Applicability of the Taylor Theory of the Polycrystalline Aggregate to Finite Amplitude Wave Propagation in Annealed Copper

Abstract

This paper provides additional experimental evidence for the Taylor theory of dislocations and the Taylor theory of the polycrystalline aggregate. For annealed copper (as had been found by Bell for annealed aluminum) the governing stress-strain curve for plastic wave propagation is a parabola, as predicted by the Taylor theory of dislocations. Using the Taylor theory of the polycrystalline aggregate, the parabolic stress-strain law for annealed copper, as had been shown earlier for annealed aluminum, is determinable from compression stress-strain curves for single crystals. These experimental data in annealed copper are obtained from the free-flight constant-velocity impact of identical specimens using the diffraction-grating technique for the measurement of strain and surface angle. From the results given in this paper, together with those obtained earlier by Bell for annealed aluminum and the recent results of Sperrazza for pure lead, it may be concluded that strain rate does not play a significant role in the dynamic plasticity of these annealed face-centered-cubic metals. As in annealed aluminum and pure lead, plastic strain propagation velocities, maximum strain amplitude, surface angle behavior, time of contact, and the coefficient of restitution for annealed polycrystalline copper are found to be given by the strain-rate independent theory of plastic wave propagation.