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An important assumption of conventional belt models is that the belt can slide over points that are fixed to bodies or the inertial space. Using finite elements sliding of the belt in all directions can be modelled. A study comparing both belt modelling techniques using the MADYMO program is described. A mid-severity frontal impact sled test using a 50th percentile Hybrid III dummy is simulated. In addition, a performance study for oblique impact situations is presented to determine the effect of multi-directional belt slip of the shoulder belt. For the situations studied, it was found that both belt models can be used if belt roll-out at the shoulder does not occur. However CPU times are significantly higher for the simulations with finite element belts. An efficient approach for those cases where multi-directional belt slip of the shoulder belt occurs is to apply the finite element belt model only after a parameter study using the conventional belt model.

MADYMO is a computer program package for the simulation of two- or three-dimensional human body gross motions. Recently a two-dimensional airbag model has become available for MADYMO 2D. The airbag is represented in the model by a non-deformable ellipsoid or elliptical cylinder. Standard MADYMO features can be used in conjunction with the airbag model. This allows e.g. the simulation of belted occupants, inclusion of a separate sternum element in the thorax and connection of the airbag to a flexible steering column. Both driver and passenger side airbags can be simulated. The airbag contact algorithms have been validated on the basis of dynamical impact tests on an airtight driver bag, with various impactor shapes and impact velocities. In addition sled tests and full scale crash tests have been simulated. In this paper a description of the airbag model theory will be presented, particularly with respect to the penetration volume and contact force calculations.