Generalized interpolation material point approach to high melting explosive with cavities under shock

Criterion for contacting is critically important for the generalized interpolation material point method. We present an improved criterion by adding a switching function. With this method the dynamical response of high melting explosive with cavities under shock is investigated. The physical model used in this work is an elastic-to-plastic and thermal-dynamical model with Mie-Grüneissen equation of state. We address mainly the influence of various parameters, including the impacting velocity v, cavity size R, etc, on the dynamical and thermodynamical behaviour 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 behaviour. Our numerical results clearly indicate that the existence of cavities in explosives helps the creation of 'hot spots'.