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.

Keywords

• laser beam applications
• finite element analysis
• internal stresses
• impact testing
• compressive testing
• high-strain material validation
• laser peening simulation
• finite element modeling
• residual stress prediction magnitude
• residual stress prediction sign
• high-strain rate response
• Johnson- Cook formulation
• low-strain rate material data
• split Hopkinson bar testing
• shock response prediction
• high-impact flyer plate tests
• quasistatic compression testing
• FE simulations
• laser peen-induced stress prediction