Estimation of the road-induced body input force transmission change due to parts substitution using the impedance method

The main focus of this study is to investigate the influence of suspension and body stiffness on the road-induced operational force change due to softening the connecting elastomer for optimizing the vibro-acoustic performance of the suspension. In this regard, a suspension coupled to a vehicle body via an elastomer is modeled using point impedance. The model is validated through an empirical testing within two different McPherson strut type suspensions in the lateral arm Y direction and Multilink type rear suspension in the front mount X direction, which represent the extremely stiff and the extremely soft coupling cases within its suspension type, respectively. Due to the difficulties in measuring road-induced operational force within an actual vehicle, the validation test is carried out using the previously developed rig that enables for a direct force pick-up without modifying the structure of the suspension. Followed by the validation, a numerical study is performed for achievable force reduction due to bush's stiffness reduction under the influence of different dynamic stiffness combinations of the suspension and the vehicle body. Additionally, the rig measured dynamic force change, which is potentially misleading due to the large deviation in dynamic stiffness between the rig and the actual vehicle, is investigated under varying combinations of suspension and bush's stiffness.