Effect of combined pressure-shear loading on explosives

The strength of highly filled composites such as plastic bonded explosives is affected by confining pressure as well as strain rate. This behavior is also observed for natural geologic materials and concretes. Mechanical property testing for explosives is typically uniaxial compression and tension. A few laboratories have included compression testing under confining pressure (triax tests). In these tests, two of the principal stresses are equal.

We have used results from the Steven test [1] to explore explosive ignition due to shear localization and performed accompanying HERMES model (High Explosive Response to MEchanical Stimulus) [2] calculations. We observed shear localizations, which are candidate ignition sites. At those sites, the three principal stresses are unequal and approach pure shear, even with the extended Von Mises model, for which the equivalent strength in pure shear is the same as pure compression. We also used a Mohr-Coulomb model, where the shear strength is about 75% of the compressive strength. In these latter calculations, shear localized in rays emanating from the impact zone.



1. S. K. Chidester et al. Proceedings, 11th Int. Det. Sym., Snowmass Village, CO, 1998, 93.



2. J. E. Reaugh et al., Propellants Explos. Pyrotech. 2018, 43, 703.