Dynamic mechanical response of magnesium single crystal under compression loading: Experiments, model, and simulations

Magnesium single crystal samples are compressed at room temperature under quasistatic (similar to 0.001 s(-1)) loading in a universal testing machine and dynamic (430, 1000, and 1200 s(-1)) loading in a split Hopkinson pressure bar system. Stress-strain curves show that (a) the fracture strain slightly increases with the strain rate; and (b) the maximum strength and strain hardening rate increase significantly when the testing changes from quasistatic to dynamic, although they do not vary much when the strain rate for dynamic testing varies in the range of 430-1200 s(-1). The operation of the secondary pyramidal slip system is the dominating deformation mechanism, which leads to a fracture surface with an angle of similar to 42 degrees with respect to the loading axial direction. A theoretical material model based on Johnson-Cook law is also derived. The model includes the strain hardening and strain rate hardening terms, and provides the stress-strain relations matching with the experimental results. Finite element simulations for the strain rates used in the experiments predict the mechanical responses of the material that agree well with the experimental data. (C) 2011 American Institute of Physics. [doi:10.1063/1.3585870]