Experimental Analysis of Chromium Molybdenum Coatings Under Mixed Elastohydrodynamic Lubrication for Film Thickness, Friction, and Wear Characterizations

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
David Pickens ◽  
Zhong Liu ◽  
Takayuki Nishino ◽  
Q. Jane Wang
Keyword(s):  
Film Thickness ◽  
Friction And Wear ◽  
Elastohydrodynamic Lubrication ◽  
Tribological Performance ◽  
Root Mean Square Roughness ◽  
Boundary Lubrication Friction ◽  
Lubricant Film Thickness ◽  
Free Surfaces ◽  
Surface Topographies ◽  
Coated Surfaces

This research aims to evaluate the tribological performance of chromium molybdenum (CrMo) coatings under point and line-contact mixed elastohydrodynamic lubrication. This article studies the coatings made from two different methods and treated in an electrifying process of different durations, which produced microchannels and micropockets in the surfaces. The resulting surface topographies had varying impacts on lubricant film thickness, friction, and wear. Root-mean-square roughness (Sq) and porosity are used to characterize the surfaces and their performances in terms of film thickness, friction, and wear. The results suggest that the coated surfaces with a lower Sq and porosity density tended to yield higher film thickness. However, their influence on friction is complicated; lower roughness and porosity are preferred for lower wear, but certain levels of small roughness and surface pores may help to reduce boundary lubrication friction when compared with the frictional behaviors of porosity-free surfaces and those with higher roughness and higher porosity.

A Three-Dimensional Model of Line-Contact Elastohydrodynamic Lubrication for Heterogeneous Materials with Inclusions

2016 ◽  
Vol 08 (02) ◽  
pp. 1650014 ◽  
Author(s):  
Kun Zhou ◽  
Qingbing Dong
Keyword(s):  
Film Thickness ◽  
Half Space ◽  
Surface Deformation ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Line Contact ◽  
Lubricant Film Thickness ◽  
Equivalent Inclusion Method ◽  
Surface Contact

This paper develops a three-dimensional (3D) model for a heterogeneous half-space with inclusions distributed periodically beneath its surface subject to elastohydrodynamic lubrication (EHL) line-contact applied by a cylindrical loading body. The model takes into account the interactions between the loading body, the fluid lubricant and the heterogeneous half-space. In the absence of subsurface inclusions, the surface contact pressure distribution, the half-space surface deformation and the lubricant film thickness profile are obtained through solving a unified Reynolds equation system. The inclusions are homogenized according to Eshelby’s equivalent inclusion method (EIM) with unknown eigenstrains to be determined. The disturbed half-space surface deformations induced by the subsurface inclusions or eigenstrains are iteratively introduced into the lubricant film thickness until the surface deformation finally converges. Both time-independent smooth surface contact and time-dependent rough surface contact are considered for the lubricated contact problem.

An Elastohydrodynamic Lubrication Model for Coated Surfaces in Point Contacts

2007 ◽  
Vol 129 (3) ◽  
pp. 509-516 ◽  
Author(s):  
Yuchuan Liu ◽  
W. Wayne Chen ◽  
Dong Zhu ◽  
Shuangbiao Liu ◽  
Q. Jane Wang
Keyword(s):  
Fourier Transform ◽  
Film Thickness ◽  
Fast Fourier Transform ◽  
Elastic Deformation ◽  
Elastohydrodynamic Lubrication ◽  
Contact Radius ◽  
Point Contacts ◽  
Compliant Coating ◽  
Influence Coefficients ◽  
Coated Surfaces

An elastohydrodynamic lubrication (EHL) model for coated surfaces in point contacts has been developed by combining the elastic deformation formulation for the coated surfaces with an EHL model. Inverse fast Fourier transform (IFFT) is employed first to obtain the influence coefficients (ICs) from the frequency response function (FRF). The subsequent calculation of elastic deformation is performed using the efficient algorithm of discrete convolution and fast Fourier transform (DC-FFT). The coating EHL model is verified by the comparison to available numerical results. The effects of coating on lubrication under various loads, speeds, rheological models, and pressure-viscosity behaviors are numerically investigated. Similar to the observations from dry contact, stiffer coatings in EHL tend to reduce the nominal contact radius but increase the maximum contact pressure, and vice versa for more compliant coatings. However, as coating thickness increases, the influence of coatings on film thickness, including the central and the minimum film thicknesses, does not follow a monotonic variation, and therefore, cannot be predicted by any simple film thickness equation. The reason for that is the pressure viscosity effect which tends to counterbalance the effect of coating. The average friction coefficient in lubricant film increases in stiff coating cases but decreases for compliant coating cases. Furthermore, two possible approaches to improving the minimum film thickness thus reducing friction and wear in mixed lubrication are indicated: a thin stiff coating for conventional EHL and a thick compliant coating for soft EHL.

scholarly journals The Effect of Ball Burnishing on Tribological Performance of 42CrMo4 Steel under Dry Sliding Conditions

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2127 ◽  
Author(s):  
Slawomir Swirad ◽  
Pawel Pawlus
Keyword(s):  
Residual Stresses ◽  
Friction And Wear ◽  
Tribological Performance ◽  
Dry Sliding ◽  
Ball Burnishing ◽  
Surface Topographies ◽  
42Crmo4 Steel ◽  
Compressive Residual Stresses ◽  
Wear Tests ◽  
Ball On Disc

Ball burnishing appears to be a very promising approach for reducing surface height, generating compressive residual stresses and increasing hardness. Ball burnishing treatment was carried out using a Haas CNC Vertical Mill Center VF-1 equipped with the Ecoroll burnishing system. After burnishing, surface topographies of machined samples and hardness were measured. Wear tests were conducted using a ball-on-disc tribotester in dry sliding conditions. During tests, the friction force was monitored as a function of time. After tests, wear volumes were determined on the basis of surface texture measurements. Tests revealed that ball burnishing in most cases resulted in minimizing friction and wear of contacting elements.

scholarly journals Grease film thickness measurement in rolling bearing contacts

2020 ◽  
pp. 135065012096127
Author(s):  
Xingnan Zhang ◽  
Romeo Glovnea
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Rolling Bearing ◽  
Thickness Measurement ◽  
Lubricant Film ◽  
Rolling Element Bearings ◽  
Lubricant Film Thickness ◽  
Rolling Bearings ◽  
Rolling Element ◽  
Film Thickness Measurement

Rolling bearings are the second most used machine components. They work in what it is called elastohydrodynamic lubrication regime. The geometry of rolling element bearings makes the direct measurement of the lubricant film thickness a challenging task. Optical interferometry is widely used in laboratory conditions for studying elastohydrodynamic lubrication however it cannot be used directly in rolling element bearings thus the only suitable methods are electrical techniques. Of these, film thickness measurement based on electrical capacitance of the contacts has been used in the past by a number of authors. One of the limitations of the capacitance method, when used in rolling bearings, is that it cannot distinguish between the contacts of every rolling element and raceway on one hand and on the other between the inner and outer ring contacts. In the present study the authors used an original test rig which can measure the film thickness for only one ball and separately for the inner and outer rings of a radial ball bearing. This paper thus shows for the first-time results of the lubricant film thickness, at the inner and outer raceways, in grease lubricated rolling bearings.

scholarly journals Maximizing the Lubricant Film Thickness Between a Rigid Microtextured and a Smooth Deformable Surface in Relative Motion, Using a Soft Elasto-Hydrodynamic Lubrication Model

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Quentin Allen ◽  
Bart Raeymaekers
Keyword(s):  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
Elastohydrodynamic Lubrication ◽  
Hydrodynamic Pressure ◽  
Lubricant Film ◽  
Operating Conditions ◽  
Design Parameters ◽  
Lubricant Film Thickness ◽  
Texture Density ◽  
Film Lubrication

Abstract We design a pattern of microtexture features to increase hydrodynamic pressure and lubricant film thickness in a hard-on-soft bearing. We use a soft elastohydrodynamic lubrication model to evaluate the effect of microtexture design parameters and bearing operating conditions on the resulting lubricant film thickness and find that the maximum lubricant film thickness occurs with a texture density between 10% and 40% and texture aspect ratio between 1% and 14%, depending on the bearing load and operating conditions. We show that these results are similar to those of hydrodynamic textured bearing problems because the lubricant film thickness is almost independent of the stiffness of the bearing surfaces in full-film lubrication.

Interaction of Asperities on Opposing Surfaces in Thin Film, Mixed Elastohydrodynamic Lubrication

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Jian W. Choo ◽  
Andrew V. Olver ◽  
Hugh A. Spikes ◽  
Marie-Laure Dumont ◽  
Eustathios Ioannides
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
Experimental Method ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
New Technique ◽  
Lubricant Film Thickness ◽  
Transverse Ridge ◽  
Film Distribution ◽  
Direct Measurements

A novel experimental method has been developed to investigate how model asperities, on opposing surfaces in an elastohydrodynamic (EHD) contact, interact to influence the lubricant film distribution. This technique allows direct measurements of lubricant film thickness during asperity-asperity collision. A surface having a single transverse ridge asperity was rubbed against a second surface having three different roughness features, a transverse ridge, multiple transverse ridges, and an array of hemispherical bumps to study the resultant micro-EHD films. This work reveals how the film thickness is greatly reduced when the peaks of opposing asperities coincide, and how asperities can combine to cause a larger volume of lubricant to be entrapped at their leading edges. The new technique described shows considerable promise for the study of mixed lubrication.

Surface roughness effects on point contact elastohydrodynamic lubrication in linear rolling guide with fractal surface topographies

2018 ◽  
Vol 70 (4) ◽  
pp. 589-598 ◽  
Author(s):  
Linlin Li ◽  
Jiajun Yang
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Fractal Surface ◽  
Content Type ◽  
Multi Scale ◽  
Surface Topographies ◽  
Scale Characteristics ◽  
Rolling Guide

Purpose The purpose of this paper is to study the effects of surface roughness on the lubrication performances of the linear rolling guide, which provides theoretical guidance for its lubrication design. Design/methodology/approach The two-variable Weierstrass–Mandelbrot function is used to represent the random and multi-scale characteristics of the rough surface topography. The elastohydrodynamic lubrication (EHL) model of contact between the steel ball and raceway is built. The full numerical solutions of the pressure and film thickness are obtained by using the multi-grid technique. Findings The presence of surface roughness can cause the random fluctuations of the pressure and film thickness, and the fluctuations can become more dramatic for the rougher surfaces. It is also found that the film characteristics can be influenced significantly by the working conditions, such as the load, velocity and ambient viscosity of lubricants. Originality/value Characterization of surface topographies regarding EHL problems in the past studies cannot reflect random and multi-scale characteristics. In this paper, the fractal-based method is introduced to analysis of the point-contact micro-EHL. It reveals the mechanism and law of contact lubrication influenced by the fractal surface roughness and enriches the lubrication principle and method of the linear rolling guide.

Pressure Calculation From Experimentally Evaluated Lubricant Thickness Within EHL Contacts

2007 ◽  
Author(s):  
M. Vrbka ◽  
M. Vaverka ◽  
R. Poliscuk ◽  
I. Krupka ◽  
M. Hartl
Keyword(s):  
Film Thickness ◽  
Contact Pressure ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Solution Technique ◽  
Lubricant Film Thickness ◽  
Smooth Contact ◽  
Friction Surfaces

This paper is concerned with elastohydrodynamic lubrication, especially determination of lubricant film thickness and contact pressure within a point contact of friction surfaces of machine parts. A new solution technique for numerical determination of contact pressure is introduced. Direct measurement of contact pressure is very difficult. Hence, input data of lubricant film thickness obtained from the experiment based on colorimetric interferometry are used for calculation of pressure using the inverse elasticity theory. The algorithm is enhanced by convolution in order to increase calculation speed. The approach gives credible results on smooth contact and it is currently extended to enable the study of contact of friction surfaces with dents.

Effect of Wear of Bearing Surfaces on Elastohydrodynamic Lubrication of Metal-on-Metal Hip Implants

2005 ◽  
Vol 219 (5) ◽  
pp. 319-328 ◽  
Author(s):  
F Liu ◽  
Z M Jin ◽  
F Hirt ◽  
C Rieker ◽  
P Roberts ◽  
...  
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Linear Wear ◽  
Wear Depth ◽  
Hip Implants ◽  
Bearing Surface ◽  
Lubricant Film Thickness ◽  
Hip Simulator ◽  
Metal On Metal

The effect of geometry change of the bearing surfaces owing to wear on the elastohydrodynamic lubrication (EHL) of metal-on-metal (MOM) hip bearings has been investigated theoretically in the present study. A particular MOM Metasul™ bearing (Zimmer GmbH) was considered, and was tested in a hip simulator using diluted bovine serum. The geometry of the worn bearing surface was measured using a coordinate measuring machine (CMM) and was modelled theoretically on the assumption of spherical geometries determined from the maximum linear wear depth and the angle of the worn region. Both the CMM measurement and the theoretical calculation were directly incorporated into the elastohydrodynamic lubrication analysis. It was found that the geometry of the original machined bearing surfaces, particularly of the femoral head with its out-of-roundness, could lead to a large reduction in the predicted lubricant film thickness and an increase in pressure. However, these non-spherical deviations can be expected to be smoothed out quickly during the initial running-in period. For a given worn bearing surface, the predicted lubricant film thickness and pressure distribution, based on CMM measurement, were found to be in good overall agreement with those obtained with the theoretical model based on the maximum linear wear depth and the angle of the worn region. The gradual increase in linear wear during the running-in period resulted in an improvement in the conformity and consequently an increase in the predicted lubricant film thickness and a decrease in the pressure. For the Metasul™ bearing tested in an AMTI hip simulator, a maximum total linear wear depth of approximately 13 μm was measured after 1 million cycles and remained unchanged up to 5 million cycles. This resulted in a threefold increase in the predicted average lubricant film thickness. Consequently, it was possible for the Metasul™ bearing to achieve a fluid film lubrication regime during this period, and this was consistent with the minimal wear observed between 1 and 5 million cycles. However, under adverse in vivo conditions associated with start-up and stopping and depleted lubrication, wear of the bearing surfaces can still occur. An increase in the wear depth beyond a certain limit was shown to lead to the constriction of the lubricant film around the edge of the contact conjunction and consequently to a decrease in the lubricant film thickness. Continuous cycles of a running-in wear period followed by a steady state wear period may be inevitable in MOM hip implants. This highlights the importance of minimizing the wear in these devices during the initial running-in period, particularly from design and manufacturing points of view.

Elastohydrodynamic Lubrication of Heavily Loaded Circular Contacts

1989 ◽  
Vol 203 (2) ◽  
pp. 133-148 ◽  
Author(s):  
C C Kweh ◽  
H P Evans ◽  
R W Snidle
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Engineering Practice ◽  
Experimental Measurements ◽  
Lubricant Film Thickness ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Steel Surfaces ◽  
Maximum Contact ◽  
Contact Pressures

The paper is concerned with theoretical analysis and experimental measurement of lubricant film thickness in heavily loaded elastohydrodynamic contacts in which the area of elastic deformation is approximately circular. The inverse elastohydrodynamic technique for numerical analysis of contacts of this type described by Evans and Snidle(9) has been used to produce solutions covering a wide range of conditions representative of engineering practice. Detailed solutions for film thickness and pressure have been obtained for conditions giving rise to maximum contact pressures of up to 4.1 GPa with steel surfaces and a mineral oil lubricant. On the basis of these results charts for film thickness have been constructed using the non-dimensional groups proposed by Moes and Bosma(12). Experimental measurements of film thickness have been made using the optical interferometry technique. The conditions used in the experiments have been numerically analysed to provide a direct comparison between theory and experiment. The comparison shows excellent agreement between the theoretical predictions and corresponding experimental measurements.

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