Improving the durability of automobile suspension systems by optimizing the elastomeric bushing compliance

Abstract The durability of the suspension system is a critical component in the development of a vehicle because it is consistently and directly exposed to dynamic loads while the vehicle is in motion. In most cases, attempts are made to improve the durability of a vehicle suspension system by changing the shapes of its parts and components. However, the authors propose to improve the overall durability performance of a vehicle suspension system by modifying the compliance of the elastomeric bushings, which pivotally connect the lower control arm to the vehicle frame. It is relatively easy and cost effective to change the compliance of the bushing components because they are made of rubber or elastomeric materials. The following procedure was used for the present analysis. Firstly, dynamic loads were obtained based on a multi-body dynamic analysis while the vehicle was driven on a virtual proving ground test. Secondly, the stress distribution of the vehicle suspension system was calculated using finite element analysis to obtain an optimal combination of the elastomeric bushing compliance and provide the maximum improvement to the stress distribution on the basis of a robust design approach. Finally, the durability performance of each component in the vehicle suspension system was evaluated using quasi-static durability analyses. The fatigue life of the optimal model was improved by 36—39 per cent when the knuckle and lower control arm passed over bumps, and by 30—41 per cent when they passed over potholes. The proposed optimal design process to improve the elastomeric bushing compliance made it easy to evaluate and improve the durability performance of the vehicle suspension system in the initial stages of the vehicle development process.