| The load spectrum plays an important role in improving the fatigue life and reliability design of engineering machinery.Aiming at the key function of the loader’s working device to the loader’s operation,this paper takes the loader’s working device as the research object and studies the compilation of its load spectrum.POT model extrapolation of external load working equipment of loader from extreme value theory and distribution fitting,threshold selection,parameter estimation,solving out for extreme value distribution of the load data loader working device of GDP distribution function,and carries on the test of goodness of fit,show that the POT model for the feasibility of the loader working device load extrapolation,developed based on the POT extrapolation method of two-dimension load spectrum loader working device.For conventional parameter method of load spectrum using a single distribution is difficult to fit the problem of load data,this paper proposes to establish mixture gaussian distribution is used for fitting the mean load data loader working device,and studied the determination of number of basic functions in the mixed distribution method and distribution parameter calculating,combined with the amplitude of three parameter weibull distribution are amplitude joint distribution model is established and completed based on mixed distribution model of load spectrum extrapolation,develop the two-dimension load spectrum loader working device.Based on kernel density estimation principle,studies the nonparametric kernel density estimation of parameters of kernel function and bandwidth for kernel density estimation precision,determine the types of kernel function and introducing the adaptive bandwidth factor to modify the bandwidth parameter,the loader working device working condition of synthesis,using nonparametric rain flow extrapolation method to complete the load spectrum extrapolation working equipment of loader and developed based on nonparametric kernel density estimation of loader working device under two-dimension load spectrum.The result of the work unit finite element analysis,selected the fatigue risk point was observed and the load-stress conversion coefficient,load spectrum can be converted to one dimensional stress spectrum,the nominal stress method,combining with three methods of extrapolation of the loader working device of stress spectrum,respectively adopt the IIW standard and BS standards to predict fatigue lifeof the loader working device;The fatigue damage values calculated by three kinds of extrapolation methods are statistically analyzed,and the differences of the three kinds of extrapolation methods applied to the load extrapolation of the loader’s working device are analyzed.The fatigue life calculated by three extrapolation methods is compared with the test results,which shows the correctness and rationality of the extrapolation of load on the working device of the loader. |
