INFLUENCE OF THE LOAD CONDITIONS ON THE FAILURE WAVE IN GLASSES

Previously, a series of plate impact experiments have provided evidenc e for the appearance of failure waves in glasses under uniaxial compre ssion. Presented herein is a continuation of research, performed on K9 crown glass and ZF1 dense flint glass at varied shock stresses with a goal to uncover the failure wave source and to make clear whether or not the failure wave can be formed at stresses above the Hugoniot elas tic limit (HEL). It has been found that, at peak stresses below the HE L, the failure wave can be initiated on both the impact surface and th e internal surface inside the sample, indicating that the glass surfac e is a direct source for the failure wave nucleation. However, when th e peak stress exceeds the HEL, brittle glasses become ductile as a res ult of irreversible densification, and the failure wave disappears. Th e high spall strength revealed in the stress range above the HEL indic ates that ductility is also preserved under the subsequent tension.