Abstract:
This paper presents a comprehensive finite element analysis of bumper beam-longitudinal systems subjected to 40% offset impact loading, executed with the non-linear code LS-DYNA, to find an efficient and accurate numerical representation of the system's crash behavior. The study centered on a finite element model where the bumper beam geometry was generated from preceding forming simulations, thereby incorporating thickness changes from the manufacturing process. A comparative analysis was conducted between a standard industrial modeling procedure using material models like MAT-24 and MAT-103, and a more sophisticated approach using a user-defined material model, MAT-41, which includes state-of-the-art anisotropic plasticity, strain-rate hardening, and ductile fracture criteria. The system was discretized using both shell and solid elements, and the simulations were validated against experimental results. The finite element analysis was extended to include sensitivity studies on physical parameters, such as strain-rate effects and the material property changes in the heat-affected zone (HAZ), and numerical parameters like the use of adaptive meshing to refine the finite element grid in areas of high strain. Results from the finite element simulations revealed good agreement with experimental tests in terms of overall deformation and energy dissipation, although accurately predicting the collapse mode for the AA7003-T1 longitudinal system proved challenging. The analysis highlighted that the user-defined MAT-41 model, especially when coupled with a fracture criterion, provided better predictions than the standard models. The study confirmed through finite element analysis that including strain-rate effects is important for capturing the correct force levels and that proper modeling of the HAZ is required for accurate deformation prediction. Furthermore, the application of the adaptive meshing technique within the finite element model was instrumental in successfully predicting the complex fracture modes observed in the bumper beam during experiments.
