, 10.1007/s10704-013-9895-3, 185, 1-2, 17-29, 2014.01. |
| 64. |
Junichiro Yamabe, Hisatake Itoga, Tohru 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, ASME 2014 Pressure Vessels and Piping Conference, PVP 2014
Materials and Fabrication, 10.1115/PVP2014-28604, 2014.01, Pressure cycle tests were performed on two types of Cr-Mo steel pressure vessels with inner diameters of 306 mm and 210 mm and notches machined on their inside under hydrogen-gas pressures, varied between 0.6 and 45 MPa at room temperature. One of the Cr-Mo steels had a fine microstructure with tensile strength of 828 MPa, while the other had a coarse microstructure with tensile strength of 947 MPa. Fatigue-crack growth (FCG) and fracture-toughness tests of the Cr-Mo steels were also carried out in gaseous hydrogen. The Cr-Mo steels showed accelerated FCG rates in gaseous hydrogen compared to ambient air with an upper bound corresponding to an approximately 30-times higher FCG rate. Furthermore, in gaseous hydrogen, the fracture toughness of the Cr-Mo steel with coarse microstructure was significantly smaller than that of the steel with fine microstructure. Four pressure vessels were tested; then, all of the pressure vessels failed by leak-before-break (LBB). Based on the fracture-mechanics approach, the LBB failure of one pressure vessel could not be estimated by using the fracture toughness in gaseous hydrogen. The fatigue lives could be estimated by using the upper bound of the accelerated FCG rates in gaseous hydrogen.. |
| 65. |
Hisao Matsunaga, Michio Yoshikawa, Hisatake Itoga, Junichiro Yamabe, Shigeru Hamada, Saburo Matsuoka, Tensile-and fatigue-properties of low alloy steel JIS-SCM435 and carbon steel JIS-SM490B in 115 MPA hydrogen gas, ASME 2014 Pressure Vessels and Piping Conference, PVP 2014
Materials and Fabrication, 10.1115/PVP2014-28511, 2014.01, Slow strain rate tests using smooth specimens of two types of steels, low alloy steel JIS-SCM435 and carbon steel JIS-SM490B, were carried out in nitrogen gas and hydrogen gas under a pressure of 115 MPa at three different temperatures: 233 K, room temperature and 393 K. In nitrogen gas, these steels exhibited the so-called cup-and-cone fracture at every temperature. On the other hand, in hydrogen gas, in both steels a number of cracks initiated on the specimen surface and coalesced with each other at every temperature, which led to a marked reduction in ductility. Nonetheless, even in hydrogen gas, JIS-SCM435 exhibited a certain reduction of area after the stress-displacement curve reached the tensile strength (TS), whereas JIS-SM490B exhibited little, if any, necking in hydrogen gas. In addition, tension-compression fatigue testing at room temperature revealed that in both steels there was no noticeable difference between the fatigue strengths in air and 115MPa hydrogen gas, especially in a relatively long life regime. Considering that there was little or no hydrogen-induced degradation in either TS or fatigue strength in JIS-SCM435, it is suggested that JIS-SCM435 is eligible for fatigue limit design on the basis of a safety factor (i.e. TS divided by the allowable design stress) for mechanical components used in hydrogen gas up to 115 MPa.. |
| 66. |
Shigeru Hamada, Takuya KINOSHITA, Kazunori MORISHIGE, Komei HAYASHI, Toshiyuki ISHINA, Hiroshi Noguchi, Engineering definitions of small crack and long crack at fatigue limit under tensile mean stress and a prediction method for determining the fatigue limit of a cracked Mg alloy, International Journal of Fatigue, 10.1016/j.ijfatigue.2013.08.006, 56, 86-94, 2013.11. |
| 67. |
Shigeru hamada, Mitsuji Ueda, Komei Hayashi, Hiroshi Noguchi, Simple Calculation Method for Stress Concentration and Stress Intensity of T-Shaped Member, International Journal of Mechanical Sciences, 10.1016/j.ijmecsci.2013.05.015, 75, 8-15, 2013.10, The objective of this study is to clarify the influence of shape parameters on the stress concentration in simple forms. In recent years, by the spread of general purpose Finite Element Method (FEM) analysis software, anyone can carry out FEM analysis now and can grasp the stress state of a structure. However, in order to grasp the influence on a stress state when some shape parameter has changed, FEM analyses for each shape are required, and it requires long time. As an example of this issue in fatigue strength design, the relation between the plate and rib in a T-shaped structure, containing a corner, is analysed. The stress concentration factor or stress intensity factor between these two connected shapes are analyzed by the FEM, and a method of approximating the stress concentration factor and stress intensity factor in an actual shape is proposed. Then, the proposed FEM-based method was validated through a comparison of the results obtained using this method for shapes of finite dimensions with existing analytical solutions for shapes of infinite dimensions.. |
| 68. |
Hao WU, shigeru hamada, Hiroshi Noguchi, Pre-strain Effect on Fatigue Strength Characteristics of SUH660 Plain Specimens, International Journal of Fatigue, http://dx.doi.org/10.1016/j.ijfatigue.2013.06.021, 55, 291-298, 2013.10. |
| 69. |
Hao WU, shigeru hamada, Hiroshi Noguchi, Fatigue strength prediction for inhomogeneous face-centered cubic metal based on Vickers hardness
, International Journal of Fatigue, http://dx.doi.org/10.1016/j.ijfatigue.2012.09.021, 48, 3, 48-54, 2013.03, To find the Vickers hardness (HV) value for predicting the fatigue strength of inhomogeneous face-centered cubic (FCC) metals, HV tests were performed on SUH660 stainless steel. The results indicate that the intrinsic hardness distribution can be obtained from the HV distribution in test zones according to the Vickers hardness definition. The soft zone greatly affects the fatigue strength of an inhomogeneous FCC metal. Therefore, for another inhomogeneous FCC metal in which fatigue cracks initiate and propagate easily in the softest zone, the fatigue limit can be predicted using the mean HV value of the softest zone.. |
| 70. |
Shigeru HAMADA, Suguru KASHIWAGI, Akio SONODA, Naoshi IZUMI and Hiroshi NOGUCHI
, Evaluation of Notch Tensile Strength for High Strength Steel with Inclusions (for Casting High Speed Steel)
, Journal of Solid Mechanics and Materials Engineering, 6, 2, 121-130, Vol.6, No.2, pp.121-130, 2012.02. |
| 71. |
M. Liu, S. Hamada, Determination of effective stress intensity factor range of mode ii fatigue crack propagation using improved experimental method, 19th European Conference on Fracture: Fracture Mechanics for Durability, Reliability and Safety, ECF 2012
19th European Conference on Fracture
Fracture Mechanics for Durability, Reliability and Safety, ECF 2012, 2012.01, Many cases of rolling contact fatigue failure, such as those that occur in railway rails, rolling bearings, and gears, are due to repeated high shear load. In order to prevent such fatigue failures, the resistance of a material against to repeated high shear load must be determined. The fatigue crack growth rate is dependent on the stress intensity factor range of Mode II ΔK II. However, Mode II crack propagation characteristics vary according to the method by which they are determined. We improved the experimental method proposed by Murakami and measured the effective stress intensity factor range of Mode II AK IIeff. Changes to the jigs and specimen were made and the experimental method was such that the ideal mechanical model was expected to be approached. Furthermore, to measure the ΔKIIeff, several strain gauges were applied to the specimen around the crack tip. Using the improved method, some ΔK IIeff values during the Mode II fatigue crack propagation tests can be measured.. |
| 72. |
Toshiyuki Ishina, Shigeru Hamada, Hiroshi Noguchi, Ductile to brittle transition in magnesium alloy with a crack, 19th European Conference on Fracture: Fracture Mechanics for Durability, Reliability and Safety, ECF 2012
19th European Conference on Fracture
Fracture Mechanics for Durability, Reliability and Safety, ECF 2012, 2012.01, We evaluated the strength of a cast non-combustible magnesium alloy that is intended for use in automobile engines. This alloy contains thin sheet-like oxides because of its production process. The size of these thin sheet-like oxides varies, and this means that the temperature dependency of the strength characteristics of the alloy cannot be determined by a tensile test alone. Initially, specimens of the alloy having an artificial pre-crack of 5 [mm] to simulate the sheet-like oxides were subject to tensile testing. The testing was carried out at room temperature (23 [°C]), 150 [°C], 200 [°C] and 250 [°C]. 250 [°C] is the temperature of the environment in which the alloy will be used in automobile engines. All the fractures propagated from the artificial pre-crack and the alloy exhibited its maximum strength at 150 [°C]. To investigate the temperature dependency of the fracture mechanism, a scanning electron microscope (SEM) was used to observe the region near the tip of the pre-crack on the fracture surface of the specimens tested at room temperature and at 250 [°C]. On the fracture surface of the specimen tested at 250 [°C], some dimples were observed over some of the surface near the tip of the artificial pre-crack; however, the fracture surface of the specimen tested at room temperature showed brittle fracture surface morphology over the entire area. For the magnesium alloy, the critical resolved shear stress for non-basal slip, which is a characteristic of a hexagonal close-packed metal, is dependent on temperature. Therefore, ductile to brittle transition was considered to be occurred at a temperature between room temperature and 250 [°C]. Mechanical restraint is also considered to be affected the ductile to brittle transition.. |
| 73. |
T. Kinoshita, K. Hayashi, Shigeru Hamada, I. Shigematsu, Hiroshi Noguchi, Evaluation of joint defects on FSW of mg alloy using statistical method, 19th European Conference on Fracture: Fracture Mechanics for Durability, Reliability and Safety, ECF 2012
19th European Conference on Fracture
Fracture Mechanics for Durability, Reliability and Safety, ECF 2012, 2012.01, To select the welding conditions that can ensure a particular fatigue strength for safe use in a structure produced by the FSW (Friction Stir Welding) of Mg alloys, this paper proposes a method for determining the range of welding conditions that can ensure a particular joint defect size limit. The welding parameters used are the rotation speed of the tool ω and the welding speed v. Generally, a welding condition is selected using only the fatigue strength as an index. However, ensuring the fatigue strength in a particular welding condition does not insure the strength and reliability of a welded part, because actual welding is not typically carried out in a particular welding condition. Therefore, a range of conditions that can ensure a particular fatigue strength is required. Moreover, we also consider parameters that represent the factors that decrease fatigue strength, namely, √area, HV, and R, because the welding conditions that can ensure a particular fatigue strength are determined by an evaluation of these factors, as well. Therefore, in this study, a method for determining a range of welding conditions that can ensure a welding defect size limit is proposed. Furthermore, FSW welding tests were carried out and the validity of the proposed method was evaluated. X-ray transmission measurements were carried out to measure the welding defect size obtained using the method. Then, the prediction of the maximum welding defect size was carried out for a welding length of 25 [m], which is representative of body of a the Shinkansen rolling stock car.. |
| 74. |
T. Fujisawa, D. Sasaki, Shigeru Hamada, Hiroshi Noguchi, Relation between fatigue crack initiation and structure in pearlitic steel, 19th European Conference on Fracture: Fracture Mechanics for Durability, Reliability and Safety, ECF 2012
19th European Conference on Fracture: Fracture Mechanics for Durability, Reliability and Safety, ECF 2012, 2012, To clarify the relation between fatigue crack initiation and the crystal structure in pearlitic steel used for railroad rails, fatigue tests are performed, focusing on crack initiation. Then, the fracture surfaces are analysed using a scanning electron micro-scope (SEM). To observe the crystal structure, before the fatigue is performed, the specimen surface is etched chemically. The crystal structure of pearlitic steel, is comprised of "pearlite colonies" which have the same lamellar structure direction, and "pearlite blocks" which have the same ferrite crystal direction. A fatigue crack initiation region should be affected by the crystal structure; however, the relation between the crack initiation region and the crystal structure in pearlitic steel has not been clarified. From the fatigue test results, the fatigue crack of the pearlitic steel was initiated at a very early stage of the fatigue test. To determine the unit of fatigue crack initiation in pearlitic steel, the relation between the crack initiation region and crystal structure was clarified by using SEM analysis.. |
| 75. |
H. Wu, Shigeru Hamada, Hiroshi Noguchi, The effect of prestrain on fatigue property of precipitation strengthening stainless steel SUH660, 19th European Conference on Fracture: Fracture Mechanics for Durability, Reliability and Safety, ECF 2012
19th European Conference on Fracture: Fracture Mechanics for Durability, Reliability and Safety, ECF 2012, 2012, In precipitation-strengthened steel, precipitation particles are considered to be cut by the prestrain treatment and affect the fatigue property of the steel. In this study, fatigue tests on prestrained specimens were performed to investigate the effect of the prestrain and precipitate cutting on the crack initiation and propagation characteristics of precipitation-hardened stainless steel (SUH660). Plain specimens were used to observe the process of crack initiation and propagation. The fatigue life was divided into the crack initiation life and the crack propagation life. The results of the fatigue test showed that the crack initiation life of a prestrained specimen was longer than that of a nonstrained specimen. The observed crack propagation mode was mainly Mode II. The measured crack propagation life of the prestrained specimen was shorter than that of the non-strained specimen, which was the opposite of the results observed for carbon steel. It was assumed that this was because Mode II crack propagated more easily and faster in the prestrained specimen, where the precipitates were cut, than in the non-strained specimen. Therefore, the relationship between the fatigue life of the prestrained specimen and the non-strained specimen is considered to be dependent on the stress level. When the crack propagation life governed the fatigue life, the fatigue life of the prestrained specimen was shorter than that of the non-strained specimen. However, when the crack initiation life governed the fatigue life, the fatigue life of the prestrained specimen would be longer than that of the non-strained specimen.. |
| 76. |
Shigeru HAMADA, Komei HAYASHI, Toshiharu MATSUMOTO, Michiru SAKAMOTO and Hiroshi NOGUCHI
, Proposed Strength Evaluation Method for Casting Material with Defects (Using Non-combustible Mg Alloy with Added-Si), Journal of Solid Mechanics and Materials Engineering, 5, 10, 534-545, 2011.11. |
| 77. |
Youhei OHMOTO, Mitsuru SATOH and Shigeru HAMADA and Hiroshi NOGUCHI, Evaluation of Estimation Method for Thermal Fatigue Crack Growth Rate in Epoxy Resign Composites, Journal of Solid Mechanics and Materials Engineering, 5, 10, 546-557, 2011.11. |
| 78. |
K. Hayashi, S. Hamada, T. Matsumoto, M. Sakamoto and H. Noguchi, Method of evaluation of distribution characteristics of flaky inclusions, Strength of Materials, 10.1007/s11223-011-9310-0, 43, 4, 411-416, 2011.10. |
| 79. |
Evaluation of Fatigue Limit Characteristics of Lamellar Pearlitic Steel in Consideration of Microstructure
. |
| 80. |
Komei HAYASHI, Shigeru HAMADA, Ichinori SHIGEMATSU, Michiru SAKAMOTO and Hiroshi NOGUCHI, Effect of Friction Stir Welding Condition on Fatigue Limit of Welded Non-combustible Mg Alloy, Key Engineering Materials, 10.4028/www.scientific.net/KEM.488-489.311, 488-489, 311-314, 2011.08. |
| 81. |
Shigeru HAMADA, Taka-aki KAWAZOE, Komei HAYASHI, Harumi MORITA, Mitsuji UEDA, Michiru SAKAMOTO, Hiroshi NOGUCHI
, Proposed Simple Determination Method for Welding Condition of Joint from Fatigue Limit Characteristics (1st Report: Application to TIG-Butt-Joint of Non-combustible Mg Alloy)
, Journal of Solid Mechanics and Materials Engineering, 5, 8, 409-424, 2011.08. |
| 82. |
To-ru ARAMAKI, Shigeru HAMADA, Hiroshi NOGUCHI, Shinya MIYAJI, Toshihiro TACHIKAWA, Arata TATSUMI, Takashi KAYAMOTO, Strength Evaluation of Alumina Spray Coating (5th Report, Consideration of the Strength in Sprayed Structure under Thermal Stress), Journal of Solid Mechanics and Materials Engineering, doi:110.1299/jmmp.5.425, 5, 8, 425-444, 2011.08. |
| 83. |
To-ru ARAMAKI, Shigeru HAMADA, Hiroshi NOGUCHI, Shinya MIYAJI, Toshihiro TACHIKAWA, Arata TATSUMI, Takashi KAYAMOTO, Strength Evaluation of Alumina Spray Coating (4th Report, Proposal for the Dangerous Volume Quantifation Method), Journal of Solid Mechanics and Materials Engineering, doi:10.1299/jmmp.5.294, 5, 6, 294-310, 2011.06. |
| 84. |
To-ru ARAMAKI, Shigeru HAMADA, Hiroshi NOGUCHI, Shinya MIYAJI, Toshihiro TACHIKAWA, Arata TATSUMI, Takashi KAYAMOTO, Strength Evaluation of Alumina Spray Coating (2nd Report, Proposal for Judgment of Crack Interference and Correction Methods of Crack-Shape), Journal of Solid Mechanics and Materials Engineering, 5, 4, 191-208, 2011.04. |
| 85. |
Microscopic fatigue crack behavior in precipitation strengthening stainless steel A286
. |
| 86. |
Proposal of Simple Determination Method for Welding Condition of Joint from Fatigue Limit Characteristics (1st Report: Application to TIG-Butt-Joint of Non-combustible Mg Alloy)
. |
| 87. |
Evaluation Method of Thermal Fatigue Crack Growth Rate in Epoxy Resin Composites
. |
| 88. |
Evaluation of Notch Tensile Strength for High Strength Steel with Inclusions (in Case of Casting High Speed Steel)
. |
| 89. |
Yuichi Suzuki, Hisatake Itoga, Shigeru Hamada, Hiroshi Noguchi, Hydrogen exposure effect on tensile strength of high strength steel sharp notched specimen, 12th International Conference on Fracture 2009, ICF-12
12th International Conference on Fracture 2009, ICF-12, 3556-3563, 2009.12. |
| 90. |
S. Hamada, Y. Sugimoto, Strength evaluation of polycrystalline silicon structure considering sidewall morphology, 12th International Conference on Fracture 2009, ICF-12
12th International Conference on Fracture 2009, ICF-12, 4249-4258, 2009.12, In order to evaluate strength of micron size polycrystalline silicon (poly-Si) structure for MEMS considering surface morphology difference between top and sidewall and effective surface area, bending strength tests of cantilever beam, surface roughness measurement and fracture surface analysis are performed. The specimens are made by CVD process for poly-Si deposition and deep RIE process for sidewall formation, and then the surface morphology of the top and the sidewall surface are different. The various size notches on the specimen are introduced in order to change effective surface area. By the fracture surface analysis, it was found that the fracture initiation point was not always maximum stress point; this is because there exist stress concentration on the surface. Surface roughness was measured using atomic force microscope (AFM). Then the maximum stress concentration of the specimen on the top and the sidewall surface respectively were presumed using extreme statistics, and effective surface area was defined. Then, bending strength and effective surface area shows good correlation.. |
| 91. |
Evaluation of Notch Tensile Strength for High Strength Steel with Inclusions (in Case of Casting High Speed Steel)
. |
| 92. |
Strength Evaluation of Alumina’s Spray Coating (5th Report, Consideration of the Strength in Sprayed Structure for Thermal Stress)
. |
| 93. |
Strength Evaluation of Alumina’s Spray Coating (4th Report, Consideration of Spray Structure Strength for Mechanical Stress)
. |
| 94. |
Shigeru HAMADA, Katsu OHNISHI, Hide-aki NISHIKAWA, Yasuji ODA, Hiroshi NOGUCHI, SIMS analysis of low content hydrogen in commercially pure titanium, Journal of Materials Science, Vol.44, No.20, pp.5692-5696, 2009.08. |
| 95. |
Strength Evaluation of Alumina’s Spray Coating (2nd Report, Proposal for Judgments of Crack Interference and Correction Methods of Crack Shape)
. |
| 96. |
Strength Evaluation of Alumina’s Spray Coating (3rd Report，Proposal for the Safety Design of Fracture Strength with Consideration of Cracks Interference)
. |
| 97. |
Akio SONODA, Shigeru HAMADA and Hiroshi NOGUCHI
, Analysis of Small Spalling Mechanism on Hot Rolling Mill Roll Surface, Memoirs of the Faculty of Engineering, Kyushu University, Vol. 69, No. 1, pp.1-14, 2009.03. |
| 98. |
Yuu Sakoda, Suguru Kashiwagi, Shigeru Hamada, Hiroshi Noguchi, Microscopic deformation behavior of lamellar pearlite steel, 17th European Conference on Fracture 2008: Multilevel Approach to Fracture of Materials, Components and Structures, ECF17
17th European Conference on Fracture 2008
Multilevel Approach to Fracture of Materials, Components and Structures, 358-365, 2008.12, Fatigue ratio of lamellar pearlite steel used for railroad rail is lower than the ratio of general steels. The reason is not clarified. It is reported the direction of lamellar microstructure in lamellar pearlite steel effects fatigue characteristics. In order to clarify microscopic deformation behavior of lamellar microstructure considered to effect fatigue characteristics, static tensile tests of lamellar pearlite steel was conducted, in this report. Using the plastic replica technique, microscopic deformation behavior, the initiation and propagation of micro crack was observed. By the observation, it is clarified that the crack initiates but does not propagate during static tensile test. The authors presume the fatigue of lamellar pearlite steel as follow: The grain size crack initiate at initial stage of fatigue process, and the crack act as initial defect of the lamellar pearlite steel. Based on the presumption, the fatigue limit of the lamellar pearlite steel was predicted, and the fatigue limit was confirmed by fatigue tests. As the result, the predicted fatigue ratio are 0.32~0.33 which show good agreement with the fatigue test result.. |
| 99. |
Takumi Fujii, Shigeru Hamada, Hiroshi Noguchi, Proposal of estimation method for notched specimen fatigue limit of commercially pure titanium, 17th European Conference on Fracture 2008: Multilevel Approach to Fracture of Materials, Components and Structures, ECF17
17th European Conference on Fracture 2008: Multilevel Approach to Fracture of Materials, Components and Structures, 2, 937-944, 2008.12, In order to identify the fatigue limit for a sharp notched specimen of commercially pure titanium, rotating bending fatigue tests on smooth and notched specimens were curried out. In previous studies, it was found that the fatigue limit for a sharp notched specimen of commercially pure titanium could not be determined and it is not sure whether it fail over N=10 7 cycles or not. Based on the experimental results, in the smooth specimen and notched specimen (p=1.0mm), they have fatigue limits and knee points, while the sharp notched specimen (p=0.1mm) does not. As an estimation method, the fatigue crack initiation of each specimen was then investigated. The investigation results are as follows. (1) The proportional relationship exists between the maximum stress K iωa at the notch root and logarithm of the number of cycles to fatigue crack initiation N i. (2) Based on the slope of the relationship between the maximum stress K iωa and the number of cycles to fatigue crack initiation N i at the notch root, there is no possibility that the fatigue crack in the same mechanism initiates over N=10 7 cycles. Therefore, the stress amplitude that is not initiated the fatigue crack at N=10 7 cycles is the fatigue limit.. |
| 100. |
Takumi FUJII, Kazunori MORISHIGE, Shigeru HAMADA, Hiroshi NOGUCHI, Michiru SAKAMOTO and Hidetoshi UENO, Fatigue Strength Characteristics of Non-combustible Mg Alloy, Journal of Solid Mechanics and Materials Engineering, Vol.2, No.6, pp.763-770, 2008.06. |
| 101. |
Hideaki NISHIKAWA, Shigeru HAMADA and Katsu Ohnishi, SIMS Analysis of Hydride in Commercially Pure Titanium, Memoirs of the Faculty of Engineering, Kyushu University, Vol. 67, No. 4, pp.191-197, 2008.02. |
| 102. |
Yu SAKODA, Suguru KASHIWAGI, Shigeru HAMADA and Hiroshi NOGUCHI, Microscopic Deformation Behavior Observation of Lamellar Pearlite during Plastic Deformation, Journal of Solid Mechanics and Materials Engineering, Vol.2, No.1, pp.137-144, 2008.01. |
| 103. |
Akio SONODA, Suguru KASHIWAGI, Shigeru HAMADA and Hiroshi NOGUCHI, Quantitative Evaluation of Heat Crack Initiation Condition Under Thermal Shock, Journal of Solid Mechanics and Materials Engineering, Vol.2, No.1, pp.128-136, 2008.01. |
| 104. |
Shigeru HAMADA and Kenji HASIZUME, Strength Reliability of Micro Polycrystalline Silicon Structure, Memoirs of the Faculty of Engineering, Kyushu University, Vol. 67, No. 3, pp.105-116, 2007.12. |
| 105. |
Shigeru Hamada and Kenji Hashizume, Strength Reliability of Micro Polycrystalline Silicon Structure, Key Engineering Materials, Vols. 345-346, pp. 777-780, 2007.01. |
| 106. |
Takumi Fujii, Kazunori Morishige, Shigeru Hamada, Hiroshi Noguchi, Michiru Sakamoto, Hidetoshi Ueno, OS4-5-5 Fatigue Strength Characteristics of Non-combustible Mg Alloy, The Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics, 10.1299/jsmeatem.2007.6._OS4-5-5-1, 2007, 0, _OS4-5-5-1-_OS4-5-5-4, 2007, The ignition point of non-combustible Mg alloy is about 300K higher than that of normal magnesium alloy. It is expected that the non-combustible Mg alloy is used in substitution for Al alloy for structures. In this paper, the fundamentals, those are a notch effect, and a long or small crack effect on fatigue strength of a non-combustible Mg alloy, are investigated. Moreover, the fatigue strength characteristics of the non-combustible Mg alloy are compared with that of Al alloy to clarify differences of fatigue strength characteristics between Mg alloy and Al alloy.. |
| 107. |
Shigeru Hamada, Kenji Hasizume, OS5-2-4 Strength Reliability of Micro Polycrystalline Silicon Structure, The Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics, 10.1299/jsmeatem.2007.6._OS5-2-4-1, 2007, 0, _OS5-2-4-1-_OS2-5-4-5, 2007, In order to evaluate strength reliability of micron size polycrystalline silicon (poly-Si) structure for MEMS, bending strength tests of cantilever beam, Weibull analysis of the strength and fracture surface analysis are performed. Recently, the importance of microelectromechanical systems (MEMS) in society is increasing, and the number of production is also increasing. The MEMS devices, which contain mechanical movement, have to maintain their reliability in face of external shock, thermal stress and residual stress from manufacturing processes. In greeting the mass production era of the MEMS, in case the material strength design of MEMS is performed, required strength data is not average value but the variation, especially minimum value assumed of the structure and material. Micron size poly-Si structure is widely employed in the MEMS such as microsensor, switching device and so on. Then, in order to evaluate strength reliability of micron size poly-Si structure, tests and analysis are performed. The specimen is made by chemical vapor deposition (CVD) process and the thickness is 3.5, 6.4 and 8.3 micrometer and the specimen has notch (stress concentration). The test specimen used for the test changed characteristics of (1)film thickness (2) stress concentration, and investigation about the influence each effect of the variation in a bending strength with fracture surface analysis are discussed.. |
| 108. |
Shigeru Hamada, Shuichi Tani, Daisuke Katagiri, Masahiro Tsugai, Makio Horikawa, Hiroshi Otani, Stress concentration and surface roughness effect on strength of polycrystalline silicon structure, ASME/Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems: Advances in Electronic Packaging 2005
Proceedings of the ASME/Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems: Advances in Electronic Packaging 2005, PART C, 1929-1934, 2005.07, In order to clarify the stress concentration and surface roughness effect on strength of the polycrystalline silicon (poly-Si) structure, bending tests of poly-Si microcantilever beam specimen and surface roughness measurement is performed. The bending test results are analyzed by means of maximum stress at the notch root calculated by FEM models, and it is found that this approach cannot describe the test results. Therefore, modified approach is taken into account by use of two parameters that are the maximum stress and area where stress is larger than 50% of the maximum stress, which indicates stress extension around the position of maximum stress representatively. By this two parameters approach, the test results are explained quantitatively and a strength design chart for stress concentration area of the poly-Si structure is obtained. On the other hand, relationship between strength and surface roughness are confirmed and useful information for the process quality control are obtained.. |
| 109. |
Eiji Yoshikawa, Masahiro Tsugai, Makio Horikawa, Hiroshi Otani and Shigeru Hamada, Influence of RTA Parameters on Residual Stress and Stress Gradient of Multilayered LPCVD Polysilicon Film, Sensors and Materials, Vol.16, No.5, pp.223-229, 2004.05. |
| 110. |
Measurement of Mode II Threshold Stress Intensity Factor Range △K_. |
| 111. |
Y. MURAKAMI, C. SAKAE, S. HAMADA, Mechanism of rolling contact fatigue and measurement of ΔKIIth for steels, Engineering Against Fatigue, 473-485, pp.473-485, 1999.01. |
| 112. |
Y. MURAKAMI, S. HAMADA, A NEW METHOD FOR THE MEASUREMENT OF MODE II FATIGUE THRESHOLD STRESS INTENSITY FACTOR RANGE ΔKτth, Fatigue & Fracture of Engineering Materials & Structures,, Vol.20, No.6, pp.863-870, 1997.06. |
