The Study Of Bending Fatigue Strength Of 20CrMoH Gear

Because of the chemical element with the symbol Mo can remarkable raise the hardenability of steel, 20CrMoH carburized gear have great processability and transmission performance. This kind of gear is widely used in driving device of medium and heavy vehicle. The gear undertake relatively large load during the working time, so the bending fatigue strength is always the key indicator for the transmission performance. There is no relative research about the bending fatigue strength of 20CrMoH carburized gear so far. Major contents of the thesis as follows:①The test of the single-tooth bending fatigue strength of 20CrMoH carburized gear have been discussed. The test method of pulse load in single-tooth and the group method have been used in the experiment, the bending fatigue strength test of tooth of the gear at 5 classes of constant stress levels was carried out on the electromagnetic resonance testing machine.②By employing planar section method and broken-line method, the root stress of gear teeth under different load levers have been calculated. The macro morphology of fatigue fracture of gear test specimens have been analyzed.③By making use of the probability theory and the principle of statistics, through hypothesis test to the test data in three different forms of probability distribution like log-normal distribution, two-parameter Weibull distribution and three-parameter Weibull distribution, the form of the probability distribution of gear bending fatigue life of 20CrMoH carburized gear have been analyzed under constant stress.④Analyzed the reliability of the bending fatigue strength of 20CrMoH carburized gear. The P - S - N curves of the gear and the limiting bending fatigue stress of gear teeth under different reliability have been achieved.⑤Combined with the equation of tooth profile and Ansys parametric design language(APDL), the parametrized finite element model of gear test specimens was presented. Then on the basis of the tooth root stress of the gear test specimen, the bending fatigue strength of gear have been analyzed based on ANSYS/FE-SAFE. It's a new approach to evaluate the bending fatigue strength of gear teeth.