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Numerical simulation of the airbag can be used as a powerful tool in the development of a SIR (Supplemental Inflatable Restraint) system leading to an optimized design and to reduce the development time. However, modeling flattened or folded airbags from the 3D CAD geometry and simulating exact airbag shapes during the deployment is a very complex problem. Especially for the passenger side airbags, generating a flattened and folded mesh from the CAD geometry of the airbag is a very difficult task as these airbags are made of non-developable surface and can not be flattened easily without introducing secondary folds, wrinkling or distortions of mesh. A novel approach called as Initial Metric methodology effectively addresses these problems. The initial metric method uses two types of meshes, A CAD reference mesh and a mapped or a scaled (compressed) mesh constructed from a CAD mesh of the airbag. In the simulation, mapped or scaled (compressed) mesh is used for airbag inflation.

In occupant safety simulations it is desirable to extend existing rigid body occupant models towards deformable Finite Element models. Thereby a wider range of occupant / structure interactions can be covered and a better accuracy can be achieved. This paper describes some aspects of the FE modelling of the EUROSID thorax for use in an explicit Finite Element code. First a single rib model is evaluated, then a full thorax is generated and inserted into a rigid body Dummy model. Experimental results from impactor tests serve as a basis for the validation of the model.

Finite element simulation of air bags as part of the automotive occupant restraint system is rapidly evolving as a new CAE tool in support of car product development. The majority of occupant computer simulations are concentrated around the study of occupant impact into the air bag when the air bag is substantially inflated. Further, the initial air bag representation in the simulation prior to deployment is of an unfolded configuration. These simplifications do not compromise simulation of crashes wherein the dummy comes in contact with the air bag after it is substantially full. The situation wherein the dummy interacts with the air bag early during the inflation is of interest when the occupant is located close to the air bag prior to deployment. In such cases the predeploy-ment geometry of the air bag in the model needs to be representative of the actual air bag folded configuration and the unfolding of the air bag needs to be simulated.

A nonlinear foam was added to a previously created three-dimensional finite element model of the Hybrid III dummy chest which consisted of six steel ribs, rib damping material, the sternum, a spine box and a pendulum. Two standard calibration pendulum impact tests for a Hybrid III dummy chest were used to validate the new model. An explicit finite element analysis code PAM-CRASH was utilized to simulate the dynamic process. At impact velocities of 6.7 m/s and 4.3 m/s, the force and deflection time history as well as the force-deflection plots showed good agreement between model predictions and calibration data. Peak strains also agreed well with experimental data.