Efficient numerical prediction of residual stress and deformation for large-scale laser shock processing using the eigenstrain methodology

Abstract

Laser shock processing (LSP) is an effective but costly process for inducing compressive residual stresses and deformation that are primarily applied in the aerospace industry. Accurate modeling of the LSP process with optimization is helpful to reduce development time and cost, but the simulation time is computationally expensive due to the long duration to capture the transient response of the material for each shock. In the present research, the eigenstrain modeling method is developed to predict the effect of large-scale LSP more efficiently compared with previous methods. In the developed eigenstrain-based method, residual stress and deformation fields are analyzed elastically using the simulated eigenstrain as initial strain, which is incorporated into the model by thermal expansion with a predefined unit temperature field and different anisotropic thermal expansion coefficients. For the large-scale LSP application, the eigenstrain in one representative cell identified through an explicit analysis is proposed as an approximation of the actual full eigenstrain field for efficient prediction. The predictions are verified by the predicted results from the explicit/implicit method for laser peening (LP) and the pure explicit method for laser peen forming (LPF) and are also validated by the experimental results of a single LP surface treatment of Ti6Al4V and a LPF bending of 1060 pure aluminum plates. Compared with the previous methods, the eigenstrain modeling method is proved to be effective and much more computationally efficient.