Study On Dynamic Characteristics Of Cracked Gear Transmission System Based On Finite Element Method

Gear Transmission system is an important part of Mechanical equipment.The running state of gear system often directly affects the running state of the whole mechanical equipment.In this paper,the finite element model of gear system is established by taking the gear crack fault simulation test-bed as the research object.The effects of root crack faults in different depths and non-penetrating root cracks and indexing circular cracks in the direction of tooth width on gear meshing stiffness and system dynamic characteristics are analyzed.And through the test method to carry on the verification.The main contents of the study are as follows:(1)The meshing stiffness of healthy gears is analyzed by finite element method and material mechanical energy method.The comparison between the two analysis methods shows that the calculation results of the finite element method are slightly smaller than those of the energy method.Then,the mean meshing stiffness of gear and the maximum meshing stiffness of single tooth are calculated by using ISO 6336:2006,and compared with the finite element method and energy method.(2)Considering the influence of gear failure with crack on meshing stiffness,the finite element model of gear with root crack with different depth is established.The effect of root crack of different depth on meshing stiffness is analyzed.At the same time,the root crack model is divided into three cases by using the relationship between the distance from the crack tip to the middle line of the single tooth and the thickness of the circular tooth at the top of the 1/2tooth.The meshing stiffness at different crack depths is analyzed by means of energy method.The effectiveness of the finite element method for calculating the meshing stiffness of cracked gear is verified.In order to get closer to the engineering practice,the influence of non-penetrating crack on meshing stiffness is considered.The finite element model of non-penetrating tooth root crack and crack in indexing circle is established.The meshing stiffness of tooth root crack and indexing circular crack gear with different penetration degree in the direction of tooth width is analyzed.(3)According to the principle of fracture mechanics,the crack propagation process of tooth root is analyzed.The finite element model for root crack formation.ANSYS finite element software is used to simulate the propagation process of root crack in depth direction and tooth width direction.Based on the analysis of the stress intensity factor near the crack tip,the crackangle is calculated.As a result,the propagation path of root crack is determined step by step.(4)Considering the influence of broken Gear with cracks on the dynamic characteristics of the system.On the basis of analyzing the meshing stiffness of cracked gear by finite element method,the dynamic model of gear system is established.The effect of different crack types on the dynamic characteristics of gear system is analyzed by means of centralized parameter method.The effects of root crack with different crack depth,non-penetrating root crack and graded circular crack on the vibration and acceleration response of the system are analyzed.Then,the validity of the simulation results is verified by comparing the measured signals with the simulated signals.