Multi-field Coupling Analysis And Structural Optimization Design Of Vehicle Exhaust Bellows

Vehicle exhaust bellows mainly play the role of compensating displacement and damping vibration in automobile exhaust system.To improve the mechanical properties of exhaust bellows,the relationship between stiffness and vibration isolation is studied.The dynamic performance experimental test and a finite element model of the exhaust bellows are established to simulate and analyze the dynamic and static performance of the vehicle exhaust bellows.And the hydroforming process and influence of the bellows are simulated.Finally,the structure of the exhaust bellows is optimized and verified.The main contents are as follows:(1)Research the basic theory about human factors engineering and vehicle NVH,introduce the basic theory of dynamic and static performance analysis of bellows,including the calculation method of axial stiffness bending stiffness and the basic theory of vibration of bellows structure,discuss the relationship between stiffness and vibration isolation performance.The method of predicting the fatigue life of bellows and how to combine the basic theory of thermodynamics to analyze the performance of bellows are also discussed.The influence of hydroforming conditions on the wall thickness reduction rate is also discussed to provide a basis for the influence of thinness on the performance of bellows.Finally,some parameters and design methods in the design of bellows structures are summarized.(2)Establish a finite element model of vehicle exhaust bellows for dynamic performance analysis including modal analysis and harmonious response analysis.Build a test bench for modal testing,damping testing and vibration isolation rate testing.The simulated modal and vibration isolation performance were compared with the performance characteristics measured by the test to verify the validity of the established finite element model.Then,a multi-field coupled finite element model of the vehicle exhaust bellows was established,and the stress distribution and fatigue life of the bellows at high temperature were calculated by means of thermo-solid coupling combined with the thermal field,compared with the analysis results at room temperature,which provides a reference for simulating the actual working conditions and design of vehicle exhaust bellows.(3)Use finite element to establish the hydroforming tube blank and mold model and apply the forming load to simulate the hydroforming process of single-layer,different wave numbers and different wave diameter bellows.And analyze the change behavior of the bellows wall thickness obtained after forming.The influence of hydroforming on the fatigue life and stress of bellows was calculated.At last,the hydroforming process of vehicle exhaust bellows was simulated.(4)According to the research foundation of bellows performance,with the goal of improving the service life and optimizing its vibration isolation performance of the vehicle exhaust bellows,a multi-objective optimization model is formed.Design the single-layer complete structure of the vehicle exhaust bellows which combined with the design theory and parametric design method.The optimization design of size parameters results is carried out,and the compensation displacement capacity,vibration isolation performance and fatigue life performance of the structure obtained by the optimal solution design scheme are again verified by finite element,and the structural design of the vehicle exhaust bellows is completed.Finally,a bellows structure for vehicle exhaust with low cost,good vibration isolation performance and long service life is designed to reduce the vibration power consumption of the system,which also improves the economy of the car and improves the riding experience of the driver and passengers.