Prediction of fatigue lifetime based on static strength and crack extension law - Fatigue test of mems materials becomes unnecessary

Abstract

This paper presents a scheme to predict the fatigue lifetime of polycrystalline silicon thin films under cyclic loading. The initial damage was characterized as an equivalent crack distribution from the results of quasi-static tensile tests, i.e., from the distribution of static strength. The fatigue crack extension process determining fatigue lifetime was then estimated by the well-known Paris law with two unknown parameters. These were fit to the results of fatigue tests performed on specimens with two different situations of etching damage. In spite of the difference in static strength, the parameters are consistent among the two cases. This implies that fatigue crack extension law is inherent to the material and that lifetime can be estimated on the basis of static strength.