Abstract
Machining a brittle material causes numerous cracks near the machined surface. Then, if it is machined in appropriate condition, the cracks for the main part are similar in dimension. Assuming that those cracks are periodic, have same dimensions and exist in a semi-infinite region under tension, a study on variation of their stress intensity factor with removing surface layer by finishing is carried out. The rearrangement of the already known results and the calculation with two and three dimensional finite element method are conducted. The results obtained are as follows : (1) If the ratio of edge crack length to their period is beyond about 0.2, the stress intensity factor is independent of the crack length. (2) If the length of inner cracks near the surface is longer than their period, variation of stress intensity factor caused by removing surface layer is negligible, until the inner cracks become edge cracks of which the length is one fifth of the initial inner crack length.
