Modal Analysis And Hangers Location Optimization Of A Vehicle Exhaust System

With the development of economy and the progress of social, the car have been integrated into our daily life. And people make excessive demands for the comfort of the car ride as well. The relentless pursuit of improving the NVH performance of vehicle will offer more powerful enterprise competitiveness in car manufactures industry. Undoubtedly, the research for NVH of cars has great realistic significance for us. In this paper, we focus on the vehicle modal analysis of the car exhaust system, and provide optimization design of hanger’s position to improve the NVH performance of the vehicle.This study for the vibration transfer of the vehicle exhaust to the body is based on YEMA auto F10. Firstly, through the test of the exhaust system, three-dimensional solid model of vehicle exhaust system is been built by using the CATIA software and have simplification on the detail part in order to mesh it easier. On the basis of the three-dimensional solid model of the exhaust system, the finite element mesh software names HYPERMESH is used to divide the grid to get the finite element model of the exhaust system. After that, the finite element analysis software NASTRAN calculates the finite element model, and the two modal parameters (restriction and freedom modes) are obtained respectively. Then, combine the data results of the model test to verify the validity of the finite element model that is been built before.On the basis of the finite element simulation model which is the validity and accuracy had been verified, modal analysis will carried out on the exhaust system, and respectively study hanging stiffness, the exhaust pipe thickness changes, hanging position change on the influence of the exhaust system modal.Using the average driving freedom displacement method, namely the ADDOFD (average driving DOF displacement) can be used to find reasonable hanging area exhaust systems of theory, and select reference standard (a, pay attention to the sum of frequency with the hanging position constraint counterforce; b, biggest heritability hanging position constraint reaction when the vibration frequency of root mean square value) for the choice of reasonable suspension point according to the presented scheme, then reduce the translation of vibration energy of exhaust system to the vehicle body, which is achieve the purpose of improve the NVH performance of vehicle.To sum up, in this paper, the modal analysis of the exhaust system and part of the sensitivity analysis of the structural parameters provides guidance for the reasonable design of suspension position for the exhaust system. Otherwise the combined scheme suspension location selection method improved the exhaust system optimization strategy of hanging position.