The crack propagation of gear can be divided into three stages: the first stage, crack initiation stage; The second stage is the stable crack growth stage; The third stage is the stage of crack propagation. The fatigue failure of gear generally goes through three processes: fatigue crack initiation, crack propagation and sudden fracture. In order to avoid the early failure of gear, it is necessary to study the factors affecting the fracture and fatigue life of gear teeth. In recent years, some achievements have been made in the aspects of crack propagation, the influence of crack on dynamic characteristics and fatigue life, and the signal processing of Cracked Gear.
In 2010, podrug. S and others proposed a calculation model to determine the bending fatigue life of gear root, studied the influence of moving load on the service life of gear, and simulated the fatigue crack propagation by using the finite element method and linear elastic fracture mechanics theory.
In 2011, Lalonde. S and others proposed a factor design model method for gear bending fatigue simulation. Considering six parameters related to gear geometry and initial crack characteristics, the two-dimensional boundary element model of factor design was used to predict the crack propagation path. The accuracy and reliability of the method were proved by detailed verification program, The disadvantage is that the numerical simulation of factor design is time-consuming.
In 2012, Wu Zhenpeng and others used ABAQUS to simulate the propagation path of gear root crack, analyzed the influence law of different depth crack on gear meshing stiffness, obtained the time-domain correlation characteristics of different crack depth according to the collected vibration signals of Cracked Gear, and finally processed the obtained data according to the correlation method, The relationship between the crack depth and the frequency spectrum amplitude of the box vibration signal is proposed, which provides a reference method for the follow-up study of crack problems.
In 2013, Pandya y et al. Analyzed the propagation path of two-dimensional gear under different ratios based on linear elastic fracture mechanics, and analyzed the influence of time-varying meshing stiffness on the crack propagation path of gear. For different crack propagation paths, the improved total potential energy model can be used to predict the change of gear meshing stiffness. This method provides some ideas for gear fault diagnosis.
In 2013, based on linear elastic fracture mechanics, Liu Shuang et al. Used ABAQUS to simulate the crack propagation trend, analyzed the influence of different flange thickness on crack propagation path and crack propagation rate, which provided the basis for the design of gear transmission mechanism.
In 2014, based on linear elastic fracture mechanics, RAD A. Amiri et al. Used the extended finite element method to simulate the crack propagation of helical gear root, and the crack propagation path was toward the top of the tooth. According to the stress intensity factor and Paris criterion, the bending fatigue life of helical gear was predicted.
In 2014, Agarwal V et al. Studied the fatigue crack propagation characteristics of gear root with inclusions. Based on linear elastic fracture mechanics, the crack propagation path was predicted by finite element method, and the influence of the size and location of circular inclusions on the crack propagation and service life of gear was analyzed.
In 2015, cur f et al. Used the extended finite element method to analyze the influence of the thickness of the web and rim on the crack propagation path. The results show that the thickness of the web and rim with different sizes has a certain influence on the crack propagation path of the gear.
In 2015, s Renping et al. Established the dynamic coupling model of the cracked gear structure support system, studied the dynamic characteristics of the cracked gear structure system and the coupled dynamic response of gear meshing, and obtained the influence degree and law of the root crack and pitch circle crack on the three-dimensional elastic body radiated sound field of the gear by using the finite element and boundary element numerical methods, It establishes a solid and reliable theoretical basis for acoustic diagnosis of gear fault.
In 2016, cur F and others used the extended finite element method to simulate the crack propagation path of planetary gear, and analyzed the influence of rim thickness and initial crack location on the crack propagation path, which provided a certain support for the design of gear.
In 2016, sun Zhijia and others used the finite element method to simulate the crack propagation process at the root of cylindrical gear. The results show that with the increase of initial crack angle, the more likely the gear is to have flange fracture, the longer the fatigue life of the gear is, and the smaller the initial crack angle is, the easier the gear is to have root fracture, and the shorter the fatigue life of the gear is.
In 2016, Liu Xinbo and others studied the fatigue crack propagation characteristics and life of two-dimensional gear tooth root. Based on linear elastic fracture mechanics, the crack propagation was linearly equivalent, and the fatigue propagation path of tooth root crack was obtained through calculation. The fatigue test bench was used for test verification, and the results show that the test and simulation are basically consistent.
In 2017, cur f et al. Used three numerical models to study gear cracks. The first one is based on the two-dimensional finite element model to analyze the influence of the interaction between bending stress and centrifugal force on the crack initiation position. The second one is based on the three-dimensional finite element model to study the influence of rim thickness and web thickness on the crack initiation position, In the third method, the crack propagation path is studied by using the extended finite element method. The results show that the rim thickness and web thickness have little influence on the crack initiation location, while the centrifugal load has a great influence on the crack initiation location and crack propagation path.
In 2017, Wan Guoxin et al. Studied the influence of fillet radius on root crack propagation. The results show that with the change of fillet radius, the trend of root crack propagation is basically the same. For the same initial crack length, the larger the fillet radius is, the smaller the root crack propagation rate is, and the longer the life of the gear is.
In 2017, cur f et al. Used the extended finite element method to study the crack propagation behavior of cylindrical gear, analyzed the effects of tube length, edge thickness and velocity on the crack propagation path, and calculated the mode I and mode II stress intensity factors with and without centrifugal load, respectively, The ratio of mode I and mode II stress intensity factors has a certain influence on the sinusoidal crack growth path, but the results need further research.
From the above research, it can be found that the research on cracked gears by scholars at home and abroad is relatively mature, and a large number of studies are trying to find a method that can timely predict the occurrence of cracks and identify the type and location of cracks, and study the changes of various performance indexes of gears after the occurrence of cracks, and most of them are aimed at general gears, There is little research on the crack of low-speed and heavy-duty gear, and some heavy-duty equipment mostly adopts low-speed and heavy-duty gear transmission. Therefore, it is necessary to comprehensively study the dynamic characteristics of crack propagation of low-speed and heavy-duty gear, as well as the stress field and propagation path in crack propagation.