Structure Optimization And Characteristic Analysis Of A Vehicle Exhaust System Hook

The exhaust system of the muffler belongs to a part of the automobile engine power assembly.Its performance directly affects the vibration,noise and the emission of the pollutants.These are the key indexes to evaluate the quality of the vehicle.Therefore,in the early stage of muffler exhaust system design,we should first consider its NVH performance and make it match reasonably with the parameters of engine and vehicle.Secondly,with the increasing awareness of environmental protection and the increasingly strict environmental regulations,the internal structure of the exhaust system of the muffler is becoming more complex and complex,and the components such as bellows and suspension adhesives are added to the exhaust system,making it a complex and multi degree of freedom nonlinear system,thus the exhaust system is made.The service performance can not be simply studied by traditional vibration theory,so we need to do a systematic finite element analysis of its vibration characteristics.First,the exhaust system of a certain type of muffler is taken as the research object.As the layout of the whole exhaust system is determined by the boundary constraints given in the chassis design,the three-dimensional model of the exhaust system needs to be established under the required boundary constraints,and then the three-dimensional model of the exhaust system is introduced into the Hypermesh.The finite element modeling is carried out by the software,and the results of the calculated free modal analysis are compared with the free mode of the sample test.Through the analysis and comparison,the free mode vibration mode and the frequency error of each order are both within the specified range,and the numerical analysis model can reflect the exhaust system more truly.The vibration characteristics prove that the finite element model established in Hypermesh is reasonable and feasible.It can be used to simulate the actual exhaust system structure of muffler,and provides a reliable basis for further analysis of the related finite element analysis.Secondly,dynamic stiffness analysis,vibration isolation analysis and static analysis of the muffler exhaust system hook are carried out.In the analysis,the RBE2 rigid element is used to connect the mass center of the power assembly with the suspended point,and the spring damping element is used to connect the chassis to the mounting point of the power assembly,and the equivalent mass and the moment of inertia are applied to the mass center of the power assembly,thus the finite element model of the automobile power assembly is established.In order to ensure that the suspension system has good damping effect and the structural strength that can be achieved in the typical working condition,the hook in the exhaust system needs to satisfy a certain stiffness value.Because its stiffness can not be obtained directly,the first order modal analysis of the hook of the exhaust system is usually adopted to determine the hook stiffness in the engineering practice.Whether to meet the requirements.Through the first order free modal analysis of all the hooks of the exhaust system,the first modal frequency of the fifth groups of hooks is less than 300 Hz,and the design requirements are not reached.All the other groups meet the design requirements,so it is necessary to further analyze and optimize the hook of the exhaust system.After the analysis of the dynamic stiffness of the hook,it is concluded that the Z direction in the initial scheme of the exhaust system satisfies the requirements of the dynamic stiffness below the 500N/mm target line,so that the linkage structure of the exhaust system is not reasonable enough,and the structure of the system needs to be further optimized.Thirdly,by changing the lap shape and lap mode of the hook,the five groups of hooks all meet the first order free mode and dynamic stiffness requirements,and the static analysis,vibration isolation analysis and constrained modal analysis are carried out again for the optimized exhaust system.The results show that when the suspension stiffness is selected to be 9N/mm,the exhaust system is in the self.Under the action of gravity,the maximum displacement of Z is 4.772 mm,which is less than the maximum value of 5mm required by the design.The maximum supporting force of the hook Z is 33.929 N less than the maximum value required by the design.The analysis of vibration isolation rate and the constrained modal analysis also meet the design requirements.Fourthly,the optimized exhaust system of the muffler is carried out by the vibration isolation test and the constrained modal test,and the experimental data are analyzed and compared with the above analysis results to ensure the good performance of the developed exhaust system in the actual work.The analysis of the vibration control of the exhaust system of the muffler is reasonable and feasible.It has some practical value for the structural analysis and optimization of the exhaust system.The finite element analysis of the exhaust system saves a lot of manpower and time for the enterprise,and solves some of the technologies encountered in the process of product development in the enterprise.The problem improves the R & D efficiency and has a certain reference value.