Vibration Performance Analysis Of Automobile Exhaust System And Fatigue Life Simulation Of Key Welding Parts

The vibration performance and fatigue life of automobile are two standards to measure the performance of automobile.The exhaust system can effectively reduce the noise produced by the engine,but because the exhaust system is a weldment and is affected by multiple vibration sources during the operation of the vehicle,the analysis of its vibration performance and fatigue life is of great significance to improve the performance of the vehicle.This article takes the automobile exhaust system provided by the enterprise as an example,analyzes its vibration performance through the combination of finite element method and test,and simulates the fatigue life of its key welded parts,,the contents are as follows:1)The finite element model of exhaust system is established in Hyper Mesh software,which includes exhaust pipe,bellows,front muffler,rear muffler and connecting flange.2)Nastran was used as the solver to analyze the free mode of the finite element model of the exhaust system,and the rationality of the finite element model was verified by the free mode experiment of the exhaust system.The free mode analysis results combined with the average driving freedom displacement method were used to design the hook distribution position.3)Hypermesh is used as the preprocessor.According to the actual situation and design scheme,the powertrain,hook and suspension rubber are added.Nastran was used as the solver to simulate the finite element model and the gravity preload.The results show that the design of hook distribution is reasonable.At the same time,the finite element model has high reliability and the simulation results are reliable through the constrained modal test of exhaust system.4)In order to investigate the vibration performance of the exhaust system,based on the harmonic response analysis,mechanical impedance,acceleration admittance theory and the boundary condition of harmonic torque generated by constraints and engine torsional excitation on the exhaust system,NASTRAN was used as the solver to analyze the dynamic reaction force and dynamic stiffness of the suspension rubber on the finite element model including power assembly,hook and suspension rubber,the results show that the dynamic reaction force and dynamic stiffness change smoothly and the peak value meets the requirements.5)Based on the finite element model including power assembly,hook and suspension glue,the static analysis of exhaust system is carried out,according to the stress distribution nephogram,the weak position of the structure is estimated.The static analysis results are imported into the ncode software and the nominal stress method is used to calculate the fatigue life nephogram of exhaust system.According to the calculation results,the durability of muffler is mainly analyzed.The results show that the muffler has reliable durability and reasonable exhaust system structure.In this paper,the hook position distribution,vibration performance and fatigue life of key parts of exhaust system are designed or studied,and the relevant process is summarized.The process is also applicable to other parts of vehicles,and has guiding significance for enterprise project research and development.