A Parametric Study on Overlapping Laser Shock Peening of 4140 Steel via Modeling and Experiments

Laser shock peening (LSP) under the water confinement regime (WCR) involves several complicated physical phenomena. Among these phenomena, the interaction between laser and coating material during LSP is very important to the laser induced residual stress, which has an important effect on the fatigue and corrosion properties of the substrate material. To gain a better understanding of this interaction, a series of experiments, including single shot, single track overlapping, and multi-track overlapping LSP, have been carried out on 4140 steel with black paint coating. A 3-D finite element model has also been developed to simulate the LSP process. Combining this with a previously developed confined plasma model, which has been verified by the experimental data from literature, the 3-D finite element model is used to predict the residual stresses induced in the substrate material as well as the indentation profile on the substrate surface. The model prediction of indentation profiles are compared with the experimental data and good agreements are obtained. The effect of process parameters on the residual stress has also been investigated both experimentally and theoretically.