Research Of Load Simulation On Loader Boom Fatigue Test

As loader is developed larger, more heavy-duty and high-speed, it demands the loader’shigher performances, especially in security and reliability. The operating conditions of loaders’frame and actuator are complex, and fatigue failure is the main form of damage which is causedby long-term accumulation under alternating loads. Through the loader fatigue test, based oncooperating and researching with enterprise, the boom’s equivalent fatigue failure mechanism isresearched between the fatigue bench test and actual conditions. Plus, the boom’s failure modesand failure location in the real job are inferred from the fatigue test, in order to carry out productdevelopment, quality control and so on. This research can also lay the foundation for othermodels loaders which will take fatigue test on this bench and the study of loader acceleratedsimulation test.The main contents include：(1) Calculating loader bucket load spectrum under theoretical and laboratory conditions.First, the resistance of the loader bucket is calculated under the laboratory loading conditions.Then Coulomb earth pressure theory is used to calculate whole cycle resistance on the loaderbucket under the theoretical loading conditions, including the bucket inserted in the materials,unloading materials until it dropping back. According to the laboratory loading conditionsmeeting the positive and negative peak loading conditions as well as non-symmetrical peak inthe middle of the transition requirements, and theoretical load cyclic loading smoother and peakfrequency changing more gently, this paper takes not only all-peak counting but also vibrationcounting to get into the load spectrum.(2) Predicting the loader fatigue life by the corrected S-N curve of loader boom. This paperestablishes a solid loader model by software PRO/E, adds laboratory conditions as well astheoretical calculations, and meshes this model in pre-processing software Hypermesh. Then thestress distribution of the laboratory and theoretical condition of loader boom is calculated byANSYS. In addition, the stress concentration factor is calculated in the particular loadenvironment. Finally the structure S-N curve is corrected by material S-N curve and the affectingfactors. Based on this S-N curve and the fatigue linear cumulative damage theory, the fatigue lifecan be predicted.(3) Researching Equivalent fatigue failure mechanism between fatigue bench test andtheoretical calculations of loader boom. This paper uses gray correlation theory to analyze correlation between the laboratory and theoretical calculation fatigue prediction curve, whosecorrelation coefficient result is0.9012; Using the acceleration factor for fatigue life predictionlaboratory conditions and theoretical analysis, the discounted correlation is analyzed; Thenprediction model is established according to correlation coefficient prediction, and the similarityabout laboratories and practical laboratory fatigue prediction curve is analyzed, and can correctmodel and improve prediction accuracy of the model by establishing several multiple models ora residual error model.