構造用セラミックスの高温における繰り返し疲労強度

抄録

The cyclic fatigue tests at high temperatures were conducted for hot-pressed silicon nitride and sintered silicon carbide, and the results were analyzed by the power-law and exponential crack growth relations. The cyclic fatigue data for both materials were fitted with straight lines in both of log-log and semi-log forms which were based on the former and latter relations, respectively. However, the experimental lifetimes of silicon nitride were substantially longer than those predicted from the results of static fatigue test using either crack growth relation, and this difference was expanded with lowering the applied stress. On the other hand, the experimental and predicted lifetimes relatively well agreed for both of the crack growth relations in silicon carbide. The sensitivity of cavitation expansion behavior to displacement rate was proposed as a cause for the longer life time of cyclic fatigue in silicon nitride.