Comparison of Modeling Techniques for Flexible Dummy Parts

An important requisite for an effective use of numerical tools in occupant safety assessment is that suitable models of crash victims are available. Reliable well validated multibody models of several crash dummies have been developed in the last two decades. Flexible parts are modeled as rigid bodies interconnected by joints that account for the flexibility. Recently the finite element method has been used for modeling such parts. In this paper an alternative method is proposed namely as a flexible body with distributed mass and stiffness.

To evaluate these methods, three models of a rib module of a EUROSID-1 dummy are compared with the rib modeled as:

• a chain of nine rigid bodies interconnected by revolute joints, and torsional springs and dampers,
• one flexible body with the deformation approximated by one predefined displacement mode,
• a finite element model using triangular shell elements with a linear elastic material behavior and mass proportional Rayleigh damping.

The numerical results are validated using EUROSID-1 rib module lateral and oblique impactor tests. In these tests the rib module is fixed vertically on one end and the other end is impacted by a falling mass. The models are evaluated with respect to their modeling capabilities and computational efficiency.

It is concluded that the three models can be used to analyze impacts from relevant directions. The displacement modes for the flexible body model can be obtained from finite element analyses or from experiments. The latter approach does not require a detailed description of the flexible structure and its material behavior. The finite element model requires considerably more computation time as compared to the multibody models.