Cyclic Fatigue Experiments and Analysis of Silicon Nitrides—Stepwise Loading

Abstract

Rotating beam fatigue test has been performed at room temperature for two types of advanced hot-pressed silicon nitrides. The test completion modes consist of fast fracture, fatigue fracture, and runout (at about 108 cycles). Some specimens tested have been subjected to step-up load testing. Application of Weibull statistical method has been made as the fatigue lives of specimens under a constant bending load are subjected to wide scatter. A maximum likelihood analysis was applied to test data obtained from the single load and step-up load tests to determine the fatigue (or crack growth) exponent. The effect of specimen surface finish on fast and fatigue fracture has also been investigated using the Weibull analysis.