In this paper simplified models for the design of vehicle structures under impact are presented. The use of multibody system dynamics based models in structural crashworthiness problems proved to be useful and accurate enough in simulating train collisions and in the optimization of energy absorption devices [
]. The presented simplified computational models are based on multibody rigid-flexible systems, where flexibility is included using the finite element method. Structural damping and contact models are also considered.
In structural impact, members can be subjected to axial or bending tensions that usually result in components’ plastic deformation in areas known as plastic elements. Plastic elements can be modeled associating cinematic joints with non-linear springs, whose constitutive relationship correspond to the components’ collapse behavior. The constitutive relationship is computationally defined using parameter identification techniques. Sometimes not all the areas where plastic deformation occurs can be predicted, so, a methodology to detect plasticity and automatically insert new plastic elements in simplified models, called remodelling, is proposed. Since simplified models are based on multibody systems, crashworthiness simulations are much faster when compared to finite element commercial software, enabling the use of genetic algorithms for the design process [
]. Dynamic analysis formulations are integrated with the multiobjective optimization evolutionary algorithm NSGAII [
] resulting in a 2D mechanical systems multiobjective optimization tool, used to perform optimization simulations where parameters most frequently used in crashworthiness problems are studied.
The presented methodologies and formulations have been implemented computationally in order to develop a tool for the first stages of vehicle design. Remodelling and multiobjective optimization examples are presented to demonstrate the presented methodologies.