Dynamic Performance Analysis Of Automobile Exhaust System

Automobile exhaust system is a device for engine exhaust emission and noise treatment,which is generally composed of flange,ternary catalyst,muffler,bellows,connecting pipe and other ancillary components,and it is an important part of automobile transmission system.It is of great significance to study the dynamic characteristics of exhaust system to ensure its NVH(noise,vibration and harshness)performance and service life.The high temperature environment has great influence on the dynamic characteristics and service life of the exhaust system,but there are few researches on the dynamic characteristics and fatigue characteristics of the exhaust system under the action of high temperature load,so it is very important to consider the influence of temperature when the modal analysis and fatigue life analysis of the exhaust system are carried out.In this paper,the finite element model of exhaust system is established based on reasonable simplification method,and the free modal frequency and mode shape of exhaust system are obtained by finite element simulation method and test method respectively,and the simulation results and test results are compared and analyzed,which have good consistency and Thus,the correctness of the simplified method and the finite element model of the exhaust system are verified.The dynamic characteristics of the exhaust system are studied by the finite element method of frequency response analysis,the theoretical method of mean square root value(RMS)method is adopted,and the hook arrangement scheme is designed according to the actual situation such as the structure and working conditions of the exhaust system.The design scheme of exhaust system hook is fully verified: the vibration characteristics of exhaust system are studied by constraint modal analysis,considering the modal avoidance;the size and overall load distribution of the overall sinking displacement of the exhaust system are obtained by static analysis;and the transfer force of the exhaust system passed through the hook to the car body is studied by dynamic analysis,ensuring the good vibration characteristics of exhaust system.Considering the actual high temperature working environment of the exhaust system,taking the exhaust system with fracture fault as the research object,the temperature distribution under the working state of the exhaust system is obtained by the test method,taking into account the influence of temperature load on the material properties,the thermal modal research in the high temperature environment of the exhaust system is carried out in the finite element software.At the same time,using the theory of fatigue life prediction and considering the influence of temperature load on the fatigue characteristics of materials,the fatigue simulation analysis of exhaust system under high temperature condition is carried out in nCode DesignLife software,and its dangerous position is obtained.This paper analyzes the research results of thermal mode and thermal fatigue life,studies the influence of high temperature environment on the vibration characteristics and fatigue life of exhaust system,and finds out the causes of fracture.