Abstract
The purpose of this study is to elucidate the validity of a sphere indentation test in order to evaluate the damage in ceramic specimens applied a constant load for a long time. Four points bending tests with a constant load were carried out on silicon nitride specimens under various conditions. After bending tests, the sphere indentation tests were done on the specimens to obtain the strength for ring crack initiation on the surface layer of the specimen. X-ray diffraction method was also used to measure the residual stress of the specimen.
