Shock compression behavior and dynamic strength properties of preheated tantalum: Role of crystal anisotropy

A Singla and K Basavaraj and A Ray, PHYSICAL REVIEW B, 110, 184111 (2024).

DOI: 10.1103/PhysRevB.110.184111

Extensive molecular dynamics simulations are performed to investigate the effects of planar shock compression and subsequent release phenomena in preheated single-crystal Ta. Hugoniot structures along three crystallographic orientations are examined with systematic increase in sample temperature towards melting conditions. Study reveals a shift in the onset of plasticity to lower impact velocities and narrowing of elasticplastic two-wave zone in preheated samples. Building upon our previous approach, we have coupled the spatial decay and strain rate rise of longitudinal stress associated with elastic waves along the (110) and (111) directions. This enabled us to predict Hugoniot elastic limit (HEL) of orders of magnitude larger thickness samples with reasonable level of accuracy. Importance of our study lies in unifying available HEL data spanned over a wide range of sample dimensions and strain rates, including our own, in a universal scaling relation. The anisotropic elastic-plastic response observed in preheated Ta, as evidenced by the temperature dependence of HEL, is comprehended through microstructural analysis focusing on twinning and dislocation-induced plastic deformation. Signature of plastic anisotropy is also reflected in the distinct temperature variation of dislocation density observed for (110) and (111) orientations. Further, influence of elevated sample temperature on shock release phenomena is examined leading to estimation of spall strength. Study for representative impact strengths reveals strong orientation dependence in tensile strength profile for preheated Ta along all three principal directions. For better insights into the compressive and tensile strength at ultrahigh strain rates, we propose a unique analytical function that explains the orientation-dependent temperature variations observed in both HEL and spall strength. A comprehensive understanding of spalling is achieved through in-depth analysis of void nucleation-growth-coalesce dynamics supported by void statistics.

Return to Publications page