Finite Element Analysis and Experiment of the Subsurface Damages on Silicon Nitride Subjected to Repeated Impact Loadings

Abstract

This paper presents characterization and evaluation of a silicon nitride plate subjected to repeated impact by a small but hard particle at velocity in a range from 80 to 160 m/s. It specifically focuses on damage patterns in relation to repeated impacts. In addition, the paper also provides a finite element analysis in conjunction with the Tuler-Butcher damage model that is employed to study the formation of the damages during the multiple impact events. The results of the analysis using a very fine mesh indicated that during the contact of the projectile and the plate, the area beneath the contact surface is mainly governed by a compressive stress state. However, a small-adjacent area encircled the compressed region was in a high tensile stress state. The largest tensile stress in the area instantly occurred after the projectile touched the ceramic within a time significantly shorter than the time required for the maximum contact. Majority of the ring cracks observed in the experiments occurred in this area. Furthermore, the ring cracks grew upon further application of impact. Finally, the analysis indicated that the growth of the ring crack led to formation of the spall or the cone crack.