Aiming at the driving arc gear of tractor gearbox as the research object

the prediction analysis and experimental verification about the methods of fatigue failure and the original area of fatigue are conducted according to the ratio distribution between shear stress and shear strength in the depth direction of gear tooth surface.The distribution of stress and strength in the depth direction of gear tooth surface can be get by calculation of gear shear stress

overlay analysis of shear stress and residual stress and the conversion between hardness and strength.Simultaneously

the mechanism of fatigue failure methods and mutual conversion of gear on the basis of judging criterion of partial shear yield strength value are analyzed

and the results are verified by analyzing a great number of fatigue gear.The experiment result shows that this method which based on overlaying shear stress and shear yield strength can predict the fatigue failure method and fatigue area directly and quickly.