Critical energy criterion for the shock initiation of explosives by projectile impact

Abstract The critical energy (Ec) criterion developed by Walker and Wasley for predicting the response of bare, heterogeneous explosives to flying‐plate impact, is modified for application to flat‐nosed rods and spherical projectiles. This modification redefines the shock duration term used in calculating Ec and implies that a minimum volume of explosive at a given shock energy is needed before initiation occurs. The modification also changes the L/D ratio of the projectile at which plate behaviour changes to rod behaviour from the currently accepted value of approximately 1/4 to 1/12. Comparisons between the modified criterion and published experimental data show that the same value of Ec can now be obtained from both flying‐plate and more complex projectile impacts into the same explosive.