Dynamic yield behaviors of aluminum under shock and ramp compression: Experiments and models

Abstract

Although dynamic yield behaviors of aluminum and its alloys have been extensively studied for decades, there is still ongoing debate regarding the loading-path dependence of yield strength. In this work, we carry out shock and ramp compression experiments to systematically measure the dynamic yield strength of aluminum under different loading paths. Experimental results indicate that the dynamic yield strength is highly sensitive to the loading path, along which strain-rate hardening, strain hardening, and high-temperature softening play competitive roles. A direct comparison of data provides the possibility to partially decouple the effects of temperature, strain, and strain rate. Based on the results, a dislocation-based constitutive model is proposed as a function of strain rate, strain, and temperature, which can effectively describe the dynamic yield behaviors of aluminum along various loading paths. It is indicated that the dislocation density saturates around 40 GPa along either loading paths, while a significantly higher dislocation velocity is observed under shock loading, resulting from a much higher temperature rise associated with plastic dissipation.