From Laser Shock Peening: Performance and Process Simulation
4.1 Introduction
This chapter presents a two-dimensional (2D) dynamic finite element simulation of single and multiple laser shock peening (LSP) on a metallic alloy using the procedure discussed in Chapter 3. The dynamic stresses and residual stress field in the laser peened material are carefully studied and evaluated with respect to some key factors of LSP.
In the analysis, a complicated three-dimensional (3D) LSP case is simplified into a 2D one because of the geometric symmetry of the specimen and the use of a circle laser spot. In order to achieve an accurate solution, the sensitivity of a finite element mesh is carefully addressed in the selection of the model. Some factors, such as bulk viscosity and material damping, in controlling and suppressing numerical oscillations to achieve a stable dynamic stress state, are also studied and evaluated. Dynamic stresses and residual stress profiles on the surface and in the depth are presented and discussed. The predicted results are correlated with the available experimental data in the literature and estimated from the analytical model presented in Chapter 3. The residual stress in the laser peened material is studied with respect to variations in LSP conditions such as pressure, pressure duration and laser spot size.
4.2 Laser Shock Peening Process
4.2.1 Laser Shock Peening Conditions
The LSP process conducted by Ballard (1991) is modelled. The laser equipment used for the experiments was a Q-switched Nd-glass laser delivering an output energy of around 150 J, laser power density of 10 GW/cm 2
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