Research Of Vibration Performance Of Automobile Exhaust System’s Structure

Exhaust system is an important part of the automobile.The automobile exhaust system is connected to the engine and the other side to the floor.Exhaust system not only has the role of purifying exhaust,but also has the function of reducing exhaust noise.In the process of the automobile,the exhaust system is subject to vibration excitation.The exhaust system has a direct impact on ride comfort.Therefore,it is very important to study the vibration performance of the exhaust system.In this paper,the object is selected as the cold end of automobile exhaust system,and the finite element method is used as the analysis method.The modal analysis of the exhaust system,suspension point position design,frequency response analysis,fatigue analysis and vibration performance optimization work.The main work is as follows:(1)According to references,make the paper work contents and technical route.According to the enterprise standard,the geometrical model of the exhaust system is simplified and the finite element model of the exhaust system is established.(2)According to the exhaust system of finite element model is established,the free modal analysis was carried out on the exhaust system.Using the average drive degree of freedom displacement method,the curve of the average drive degree of freedom displacement and position is drawn to establish the position of the potential suspension point.After the position of the suspension point is determined,the modal analysis of the exhaust system is carried out.The natural frequency of the exhaust system avoids the engine excitation frequency.A preliminary evaluation of the durability of the lifting system of the exhaust system was carried out by using the static method.The results show that the durability requirement is met initially.(3)The frequency response of the exhaust system is analyzed,and the dynamic reaction force of the rubber lug is restrained.The results show that the dynamic reaction force peak is too large,need to be further improved.The dynamic stiffness analysis of the exhaust hook is carried out.The exhaust system is analyzed for vibration fatigue.(4)To reduce the exhaust system transfer load to the body floor,optimize the exhaust system parameters.Based on the stiffness of the bellows and the vertical stiffness of the rubber hanging ear,the objective function of considering the rubber lug durability and the dynamic reaction force of the exhaust lug was established.Sensitivity analysis is used to filter the design variables.Select the more sensitive factor as the design variable in the next optimization scheme.The optimal Latin hypercube design and multi-island genetic algorithm are used to optimize the experiment.After optimization,the exhaust system optimization before and after the data were compared.The results show that the optimization of the treatment ensures that the durability of the lifting ear is initially satisfied and the dynamic load of the exhaust system is improved.