| In the service state,the failure of key structural parts is mainly form of fatigue fracture.In the gear fatigue failure,the failure like surface spalling and pitting and other forms of failure caused by contact fatigue occupy a large proportion.The study on the simulation method of gear contact state and contact fatigue crack play an important role in giving the theoretical basis and guiding significance of the key structure reliability and contact fatigue life of gear.Based on the fatigue analysis method,the fracture mechanics theory and the finite element method and the boundary element method,the numerical simulation of the gear contact state and the contact fatigue life is carried out.The concrete contents are as follows:1.The three-dimensional finite element model of the modified cylindrical spur gear was established in ANSYS,then the dynamic contact process of the gear pair is analyzed.The fatigue life of the gear pair is predicted by the S-N curve of the material combined with mean stress method,while the effect of various load factors and the various friction factors on fatigue life of modified gear are discussed.2.Based on Smith-Watson-Topper relevant maxim(namely SWT),the contact fatigue crack initiation life was predicted.Using the three-dimensional fracture analysis software Franc3 D,the contact fatigue model after pre-crack was analyzed by boundary element analysis,and the crack tip stress intensity factor was calculated.Combined the prediction and formulation,the contact fatigue life were calculated.Prediction of crack propagation life under various loads was carried out according to the change curve of stress intensity factor.On the other hand,the influence of various crack shape ratios and initial crack angles on the stress intensity factor of contact fatigue crack were discussed.3.In terms of the contact fatigue reliability method of cylindrical spur gear,the contact fatigue reliability of cylindrical spur gear was calculated under the condition of 1440r/min of the driving wheel and the moment at 239.3N ? m of the driven wheel.The value is 85.76%.The contact fatigue test of 42 CrMo steel was carried out.The contact fatigue failure morphology was analyzed.Compared simulation and test,the performances of contact fatigue life and crack path are consistent,the correctness of Franc3 D simulation on crack propagation was verified. |
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