Multiple elastic shock waves in cubic single crystals

Abstract

Multiple elastic shock waves carry the information on elastic properties under dynamic extreme conditions, but may complicate the interpretation of wave structure including the elastic–plastic transition. On the basis of the acoustic wave-equation analysis, we predict the absence or presence of multiple elastic shock waves in a single crystal subjected to shock loading along a specific crystallographic orientation. Typical FCC and BCC single crystals are taken as validation and application cases. Large-scale molecular dynamics simulations are performed for Cu and Ta; double-wave or triple-wave structures of elastic shock waves (quasilongitudinal and quasitransverse) are observed in the simulations, and the multi-wave structures are in excellent agreement with the wave-equation analysis. Also, the acoustic wave-equation analysis is used to analyze MD calculations, as well as the complex structure of the shock wave during plastic deformation. Free-surface velocity history, transverse velocity history of free surface, and ultrafast X-ray diffraction are explored as experimental means to resolve multiple elastic shock waves.