Failure Strain and Fracture Prediction During Shock Tube Impact Forming of AA 5052-H32 Sheet

The present study deals with both numerical and experimental evaluation of failure strain and fracture pattern during shock tube impact forming of 1.5 mm thick AA 5052-H32 sheet. A hemispherical end nylon striker is propelled to deform the sheet at different velocities. Here, the main objective is to understand the effect of flow stress models and fracture models on the forming outputs. The experimental situation is modeled in two stages, i.e., incorporating the pressure in the first stage and displacement of the striker in the second stage in finite element simulation using the finite element (FE) code (DEFORM-3D). A new strategy followed to evaluate the rate-dependent flow stress data from the tensile test of samples sectioned from shock tube-based deformed sheet is acceptable, and finite element simulations incorporating these properties predicted accurate failure strain and fracture pattern. Out of all the flow stress models, the modified Johnson–Cook model has a better flow stress predictability due to the inclusion of the non-linear strain rate sensitivity term in the model. During the prediction of the failure strain and necking location, the Cockcroft–Latham failure model, Brozzo failure model, and Freudenthal failure model have a fair agreement with experimental data in combination with the two flow stress models, i.e., Johnson–Cook model and modified Johnson–Cook model.