J. Kmmberger proposed that it is necessary to carry out anti fatigue design for mechanical components bearing periodic load. Therefore, a numerical model of bending fatigue life of thin ring gear in truck gearbox is proposed. The bending fatigue life of thin rim spur gear of truck gearbox is studied. It is considered that the service life of gear is divided into the initial stages of damage accumulation and crack propagation. Finite element method and boundary element method are used to analyze the fatigue life of thin rim gear. The method based on continuum mechanics is used to predict the start-up stage of fatigue process, in which the basic fatigue parameters of materials are considered. Linear elastic fracture mechanics is used to evaluate the residual life of gears with initial cracks. The results show that with the decrease of rim thickness, the key position of crack initiation moves to the root area.

Podmg et al. Proposed a calculation model for determining the bending fatigue life of gear tooth root. This study determined the influence of gear tooth load on gear fatigue life, and considered the crack closure effect when simulating the propagation behavior of fatigue crack by using numerical simulation and linear elastic fracture mechanics theory. It is proved that the critical plane method can not only predict the crack initiation life, but also predict the crack initiation direction, which is a good basis for further analysis of crack propagation. Through the numerical simulation considering two closure mechanisms (crack closure caused by roughness and oxide), the prediction of crack propagation life and crack path of gear tooth root stress is closer to the experimental results than the existing methods.

Rada. Amir et al. Used linear elastic fracture mechanics to simulate the fatigue crack propagation of helical gear tooth root, and used the extended finite element method to simulate the fatigue crack propagation in three-dimensional state and obtain its propagation path. It is proved that the crack tends to extend to the top of the gear tooth. The crack propagation path in the plane cuts the initial crack into two halves, which is similar to the growth path of the straight crack in the spur gear.

Agarwiv et al. Proposed a calculation model to study the fatigue crack propagation characteristics of gear root in the presence of inclusions. The crack propagation path and fatigue life are predicted by linear elastic fracture mechanics and LEFM based finite element model. The results show that for hard inclusions close to the original crack path, the crack propagation tends to slow down. The size of inclusions and the proximity of inclusions to the original crack path are significant. Curaf et al. Studied the correlation between the thickness of rim and web of thin tooth gear on the crack propagation path, and involved the bending failure. The numerical simulation was carried out by using the three-dimensional finite element method. The results show that the interaction between web and rim thickness may affect crack propagation and corresponding safety or catastrophic failure.

Srenping and others regard the supporting gear shaft as elastic support according to the actual working condition of the gear. Its influence on gear vibration is considered and studied, and the dynamic response of elastic teeth and gears is analyzed. On this basis, the gear body is regarded as a three-dimensional elastic disk, and the gear teeth are regarded as an elastic cantilever beam. Under the condition of elastic boundary (support shaft), combined with the influence of elastic disk and elastic teeth, including three-dimensional elastic disk on the meshing tooth response under the condition of elastic boundary, the dynamic model of gear support system and the calculation model of tooth response are established. The influence of pitch circle crack on the radiated sound field of gear structure is greater than that of tooth root crack, and the influence of crack position is greater than that of crack depth. For the gear with crack defects, the sound radiation characteristics of Cracked Gear and normal gear structure are not the same, and the sound radiation characteristics are abnormal and change violently. It lays a solid and reliable theoretical foundation for the study of gear fault by acoustic diagnosis method.

The above research on gear bending fatigue shows that the combination of test technology and virtual test analysis technology has become the trend of mechanical product design. By using finite element simulation technology, the R & D cost can be effectively reduced. The research on fatigue and damage of ordinary gears at home and abroad is becoming mature, but the research results of transmission gears for heavy equipment are less and the progress is slow. Compared with ordinary gears, the application place of transmission gears in heavy equipment is more special and the production position is more important. However, there are few analysis and Research on its life and damage, and there are few relevant research results and literature. In order to effectively predict the fatigue life and fatigue damage of transmission gears of heavy equipment. The fatigue damage and fatigue life of heavy-duty gears will be studied from two aspects of test and numerical simulation. It is hoped that the analysis results can be used as a reference for the design and use of heavy-duty gears. In the design and analysis of gear bending fatigue reliability, the combination of these two methods can greatly improve the quality performance and design level of gear products.