Cyclic Fatigue-Crack Propagation Behavior in Silicon Carbide: Long- and Small-Crack Behavior

Abstract

Cyclic fatigue properties of high-toughness SiC with additives of Al2O3 and Y2O3 were examined, with a focus on differences between long- (>3 mm) and small-crack (<200 <mu>m) behavior. Small cracks were initiated with Vickers indents placed on the tensile surfaces of beams, and crack extension was monitored optically under cyclic load. For small cracks, high growth rates which exhibited a negative dependence on the far-field driving force were observed. Such behavior was explained by both indent-induced residual stresses and the relative size of cracks compared with bridging zone lengths.