Frictional interactions at compressed Al interfaces

We discuss the velocity and temperature dependence of the frictional force at sliding Al-Al interfaces. A series of 3-D 1.5 million atom Non Equilibrium Molecular Dynamics (NEMD) simulations for single crystal Al incommensurate interfaces have been carried out for a range of imposed boundary temperatures and sliding velocities at an imposed boundary pressure of 15 GPa in the solid state. Velocities in the range 50-2000 m/s are considered for temperatures of 232, 464, and 696 K. We discuss the regimes of interfacial stability, from stable, anharmonic phonon dominated at low velocities, through plasticity dominated interfacial instability at intermediate velocities, to high velocity Couette flow, and present a scaled model for the frictional force in the intermediate to high velocity regimes. Connection will be made to recent dynamic friction experiments carried out at the DOE ATLAS pulsed power facility.