Dynamic Simulation And Life Prediction Of Loader Working Device

Loaders are widely used in various kinds of engineering construction and play an increasingly important role.The performance of their working devices directly affects the efficiency of the whole machine.Due to the changeable working environment of loader and the alternating load acting on the working process,the working device of loader often suffers from fatigue damage.Fatigue life assessment and prediction of loader working device plays an important role in lifting loader working performance.In this thesis,the working device of ZL50 G loader is taken as the research object,and the fatigue life of its welded structure and non-welded structure are analyzed respectively.With the help of ADAMS and ANSYS software,the rigid-flexible coupling model of loader working device is established,and the accuracy of the model is verified by comparing the modal analysis results of the two software.By adding the measured data of cylinder displacement,pin load and pull force of pull rod,the dynamic analysis of loader working device is completed in ADAMS.The main fatigue hazard points on the loader working device are selected by analyzing the stress nephogram changes between the working cycles of the working device,and the stress time history data are extracted to provide data basis for the subsequent compilation of the stress spectrum.The rain flow matrix is obtained from the stress time history data by rain flow counting method,The load spectrum is extrapolated to a two-dimensional 64*64 stress spectrum with full life cycle by non-parametric extrapolation method under nuclear density estimation.Considering the influence of mean stress on fatigue life of welded structure and base metal,the variable mean method and equal life conversion method are used to compile one-dimensional stress spectrum of fatigue dangerous points in welded and base metal structure respectively,which lays a foundation for fatigue life prediction.For the fatigue life prediction of welded structures,the S-N curves of the selected fatigue points of welded structures are obtained by BS standard,and the fatigue life of the fatigue points of welded structures is obtained by combining the stress spectrum compiled above with Miner’s linear cumulative damage theory.For the life prediction of non-welded structures,the influencing factors of fatigue life are determined firstly,including surface condition factor,size effect factor,shape factor and average stress factor.At the same time,the S-N curves of components are obtained based on material S-N curves.The fatigue life of non-welded structures in the fatigue point region is calculated by using the stress spectrum of non-welded fatigue points compiled above and Miner’s linear cumulative damage theory.According to the actual fatigue test results of the working device,the accuracy of the fatigue life results and the feasibility of the treatment method in this thesis are verified.