著者

田中 啓介 鈴木 健太 藤井 貴之 渋江 隆治 藤山 一成

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:18848338)

巻号頁・発行日

vol.79, no.799, pp.266-280, 2013 (Released:2013-03-25)

参考文献数

14

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Fatigue crack propagation tests of center-notched plates of lead-free solder were conducted under displacement-controlled conditions with mean strain and load-controlled conditions with mean stress. The J-integral range was evaluated from load-displacement curves by using the simple estimate method. The mean stress introduced by the initial (mean) tensile strain in displacement-controlled tests was relaxed very quickly with cycles. The crack propagation rate was nearly constant during crack extension and was not much influenced by the mean strain. The crack closure did not take place under tensile mean strains, while it occurred under compressive strains. In load-controlled tests with mean stress, the ratcheting deformation was accumulated during fatigue tests. The crack propagation rate increased with crack length, and was not influenced by the tensile mean stress. The crack propagation rate was lower as the mean compressive stress was larger and as the stress range was lower. The crack closure took place only for the cases of compressive mean stresses. When the J-integral range was evaluated by taking into account of crack closure, the crack propagation rate was expressed as a power function of the J-integral range for all cases examined, The effective fractions of the applied load, strain and J-integral were unity for zero and positive mean stresses. They deceased linearly with increasing mean compressive stress down to -4 MPa, and remained nearly constant below -4 MPa.