Numerical simulation of plasma dynamics in laser shock processing experiments

Laser shock processing (LSP) is based on the application of a high intensity pulsed laser beam (I > 1 GW/cm2; τ < 50 ns) at the interface between the metallic target and the surrounding medium (a transparent confining material, normally water) forcing a sudden vaporization of the metallic surface into a high temperature and density plasma that immediately develops inducing a shock wave propagating into the material. The shock wave induces plastic deformation and a residual stress distribution in the target material.Laser shock processing is being considered as a competitive alternative technology to classical treatments for improving fatigue, corrosion cracking and wear resistance of metallic materials.The description of the relevant laser absorption phenomena becomes hardly complicated because of the non-linear effects appearing along the interaction process and which significantly alter the shocking dynamics.A simulation model (SHOCKLAS), dealing with the main aspects of LSP modelling in a coupled way, has been developed by the authors. In this paper the study will be centred on the simulation of the hydrodynamic phenomenology arising from plasma expansion between the confinement layer and the base material using HELIOS (1-D radiation-hydrodynamics lagrangean fluiddynamic code).This code is used to study plasma dynamics under laser shock processing conditions. The influence of the confining layer (medium and thickness) on plasma pressure is also studied.