Very High Cycle Fatigue Properties And Reliability Evaluation Of High-strength Carburized Gear And Material

Gear as one of the important transmission parts in the industry,its fatigue life and reliability have important influence on whole machine.And high-strength steel as a main material of gear manufacture,studies its fatigue behavior and failure mechanism is of great significance.However,with the discovery of high cycle fatigue failure phenomenon,traditional fatigue life prediction and reliability evaluation method is difficult to meet the modern design requirements.At first,in this paper,the very high cycle fatigue test of high-strength carburized smooth specimen under axial loading condition with stress radio of zero was carried out firstly,meanwhile its S-N and P-S-N characteristics were clarified.Fracture surfaces were observed by optical microscope,its failure modes and failure mechanisms were analyzed.The smooth specimen crack initiation and propagation behaviors were discussed,and the fatigue life and fatigue limit in very high cycle fatigue regime was predicted.Then,the very high cycle fatigue test of notch specimen under axial loading condition with stress radio of minus one was carried out,and its S-N characteristics were clarified.By the observation of fracture surface by optical microscope,the influence of stress concentration caused by notch on the failure modes and failure mechanisms were analyzed.Crack initiation and propagation behaviors were explored and fatigue life was predicted.Based on the theory of short crack,the equivalent relation between the smooth specimen fatigue life and the notch specimen fatigue life was studied,and the notch specimen fatigue life could be predicted according to the smooth specimen fatigue life.Next,the gear bending fatigue test of high-strength carburized gear was carried out,and its S-N characteristics were clarified,and its P-S-N characteristics based on two statistical distributions were discussed.One predicted model of gear bending fatigue life was proposed,and the crack propagation at gear root was simulated.Finally,based on the fatigue data under variable stress amplitude,compared the prediction accuracy of five fatigue prediction models.Based on the detail fatigue rating theory,a new reliability evaluation method for constant stress amplitude and variable stress amplitude was presented.