Zonglin Gu, Caichao Zhu, Huaiju Liu and Xuesong Du
This paper aims to compare the tribological performances of four different types of tooth surface finishing, namely, form grinding, generating grinding, super finishing and…
Abstract
Purpose
This paper aims to compare the tribological performances of four different types of tooth surface finishing, namely, form grinding, generating grinding, super finishing and grinding and coating, and to reveal the details at dry contact nodes.
Design/methodology/approach
Real measured roughness is input to a finite line contact mixed elastohydrodynamic lubrication model developed for helical gear pairs. Their tribological performances are compared. The variation throughout one meshing period is analyzed. The influence of the root mean square (RMS) is studied. The textures are also scaled to the same RMS values to make comparisons while excluding the influence of roughness amplitude.
Findings
Roughness is directly reflected in pressure and film thickness. Average film thickness sees major changes while entering and leaving the single-tooth-contact region. The textures have different performances even under the same RMS. Roughness peaks incurring dry contact are those higher than the smooth-situation film thickness plus the sum of variation in normal approach and elastic deformation compared with the smooth situation. To lower dry contact severity, the surface finishing process should take care of both the overall amplitude and the portion of peaks with maximum height. When RMS value is the same, the latter plays a decisive role.
Originality/value
This paper interprets the differences between the tribological performances of four different types of tooth surface finishing from the aspect of roughness features and presents a way to analyze the details at dry contact nodes.
Details
Keywords
Ye Zhou, Caichao Zhu, Huaiju Liu, Chaosheng Song and Zufeng Li
Coatings are widely used in gears to keep interface from wearing excessively. The purpose of this paper is to study the effect of coating properties and working conditions on the…
Abstract
Purpose
Coatings are widely used in gears to keep interface from wearing excessively. The purpose of this paper is to study the effect of coating properties and working conditions on the pressure, the shear traction, stresses as well as the fatigue life of spur gear.
Design/methodology/approach
A numerical contact fatigue life model of a coated spur gear pair under elastohydrodynamic lubrication (EHL) is developed based on the characteristics of gear geometry and kinematics, lubrication conditions and material properties. Frequency response functions and the discrete convolute and fast Fourier transform (DC-FFT) algorithm are applied to obtain elastic deformation and stress. Mutil-axial fatigue criteria are used to evaluate the contact fatigue life based upon the predicted time-varying stress fields of coated bodies.
Findings
The maximum Mises stress decreases while the fatigue life increases as the coating modulus decreases. A thinner coating leads to a longer life and a smaller maximum Mises stress for hard coatings. The load has more significant effect on the contact fatigue life of soft coatings.
Originality/value
The developed model can be used to evaluate the contact fatigue life of coated gear under EHL and help designers analyze the effect of coating elastic modulus and thickness on the contact pressure, film thickness and stress.