A lubrication contact pair model for simulating gear micro-pitting damage characteristics based on contour integral

Yang Zhao,Wenhao Huo,Chuan Wu,Yong Liao,Yang Xiao,Song Feng,Hao Sun

doi:10.1177/16878140211039431

Abstract

A new two-dimensional finite element model of a lubricated contact pair, based on a contour integral, is proposed to investigate the formation of micro-pitting on gear tooth surfaces. Meanwhile, the contact properties and elasto-hydrodynamic lubrication (EHL) conditions of the gears are considered in the lubricated contact pair model. Then, the stress intensity factors (SIFs) KI and KII and the propagation angle θ C at the crack tip are analyzed by ABAQUS software. Next, the equivalent SIF Kσ can be calculated according to the maximum tangential stress (MTS) criterion, which is often used as the criterion for crack propagation. Considering the effect of a moving contact, the crack more easily propagates under the load x0/ b = −0.895. Furthermore, the pit shapes and variation of stress intensity factor are determined for various combinations of initial crack length a0 and angle β. The results show that longer germinated cracks propagate in areas that are deeper below the tooth surface. And the total length of final crack increases with the initial length and germination angle. These research results provide theoretical support for contact fatigue life analysis and meshing stiffness calculations of micro-pitting gears.

Highlights

After a gear is put into service, many micropits may form on the surfaces of gear teeth and cause gear wear
It is necessary to study the formation of the micro-pitting starting from crack initiation and propagation to the surface and reveal the influence of elastohydrodynamic lubrication (EHL) conditions on the damage characteristics of micro-pitting, which provides a theoretical reference for slowing gear wear and prolonging gear lifetime
The main conclusions are as follows: (1) The contact pair model with an EHL pressure distribution is more consistent with the actual operating conditions of a gear, and the crack propagates more for the load x0/ b = 20.895 used in the range of calculations in this paper

Summary

Introduction

After a gear is put into service, many micropits may form on the surfaces of gear teeth and cause gear wear. Previous studies on crack propagation and pitting of gears mainly based on Hertz theory and EHL theory to establish a numerical equivalent contact model of a gear tooth surface with micro-cracks. This paper considers the influence of the EHL condition of the gear as well as the contact between the crack and the opposite tooth surface on the formation of micro-pitting. Based on a contour integral, a numerical finite element model of lubricated contact pairs is established to study the formation of micro-pitting on gear tooth surfaces. The results show that the micro-pitting crack contacts the opposite tooth surface in the early stage of propagation, and the lubricated contact model is closer to the real situation. In this scanning electron microscopic image (SEM), as shown in Figure 5, micro-pitting is characterized by shallow pits with depths that usually do not exceed

III IV V VI VII

Conclusions