Research On The Load Spectra Acquisition And Application Of Loader Powertrain

This paper is combined with the project supported by the National Natural ScienceFund Project "Study on key technologies of load spectrum for wheeled vehicle powertrain"and the subject "Development of75m3large open-pit mining excavator", branch of theNational "863" Program Project "Large-scale open-pit mining technology and equipment",and the university-enterprise cooperation project "Load spectrum compiling method andapplied research on a type of loader powertrain ". A loader powertrain is taken as theresearch object, and Mathematical statistics, signal analysis and processing, finite elementstructural analysis and fatigue analysis methods are adopted comprehensively. Based on loadtime history of actual measurement for loader powertrain with multiple load cases, thefatigue load spectrum can be compiled and the fatigue life of typical parts can be predicted.Therefore，a comprehensive set of research methods for test, compilation and application ofload spectra can be established so that the level of independent research and development ofdomestic loader would be raised.On the basis of widely consulting the related literatures of home and abroad, theresearch status of load spectrum testing and its compiling technology are summarized.According to characteristics of loader powertrain load, the load spectrum test scheme isproposed. The dynamic torques and revolving speed data of main powertrain parts in fivekinds of working conditions are obtained. Then, wavelet fractal method is proposed, whicheffectively removing singularity points of the measured load signal in the loader powertrain,compared with Amplitude threshold method, Gradient threshold method and Statisticalsmoothing method, this method can remove singularity more effectively. It can be used forthreshold filtering to eliminate the noise in the signal, and improves the efficiency of signalprocessing.According to the obvious segmented working characteristics of loader, the manner ofdividing operation section is presented. It gives a basic method of quantile extrapolation thatmeasures load spectra dispersion from loader powertrain, compared with time domain andrain-flow frequency extrapolation, the “shovel-continuation-shovel” spectrum compilationmethod is put foreword based on nonparametric extrapolation reconstruction of operationsection rain-flow. The load spectrum from above method is the nearest to the load from loader’s practical use. Moreover, above method reflects the cycle-working process when theloader shifts frequently. In order to facilitate the implementation of fatigue test, this papercompiles the shaft of the8grade program load spectrum which used by the method ofequivalent damage. Compiling multiple conditions synthetic load spectrum, stress fatiguelife of the gearbox output flange is estimated with the stress fatigue analysis method basedon finite element method.Based upon the load tests on the transmission gear parts, a load spectrum compilationmethod of transmission agent gears is proposed by counting processing, composition andextrapolation of gear load count in fixed-axis transmission and planetary gear one. Bycompiling the load spectrum of the wheel-side reducer for loader during the period ofsynthetic operation, using Romax, we can predict the flexible fatigue life on the wheel-sideplanetary transmission gear for loader. The prediction results show that gear strength of thereducer meets the design requirement. Through the sensitivity analysis, the influence of theinput load parameters for gear and the tooth root filler parameters on fatigue life is studied.The conclusion shows that the damage of sun gear on the increase of load amplitude and thedeterioration of tooth root filler parameters is more sensitive compared with the planetarywheel. In addition, the damage of the sun gear tooth has the larger increase magnitudes.A durability test method of loader proving ground is proposed, the load and damagemechanism of the loader in practical use is reproduced by this way and the blindness of testis avoided. By discussing collection, compression and processing of the input data,equivalent load spectrum and other key technologies to make effective plan of durability test,the experimental technique and the optimization objectives associated with proving groundare analyzed. The multi-objective optimization problem aim at minimum error and minimumtest time is established, and feasible solution set to meet the requirement is obtained withNSGA-II algorithm, with a multi-objective optimization method based on the referencepoints, the preference of experts can be reflected from Pareto optimal solution set. Thismethod can effectively reflect the load condition of an actual usage and deviation, and cantimely discover and improve the deviation of equipment life design. A valuable reference isprovided for the loader’s product-forming and verification test.In the paper the measured load spectrum is important data for structure fatigue resistantdesign and fatigue test loads of the loader. The proposed method in this paper gives areference for other engineering vehicle in load spectra measurement and fatigue design.