Fatigue Life Prediction Research Of Main Bearing Gear Of Shield Machine Drive System

The shield machine drive system is the power output center of the shield machine,and its main bearing gear usually adopts the transmission form of multi-point drive,which is a key component of power transmission.The fatigue fracture of the main bearing gear will cause the shield machine to be forced to stop for repair and even cause safety accidents.Therefore,it is of great scientific significance and engineering value to realize the fatigue life prediction of the main bearing gear of the shield machine drive system and scientifically guide the construction decision-making.Firstly,this thesis aims at predicting the fatigue life of the main bearing gear of the shield machine drive system.Based on the main bearing structure and its bearing form,combined with specific drawings and measured data,three-dimensional models of single point drive and multi-point drive of the main bearing gear are established by using parametric modeling technology.Through simulation and analysis of the model by ADAMS software,the meshing force of the multi-point drive gear was obtained;A theoretical model of multi-point drive meshing force under frictional conditions was established by the lumped parameter method.The average meshing force of the gear was calculated by using Matlab software,and the relative error between the theoretical value and the simulation value was 3.05%,verifying the correctness of the multi-point drive model.Secondly,in order to obtain the dangerous points and load conditions of the main bearing gear transmission system,the single point drive model and the multi-point drive model of the main bearing gear were simulated by finite element technology under the condition of considering the friction factors and inertia effects,and it was analyzed that the maximum stress at the root of the large gear ring,thus scientifically determining the location of the dangerous points and extracting the load time history of the dangerous points.And the location of the danger point is consistent with the actual project.Finally,in order to realize the full life prediction of crack initiation and propagation of main bearing gears,a theoretical model for predicting the crack initiation life of main bearing gears based on S-W-T formula was established by using the local stress-strain method.The theoretical value of the gear crack initiation life was15492.6h,and the relative error between the theoretical value and the n Code simulation value was 7.18%;A theoretical model for predicting the crack growth life of the main bearing gear based on Paris formula was established.The stress intensity factor was calculated by the weight function method.The theoretical value of the crack growth life of the gear was 1726.3h,and the relative error between the theoretical value and the n Code simulation value was 1.16%.In addition,the theoretical value of the whole life of crack initiation and propagation of the main bearing gear meets the design requirements,and the relative error between the theoretical value of the whole life and the simulation value is 6.61%,which verifies the rationality of the theoretical solution method of the crack initiation and propagation life,and has been verified by engineering experiments.The research results provide a scientific method for the fatigue life prediction of the main bearing gear of the shield machine drive system.