Improving Vehicle NVH Behavior via Tuning the Engine Mount Stiffness Using DOE Method 2011-01-1510

The main purpose of this research is to tune the stiffness of engine mounts of a passenger car in order to reduce the transmitted vibration to driver with regard to the permissible values of natural frequencies of engine using DOE method. Based on the previous experiments, prevalent criteria are introduced by automakers which would lead the designer to optimum values of mountings' stiffness. In this paper we benefit the usage of experimental frequency bands introduced by the NVH authoritative references.

To achieve this, we use a mixed Finite element and multi body dynamic modeling. The FEM model of the body front end and engine subframe is developed using Hypermesh. The engine block is modeled as a rigid body attached to the neighbor parts with rubber mounts. The modal natural file of the whole system is created by the aim of MSC/Nastran and exported to the ADAMS/View for further analysis. DOE approach is used to identify the most effective parameters in reducing the transmitted vibration to the occupants. Nine design variables consist of three axial components of mountings' stiffness is selected to determine the major design variables. Finally the optimum values of the selected parameters are derived to attain acceptable natural frequencies of the engine system using RSM method, which in turn will lead to reduced vibration transmissibility.

To evaluate the effect of the proposed set of mountings' stiffness, on the overall vibration behavior of the power train chain and body structure, the results of the original and modified mountings are simulated and compared in an extended model in ADAMS. This model includes the full body floor, engine, subframe and exhaust system. Comparison of the acceleration amplitude of the driver seat rail in a wide frequency range indicates remarkable improvement through proposed tuning.