Generalized Interpolation Material Point Approach to High Melting Explosive with Cavities Under Shock

TL;DR

This paper improves the GIMP method with a new contact criterion and investigates the dynamic response of high melting explosive with cavities under shock, revealing cavity effects on hot spot formation and impact behavior.

Contribution

An improved GIMP contact criterion with a switching function enables more accurate simulation of explosive cavity dynamics under shock.

Findings

Cavities influence hot spot formation in explosives.

Impact velocity affects cavity collapse symmetry.

Secondary impacts and maximum separation distances are observed.

Abstract

Criterion for contacting is critically important for the Generalized Interpolation Material Point(GIMP) method. We present an improved criterion by adding a switching function. With the method dynamical response of high melting explosive(HMX) with cavities under shock is investigated. The physical model used in the present work is an elastic-to-plastic and thermal-dynamical model with Mie-Gr\"uneissen equation of state. We mainly concern the influence of various parameters, including the impacting velocity $v$, cavity size $R$, etc, to the dynamical and thermodynamical behaviors of the material. For the colliding of two bodies with a cavity in each, a secondary impacting is observed. Correspondingly, the separation distance $D$ of the two bodies has a maximum value $D_{\max}$ in between the initial and second impacts. When the initial impacting velocity $v$ is not large enough, the cavity collapses in a nearly symmetric fashion, the maximum separation distance $D_{\max}$ increases with $v$. When the initial shock wave is strong enough to collapse the cavity asymmetrically along the shock direction, the variation of $D_{\max}$ with $v$ does not show monotonic behavior. Our numerical results show clear indication that the existence of cavities in explosive helps the creation of ``hot spots''.