Predicting explosive response to jet attack is dif®cult due to the complex nature of the projectile. The shock duration term in the critical energy (Ec) criterion developed by Walker and Wasley for plate impact is modi®ed for application to round-nosed rods which appear to simulate jet attack. Experimental data on explosive initiation threshold in the cases of plate or rod impacts, LS DYNA2D simulations and data obtained with the new criterion are in good agreement.

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The critical energy criterion (E c ) developed by Walker and Wasley is widely used to determine the response of explosive submitted tō yer plate impacts. As it has been shown previously to be limited in the pressure range over which it applies, in the number of explosive formulations which appear to obey it and in the range of projectiles covered by it, we have modi®ed twice this criterion. The ®rst mod-i®cation, taking into account a trend toward lower minimum energy with increasing pressure (pressure¯uence) enables it to be applied to explosives previously found to be outside the original criterion and to extend the pressure range. The second modi®cation taking into account a trend toward higher minimum energy with decreasing impact surface area (impact surface dependence) is a bidimensional extension of the critical energy concept. The threshold energy per unit area thus de®ned allows to predict the shock initiation limits of bare explosives (PBX and cast formulations) impacted by shaped charge jets.

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