Numerical modeling of the confined laser shock peening of the OFHC copper

The confined laser shock peening is an innovative surface treatment technique designed to improve the structural integrity by imparting compressive residual stresses into materials. The plasma-induced shock wave pressure (GPa) is applied on the material surface within several tens of nanoseconds, which results in local plastic deformation at an extremely high strain rate and triggers the non-Arrhenius manner of dynamic flow stress due to strain rate sensitivity. A 3D finite element model, which incorporates a unified material model characterizing the Arrhenius and non-Arrhenius manners of flow stress and the temporal-spatial distribution of shock wave pressure, was developed to simulate the confined laser shock peening of the oxygen-free high conductivity (OFHC) copper. The modeling procedure consists of two successive explicit analysis steps: one for shock loading with a very small time increment and another for rebound analysis with a larger time increment. The performance of finite element model was examined by investigating the material model, bottom boundary conditions and analysis step time, and its effectiveness was verified by comparing the predicted dimple profile and micro hardness with the experimental data. With the validated finite element model, the interactive effects of laser power density and full width at half maximum (FWHM) of laser pulse was quantitatively investigated, which can be used to mentor the optimization of the process parameters of laser shock peening. (C) 2016 Elsevier Ltd. All rights reserved.