Assessing and Validating the Crash Behavior of Securalex®HS, a High-Strength Crashworthy Aluminum Alloy, Using the GISSMO Model

Specialized aluminum alloys play an ever increasing role in today’s automotive industry. The desire for lightweighting is driven by both performance aspects as well as the legislative framework regarding emissions and fuel efficiency. Using aluminum rolled products for structural car body parts requires good formability and high mechanical properties paired with predictable and safe performance under crash loading. Simulating and predicting the crash behavior requires a detailed material model including damage and failure. To this extent, a vast range of experiments are performed on Securalex ® HS samples. The relevant state of the material is the in-service temper, so that a heat treatment is applied to all samples prior to testing. In order to compare the simulation results to the experiments, digital image correlation techniques are used to measure strains on the specimen surfaces during testing. After calibrating the plastic material response, a detailed failure model is required. Using the GISSMO model, an equivalent plastic strain to failure curve depending on stress triaxiality is defined. It is parametrized with three variables and coupled with an optimizer based on the simplex method. By defining suitable error functions based on the simulation results, it is possible to optimize the failure curve and obtain a good correlation with the experiments. The final step lies in validating the failure model. To this end, the calibrated model is used to simulate and predict the deformation and crack initiation during the quasi-static axial crush of a square profile. The results are compared to experiments done on two-piece friction-stir welded boxes.