On the thermomechanics and footprint of fragmenting blasts

In this paper, a mathematical model is developed to simulate the progressive time-evolution of an object that fragments, which may contain biohazardous materials or materials that may thermally degrade into a toxic state. Estimates are made for the blast radius that one can expect for a given amount of detonation energy and the resulting atmospheric heating of fragments. The atmospheric heating of the fragments is important, since if the heating is sufficiently high, the biohazardous material can be neutralized. If the material is not heated sufficiently, then the location in which it lands can be considered as “contaminated”. This analysis is useful is determining safe areas after such a blast. Ascertaining the temperature of the fragments is extremely difficult to measure in experiments, thus motivating the development of the model. The model balances the released energy from the initial blast pulse with the subsequent kinetic energy and then numerically computes the trajectory of the fragments under the influence of the drag from the surrounding air and gravity. Preliminary field experiments with explosives are described and the results are compared to the output from the model. The subsequent drag heating of the material is then computed in order to ascertain the temperature of the blast fragments.