Laser Short Pulse Heating and Elastic-Plastic Wave Generation

Abstract

Laser induced shock processing improves the mechanical and tribological properties of metallic surfaces. During the high power intensity laser beam interaction with the solid substrate ablation of the surface occurs, which in turn results in a recoil pressure developing in the interaction zone. This triggers the generation of elastic-plastic waves that propagate in the solid substrate and as a consequence a plastic region is developed in the vicinity of the substrate surface. In the present study, short pulse laser heating of steel is considered, and the Fourier and the electron kinetic theory models pertinent to laser heating are introduced. The governing equations of heating are solved numerically with the appropriate boundary conditions considered. The recession and vapor front velocities, and vapor pressure and recoil pressures are determined for different laser power intensities. The elastic-plastic wave propagation in the solid substrate is modelled and findings are compared with the results of the previous studies. It is found that the rapid rise of the surface temperature occurs at high laser power intensities and the recoil pressure generated at the interface substantiates, which in turn results in elastic-plastic wave propagation in the solid substrate. This develops a plastic region in the order of 0.9 µm in the surface vicinity of the solid substrate and the time required for this deformation is in the order of 25 ns. In addition, the depth of the plastic region developed in the present study agrees well with the previous results.