High Strain‐Rate Material Model Validation for Laser Peening Simulation

Abstract

Finite element modeling can be a powerful tool for predicting residual stresses induced by laser peening; however the sign and magnitude of the stress predictions depend strongly on how the material model captures the high strain rate response. Although a Johnson‐Cook formulation is often employed, its suitability for modeling phenomena at very high strain rates has not been rigorously evaluated. In this paper, we address the effectiveness of the Johnson‐Cook model, with parameters developed from lower strain rate material data (∼10 3 s –1 ), to capture the higher strain rate response (∼10 5 –10 6 s –1 ) encountered during the laser peening process. Published Johnson‐Cook parameters extracted from split Hopkinson bar testing were used to predict the shock response of aluminum samples during high‐impact flyer plate tests. Additional quasi‐static and split Hopkinson bar tests were also conducted to study the model response in the lower strain rate regime. The overall objective of the research was to ascertain whether a material model based on conventional test data (quasi‐static compression testing and split Hopkinson bar measurements) can credibly be used in FE simulations to predict laser peen‐induced stresses.