The fatigue crack evolution test and numerical simulation of transmission gears of heavy equipment are studied. The preparation of compact tensile samples is completed in ZHY gear, the fatigue crack growth test of compact tensile samples is completed in the State Key Laboratory of new metal materials, University of science and technology of Beijing, and the cutting of damaged samples is completed in the engineering training center of North China University of technology The macro and micro observation of the sample was completed in the analysis and test center of North China University of technology, the processing and preparation of the gear sample was completed in ZHY gear, and the gear bending fatigue strength test was completed in the environmental test center of Southwest Institute of technology and engineering. With the help of compact tensile specimen fatigue crack propagation test and gear bending fatigue test, as well as the corresponding simulation tests of two groups of tests, the fatigue fracture was observed by scanning electron microscope. This research will have important social and economic value for the analysis of fatigue and life of transmission gears of heavy equipment, and the design and manufacture of gears.
The fatigue crack growth behavior of 42CrMo steel was studied by fatigue crack growth test. The laws of fatigue crack growth rate under different stress levels were compared and analyzed, and the Paris formula of fatigue crack growth in stable growth stage was calculated and verified by numerical simulation method; The fatigue fracture was observed and analyzed by scanning electron microscope, and the influence of microstructure on crack propagation and fatigue life was obtained. The bending fatigue test was carried out on the transmission gear of heavy equipment, the fatigue life of the gear was deduced, and the dynamic characteristics and crack propagation path of the crack of the transmission gear of heavy equipment were deduced. The main research contents are as follows:
1) The mode I fatigue crack growth test of compact tensile specimens under different stress ratios is carried out. According to the obtained test data, the relationship between crack length, crack growth rate, crack tip stress intensity factor and fatigue life is studied. The macro and micro morphology of fatigue fracture at different growth stages were observed and analyzed by scanning electron microscope, and the laws and influencing factors of fatigue crack propagation and fatigue life were studied from the micro point of view.
2) The fatigue crack propagation model of compact tensile specimens is established by using ABAQUS software, the variation law of the plastic zone at the crack tip under different stress ratios and crack lengths is studied, and the effects of load variation and crack length on the stress intensity factor at the crack tip are analyzed.
3) The bending fatigue test of 42CrMo gear under different load levels is carried out by using the bending fatigue test machine. Then the test data are analyzed and processed by mathematical statistics, the P-S-N fitting curve relationship is obtained, and the P-S-N curve of fatigue test is drawn.
4) The numerical simulation software ABAQUS / FE-SAFE is used to simulate the bending fatigue test and predict the life of the gear, analyze the characteristics between the survival rate of the gear and the fatigue life of the gear, obtain the Mises equivalent stress nephogram of the gear teeth under different load levels, and analyze the mechanism of fatigue cracks on the tension side and compression side of the gear teeth. The logarithmic fatigue life nephogram of gear teeth under different load levels is obtained, and the bending fatigue life results obtained from numerical simulation and test are compared and analyzed.
5) Based on the simulation principle of finite element crack propagation, the crack propagation of meshing gear with crack is analyzed by ABAQUS, and the effects of different factors on the stress intensity factor at the crack front and the crack propagation rules of different initial crack positions and angles are studied.