Combined Pressure-Shear Ignition Sensitivity Test

A procedure is described for using a high pressure activator to test explosives and propellants for sensitivity to ignition under conditions of combined pressure and shear. Data are presented for TNT and Comp B explosive and Composite Modified Double Base (CMDB) propellant showing that sensitivity increases from TNT to Comp B to CMDB. The maximum pressure and shear velocity were around 1.0 GPa and 60 m/sec, respectively. An analysis of the data in terms of viscous heating of the shear zone is presented. In this analysis, the energy deposition rate per unit volume (due to viscous heating) was equated to the energy loss rate per unit volume (due to thermal conduction) to obtain a relationship between pressure and shear velocity required for ignition. This relationship defines a boundary curve in the pressure-shear velocity plane between ignition and non-ignition.