With the development of mechanics and computer simulation technology, the research on fatigue crack of spur gear has made great progress, and many problems have been solved in engineering application, but there are also some problems.
At present, most studies are based on linear elastic fracture mechanics, which simplifies the problem and can meet the requirements in practical engineering application. However, this engineering simplification method can not clearly study the generation of micro cracks and the propagation behavior of macro cracks. From material mechanics, we know that when the load borne by the entity reaches a certain value, the entity will have elastic deformation and plastic deformation at the same time. If linear elastic fracture mechanics is used, the influence of plastic deformation will be ignored, and plastic deformation has a decisive influence on the mechanical properties of materials; Moreover, under the action of cyclic load, the cumulative effect of plastic deformation produced in each load cycle in the whole load history is not considered. Although the plastic behavior of materials is considered, the J-integral can only be used for the analysis of two-dimensional crack problems, and the plastic effect in three-dimensional crack problems and composite crack problems is still not solved. The crack closure effect of spur gear is the most commonly used model at present, but whether the crack closure effect is correct or not is still controversial, and the crack closure effect of spur gear itself is not a mechanical parameter.
The computer simulation technology based on the existing mechanical theory also has great defects. ANSYS is a powerful general software with a special module for crack analysis, but it is only static analysis. APDL language can be programmed to simulate crack propagation, but the determination of propagation parameters is controversial. The special software FRANC2D and FRANC3D for crack analysis of spur gears can not only analyze the static characteristics of two-dimensional and three-dimensional cracks, but also analyze the crack propagation; However, the crack shape is artificially specified, and the leading edge is fixed as the initial crack leading edge in the crack propagation process of spur gear, which implements the “standardized” control of the crack propagation process, which is far from the actual crack propagation process. The research on fatigue crack of spur gear has very important practical significance. Many scholars continue to study and explore, trying to find more accurate and effective theories and methods.