著者
秋庭 義明 木村 英彦 鶴 尋貴 中村 亜有子
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 A編 (ISSN:03875008)
巻号頁・発行日
vol.74, no.742, pp.879-884, 2008-06-25 (Released:2011-03-02)
参考文献数
18

Fatigue test system for thin sheets was constructed using an ultrasonic fatigue testing machine. Specimens were fixed at the location where the displacement amplitude became the maximum. The specimen was fatigued under full-reverse bending. Displacement at a fixed edge of the specimen and the deflection of the specimen were measured with a laser displacement gage during fatigue tests. Modal analysis was carried out to determine the dimensions of the specimen and to calculate the applied stress on the basis of the flexural displacement amplitude. The maximum stress was observed on the free side edge near the fixed edge. Two kinds of martensitic stainless steel sheets, SUS301-CSPH and SUS632J1-CSP, were fatigued with the fatigue test system. The thickness of the specimen was 83 and 106μm, respectively. The 3rd vibration mode was selected for fatigue tests. The fatigue cracks initiated from the free side edge of the specimen. For the case of shorter fatigue life, fatigue strength for both stainless steels were almost identical. On the other hand, for longer fatigue life, fatigue strength of SUS632J1 is higher than that of SUS301.
著者
秋庭 義明 田中 啓介 村雨 勇治
出版者
一般社団法人日本機械学会
雑誌
年次大会講演論文集 : JSME annual meeting
巻号頁・発行日
vol.2003, no.1, pp.135-136, 2003-08-05

A bearing steel (JIS SUJ2) and nickel chromium molybden steel (SNCM439) were fatigued with the ultrasonic fatigue-testing machine (20kHz) in laboratory air. In the very long-life regime, the decline of fatigue limit was seen. The origins of crack initiation were mostly internal inclusions. However, even when the specimen broke in a long life region, some cracks were initiated from specimen surface. Fracture surface were observed with a scanning electron microscope (SEM). The fish-eyes were observed in the specimens broken from the internal inclusions. The fracture surface could be divided into three regions. The first region surrounding inclusion was a facet area. The crack propagation in the facet region was Stage A and the crack propagation outside the facet region was Stage B. When the fatigue cracks reached the specimen surface, the fatigue cracks propagated as surface cracks. The crack propagation rate in each region was estimated to be a power function of the stress intensity range. Fatigue life was calculated by integrating with the crack propagation laws determined from the data obtained for the rotating bending. The predicted fatigue life agrees with the experimental result.
著者
田中 啓介 秋庭 義明 田中 拓
巻号頁・発行日
1997-03 (Released:2010-03-30)

科学研究費補助金 研究種目:基盤研究(B)(2) 課題番号:07455052 研究代表者:田中 啓介 研究期間:1995-1996年度
著者
秋庭 義明 木村 英彦 原 航平 田中 啓介
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.54, no.7, pp.698-703, 2005 (Released:2006-04-07)
参考文献数
13

Single edge notched specimens of a unidirectional SiC long fiber reinforced titanium alloy were fatigued under four point bending. Propagation behavior of fatigue cracks was observed on the basis of the effect of the fiber bridging. The branched fatigue cracks were initiated from the notch root. The crack propagation rate decreased with crack extension due to the crack bridging by reinforced fibers. The longitudinal stress in the reinforced fiber was measured by using high spatial resolution synchrotron radiation. The interfacial frictional stress between the matrix and the fiber could be directly determined by X-ray method. The bridging stress was also measured as a function of a distance from a crack-tip. The stress intensity factor range corrected on the basis of the shielding effect agreed well with that for the monolithic titanium alloy, when compared at the same crack propagation rate.