Mechanical Property Of Bending Deformation And Dynamic Performance Analysis Of Automobile Bellows

The automobile bellows is a kind of double-layer bellows with S-type ripples.As the main flexible component of the automobile exhaust system,it connects the engine with the exhaust pipe and has the functions of reducing noise,displacement compensation and vibration reduction.The mechanical properties of automobile bellows will affect the NVH performance of the whole vehicle,so it is necessary to work on the rigidity,strength,dynamic performance and fatigue characteristics of automobile bellows.According to the analysis of load spectrum data of automobile bellows,bending deformation is the main deformation form.Bending stiffness is an important mechanical performance index,which can affect the displacement compensation,decoupling ability and fatigue life of automobile bellows.The finite element single-layer automobile bellows model of shell element was established to analyze the influence of wave height,wall thickness,diameter,wave number and wave distance on the bending stiffness quantitatively.The conclusion shows that the bending stiffness of automobile bellows can be optimized by increasing the wave height,decreasing the wave diameter and controlling the wave number properly.The finite element double-layer automobile bellows models of solid shell and solid were established to analyze the effect of interlayer contact state and the loss of wall thickness on the result of calculation,and measure the advantages of the two cell types and the differences of the finite element results.It is proved that the calculation of the finite element double-layer automobile bellows model of solid shell with wall thickness reduced is accurate by comparing the finite element results with the experimental results,and the margin of error is about 10 percent.On the basis of statics analysis and the theory of fatigue damage accumulation,the finite element model of solid shell with wall thickness reduced was established to calculate the fatigue life and damage degree of double-layer automobile bellows,and then the influence of friction between the layers on the calculation was analyzed.The result shows that the calculation result of the damage degree considering the friction contact between layers is 46.73% higher than ignoring the contact,and friction between the layers can’t be ignored when we calculate the fatigue life and damage degree of double-layer automobile bellows.The exhaust system finite element model,which contained the three-dimensional model of the automobile bellows,was established to calculate the natural frequency of the exhaust system and the dynamic reaction force transmitted to the bodywork,and then analyzed the influence of the overall rigidity of the automobile bellows on the performance of the vehicle’s NVH.