Elastic Wave Amplitude and Attenuation in Shocked Pure AL

Shock-induced elastic-plastic deformation in pure aluminum was examined at 4 GPa peak stress by measuring wave profiles in thin (40$-$180 $\mu$m) samples under plate impact loading. Large elastic wave amplitudes ($\sim$1 GPa) and rapid elastic wave attenuation with propagation distance were observed, indicating a time-dependent elastic-plastic response. These results are in contrast to the $\sim$0.1 GPa elastic wave amplitudes observed in past work (\textit{J. Appl. Phys.} \textbf{98}, 033524 (2005)) using thick ($>$1 mm) samples. The combination of large elastic wave attenuation in thin samples and differences in sample thicknesses between the present and past work suggests a consistent picture of shock wave propagation in pure aluminum: manifestations of time-dependent elastic-plastic response are confined to material very near the impact surface. The present results cannot be fully reconciled with recent shockless compression results (\textit{Phys. Rev. Lett.} \textbf{98}, 065701 (2007)). Work supported by DOE.