Technique for Hanger Location of Vehicle Exhaust System Using Finite Element Method

Abstract

A simulation technique using a finite element method (FEM) model for predicting, reducing and optimizing vibrations of the exhaust system was developed in this paper. This paper postulates the first stage in the design analysis of an exhaust system. Under excitation of the engine and road surface, the vibration energy of the exhaust system will result in the vibration of the body and produce structure noise transfers to the body from the hanger. These problems will effect or compromise noise, vibration and harshness (NVH) performance of the vehicle. A method called averaged driving DOF displacement (ADDOFD) is used to determine and optimize the exhaust hanger locations in this paper. Based on a sample vehicle, the HyperMesh and MSC Nastran software are adopted for meshing and calculation in the FEM modeling and vibration modal analysis of the exhaust system. Exhaust system’s free-free mode and sum of its eigenvectors are solved using MSC Nastran. Hanger locations are recommended at the position where the ADDOFD is relatively lower. Then static analysis and dynamic analysis of the exhaust system are performed, and finally hanger locations of the exhaust system are selected. When reasonable hanger positions have been decided, the vibration level of the body and the internal noise would have been decreased. This method can effectively select better NVH performance hanger locations in the earlier vehicle development process and can be extended to other types of vehicle, thus is effective for saving both the time and the cost of operation.