Laser short-pulse heating with time-varying intensity and thermal stress development in the lattice subsystem

Abstract

Laser short-pulse heating of solid surfaces results in non-equilibrium energy transport in the region irradiated by the laser beam. Owing to the large temperature gradients in the lattice subsystem, high stress levels develop in the surface region of the substrate material. In the present study, temperature and stress fields in the substrate material are presented for the case of the laser short-pulse heating of gold. Electron kinetic theory and a two-equation heating model are introduced to account for non-equilibrium energy transport during the laser heating pulse. Laser pulses exponentially decaying with time are accommodated in the simulations. It is found that lattice site temperature gradients attain high values inspite of the low magnitude of the lattice site temperature. This, in turn, results in high stress levels in the surface region of the substrate material. Thermal stress is compressive owing to high thermal strain development and low displacement of the surface.