Influence of Discretisation on Stiffness and Failure Prediction in Crashworthiness Simulation of Automotive High Pressure Die Cast Components

摘要

Comparison of the results of different tetrahedron and shell meshes in the performed tests reveals the superior performance and higher reliability of solid elements. The capability of fracture prediction in geometries with complex stress states is found to be insufficient and strongly mesh dependent using thin shell elements. Although between thin shells and solids a satisfying accordance in the elastoplastic range is found under testing conditions, significant deviations in fracture prediction are noted. Besides the fact that failure is predicted at a wrong location by both shell models, no elevated risk is yielded at the spots where cracks initiate in the experimental tests. In contrast to that, both tetrahedron models give an accurate prognosis of the critical location in the shocktower. As already observed in the previous basic studies, the refinement of the tetrahedron mesh yields no more improvements in stiffness but in the quantitative prediction of fracture. However, global splitting of all tetrahedron elements increases the number of elements - and thus also the CPU-time - by a factor of 12. Hence, using the current resources in the industrial development process, only a qualitative but reliable finite element analyis of automotive castings with quadratic tetrahedrons and a physically motivated material model appears to be the most promising way to derive suggestions for improvement in design, construction and material selection.