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2011
Conference Paper
Titel
Numerical analysis of the initiation of high explosives by interacting shock waves due to multiple fragment impact
Abstract
A detailed understanding of the initiation of high explosives by shock waves is of general interest for defense applications. Numerical simulations of such processes with hydrocodes require physics-based models describing the initiation and evolution of a detonation based on state variables such as pressure and specific volume. In this context, the Ignition and Growth model of Lee and Tarver and its modifications are widely used. For this model, simulation parameters for many explosives are available in the literature, and agreement between simulation and experiment is achieved for the threshold velocity of impact-induced shock initiation. In the present investigation, we consider impact processes below the critical velocity for initiation by a single projectile. In a numerical analysis, we show, how shock waves generated by independent fragment impacts interact, and how the overall process may evolve into a detonation even though all impact velocities are below the threshold velocity for single particle impact. A prerequisite for our investigation was a detailed analysis of the simulation model and of different parameter sets for the considered PBX 9404 explosive. We conclude that the available Ignition and Growth model can be used to capture phenomena occurring even below the critical velocity. Nonetheless, a shock-induced initiation (detonation) of a high explosive may under certain circumstances rather be achieved by many fragments at lower velocity than by a single fragment of higher speed.