Dynamic Modeling And Analysis For Gear Tooth Surface Crack And Its Propagation

Gear transmission has the advantages of small size,high transmission power and efficiency,strong bearing capacity,stable transmission ratio,stable and reliable working performance,etc.It is widely used in various fields such as automobiles,ships,aerospace,wind power generation,agricultural machinery,engineering machinery,etc.However,due to the fact that gear systems often work under severe conditions such as high speed,high temperature,and heavy load,and the complexity of their internal structure and excitation,local failures such as pitting,spalling,and crack often occur during operation.Especially for early failures such as gear tooth surface crack,if they cannot be detected in time,the degree of failure will further deepen,also aggravate the vibration and noise of the gear system,reduce the accuracy and stability of transmission system,accelerate the failure of the entire transmission system,and cause serious consequences.The occurrence of faults will affect the mesh stiffness of gears and thus the dynamic response of the gear system.However,at present,there is still a lack of research on the mesh stiffness of gear tooth surface crack and its response characteristics,so that the vibration changes of the gear system caused by the failure cannot be effectively judged and identified.Therefore,there is an urgent need to study the impact of tooth surface crack failure on mesh stiffness and dynamic response of the gear system,and to enrich the early fault diagnosis content of the gear system,which is of great significance in academic and engineering.This paper focuses on the problem of tooth surface crack fault that often occur in gears,starting from the mesh stiffness excitation of fault,around the calculation method of time-varying mesh stiffness and the effect of tooth surface crack on the dynamic response of gear system.A series of research work has been carried out.The main research contents of this paper include:(1)For the calculation of mesh stiffness excitation of gear tooth surface crack,based on the cantilever beam theory,an analytical calculation model of mesh stiffness of gears with tooth surface crack is established by using the potential energy method and considering the Fillet-Foundation stiffness.The evolution law of mesh stiffness is revealed when the tooth surface crack extends along different directions and when the crack fault position changes,and the relationship between the mesh stiffness of the same size spalling and the mesh stiffness of tooth surface crack is obtained.(2)For the influence of tooth surface crack on the dynamic response of the gear system,based on the calculation model of mesh stiffness of gears with tooth surface crack proposed in this paper,the lumped mass method was used to establish a gear system dynamic model which considering the tooth surface crack failure.The dynamic transmission error and vibration characteristics of the gear system are obtained when the tooth surface crack propagate and the operating conditions change.It has laid a theoretical foundation for the fault diagnosis of tooth surface crack.(3)For the selection of signal measurement methods of gearbox fault diagnosis,the difference between the dynamic transmission error and acceleration of gear system with tooth surface crack is analyzed.The advantages and disadvantages of the methods for using various sensors to measure the dynamic transmission error and acceleration are also researched.The proper selection method of fault diagnosis and measurement methods for gearbox system is given to further improve the accuracy of measurement.(4)The mesh stiffness calculation model of gears with tooth surface crack proposed in this paper is applied to the root crack which run through the tooth surface,and the mesh stiffness and the dynamic response results of the system are compared and analyzed with the results of other references to be in good agreement,which verifies the correctness of the theoretical model in this paper.