Research On Fatigue Life Prediction Of Vehicle Wheel Hub Based On Road Load Spectrum

When the vehicle is running at a high speed,the wheel hub is continuously subjected to the alternating stress produced by the road obstacles impact,the bump road,and the vehicle turning and braking.The fatigue damage is caused by the complex and varying stress loading,which eventually leads to fatigue failure of wheel hub and affects the driving safety of vehicle.In this paper,the research on fatigue life prediction of the wheel hub is carried out based on the collected road load,including the fatigue strength prediction,load distribution model establishment,load spectrums compiling and fatigue life prediction.The main contents of this paper are shown as follows:(1)Based on the fatigue test data of the wheel-hub material sample,the nonparametric hypothesis test of the small sample roughness data is carried out and the distribution model is established by using the exact probability method.The improved Bootstrap method is used to estimate the distribution parameter and confidence interval of roughness coefficient.Considering the uncertainties of the machined surface,size,working load and temperature which affect the fatigue strength of wheel hub,Based on the interval analysis theory,the correction factors of these factors are determined to obtain the distribution parameters of fatigue limit and fatigue strength of wheel hub,and the S-N curve cluster of wheel hub is formed,which lays the foundation for the subsequent fatigue life prediction.(2)The road load collected by the six component measuring instrument is pre-treated,including the abnormal value screening and elimination,signal denoising and low amplitude load filtration.According to the load transfer coefficient,the load-time series of wheel hub are obtained and extrapolated by using the super threshold extrapolation.The load cycles are extracted by the rain-flow counting method,and the mixed distribution is used to analyze the distribution characteristics of load cycles,and eventually the two-dimensional joint distribution of mean and amplitude is determined.(3)In order to take full account of the effect of the mean and amplitude values on the fatigue damage,the equal and unequal interval methods are used to divide the mean and amplitude values,respectively.The frequency of each load level is counted based on the two-dimensional joint distribution model,and then the one-dimensional and two-dimensional program load spectrums of wheel hub are compiled.(4)For the asymmetric cyclic loading,the Goodman fatigue empirical formula is applied to transform the mean and amplitude values of each level into the equivalent life load corresponding to the S-N curve.Based on the modified linear fatigue cumulative damage theory,according to the S-N curve cluster and one-dimensional and two-dimensional program load spectrums,the interval life mileage of wheel hub is predicted.The research results of this paper lay the foundation for fatigue life prediction and fatigue durability test of automobile parts under the complex and varying working condition.At the same time,the research method is also applicable to the fatigue life prediction of other bearing parts or high-speed moving parts and assemblies.