The release and reshock behavior of aluminum from an initial shock stress of 2 GPa (20 kbar) has been examined. It is found that a twohyphen;wave structure characterizes both release and recompression, although a definite elastichyphen;plastic structure is not obtained in either case. The velocity of the initial disturbance for both recompression and release agrees with the extrapolated ultrasonic longitudinal velocity, which implies initial elastic response from the precompressed state. The present results are discussed in terms of a ratehyphen;independent model which incorporates a distribution of yield states in the precompressed material. Reasonable agreement with experimental reshock and release wave profiles is obtained with this model. A brief discussion of rate effects estimated from an acceleration wave analysis is also presented.
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