| The logarithmic spiral bevel gear is a new type of gear which takes the logarithmic spiral of the cone as the tooth line.The gear makes full use of the excellent characteristics of the logarithmic spiral,and can realize that the spiral angle is equal everywhere in the meshing process,so it is more suitable for the working environment of high speed and heavy load.However,in the process of gear pair running under high speed and heavy load,when the bending stress generated by the load on the gear teeth is too large,cracks will appear and gradually expand at the maximum tangential tensile stress on the gear pair,which will eventually lead to the fracture of the gear teeth and affect the normal production operation of the equipment.Therefore,in order to determine the dynamic characteristics and meshing stiffness of the gear pair and make the gear pair obtain higher application,it is necessary to study the process and law of crack formation and propagation.The main contents of this paper are as follows:1.Calculation of stress intensity factor of crack front.The stress intensity factor(SIF)at the crack tip is an important index of material fracture,which is usually expressed as a parameter of the stress field intensity near the crack tip under the action of external force.In this paper,the dynamic analysis of the logarithmic spiral bevel gear is carried out by using the finite element method,and the maximum stress position(dangerous position)of the tooth root is obtained.Then the initial crack is implanted in the dangerous position by using the FRANC3 D software,and the size of three kinds of stress intensity factors is calculated and the variation law is analyzed.2.Crack propagation analysis.Based on the existing three-dimensional model of logarithmic spiral bevel gear,the crack propagation process of logarithmic spiral bevel gear is studied by using the extended finite element method through mesh generation,parameter definition,applied load and boundary adjustment,and the variation law of stress intensity factor with the change of crack size,shape and tooth load is revealed.3.Influence of crack propagation on meshing stiffness: meshing stiffness determines the load-carrying capacity of a pair of gears,and it is also an important factor affecting the dynamic characteristics of gear pairs.In this paper,firstly,the meshing stiffness of healthy gear pair is calculated by energy method,then the finite element model is established and the meshing stiffness of healthy gear pair is calculated again by finite element method,and the results are compared to ensure the feasibility of finite element method.Finally,the meshing stiffness of logarithmic spiral bevel gear pair with cracks is analyzed by finite element method,and the influence of different crack size and shape on it is studied. |
