Experimental measurements of weak-shock profiles in the alloy $6061-T6$ Al are analyzed by irreversible-thermodynamic finite-strain theory to obtain a complete description of the flow process through the shock compression, including the entropy production and the relations among the flow variables of shear stress, plastic strain, and plastic strain rate. The primary quantities, the normal stress and the normal strain, are determined entirely from the equations of motion and the shock-profile data; the secondary quantities, the shear stress, plastic strain, temperature, and entropy, are then determined by thermodynamics. It is shown that infinitesimal strain theory gives unreliable results as soon as the plastic strain becomes of the same order of magnitude as the elastic strain.

• Received 17 April 1979

DOI:https://doi.org/10.1103/PhysRevB.22.1487