Research On Meshing And Dynamic Characteristics Of Cracked Planetary Gear Systems

Planetary gear system is an important part of mechanical transmission system.It is widely used in aerospace,automobile,ship and other fields.The planetary gear system can achieve larger transmission ratio and the synthesis and decomposition of motion,and save a lot of space.However,the planetary gear transmission system is relatively complex,and it is very important to carry out the necessary vibration and noise detection.Especially,the monitoring of the fault signal is beneficial to the early warning of the mechanical system.In this paper,the influence of cracks on the meshing and vibration characteristics of planetary gear trains is studied based on a planetary gear train of a speed reducer for a rolling machine.First,the finite element model of a healthy planetary gear train considering gear train structure is established to study the effect of torque,lightening hole and fixed hole on mesh stiffness.Secondly,the crack propagation simulation of plane planetary gear train is carried out by ANSYS,and the influence of plane crack on meshing characteristics is studied.Then,based on ABAQUS,the crack propagation of the space planetary gear train is simulated,and the influence of space crack is studied.Finally,the dynamic model of planetary gear train is set up for vibration research.The main contents of this paper are as follows:(1)The mesh stiffness of a more complex planetary gear system can not be calculated effectively.For example,the mesh stiffness of a planetary gear system with a flexible carrier and system structure,such as a gear with lightening hole and a fixed hole,can not be calculated in analytical method.Through the ANSYS software,a planetary gear train with flexible ring gear and carrier is set up,and the influence of flexibility of the ring gear body and the fixed hole and the lightening hole of the sun gear on the mesh stiffness is studied.At the same time,the mesh stiffness of planetary gear train with modification is calculated.(2)Based on the linear elastic fracture mechanics,the stress intensity factor of crack tip is calculated by ANSYS software and the crack growth is simulated.The effectiveness of the ANSYS results of this method is verified by comparing with the experimental results of board parts in the literature and ABAQUS software simulation.At the same time,the gear failure test rig is used to simulate the fatigue failure of gears,and the experimental results are also very good to verify the effectiveness of the simulation.Secondly,ANSYS software is used to simulate the crack propagation of planetary gear trains,including sun gear,planetary gear and ring gear.Finally,the finite element model of mesh stiffness is established based on the crack path obtained by ANSYS simulation,and the effect of crack on mesh stiffness of planar planetary gear train is analyzed.(3)There are the problems that the analytic method can not calculate the stiffness of space cracked gears with complex forms and the situations that many assumptions about the crack form are made in the literature.This paper uses the extended finite element method to study the crack propagation of space planetary gear trains on the basis of the plane planetary gear train crack propagation.Moreover,the influence of space crack on mesh stiffness is analyzed.At the same time,the influence of installation error of tooth width direction on mesh stiffness and stress distribution is analyzed.(4)The rigid-flexible hybrid dynamics model basing on the ADAMS software and lumped parameter dynamic model are established to analyze the vibration response.The vibration signals of planetary gear trains,such as the time domain and frequency domain diagrams of a planetary gear train,are extracted to compare the responses of healthy and cracked planetary gear trains under mesh stiffness excitation.In addition,it provides reference for fault detection of planetary gear trains.