Simulation has become an integral part of the product development process for mechanical and mechatronic components. While physical testing provides results at the end of a development loop, CAE based simulation can already be utilized at the very beginning. Therefore reliable simulation results (e.g. fatigue assessment, structural vibration behavior, acoustics …) are crucial for a rapid and efficient product development process.
Due to limitations regarding the available computational resources the numerical models often consider a limited number of physical effects only, leading to a broad variation of result interpretation. The stresses within joint contact interfaces are a typical example for such a neglected effect as the constituting nonlinear relations are expected to increase the computational effort tremendously. As a consequence detailed joint models are rarely used even though this might significantly influence the predicted characteristics of a certain component.
Within this contribution a novel model order reduction method for the dynamic simulation of structures containing joint contact interfaces is presented. The according simulation process and the major steps involved are outlined. Due to the reduction step, dynamic simulations can be carried out with manageable computational effort, even if the excitation time interval comprises many time increments. This facilitates carrying out several dynamic simulations within an optimization loop as well. Finally the fatigue analysis results of a passenger car battery carrier demonstrate the applicability of the proposed simulation process and the necessity to consider joint contact interfaces for reliable simulation results.
The multi body dynamics (MBD) theory is a logical choice for the simulation of mechanisms undergoing large displacements. The nonlinearities, either from a kinematic or kinetic point of view, are considered and accounting for the linearized structural flexibility of certain parts is state of the artand available in certain commercial codes. If the behavior of structural parts is influenced by nonlinear effects like contact within joints, new methods are necessary.
The method presented in this paper is based on reduced order modeling of finite element structures. By extending the Craig Bampton mode base with a new type of trial functions, so called joint Interface modes, it is possible to account for the local deformation within the joint area of flexible structures.This enables the efficient computation of contact stresses within the framework of multi body Dynamics and is outlined in the first part of this contribution.
The second part describes the utilization of this method for two examples. The first one is an academic example of a bolted cantilever beam which is investigated in terms of deformation and stresses. The second one is an industrial application, the dynamic simulation of a door slam which is investigated regarding the fatigue performance of the door structure. The comparison with finite element based solutions shows a clear advantage in terms of computational efficiency for the proposed method.