Multiscale Modeling of Laser Shock Peening Process involving Laser Induced Plasma Shock Wave Simulation

Laser shock peening is a surface modification technique which improves the fatigue performance of metallic structures by inducing compressive residual stresses for mitigation of crack growth. A pulsed laser vaporizes the first layer of the component and turns the solid material into plasma. Thermal expansion of the plasma in the confining medium initiates high pressure shock waves propagating into the material. Residual stresses are the result of local plastic deformations caused by the pressure waves. The process is highly nonlinear and difficult to optimize based on experiments alone due to the high number of process parameters, short time events and extreme values of physical quantities which are hard to measure (e.g. shock wave propagation, plasma forming). Aiming at deeper understanding of the process and an optimized residual stress profile, a multiscale approach is proposed. Starting with a laser induced plasma shock wave simulation, a global model for determining the shock pressure depending on the laser parameters is implemented. The results of the shock pressure distribution over time are used in a subsequent finite element model, to predict the resulting residual stress profile within the material. Afterwards the numerical results are compared and validated on basis of the experimental results for different aluminum alloys.