  A novel explanation of the quasielastic release phenomenon in shock
compressed aluminum is presented. A dislocation-based model, taking into
account dislocation substructures and evolution, is applied to simulate the
elastic plastic response of both single crystal and poly crystalline aluminum.
The calculated results are in good agreement with experimental results from not
only the velocity profiles but also the shear strength and dislocation density,
which demonstrates the accuracy of our simulations. Simulated results indicate
that dislocation immobilization during dynamic deformation results in a smooth
increase of yield stress, which leads to the quasi-elastic release, while the
generation of dislocations caused by the plastic release wave results in the
appearance of a transition point between the quasielastic release and the
plastic release in the profile.
