Using a quarter-vehicle multi-body model to estimate the service loads of a suspension arm for durability calculations

Predicting the fatigue life of an automotive component requires stress histories that accurately reflect loading conditions. In practice, these loads can only be determined experimentally once a physical prototype exists. If durability is to influence the design process at an early stage, representative loading conditions must be evaluated virtually using tools such as the multi-body system (MBS) technique. This paper investigates the simulation of loading conditions for a suspension arm of a multipurpose vehicle using a quarter-vehicle model (QVM) of varying complexity. Like the physical durability test, the model is driven over a virtual pave road, which subjects the virtual prototype to inputs likely to cause significant damage, thus placing exacting demands on the model. Though predicted resonant frequencies are close to those measured, comparison between experiment and simulation reveals discrepancies in the amplitudes of acceleration. Possible causes are investigated by studying the sensitivity of the QVM to parameters such as the tyre model and bushing. The paper concludes that, if the virtual prototype is subjected to large amplitude inputs such as those generated by a pave road, the QVM may not adequately predict representative loading conditions, and a full-vehicle model may be required.