Prediction of the residual state in 304 austenitic steel after laser shock peening – Effects of plastic deformation and martensitic phase transformation

• A numerical model capable of predicting the material behavior during LSP has been presented.
• Plastic strains and the amount of martensite in austenitic steel after LSP are numerically predicted.
• An elasto-plastic model for phase transformation capture the rate dependency of plastic deformation.
• The influence of temperature, laser pulse duration and laser intensity on the residual state is studied.
• At lower temperatures, the phase transformation is the main cause for residual stress formation.

Laser Shock Peening (LSP) can be used to improve the surface properties of metallic materials. During the LSP process, martensitic phase transformation can take place in austenitic steels under certain processing conditions in addition to plastic deformation. In this study, the plastic strains and the amount of martensite in 304 austenitic stainless steel after LSP is numerically predicted. In order to simulate the response, an existing elasto-plastic model that includes phase transformation is extended to capture the rate dependency of plastic deformation during LSP. The influence of temperature, laser pulse duration and laser intensity on the residual state is studied. It is, for example, found that martensite formation is accelerated by lowering the processing temperature, increasing the peening pressure as well as extending the laser pulse duration.