Nonlinear Dynamic Characteristic Analysis And Crack Fault Diagnosis Of Gear

As one of the main forms of mechanical transmission,gear transmission has the advantages of constant transmission power,strong bearing capacity,high transmission efficiency,long service life,excellent working reliability and compact structure,therefore,it is widely used in all kinds of mechanical equipment and industrial production.However,the structure of gear itself is complex,it is often in high-speed and heavy-duty working environment,which greatly increases the probability of gear and gearbox failure and damage,that directly affects the safe operation of equipment.Research on the fault mechanism and key diagnostic techniques of gear system can provide theoretical basis for the fault diagnosis and detection of gear,and also can find the fault of gear early and track its development in real time,therefore,it is of great academic significance and practical value to avoid the occurrence of serious accidents.In this paper,the study of dynamic excitation of gear meshing is carried out respectively,taking the spur gear pair and planetary gear set as the research objects,the meshing stiffness models of healthy gears and cracked gears are established,and the dynamic response of multi-degree-of-freedom system under stiffness excitation is discussed.The main content of this paper is as follows:(1)On the basis of the traditional potential energy method,considering the influence of the deformation of the fillet foundation and the gear hole on the meshing stiffness,an improved potential energy method is proposed to calculate the time-varying meshing stiffness of the gear pair,and the correctness of the method is verified by the finite element model.According to the improved model,the influence of different design parameters and excitation on the spur gear pair system dynamics is studied.(2)According to the characteristics of tooth profile and structure of gear,the improved meshing stiffness calculation model of healthy planetary gear pair is deduced under the boundary condition when the tooth number is less or more than 42.Then the stiffness calculation methods of outer meshing and inner meshing gear pair are obtained,also the stiffness of gear with cracks are analyzed and deduced.In addidation,the influence of different crack extension depth and crack extension angle on the meshing stiffness of planetary gear are studied.(3)Based on the dynamic method,the dynamic model of multi degree of freedom planetary gear system is established,and the root crack existed on the sun gear is studied to reveal the the influences on vibration characteristics of the planetary gear system.Simultaneously,the fault characteristics of tooth root crack in time domain and frequency domain are both analyzed.By eliminating the vibration signals of the normal gears from the original signals,the residual signals which can reflect the fault effectively can be obtained,and then the relative range of the residual signals can be characterized by using various statistical indexes.Therefore,it can effectively reflect the various stages of crack evolution and monitor and diagnose the gear faults in turn.(4)Based on the GDS gearbox test bench,the vibration response characteristics of parallel axle gear box are analyzed.The effects of input speed and transmission path on the vibration characteristics of the gearbox are studied.The vibration signals at different speeds and at several test bearing points are collected respectively,and then the general vibration characteristics of the gear pair are obtained by processing the test data.