Open AccessCompaction Waves in Granular HMX
Author(s) -
E Kober,
R Menikoff
Publication year - 1999
Language(s) - English
Resource type - Reports
DOI - 10.2172/2712
Subject(s) - granular material , mechanics , materials science , compaction , porosity , porous medium , terzaghi's principle , dissipative system , geotechnical engineering , composite material , pore water pressure , thermodynamics , physics , geology
Piston driven compaction waves in granular HMX are simulated with a two-dimensional continuum mechanics code in which individual grains are resolved. The constitutive properties of the grains are modeled with a hydrostatic pressure and a simple elastic-plastic model for the shear stress. Parameters are chosen to correspond to inert HMX. For a tightly packed random grain distribution (with initial porosity of 19%) we varied the piston velocity to obtain weak partly compacted waves and stronger fully compacted waves. The average stress and wave speed are compatible with the porous Hugoniot locus for uni- axial strain. However, the heterogeneities give rise to stress concentrations, which lead to localized plastic flow. For weak waves, plastic deformation is the dominant dissipative mechanism and leads to dispersed waves that spread out in time. In addition to dispersion, the granular heterogeneities give rise to subgrain spatial variation in the thermodynamic variables. The peaks in the temperature fluctuations, known as hot spots, are in the range such that they are the critical factor for initiation sensitivity