Fracture Mechanics Fatigue Testing Technique for Measuring Stable Crack Growth in Ceramics at Very High Temperatures

摘要

The fracture mechanics fatigue testing technique for ceramics which had been developed by the authors was examined to improve the dynamic instability caused by relaxation of crack tip stress concentration at high temperatures. Double eccentric pulsating compressive loading applied by a computer controlled fatigue testing machine was combined with negative double cantilever loading by soft springs. The testing conditions were extended to include the negative R-ratio of K-value, and the stability of crack growth was statically increased. For measuring the crack growth by the quasi-elastic compliance method and controlling the crack growth rate, an on-line computer software was newly developed, which increased the dynamic stability of testing. Consequently, the fracture mechanics fatigue testing for stable crack growth in silicon nitride became possible beyond 1 300K.