| In recent years,China has continuously strengthened domestic infrastructure construction,and loaders are playing an increasingly important role in it.The diversity of the working objects of the loader,the constantly changing state of the operating process and the harsh working environment will lead to the fatigue damage or even failure of loader components,and the safety and reliability of the loader has become an increasingly prominent issue.Drive axle is the core component of the loader drive system,and its fatigue life directly affects the life of the loader.Therefore,in this thesis,the front and rear output shafts of the loader drive axle were taken as the research object,and carried out the research on the compilation method of its fatigue load spectrum and fatigue life prediction.The main research contents and research results are as follows:(1)The load information of front and rear output half shafts of loader drive axle was collected,and the load information measured by the output half-shaft was compound reconstructed,which will obtain the whole-axle load information of the front output shaft and the rear output shaft,so that the loader load information was expanded in terms of data volume,and finally four sets of data were obtained: the right rear half-axle,the rear output axle load of the compound reconstructed by right rear half-axle and left rear half-axle,the right front output half-axle,the front output axle load of the compound reconstructed by right front half-axis and left front half-axis were obtained.The following processing were carried out for the load data respectively: removing singular values,zero-drift processing,wavelet processing,segmentation and splicing of operating sections,and data processing for stationarity inspection.The first-order difference threshold method is proposed to remove the singular values from the measured output half-axis load data,and this method is superior to other methods for removing singular values.(2)The POT model and the BMM model were used to extract the extreme samples of the measured loads respectively.The influence of four distributions(GPD distribution,GEV distribution,Weibull distribution and Rayleigh distribution)on the fitting effect of the extreme loads extracted from the POT model and the BMM model was compared and analyzed.The result shows that the GPD distribution fits best to the extreme values of the POT model,and the GEV distribution has the best fitting effect on the BMM model.The measured load signals were extrapolated by the time-domain extrapolation method,and the two-dimensional torque load spectra of the front and rear output shafts of the loader based on the extreme value fitting of the POT model and the BMM model were obtained.(3)The nominal stress method based on the modified SN curve which modified by the Modified Minner’s law and the comprehensive influence coefficient of the gear on the gear was taken,and the linear cumulative damage theory is used to calculate the fatigue life of the output half-shaft and the composite reconstructed output shaft.Compared with the life results of the compiled loading spectrum test,the result shows that the fatigue life prediction results based on the load data of the composite reconstructed output shaft are more accurate than that based on the load data of the output half-shaft,and the accuracy of the fatigue life prediction based on the one-dimensional stress spectrum compiled by POT model is better than that of the BMM model. |
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