Flexibility in Multibody Dynamics with Applications to Crashworthiness

Formulations based on multibody dynamics for the analysis of crashworthiness and impact of vehicles and structural systems are reviewed in this paper. A methodology to incorporate the elastodynamics effects, suitable to describe the elastic deformations of flexible bodies, is discussed. The limitations of this methodology for crash impact are overcome in a more general formulation where the deformation of the flexible (or partially flexible) bodies is described using an updated Lagrangian formulation. This allows for geometric and material nonlinear behavior of the multibody components. A major drawback of this nonlinear formulation is the inability to describe zones of concentrated deformation due to local instabilities. For this purpose the plastic hinge concept, where the structural plastic deformation is modelled by nonlinear joint-spring set-up, is used. The validity of this model is assessed by carrying out an experimental test where a hollow steel extruded beam collide with a rigid block. By predicting where and when failure is likely to occur using a flexible model, the present technique provides an efficient tool to access the crashworthiness design of a broad class of impact excited structural configurations with general kinematic constraints. Finally these methodologies are applied to model the rollover of a truck in order to illustrate their capabilities.