| In compound planetary gear transmission under high speed and large load condition, in order to investigate the grow mechanism of contact fatigue wear and two-sides coupling relation between contact fatigue wear and load sharing behavior, taken into account the contact fatigue wear, a study on dynamics of compound planetar gear transmission is proceeded on in this work. Due to complicated effects of dynamic load and load sharing characteristic on the tooth contact fatigue wear, a static prediction model for the tooth wear accumulation is built to investigate the internal excitations generated by tooth accumulated wear. Taken into account the effects of eccentric load on tooth accumulated wear, a dynamic tooth wear prediction model of compound planetary gear set is proposed and built based on the effects of eccentric load on tooth accumulated wear, to study the effects of tooth accumulated wear on system dynamic characteristic, to investigate the two sides coupling relation between tooth contact fatigue and load sharing behavior, and the dynamic evolution of load sharing behavior, backlash, meshing stiffness and wear accumulation ration with the tooth wear accumulation, to lay the theory foundation for revealing the wear accumulation mechanism and dynamics evolution in compound planetary gear set under high speed and large load condition. The main contents and results are as follows:1. Based on Archard wear theory, for a parallel axis meshing pair, a static prediction model of tooth contact fatigue wear is built to calculate the wear distribution along tooth profile. Based on this model and numerical transformation and cycle extension, the wear distribution function along tooth profile is transformed into cycle internal excitation due to tooth wear accumulation. Incorporated with the Weber-Vanaschck equtions, the tooth chord length after tooth wear is calculated and the time-varying meshing stiffness due to tooth wear accumulation is calculated, as well as the influence of the tooth contact fatigue wear on meshing stiffness.2. Based on lumped-parameter method and Lagrange-Equation, incorporated with the backlash and meshing stiffness generated by tooth contact fatigue wear, a dynamic model of compound planetary gear transmission that includes the "translational and rotational" vibration of all the parts is proposed, to calculate the contact fatigue wear accumulation under contact ratio=1 or>1 condition. Then based on the dynamic meshing force calculated in this model, the initial condition and iteration step length is given to establish the dynamic prediction model of the tooth contact fatigue in compound planetary gear transmission under the eccentric load effects. The results show that:compared with the static prediction model, dynamic prediction model takes into account the effects of eccentric load on tooth wear accumulation. With the dynamic prediction model, the growth rate of tooth wear accumulation increases nonlinearly, which is more fit with practical situation.3. Based on harmonic balance method, incorporated with dynamic model of the compound planetary gear transmission, the shock-vibration characteristic is investigated. Based on numeric method, the effect of tooth wear accumulation on dynamics is investigated. Based on phase trajectories and poincare interface, the periodic motion characteristic is investigated. The results show that:tooth contact fatigue wear causes low frequency resonance movement obviously, which is prejudice to across the resonance range at initialization phase. Tooth contact fatigue wear causes bilateral impact phenomenon at high frequency motion range, and causes wavelike rise for dynamic meshing force. Due to the tooth wear, unilateral shock even the phenomenon of tooth separation occurred. Tooth contact fatigue wear expands the chaotic range at high frequency motion range, which causes a less critical frequency when entering into chaos. For the compound planetary gear set in this work, in order to reduce the effects of tooth wear accumulation on periodic motion features, the non-dimensional meshing frequency should be controlled between 0.6 and 1.2.4. Based on the influence mechanism research, incorporated with the dynamic prediction model of tooth contact fatigue in compound planetary gear transmission that is based on the effects of eccentric load, the two sides coupling relation between tooth contact fatigue wear and load sharing characteristic is proceeded on. By laterally comparising tooth surface contact fatigue wear with other incentives on the load sharing behavior, and longitudinally excavating the mechanism of internal excitations generated by tooth accumulated wear on load sharing behavior, the unilateral effect mechanism of the internal excitations generated by tooth contact fatigue wear on load sharing behavior is investigated. Based on the unilateral effect mechanism, the dynamic evolution of contact fatigue wear grow ratio, backlash and meshing stiffness generated by tooth accumulated wear is investigated, to study the two sides coupling relation between tooth contact fatigue wear and load sharing behavior. The results show that:tooth contact fatigue wear improves the load sharing behavior. The results of coupling relation between tooth contact fatigue wear and load sharing characteristic is that:with the tooth contact fatigue wear accumulation, the eccentric load coefficient rises for the meshing pair in underload, the eccentric load coefficient drops for the meshing pair in overload, and the growth rate of increasing backlash, meshing stiffness and tooth wear accumulation tends to be uniform, and the tooth wear accumulation on planets around the central gear tends to be uniform, which indicate that load sharing behavior improves.5. Based on solid modeling to restore the tooth profile after tooth contact fatigue wear, incorporated with the nonlinear contact element of the virtual prototype, the tooth profile meshing behavior after tooth wear is simulated and a dynamic model of compound planetary gear transmission based on tooth contact fatigue wear in virtual prototype is established, to simulate the dynamic behavior of compound planetary gear transmission under tooth contact fatigue wear condition. Based on the simulation model, the influence of toot contact fatigue wear on meshing force and load sharing behavior are investigated under different eccentricity errors, as well as the influence of eccentric load characteristic generated by eccentricity error on tooth contact fatigue wear. The results from simulation and numerical calculation are coincided, which indicates the validity of simulation model and theoretical model. |
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