Dynamic elastic-plastic properties of single-crystal pentaerythritol tetranitrate

Abstract

The dynamic elastic-plastic behavior of single crystals of the secondary explosive pentaerythritol tetranitrate (PETN) have been studied at input shock strengths between 0.6 and 4.0 GPa (6–40 kbar). Crystals with surfaces cut perpendicular to the 〈110〉 and 〈001〉 directions were struck by gas-gun projectiles and stress histories at both sample faces were determined with quartz dynamic stress gauges. The amplitude of the elastic wave increases markedly with input shock strength and decreases with distance of run. A viscous relaxation model based on the theory of dislocation dynamics is consistent with the observations and yields estimates of 6.8 GPa μs (6.8×104 P) for the dynamic viscosity at the shock front and 1.1×1010 m−2 for the dislocation density. Observed impact-face shock states correspond to the hydrostat Hugoniot, suggesting that little shear stress is retained after yielding begins. With input shock strengths of 4.0 GPa, pressure buildup at the impact face is observed, indicating energy relase near this surface. This occurs at about half the input shock strength that would be expected from previous initiation experiments and theoretical calculations on single-crystal PETN.