Minimum Strength of Ceramics After Proof Testing : (The Case When Slow Crack Growth Occurs on Unloading)

Abstract

This paper is concerned with the theoretical aspect of proof testing of ceramics. In the case when slow clack growth occurs during the unloading process of proof testing of ceramics, the minimum strength after proof testing, S_{f min}, becomes lower then the proof stress σ_p. The equations for S_{f min} in such cases were derived by Evans and Ritter. However, existence of he three distinct regions I, II and III in da/dt-K diagram was not fully taken into account in their equations. Thus, in this paper, a detailed analysis was carried out taking into account the actual crack growth characteristics, and the equation for S_{f min} was derived. A convenient diagram for determining the proof testing condition was also proposed.