Dynamic Response of Aluminum

Abstract

The dynamic stress-strain relation of aluminum was measured in compression to a stress of 22 kbar using plate impacts to induce uniaxial strain. The results were compared to a uniaxial strain curve constructed from elastic moduli and quasistatically determined stress-strain curves. The dynamically determined stress-strain relation was not unique in that it varied as a function of the magnitude of the induced stress and was offset from the quasistatic curve. These small deviations are attributed to strain rate effects. The rate effects were further demonstrated by observing the transmission of an elastic compression stress wave in aluminum after the aluminum was dynamically stressed beyond the yield point and held at constant strain for a period of approximately 2 μsec. The dynamic stress-strain relation was measured upon the release of a shock induced compressive stress of 10.5 kbar to a tension of −9 kbar by observing the effects of tensile stress waves. The deviation of the unloading stress-strain relation from that predicted by simple elastic-plastic theory is attributed to strain rate and Bauschinger effects.