F2008-12-296
Structural Optimization Regarding Dynamics and Durability
Structural Optimization established as common used simulation discipline within the last decade and is a widespread technique today. The propagation of structural optimization tools was stimulated by the implementation of very efficient optimization algorithms and enabling the easy set up of the optimization task. Optimality criteria approaches are very efficient for a certain optimization task because of including engineering knowledge in the optimization algorithm. Mathematically based structural optimization methods combined with internal approximation models are extreme efficient too.
Every deterministic optimization leads to an optimal solution regarding the considered input parameters. Optimized structures can be sensitive regarding scattering of parameters or regarding not considered effects. E.g. topology optimization can lead to structures including thin walls or small ribs which may be sensitive regarding resonance. Another important factor for the usability of optimized structures are the considered loads for the optimization. To overcome the mentioned weak points of structural optimization an extension of the simulation process which is used for the optimization is presented in this article.
Coupling between durability simulation and structural optimization is available since years. Including durability analysis in the optimization procedure enables the consideration of material properties like strength limits, ductility, mean stress and notch sensitivity. In the automotive area structures are mainly affected by non correlated dynamic multi axial loads. Durability analysis enables the direct use of complex load input for structural optimization and there is no need to reduce complex multi axial loads to simple representative load cases any more. The structure is directly adapted according the actual durability load at each point of the design area. Multiple applications prove the efficiency of the method both for shape and for topology optimization.
A further extension of the optimization procedure is to additionally include Multi Body Simulation (MBS) in the optimization loop. This approach allows an adaptation of the loads acting on the part to be optimized in each iteration. Also feedback of the modified inertia behavior and stiffness to the overall system is covered by introduction of multi body simulation into the optimization process. This can influence results of topology optimization significantly since the material distribution varies throughout the optimization process. A further advantage is the possibility to consider dynamic effects like vibrations within the flexible structure itself. Computed time series for modal coordinates, coming from MBS, coupled with according modal stresses enable a multi axial durability analysis based on a defined number of modes. Putting these results at the optimizer leads to design changes which are fully driven by all relevant effects coming from loads, system interaction and structure dynamics.
In this article extended methods for the automated structural optimization of dynamically loaded parts in mechanical systems including durability analysis and MBS are presented. Results of different optimizations will be compared and discussed.
Consideration of durability analysis and dynamic effects in the optimization procedure enables to find light weight structures for complex loadings with optimal utilization of the material. Using topology optimization in the concept phase, target oriented design development is enabled from the very beginning. This leads to a clear advantage regarding development time and costs.
Session: Comfort, Body