Study On Vibration Characteristics Of Typical Faults In Gear Transmission System

The gear transmission system is widely used in many kinds of mechanical equipment due to its advantages of high transmission accuracy,wide application range,high transmission efficiency and compact structure.However,due to the working environment of the traditional gear system is very bad,and key components such as gear pairs and supporting rolling bearings are easy to failure before reaching the design life,which leads to the failure of the gear transmission system and seriously affects the safety and stability of the mechanical equipment.Although a large number of diagnostic methods have been applied to identification of gear transmission system faults,they are mostly used to process the vibration signals of gear transmission system,so as to judge the operating conditions of the key components of gear transmission system.Because of the complex structure of the gear transmission system,there are many contact interfaces,and the frequency of vibration signals generated by key components such as gear pair and supporting rolling bearing are mixed,which undoubtedly brings some difficulties to the accurate identification of gear transmission system failures.It is urgent to study the fault mechanism of the gear transmission system for assistance,especially the influence of component fault on the vibration characteristics of the gear transmission system.Therefore,this paper studies the influence of typical faults,such as tooth root crack and local fault of supporting rolling bearing on the vibration characteristics of gear transmission system.The specific contents are as follows:(1)The energy method is used to calculate Hertz contact stiffness,bending stiffness,shear stiffness,radial compression stiffness and matrix flexible deformation stiffness,and the time-varying meshing stiffness of the gear pair is comprehensively formed.Combined with the lumped mass method and the Lagrange equation,the 8-DOF dynamic model of the gear pair is established.The root crack is introduced into the dynamic model of the gear pair through the bending stiffness and shear stiffness,the vibration characteristic analysis method of gear pair with root crack is used to analyze the influence of key parameters of root crack,such as crack depth and spread angle,on the time-domain and frequency-domain characteristics of time-varying meshing stiffness of gear pair and vertical displacement of driving wheel,and to obtain the variation law of vibration characteristic of gear pair with root crack.(2)Based on Hertz contact theory and Lagrange equation,a 5-DOF dynamic model of rolling bearing is constructed by using the lumped mass method.Local failures of bearing components such as outer raceways,inner raceways,and rolling elements introduce bearing power through contact deformation.A mathematical model to form a vibration characteristic analysis method for local faults of rolling bearings,in-depth analysis of the influence of single-point faults and composite faults on the frequency domain characteristics of the vertical speed of the outer ring of the bearing,and reveals the changes of vibration characteristics of local faults of rolling bearings.(3)Based on the established dynamic models of gear pair and rolling bearing,the 36-DOF dynamic model of gear transmission system is constructed by connecting the inner ring with the displacement and speed of pinion and gear,forming the typical failure vibration analysis method of gear transmission system.By comparing the existing analysis results of the local faults of the gear pair and the rolling bearing with the root crack,the influence of the root crack,the local fault of the bearing and other typical faults on the time-domain and frequency-domain characteristics of the vertical speed of the outer ring of the supporting bearing in the gear transmission system is analyzed in depth,and the variation law of the vibration characteristics of the typical faults in the gear transmission system is revealed,which provides the theoretical basis for the accurate identification and diagnosis of the fault of the gear transmission system.