Shock wave response of amorphous solids by mesoscale simulations
Abstract
<p indent="0mm">Amorphous solids lack the traditional mechanisms of crystal plasticity such as dislocation motion; instead, their plastic deformation results from mesoscale “shear transformations” operating within atomic groups. Due to spatiotemporal-scale limitation, it is extremely challenging to investigate the dynamic processes of shear transformations under dynamic impact, leaving the response of amorphous solids to shock waves largely unclear. To this end, we have developed a dynamic mesoscale model based on shear transformation dynamics, and systematically investigate the evolution of the elastoplastic shock-wave response of amorphous solids with respect to impact velocity and propagation distance through finite element simulations. The results indicate that as the impact velocity increases, the activation of shear transformations intensifies and gradually catches up with the elastic wavefront via a plastic wave mode. The strong interaction between the plastic wave of shear transformations and the loading shock wave results in an exponential decay of the Hugoniot elastic limit with propagation distance, as well as a more rapid rise of the plastic wave front at higher impact speeds. By adjusting the eigenstrain of shear transformation, we further explored the power-law relationship between the plastic strain rate at the plastic wave front and Hugoniot state stress, finding that the non-4 power-law exponent is closely related to the nonlinear multiplication of shear transformations in amorphous solids before Hugoniot elastic limit.</p>
