The Effects of Suspension Component Stiffness on the Road Noise: A Sensitivity Study and Optimization

This paper investigates the sensitivity of stiffness of front and rear suspension systems on the structure-borne road noise inside a vehicle cabin. A flexible multi-body dynamics based approach is used to simulate the structural dynamics of suspension systems including rubber bushings, suspension arms, a subframe and a twist beam. This approach can accurately predict the force transfer to the trimmed body at each suspension mounting point up to a frequency range of 0 to 300 Hz, which is validated against a force measurement test using a suspension test rig. Predicted forces at each mounting point are converted to road noise inside the cabin by multiplying it with experimentally obtained noise transfer functions. All of the suspension components are modeled as flexible bodies using Craig-Bampton component mode synthesis method. To conduct a sensitivity analysis of the rubber bushings’ stiffness, an accurate nonlinear dynamic model of rubber bushings is constructed and validated against sample specimen tests. This model is based on a modified dual Kelvin-Voigt model and the Bouc-Wen hysteresis model to simulate the complex nonlinear behavior of the rubber bushing; both the frequency and amplitude dependent characteristics of the viscoelastic material are taken into account. The dynamic stiffness of the rubber bushings is changed from 50 to 150 percent to identify the sensitivity of each bushing on the road noise. To study the effect of rigidity of the suspension arms and frames on the road noise, Young’s moduli of the components are changed to examine corresponding sensitivity. Based on the identified sensitivity information, optimization of the bushing stiffness is conducted. The results and process introduced in this paper has been applied to the early stage development process of a C-segment chassis platform.