Quantification of the kinetic energy conversion to temperature increase in metal-on-metal impacts up to hypervelocity conditions by molecular dynamics simulation

The dynamic impact loading of metals goes along with energy conversion from kinetic energy to internal energy and, ultimately, temperature increase. The fraction of the kinetic energy partitioned into heating is strongly dependent on the impact velocity. Limiting cases are already well characterized, both experimentally and numerically. At low velocities, plastic work is the main source of internal energy increase and contributes to approximately 100% to material heating. Toward high velocities, approaching a hydrodynamic-like condition but still below the threshold for material melting or vaporization, about 50% of the kinetic energy is converted to internal energy. The current work addresses the intermediate regime of mixed phenomenology, where analytical descriptions are hardly feasible and typical simulation methods of impact engineering, namely hydrocodes, fail to make reliable numerical predictions. For this purpose, we here alternatively apply molecular dynamics simulations at the nanometer scale, taking iron as exemplary test case. The results complement early findings by extending them to a broader range of validity.