著者

大田 祐太朗 久布白 圭司 山崎 泰広

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.8, pp.599-604, 2020-08-15 (Released:2020-08-20)

参考文献数

27

被引用文献数

2

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Ti alloys are widely applied to jet engine components. Low cycle fatigue (LCF) strength of Ti alloys decreases with tensile stress dwell at room temperature (Cold Dwell Fatigue, CDF). CDF strength was influenced by stress level, microstructure, and dwell time. In order to study the effect of long time dwell for CDF properties, LCF test (0s dwell), CDF tests (120s~7200s dwell), and creep test were carried out. With increase of dwell time, fracture cycle decreased and fracture elongation increased. Fracture surface of long time dwell CDF tests corresponded to that of creep test. Additionally, strain accumulations during stress dwell at long time dwell CDF tests were similar to strain change of creep test. From SEM/EBSD analysis, inelastic strain was obviously increased after CDF tests and creep test, compared to LCF test. Hence, it was considered that long time dwell CDF was greatly influenced by creep deformation.

著者

山崎 泰広

出版者

静岡県立大学

雑誌

基盤研究(C)

巻号頁・発行日

2013-04-01

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肝毛細胆管膜に存在するコレステロールトランスポーター・Abcg5/Abcg8の機能亢進は、コレステロール胆石症を引き起こすと考えられている。我々はこれまでに過栄養状態が肝毛細胆管膜におけるAbcg5/Abcg8の機能、および発現を顕著に増加させることを見出したが、その機構に関しては不明であった。本研究では、過栄養状態がAbcg5/Abcg8のトラフィキング、および機能発現に与える影響について解析した。その結果、肝臓にコレステロールが蓄積した状態では、細胞内小胞に蓄えられたこれらトランスポーターの毛細胆管膜への移行が促進すること、その機構にcAMPシグナルが関与することを明らかにした。

著者

布村 成具 山崎 泰広 大滝 秀治

出版者

社団法人日本材料学会

雑誌

材料 (ISSN:05145163)

巻号頁・発行日

vol.50, no.10, pp.1102-1107, 2001-10-15

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Fatigue characteristics are of fundamental importance when choosing a structural materials, especially when deciding upon the materials for reactor structure where long-term safety is primary importance. In this field, recently, the propagation behavior of mode II and mode III fatigue cracks has attracted special interest. The mode II and mode III fatigue testings involve greater difficulties compared with the mode I testing and the testing procedure has not been established. SS400 carbon steel was fatigue tested by a torsion fatigue testing machine. In the torsion test, fatigue cracks can propagate in all modes. To identify their behavior, surfaces of the specimen were observed by CCD camera and the behavior of surface cracks were recorded in a time-lapse video recorder which can record up to for 40 days. To reveal the morphology of the mode II and mode III Crack propagation, some of test interrupted specimens were sliced and observed by a two dimension measuring microscope. To investigate the crack morphology three dimension crack demonstrate computer program was developed. In the torsion test of plain surface specimen the mode II crack initiates first, but it transits to mode I in the early stage. However, according to the 3D view a large mode III crack propagates into inside in this stage. Persistent slip band like patterns were observed on the surface and the cross section of the fatigue cracked specimen and all mode III cracks propagate in the band. Some of them grew across the center of the specimen. The da/dN – ΔK diagram of the surface mode II fatigue crack propagation was compared with that of mode I by CT type specimen of the same material. Mode II Propagation rate agreed with mode I propagation rate where the stress intensity factor range was converted as ΔK_I= 2ΔK_II. It means that to design the structure by mode I crack propagation data alone may be acceptable under above conversion. To establish this relationship and to elucidate the behavior of mode III fatigue cracking, more investigations are required.