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From Complex 3D-Foam Parts to Ready LS-DYNA Inputdata in Less than One Hour - Examples from Occupant Simulation at DaimlerChrysler

Daimler-Chrysler in particular needs to model the behaviour of padding and dummy parts for the numerica1 simu1ation of vehicle side impact and FMVSS201 interior head-impact. A common problem is the geometrical complexity of the parts involved. In the quest for a faster and easier way to represent these bulky, complex geometries with finite elements, the use of the 4-node tetraeder element in LS-DYNA was systematically investigated. At first we examined the response of the T4 (4-node tetrahedron)-element under simple load cases such as pure shear and uniaxial compression. The behaviour of the classical hexagonal (H8) element was compared to the T4 element in different (regular and free) meshing configurations. The same procedure was applied in a second phase to a combined shear-compression load case and a simple impact load case with a cylindrical penetrator. The conclusion of this work was that although some care must be taken in the use of T4-elements, the element seems to be failsafe in conditions where compression is the dominant deformation mode. In a brief application overview, the important savings that can be achieved in the model preparation phase due to the use of T4 elements are illustrated. An example of FMVSS201 head-impact is used to show that the differences in results with respect to a hexagonal mesh are within a range that is acceptable for engineering applications. A summary and conclusions complete the paper.