著者

池田 義雅 高村 正人 箱山 智之 大竹 淑恵 熊谷 正芳 鈴木 裕士

出版者

一般社団法人 日本鉄鋼協会

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

pp.TETSU-2017-080, (Released:2018-02-05)

参考文献数

17

被引用文献数

8

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Neutron engineering diffraction is a powerful technique which provides the information of the micro structure of steels in bulk-average, while X-ray diffraction or Electron backscatter diffraction can provide information only from the surface layer. However, such measurement using neutron diffraction is typically performed in a large facility such as a reactor and a synchrotron, while a compact neutron source has never been used for this purpose. Authors have recently developed a neutron diffractometer installed in Riken Accelerator driven compact Neutron Source (RANS) and succeeded in the measurement of texture evolution of a steel sheet. In this study, we made an attempt to measure the volume fraction of retained austenite by RANS. Background noise was carefully eliminated in order to detect as many diffraction peaks as possible with low flux neutrons. The volume fraction was estimated by Rietveld analysis. The accuracy of the measurement result was discussed by comparing with those obtained by a large neutron facility (J-PARC TAKUMI). The volume fraction obtained by RANS with reasonable measurement time, i.e. 30-300 min, showed only 1-2% discrepancies with those obtained in J-PARC. These comparisons suggest that neutron diffraction by RANS is capable of quantitative analysis of the volume fraction of crystal phases, showing the possibility of practical use of an in-house compact neutron source in the industry.

著者

熊谷 正芳

出版者

日本材料試験技術協会

雑誌

材料試験技術 (ISSN:02852470)

巻号頁・発行日

vol.67, no.2, pp.40-45, 2022-04-15 (Released:2023-05-15)

参考文献数

30

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AbstractX-ray diffraction line profile analysis(LPA)assesses dislocation status, which is highly correlated with mechanical properties. In addition to dislocation density, a measured line profile contains information such as crystallite size, dislocation character, and dislocation arrangement parameters, which can be analyzed by the LPA. In particular, dislocation density significantly impacts metallic materials'mechanical properties, such as yield stress. Examples of research examining the relationship between its quantification and mechanical properties are presented. We also provided an example in which the dislocation structure formed by plastic deformation can be characterized by parameters other than the dislocation density.

著者

熊谷 正芳 石渡 正人 大谷 眞一

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.84, no.863, pp.18-00139, 2018 (Released:2018-07-25)

参考文献数

18

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Residual stress measurements on pipe-shaped Ni-alloy, Inconel 625, were conducted. The pipes were made from a thin plate by roll-bend and weld along longitudinal direction of the pipe. Shot peening processes were performed to the outside surface of the pipes. The stresses were measured using X-ray stress measurement method. The residual stresses on the specimen before shot peening process were around 100 MPa toward longitudinal direction and around 250 MPa toward transvers direction to the welding direction. The residual stresses changed to 800 MPa in compressive by shot peening process. After thermal aging at 1173 K for 1 and 10 hour, the residual stresses changed to −100 MPa on the specimens with and without shot peening in both longitudinal and transvers directions. In addition, optical microscopic observation and the analyses of X-ray diffraction peaks were performed to reveal microstructural features due to welding, shot peening, and thermal aging. Equiaxed and columnar dendrites were generated in the center and the outer of fusion zone, respectively. The grains in the heat affected zone, between the fusion zone and base metal became larger. The grains near the surface even in welds became small by shot peening processes according to analyses of X-ray diffraction peaks. Even though induced compressive residual stresses were released during thermal ageing, refined grains had been smaller than before shot peening process.

著者

水野 湧太 熊谷 正芳 田邉 晃弘 新部 純三

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

pp.23-00242, (Released:2024-01-11)

参考文献数

11

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Since it is known that tensile strength and hardness are roughly proportional, a hardness test is often used as a simple and substitute test. However, it has been reported that the proportional relationship between tensile strength and hardness is broken above 595 HV (≈55 HRC). Besides, there are few examples of mechanical properties determined by compression tests despite the fact that high-hardness and high-strength materials subjected to significant compressive stress are used in machine element parts, e.g. bearings. Tensile strength is used instead of compressive strength for the design. Thus, the relationship between hardness and compressive strength in hard materials, quenched medium carbon steel, was revealed. The compressive strength at 8% plastic strain (compressive strength) was almost the same as the maximum compressive strength. The compressive strength and hardness were at their maximum in the as-quenched specimen and decreased with the increase in tempering temperature. The compressive strength and hardness had a linear relationship up to 2000 MPa similar to the relationship of tensile tests. However, the compressive strength increased slightly in relation to the hardness above 2000 MPa in contrast to tensile tests. Thus, the work-hardening index was introduced as a variation parameter to the function that expresses the relationship between compressive strength and hardness to obtain better estimation. The estimated compressive strengths using the work-hardening index are agreed well to the experimental results.

著者

熊谷 正芳

出版者

公益社団法人 日本材料学会

雑誌

材料 (ISSN:05145163)

巻号頁・発行日

vol.69, no.9, pp.698, 2020-09-15 (Released:2020-09-20)

著者

熊谷 正芳

出版者

公益社団法人 日本材料学会

雑誌

材料 (ISSN:05145163)

巻号頁・発行日

vol.67, no.8, pp.828, 2018-08-15 (Released:2018-08-20)

参考文献数

3

著者

佐藤 成男 黒田 あす美 佐藤 こずえ 熊谷 正芳 ステファヌス ハルヨ 友田 陽 齋藤 洋一 轟 秀和 小貫 祐介 鈴木 茂

出版者

一般社団法人 日本鉄鋼協会

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

vol.104, no.4, pp.201-207, 2018 (Released:2018-03-31)

参考文献数

20

被引用文献数

10

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To investigate the characteristics of dislocation evolution in ferritic and austenitic stainless steels under tensile deformation, neutron diffraction line-profile analysis was carried out. The austenitic steel exhibited higher work hardening than the ferritic steel. The difference in the work hardening ability between the two steels was explained with the dislocation density estimated by the line-profile analysis. The higher dislocation density of the austenitic steel would originate from its lower stacking fault energy. Dislocation arrangement parameters indicated that the strength of interaction between dislocations in the austenitic steel was stronger than that in the ferritic steel. This would mainly originate from the difference in dislocation substructures; while dislocation tangle, which can be prompted by the cross slip, was expected in the ferritic steels, highly dense dislocation walls induced by planar glide of dislocations as well as the tangle were expected in the austenitic steel. It was confirmed that the stronger interaction between dislocations in the austenitic steel resulted in the smaller strain field of dislocation. Consequently, the coefficient for the root square of dislocation density in the Bailey-Hirsh equation became smaller in the austenitic steel. X-ray diffraction line-profile analysis was also carried out for the tensile-deformed specimens. The dislocation arrangement parameter evaluated by X-ray diffraction was smaller than that evaluated by neutron diffraction. This would be caused by the difference in the relationship between the loading direction and the scattering vector. On the other hand, the dislocation density evaluated by both methods was almost identical.

著者

新部 純三 熊谷 正芳 田邉 晃弘 水野 湧太

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

pp.21-00082, (Released:2021-08-05)

参考文献数

13

被引用文献数

2

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Although elastic limit and tensile strength are essential for mechanical strength design, the measurement of high hardness materials is a challenge due to their sensitivity on notches. As an alternative, the tensile strength can be easily assumed from hardness using the conversion table (e.g. SAE J 417); however, the table does not include the data for high hardness region, namely tempered materials at low temperature. We performed tensile tests and obtained elastic limits and tensile strengths of quenched martensitic medium-carbon steel with tempering at several temperatures. The hardness was monotonically decreased with the increase of tempering temperature. However, the tensile strength and elastic limit improved as the increase of temperature at low tempering temperature. In contrast, at high tempering temperature, the tensile strength and elastic limit were decreased with increase of tempering temperature. Consequently, the ratios of hardness to tensile strength or elastic limit were changed below or above the transition point. The ratios were constant below a tempering temperature (290 ℃ for elastic limit and 200 ℃-300 ℃ for tensile strength in the present experiments) and increased with the increase of the tempering temperature above the temperature. The variation of the ratio, hardness to tensile strength, is due to the brittle fracture on high hardness specimens before reaching the threshold to start plastic instability. In addition to, it is considered that the variation of the ratio, hardness to elastic limit, is caused by another mechanism, a decrease in elastic limit due to mobile dislocations.

著者

熊谷 正芳 横山 亮一

出版者

公益社団法人 日本材料学会

雑誌

材料 (ISSN:05145163)

巻号頁・発行日

vol.69, no.3, pp.277-283, 2020-03-15 (Released:2020-03-20)

参考文献数

40

被引用文献数

2

著者

熊谷 正芳

出版者

公益社団法人 日本材料学会

雑誌

材料 (ISSN:05145163)

巻号頁・発行日

vol.67, no.9, pp.889, 2018-09-15 (Released:2018-09-20)

著者

安川 昇一 大谷 眞一 熊谷 正芳 菊地 拓哉

出版者

公益社団法人 日本材料学会

雑誌

材料 (ISSN:05145163)

巻号頁・発行日

vol.67, no.3, pp.375-382, 2018-03-15 (Released:2018-03-20)

参考文献数

10

被引用文献数

1

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Shot peening, which imparts compressive residual stress, is a very effective means for improving the fatigue strength and is widely used for manufacturing process such as automobile industry and aircraft industry. In this study, with the aim of clarifying experimentally the microscopic residual stress distribution of a single dent by projecting a fine ceramic ball with a diameter of 3 mm onto an aluminum alloy material, and the existence of shear stress is clarified by triaxial stress analysis. Furthermore, the change of the residual stress distribution when multiple shots are given to the same position of single dent is also clarified. Obtained results are summarized as follows: (1) The central portion of the dent has a tensile residual stress in both radial and circumferential directions of the dent. A residual stress in the radial direction of the dent has a peak of compressive residual stress outside the dent mark, and a compressive residual stress is given up to an area up to about four times the dent diameter. On the other hand, a tensile residual stress is generated in the circumferential direction of the dent to the region of four times the dent diameter, and the peaks of the tensile residual stress are present on the central part of the dent and outer of the dent. (2) The macroscopic residual stress in the radial direction gradually changes to compressive stress in accordance with the number of shot projections, but does not change substantially in the circumferential direction. (3) As a result of triaxial stress analysis on a single dent, shear stress components σ12 and σ23 does not exist, but it became clear that shear stress σ13 is generated at the dent boundary.

著者

大村 悦二 小川 健輔 熊谷 正芳 中野 誠 福満 憲志 森田 英毅

出版者

一般社団法人日本機械学会

雑誌

日本機械学會論文集. A編 (ISSN:03875008)

巻号頁・発行日

vol.76, no.764, pp.446-448, 2010-04-25

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In stealth dicing (SD), a permeable nanosecond laser is focused inside a silicon wafer and scanned horizontally. A thermal shock wave is propagated every pulse toward the side to which the laser is irradiated, then a high dislocation density layer is formed inside a wafer after the thermal shock wave propagation. In our previous study, it was supposed that an internal crack whose initiation is a dislocation is propagated when the thermal shock wave by the next pulse over-laps with this layer partially. In this study, a two-dimensional thermal elasticity analysis based on the fracture mechanics was conducted. The internal crack propagation was analyzed by calculating the stress intensity factor at the crack tips and comparing with a threshold of that. As a result, validity of the previous hypothesis was suggested.

著者

大村 悦二 小川 健輔 熊谷 正芳 中野 誠 福満 憲志 森田 英毅

出版者

一般社団法人日本機械学会

雑誌

M&M材料力学カンファレンス

巻号頁・発行日

vol.2009, pp.73-74, 2009-07-24

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In stealth dicing (SD), a permeable nanosecond laser is focused inside a silicon wafer and scanned horizontally. A thermal shock wave is propagated every pulse toward the side to which the laser is irradiated, then a high dislocation density layer is formed inside a wafer after the thermal shock wave propagation. In our previous study, it was supposed that an internal crack whose initiation is a dislocation is propagated when the thermal shock wave by the next pulse overlaps with this layer partially. In this study, a two-dimensional thermal elasticity analysis based on the fracture mechanics was conducted. The internal crack propagation was analyzed by calculating the stress intensity factor at the crack tips and comparing with a threshold of that. As a result, validity of the previous hypothesis was suggested.