Flexible multibody dynamics with nonlinear deformations:: Vehicle dynamics and crashworthiness applications

Practical formulations to describe both linear and nonlinear deformations of flexible multibody systems are presented, discussed and applied to complex industrial systems. Initially the flexibility of the multibody system is described with rigid bodies connected by highly deformable elements using the finite segment and plastic hinge approaches. In tuns, these formulations are used in the optimization of multibody systems. A Lagrangian formulation is used to describe the nonlinear geometric and material deformations of flexible multibody components. The coupling between the deformation and the rigid body motion is preserved though the method proposed only uses invariant diagonal mass matrices. Applications to the simulation and design for crashworthiness of transportation vehicles are presented to illustrate the use of these techniques. The formulation is also specialized to model flexible multibody systems with linear elastic deformations. It is shown that with the proposed approach, the body elastodynamics effects are all evaluated using standard commercial finite element codes. In this manner, the analyst can use any type of Linear finite element in the multibody model and the same finite element model can also be used to evaluate the structural integrity of the system components. The methodology is applied to model a vehicle with a complex flexible chassis, which is simulated for different riding scenarios.