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

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 μm) 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.