Effects of Crack Size on Fatigue Behavior in Silicon Nitride

Abstract

The fatigue behavior of gas pressure sintered silicon nitride ceramics at room temperature in air was investigated. Cyclic and static fatigue tests were carried out for smooth specimens and precracked specimens. Precracks were introduced by indentation at the center of the tension side surfaces. All the testing was conducted by the 3-point bending method. Smooth specimens showed no significant enhancement of the subcritical crack growth by cycling. On the other hand, enhanced fatigue was observed for precracked specimens. In addition, it is suggested that the fatigue behavior depends on the size of the precracks. Cyclic fatigue behavior was not influenced by residual stress introduced by Vickers indentation.