EHL of Coated Surfaces: Part I—Newtonian Results

1994 ◽  
Vol 116 (1) ◽  
pp. 29-36 ◽  
Author(s):  
A. A. Elsharkawy ◽  
B. J. Hamrock
Keyword(s):  
Coating Thickness ◽  
Numerical Solutions ◽  
Complete Solution ◽  
Elastohydrodynamic Lubrication ◽  
Elastic Half Space ◽  
Hard Coatings ◽  
Coating Materials ◽  
Pressure Profiles ◽  
Pressure Spike ◽  
Coated Surfaces

A complete solution for the Newtonian elastohydrodynamic lubrication of coated surfaces in line contact is introduced in this paper. The formulation is based mainly on solving the Reynolds equation coupled with the elasticity equations of the multilayered elastic half space. The effects of pressure inside the lubricated conjunction on the lubricant viscosity and density are considered. The mathematical model for this problem is a nonlinear one, and an iterative Newton-Raphson scheme is used for numerical solutions. The effects of coating material and coating thickness on the pressure profiles and the film shapes are presented. Two different coating materials (molybdenum disulfide as a soft coating and titanium nitride as a hard coating) are considered. The results show that the pressure spike is higher for hard coatings than for uncoated surfaces but that the pressure spike disappears for soft coatings. Furthermore, the coating thickness has a significant influence on the minimum film thickness and the maximum contact pressure for both soft and hard coatings.

EHL of Coated Surfaces: Part II—Non-Newtonian Results

1994 ◽  
Vol 116 (4) ◽  
pp. 786-793 ◽  
Author(s):  
A. A. Elsharkawy ◽  
B. J. Hamrock
Keyword(s):  
Newtonian Fluid ◽  
Reynolds Equation ◽  
Fluid Model ◽  
Elastohydrodynamic Lubrication ◽  
Elastic Half Space ◽  
Hard Coatings ◽  
Surface Shear Stress ◽  
Coating Materials ◽  
Surface Shear ◽  
Pressure Profiles

A complete non-Newtonian elastohydrodynamic lubrication solution for multilayered elastic solids is introduced in this paper. A modified form for the Reynolds equation was derived by incorporating the circular non-Newtonian fluid model associated with a limiting shear strength directly into the momentum equations that govern the instantaneous equilibrium of a fluid element inside the lubricated conjunction. The modified Reynolds equation, the elasticity equations of multilayered elastic half-space, the lubricant pressure-viscosity equation, the lubricant pressure-density equation, and the load equilibrium equation were solved simultaneously by using the system approach. The effects of the surface coating on pressure profiles, film shapes, and surface shear stress profiles are shown. Furthermore, the effects of coating thickness on the minimum film thickness and on the coefficient of friction are presented for different coating materials. The results show that for hard coatings non-Newtonian fluid effects on the pressure profiles and film shapes are significant because of the increase in the contact pressure.

Elastohydrodynamic Lubrication of Elastomeric-Coated Surfaces in Line Contact

1995 ◽  
Vol 209 (2) ◽  
pp. 119-130 ◽  
Author(s):  
A A Elsharkawy ◽  
B J Hamrock
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Elastic Cylinder ◽  
Elastic Half Space ◽  
Operating Conditions ◽  
Elasticity Analysis ◽  
Elastic Substrate ◽  
Pressure Profiles ◽  
Dry Contact ◽  
Coated Surfaces ◽  
Raphson Method

Elastohydrodynamic lubrication analysis for an elastomeric layer bonded to an elastic substrate and indented by a rotating elastic cylinder is introduced. The surface elastic deformations are computed from full elasticity analysis of layered elastic half-space. The dry-contact problem was solved first, and the iterative Newton-Raphson method was used to solve the elastohydrodynamic lubrication problem. The lubricant rheological equations were considered in the present analysis. The significant effects of the elastomeric layer thickness on the pressure profiles and film shapes at different operating conditions are presented and discussed.

The line contact problem of elastohydrodynamic lubrication - I. Asymptotic structure for low speeds

1989 ◽  
Vol 424 (1867) ◽  
pp. 393-407 ◽  
Keyword(s):  
Asymptotic Solution ◽  
Contact Problem ◽  
Film Thickness ◽  
Numerical Solutions ◽  
Elastohydrodynamic Lubrication ◽  
Thin Layers ◽  
Line Contact ◽  
Asymptotic Regime ◽  
Lubricating Film ◽  
Pressure Spike

This paper reports the first formal asymptotic solution to the line contact problem of elastohydrodynamic lubrication (EHL), a fundamental problem describing the elastic deformation of lubricated rolling elements such as roller bearings, gear teeth and other contacts of similar geometry. The asymptotic régime considered is that of small λ , a dimensionless parameter proportional to rolling speed, viscosity and the elastic modulus. The solution is shown to possess four regions: a zone where the lubricating film is both thin and slowly narrowing and which is closely related to the contact area that occurs in the absence of lubricant, an upstream inlet zone of low pressure, and two thin layers on either side of the contact zone. The solutions in the first two just-mentioned zones are given by simple analytical expressions. The solutions in the two thin layers are obtained from two universal functions obtained by Bissett & Spence ( Proc. R. Soc. Lond . A 424, 409 (1989)). Although these two functions, related to the local film thickness, are obtained by numerical techniques by Bissett & Spence, it should be emphasized that all cases in the asymptotic régime considered are hereby solved definitively without recourse to further computation. Although some features of this structure have been suggested by other solution approaches, generally, these are numerical or ad hoc approximations. See the texts by Johnson ( Contact Mechanics , pp. 328 (1985)) and Dowson & Higginson ( Elasto-hydrodynamic lubrication (1977)), this work provides a formal mathematical basis for understanding most of the principal features of EHL. The solution provides a simple formula for minimum film thickness and displays the sharp narrowing of the lubricating film in the thin layer near the exit. In the basic asymptotic solution provided here, the dimensionless pressure-viscosity coefficient, α , is assumed to be O (1), and in this parameter régime, no pressure spike will occur. By comparing with the work of Hooke ( J. mech. Engng Sci . 19(4), 149 (1977)), we can show that an incipient pressure spike occurs when α becomes as large as O ( λ -1/5 ). However, asymptotic solutions in this latter parameter régime require new numerical solutions for each case of interest and are not pursued here.

Formation Mechanism of Steady Multi-Dimples in Thermal EHL Point Contacts

2003 ◽  
Vol 125 (2) ◽  
pp. 241-251 ◽  
Author(s):  
M. Kaneta ◽  
P. Yang
Keyword(s):  
Steady State ◽  
Flow Model ◽  
Numerical Solutions ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
Newtonian Flow ◽  
Pure Rolling ◽  
Pressure Spike ◽  
Thermal Ehl

With optical interferometry technique, an interesting multi-dimple phenomenon has been discovered under pure-sliding conditions in the point contact between a glass disk and a 3-inch diameter steel ball. At low sliding speeds, two or three stable dimples can be generated in the contact, but at higher sliding speeds, such multi-dimples become unstable. At even higher sliding speeds, however, dimples become stable again, but two dimples become single dimple, or three become two. Numerical solutions of the steady-state thermal elastohydrodynamic lubrication (EHL) theory based on the Newtonian flow model can simulate the stable multi-dimples very well. By changing the slide-roll conditions from pure-rolling to pure-sliding, the theoretical analysis shows clearly that the stable multi-dimples are produced by the thermal effect through the familiar EHL pressure spike.

Thermal Elastohydrodynamic Lubrication Analysis for Point Contact Transmission

2009 ◽  
Author(s):  
Hai-zhou Huang ◽  
Xi-chuan Niu ◽  
Xiao-yang Yuan
Keyword(s):  
Film Thickness ◽  
Numerical Solutions ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Surface Velocity ◽  
Squeeze Film ◽  
Elastic Displacement ◽  
Circular Arc ◽  
Tooth Width ◽  
Contact Transmission

To investigate the thermal EHL (elastohydrodynamic lubrication) in point contact transmission, a model considering the two-dimensional surface velocity of tooth face and the running-in is proposed. The numerical solutions for pressure, temperature and film thickness distribution in the contact zone are obtained by solving equations including the Reynolds, Energy and the elastic displacement with variable dimension meshing method. The model was used to study the point contact transmission of the circular arc gear in a windlass. The main results show that it is pure rolling along the direction of tooth width, and the rolling speed plays a leading role in improving the lubricating performance and transmission efficiency of circular arc gear. The squeeze film effect makes the pressure peak tend to be gentle and the film thickness increase slightly.

Wear of Coated Cutting Tool Based on AdvantEdge

2014 ◽  
Vol 551 ◽  
pp. 221-227
Author(s):  
Zhi Qiang Zhang ◽  
Tie Qiang Gang ◽  
Yi Kai Yi
Keyword(s):  
Wear Rate ◽  
Coating Thickness ◽  
Cutting Tool ◽  
Cutting Tools ◽  
Simulation Software ◽  
Machining Process ◽  
Sliding Velocity ◽  
Coating Materials ◽  
Element Simulation ◽  
Coated Tool

In this paper, based on finite element simulation software AdvantEdge, the effects of different coating materials and thickness on the wear of cutting tools during the machining process have been studied. For the tools with coating materials of TiAlN, Al2O3, TiN, TiC, we can calculate the wear rate according to the Usui mathematical model of tool wear, and then consider thickness factor of TiC coating. Because of the lowest thermal conductivity, the workpiece cut by TiC coated tool will soften first and more over cutting time, it result in the lowest wear rate. And with the increase of coating thickness, the effect of "thermal barrier" is more obvious for the relatively thicker coating tool, but the relative sliding velocity between the chip and tool is increasing meanwhile, so a suitable coating thickness is necessary.

A Theoretical Tribological Comparison Between Soft and Hard Coatings of Spur Gear Pairs

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Huaiju Liu ◽  
Caichao Zhu ◽  
Zhanjiang Wang ◽  
Ye Zhou ◽  
Yuanyuan Zhang
Keyword(s):  
Surface Deformation ◽  
Tribological Behavior ◽  
Elastohydrodynamic Lubrication ◽  
Spur Gear ◽  
Hard Coatings ◽  
Radius Of Curvature ◽  
Maximum Pressure ◽  
Gear Pair ◽  
The Coefficient Of Friction ◽  
Squeeze Effect

A thermal elastohydrodynamic lubrication (TEHL) model is developed for a coated spur gear pair to investigate the effect of soft coatings and hard coatings on the tribological behavior of such a gear pair during meshing. The coating properties, i.e., the ratio of the Young's modulus between the coating and the substrate, and the coating thickness, are represented in the calculation of the elastic deformation. Discrete convolution, fast Fourier transform (DC-FFT) is utilized for the fast calculation of the surface deformation. The variation of the radius of curvature, the rolling speed, the slide-to-roll ratio, and the tooth load along the line of action (LOA) during meshing is taken into account and the transient squeeze effect is considered in the Reynolds equation. Energy equations of the solids and the oil film are derived. The temperature field and the pressure field are solved iteratively. The tribological behavior is evaluated in terms of the minimum film thickness, the maximum pressure, the temperature rise, the coefficient of friction, and the frictional power loss of the tooth contact during meshing. The results show discrepancies between the soft coating results and hard coating results.

Sign in / Sign up

Export Citation Format

Share Document