抄録
Fatigue crack propagation tests in a pure plane strain condition were performed by realizing a concentric circular crack propagation on the round-bar specimen with a circumferential notch under direct loading, and the crack propagation rate and crack closure behaviors were investigated by using the unloading elastic compliance method. In addition, the crack propagation behavior under a nearly plane strain condition could be examined for a wide range of K by using the compact-type specimen with side-groove of a proper configuration.
Two-step tests of Hi-Lo loading were carried out on the both specimens and retardation behaviors of crack propagation were investigated. It was found that there existed more than two reasons for retardation. One of them is the change of crack opening level due to the change in loading level, and the retardation observed in the relatively high K region could be explained by the effective stress intensity factor. However, the retardation in the low K region was found not to be explained only by the change of crack opening level.
