Analysis of mesoscale heating by piston supported waves in granular metalized explosive

Abstract

Deformation-induced heating of explosive composites is influenced by the material microstructure (i.e. porosity and particle sizes, shapes and packing), and component-specific thermomechanical properties and mass fractions. In this study, an explicit, 2D, Lagrangian finite and discrete element technique is used to examine thermomechanical fields in mixtures of explosive (HMX, C4H8N8O8) and metal particles (Al) induced by piston-supported deformation waves (piston speed 50 ⩽ Up ⩽ 500 m s−1). The mesoscale description uses a plane strain, thermoelastic–viscoplastic and friction constitutive theory to describe the motion and deformation of individual particles, and an energy consistent, penalty based method to describe inter-particle contact. The deformation response of material having an initial solid volume fraction of φs0 = 0.835 (porosity 1 − φs0 = 0.165) is characterized for different metal mass fractions and wave strengths. Transition from a strength-dominated to a pressure-dominated wave structure is predicted to occur with increasing wave strength due to the elimination of porosity. Average thermomechanical fields that define the effective wave structure differ both qualitatively and quantitatively for the two types of structures. Explosive component mass locally heated to elevated temperature behind waves is shown to be affected by the wave structure and the value of friction coefficient.