Assessment of stress-strain constitutive models and failure models on the shock tube based impact forming of AA 5052-H32 sheet

Abstract

The present study focuses on the numerical and experimental investigation of the shock tube based forming of AA 5052-H32 sheet using a rigid nylon striker. During the shock tube impact forming, the pressure developed and the velocity of the striker are modelled in two stages, i.e., incorporating pressure in the first stage and striker displacement in the second stage during finite element simulation using DEFORM 3D. The main aim of this study is to understand the effect of different flow stress models and failure models on the forming outputs such as dome height, velocity of the sheet, effective strain distribution, and failure modes. A new strategy is followed to evaluate the rate-dependent mechanical properties by the tensile test of the sheet deformed using the shock tube. The forming outputs predicted by incorporating these properties have an acceptable agreement with the experimental data. Out of all flow stress models, modified Johnson-Cook model shows better flow stress predictability because of the inclusion of nonlinear strain rate sensitivity terms. The failure pattern analysis shows both Johnson-Cook model and Modified Johnson-Cook model have a fair agreement with experimental results. Failure strain and petal formation predicted by Brozzo failure model and Freudenthal failure model match acceptably with the experimental results. SEM images confirm deeper and larger parabolic dimples on the fracture surface of shock tube-based deformed sheet, indicating enhanced formability as compared to the sheet formed by quasi-static deformation.