Structural Dynamics at Higher Frequencies using the Finite Element Method : Assessment of Solver Algorithms and Component Mode Synthesis for Dynamic Response Analysis of Large Structures

Abstract: Scania is making a transition from traditional combustion engines to electric vehicles and therefore developing methodology for high frequency analysis of large structures. The computational time size of results files are impractically high, making any analysis infeasible. The objective is to establish methodology wherein the dynamic response of an excited structure can be determined at lower computational costs, without significant loss of accuracy. A Finite Element representation of a chassis structure is built and current solver algorithms are evaluated. A mode based solver and a direct integration solver are compared. The results indicate that the accuracy of the mode based solver may be improved by augmenting the solver with residual modes and including all rigid body modes of the system. The dynamic response at higher frequencies is determined experimentally on a real-life chassis and numerically using the FE model. The results show good agreement for the entire frequency spectrum, although the deviation increases at higher frequencies. In order to reduce computational time and results file size, Component Mode Synthesis is implemented. The Craig-Chang method of CMS is implemented. Substructures are generated at component level, the dynamic response is evaluated locally at substructure level and used to determine the global dynamic behavior of the reassembled structures. After implementing the methodology, computational time is reduced by a factor of approximately 47 for the mode based solver and 579 for the direct solver. The results file size for the modal solver is reduced by a factor of 11 933 for the modal solver and 5 192 for the direct solver. The dynamic response of the reduced system deviates from the original results but falls within accepted limits.