Under plane shock wave compression, a glass may undergo elastic deformation at the shock wave front, and fail catastrophically at a later time. Since this time delay increases with the distance into the material, the phenomenon has been interpreted as a failure wave. In this article, a new theory of failure formation and propagation in shocked glasses is presented. Stress concentration due to the defects and transient loading conditions on the impact surface is assumed as the origin for initiating heterogeneous microdamage. The progressive percolation of microfissures into the material bulk gives rise to the failure wave phenomenon. Through the failure process, the deviatoric strain energy in the intact material is converted to the volumetric potential energy in the comminuted and dilated material. The state of material damage is measured in terms of the dilated volume of comminuted material at full release. The failure propagation is governed by coupled nonlinear diffusion and time-dependent evolution of the dilated volume. Numerical results are presented and compared to the lateral stress gauge measurements in two shocked glasses. It is shown that the proposed theory and simple modeling can capture the essence of the failure wave phenomenon. The theory also eliminates the ambiguity in the previous modeling work on the failure wave phenomenon in shocked glasses.
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