抄録
It has already been reported by the authors that the two indentations facing each other near the tip of a crack are especially effective on retardation of crack propagation. The purpose of this paper is to examine the effectiveness of indentations in plate specimens with various types of notch. The experiments show that the pre-additional indentations near the notch root are especially valid in retardation of a crack. The effect of the indentations can be explained approximately from the existence of residual stresses produced by the indentations.
