| Multi-stage planetary gear transmission system is a common mechanical power transmission device.Because of its characteristics of power dividing and uniform load distribution,it has the advantages of strong carrying capacity,high efficiency,small size,large transmission ratio,etc.,and it has a wide range of applications,so it is often used in bad environment,complex and changeable load occasions,therefore,its reliability and early fault monitoring have higher requirements.Reasonable structure design,speed ratio matching,scientific processing technology and good precision control of multi-stage planetary gear transmission system are beneficial to the improvement of its reliability.However,due to the objective existence of its meshing characteristics and machining precision level restrictions,it is inevitable to be affected by the impact caused by internal excitation such as the meshing stiffness of the gears,various manufacturing errors and toothed clearance in the process of operation,resulting in the vibration and noise of the system,so that the vibration problem of the gear transmission system is highlighted.Various faults may occur in the key parts of the multi-stage planetary gear transmission system.The occurrence of various faults will affect other components.Failure to prevent and eliminate the faults in time will result in potential risks,especially the broken teeth of the gears.It causes the entire power transmission system to fail or shut down,and cause a major accident.Tooth broken is the most deadly among various faults of the multi-stage planetary gear transmission system,and the tooth root crack is the most direct cause of the early tooth broken accident.Therefore,the mechanism of the early tooth root crack failure of the multi-stage planetary gear transmission system is necessary to research on mechanism and identification to avoid related accidents.From the theoretical analysis of dynamic characteristics,dynamic simulation analysis,test verification of multi-stage planetary gear transmission system,the dynamic characteristics of the multi-stage planetary gear transmission system and the identification of early cracks in the gear tooth roots are studied in this thesis,the research on the dynamic characteristics of the planetary gear transmission system and the identification of early crack faults in the gear tooth roots provides theoretical basis and effective methods,which promotes the improvement of equipment reliability and to avoid related major accidents.The main research contents of this article are as follows:(1)Based on the energy method,the time-varying meshing stiffness of multistage planetary gear transmission system was numerically calculated.The time-varying meshing stiffness of each gear pair in planetary gear train in the normal meshing state and the input state of the sun gear with tooth root crack were solved,and the time-varying meshing stiffness was used to solve the dynamic response characteristics of the gear transmission system by means of the dynamic equation;(2)The concentrated parameter method was used to establish the dynamic model of the multi-stage planetary gear transmission system,considering the effects of the time-varying meshing stiffness and tooth backlash of the planetary gear trains and the meshing method,a nonlinear time-varying pure torsional dynamic model was established for multistage planetary gear transmission system.The time-varying meshing stiffness of each planetary gear trains and each meshing mode in normal state and with tooth root crack was used to solve the dynamic characteristics of the multi-stage planetary gear transmission system;(3)The finite element model of the multi-stage planetary gear transmission system in the normal state was established,and its dynamic response characteristics were simulated and analyzed,and the dynamic response characteristics of the transmission system in the normal state was studied;(4)Based on the finite element model of the multi-stage planetary gear transmission system in the normal state,the finite element model of the input sun gear with root cracks was established,the dynamics simulation of the multistage planetary gear transmission system with tooth root crack was carried out,and the vibration response and spectrum characteristics of the system were analyzed;(5)A multi-stage planetary gear transmission system test system based on torsional vibration signals was built,and the torsional vibration signals of the two-stage planetary gear transmission system in the normal meshing and root crack condition were collected and monitored in real time,the dynamic torsional vibration signals collected were analyzed by order analysis and time-domain synchronous average analysis.The early root crack fault state of multistage planetary gear transmission system was identified and analyzed. |
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