| importance of S-N curve and Load spectrum, and begin to gradually establish these core database, with the introduction of foreign advanced design technique and the application of some design software.Based on above, this paper together with the National Natural Science Foundation "Study on Key Technologies of Load Spectrum for Wheeled Vehicle Power-train" (50805065) and the research co-operation project "Load Spectrum Test and Applied Research of Wheel Loader Transmission Agent", tests the load spectrum and estimates fatigue life of CLG856 wheel loader axle shaft. By using knowledge in various fields, such as statistics, finite element analysis and fatigue analysis, this paper tabulates the load spectrum of axle shaft load, estimates fatigue life of axle shaft load, and discusses influence of uncertainty factors on fatigue life results in the end. The main contents of this paper are as follows:(1) Load spectrum is tabulated. This paper makes research on load spectrum compilation method, statistically analyzes and processes the acquired load data using the data-processing module of nSoft software. The paper extrapolates the sub sample load spectrum to the load spectrum in full-life period using nonparametric estimation method, and eventually obtains the fatigue load spectrum under multi-condition.(2) The paper makes static load intensity finite element calculation of the axle shaft by using ANSYS software, and obtains the overall stress distribution of the axle shaft. The analysis results show that the optical axis of the axle shaft is mainly in torsion, blank tears in spline roots compose stress and the static intensity is qualified. We solve the problem that entity unit cannot accurately reflects the surface stress, by adding one layer of crust unit materially identical to the entity unit onto the surface of the axle shaft in the process of finite element analysis, and provide the response relationship between the surface stress of the axle shaft and the external applied load for the subsequent fatigue analysis.(3) The bending S-N curve and the torsion S-N curve of the axle shaft are obtained respectively by modifying the material S-N curve with effective stress concentration coefficient, size efficient and surface processing coefficient.(4) The fatigue life is calculated when the survival rate of the axle shaft is 50% by making fatigue analysis on axle shaft using the fatigue analysis module of the nSoft software, and the results show that fatigue failure happens in spine site after normal operation of the axle shaft for fifteen months. After analyzing the contributions of different working conditions to the fatigue damage of the axle shaft, the results show that the working conditions of primary soil and semi-wet soil make large contribution to damage, over 60% together, and the working condition of small stonework makes small contribution to the damage of the node. Meanwhile, the paper also makes sensitivity analysis on the fatigue life of the axle shaft, considering the influence of the uncertain factors to fatigue life, and then obtains the discrete situation of the fatigue life and the most important factor to influence the fatigue life. For example, it can increase the fatigue life of the axle shaft to decrease the load, increase the surface residual compressive stress, improve the surface processing technology and decrease the notch coefficient.The research of this paper is practically significant and valuable to promote. Load spectrum tabulated in this paper is the basis for the fast indoor simulation of the load fatigue test. The results of the axle fatigue life can provide a theoretical basis and reference value for the design of transmission agent. The load spectrum compilation method and the fatigue life estimation method in this paper can also be used in the fatigue analysis on other loader transmission components or on other mechanical fields.
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