Inelastic deformation mechanisms and damage in structural ceramics subjected to high-velocity impact

Abstract

The inelastic deformation mechanisms and damage features observed in structural ceramics subjected to nonpenetrating, high-velocity impacts are similar to those seen in quasistatic Hertzian indentation, albeit more severe. For impacts on large ceramic bodies (relative to impactor diameter), cone cracking is the primary mechanism in regions of high tensile stresses. In regions of nonhydrostatic compressive stresses, depending on the material characteristics, elasticity, grain-boundary microcracking, or plasticity are the primary mechanisms, and depending on their associated energetics, may be able to compete with the initiation and growth of cone cracks. In this regard, a new model is presented that examines the effect of grain-boundary microcracking on cone cracking through shear-induced dilatancy (i.e., bulking) within the quasiplastic zone that forms just underneath the impact site. Depending on the size of the quasiplastic zone and bulking pressure, it is shown that the bulking phenomenon has the potential to suppress cone cracking. Lastly, examples of other shear-driven inelastic deformation mechanisms are presented. © 2010 The American Ceramic Society.