| As an important transmission system assembly,the manual transmission is widely used in various passenger cars and commercial vehicles.Owing to the nonlinear factors such as clearance and time-varying mesh stiffness,and the complicated driving conditions during vehicle running,it is difficult to evaluate fatigue durability of the transmission assembly.Aiming at the requirement of the life cycle of transmission assembly in QC Industry Standard,a dynamic modeling method of transmission assembly and a fatigue prediction method of transmission gear based on rigid flexible coupling model are put forward.Based on the analysis of transmission assembly topology,a virtual prototype model of transmission is established with ADAMS,and parameters are calculated through kinematics and dynamics analysis of gear such as the gear meshing stiffness,damping etc.Static structural analysis of the gear pair is carried out with ANSYS and the finite element model is calibrated by calculating the bending stress and the contact stress.The modal neutral file is generated,and the flexible body model of the gear pair is established with ADAMS.Transient dynamics analysis of the gear pair based on modal superposition method is carried out and the result is compared with the results of finite element analysis with ANSYS which verifies the validity of the flexible body model.The stress load spectrum on the dangerous point of the rigid-flexible coupling model is output,and the fatigue stress prediction of the transmission gear is carried out by using the nominal stress method and Miner damage accumulation theory.Fatigue evaluation of gear pairs with transmission test bench is performed and the simulation results are in good agreement with the experimental results.Compared with the traditional methods,the efficiency of the related methods has been significantly improved.Based on the virtual prototype model,the modeling method of the reliability model of the transmission assembly is put forward,and the evaluation method of the key factors of the assembly reliability is proposed.The torque and speed signals of the transmission in the urban and suburban areas are gathered.The mean value of torque was found to obey normal distribution,and the torque amplitude can be ignored on account of rain-flow counting result.Based on the stress-strength interference theory,Monte Carlo method is used to simulate the time-varying reliability of each gear,and the reliability of the bearings is evaluated by the improved L-P computing theory.Meanwhile,according to criticality analysis,a failure model of transmission assembly is established.Based on the reliability analysis results of internal parts,a time-varying reliability model of transmission assembly is established.The sensitivity analysis of the time varying reliability model of the transmission assembly is carried out,and the components with larger contribution to the reliability of the assembly are identified,and the parameters are adjusted.The influence of parameters such as effective diameter of bearing roller,effective length of roller,gear module and gear helix angle on the reliability of transmission key components and assembly is evaluated.Finally,based on the analysis of the influence factors of the reliability of the transmission assembly,the reliability of the transmission assembly is preliminarily optimized. |
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