Research on displacement cyclic load life of automobile bellows based on S-N curve
The finite element model for automotive bellows was established,and the influence of displacement cyclic loads on the fatigue life of automobile bellows was investigated.The relationships between different structural parameters of automobile bellows and equivalent stress,strain and fatigue life were elucidated.Furthermore,the structure parameters of bellows were optimized through orthogonal tests.The microstructure of 309S stainless steel automotive bellows after fatigue failure was analyzed.The results show that with the increase of displacement cyclic loads,the fatigue life of the bellows decreases.The error between finite element and test results is less than 8.8％.Increasing wave height,wave distance,wave width and reducing wall thickness can improve the fatigue life of bellows.Through orthogonal tests optimization,the equivalent stress is reduced from 670.5 MPa to 582.3 MPa,and the fatigue life is increased from 80060 times to 241450 times.During the water swell forming stage,partial martensite is produced due to cold deformation.Under the effect of displace-ment cyclic loads,the hardness near the fracture area of the bellows approaches 200 HV,with noticeable cracks at the wave peak,indica-ting the presence of internal fatigue characteristics.
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