Point Contact EHL Based on Optically Measured Three-Dimensional Rough Surfaces

1997 ◽  
Vol 119 (3) ◽  
pp. 375-384 ◽  
Author(s):  
Dong Zhu ◽  
Xiaolan Ai
Keyword(s):  
Rough Surface ◽  
Rough Surfaces ◽  
Three Dimensional ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Peak Height ◽  
Machining Process ◽  
Maximum Pressure ◽  
Pressure Peak ◽  
Surface Profiles

This paper presents a numerical solution for the elastohydrodynamic lubrication in point contacts, using optically measured three-dimensional rough surface profiles as input data. The multi-grid computer program originally developed by Ai and Cheng (1993, 1994) is modified, so that both contacting surfaces can be three-dimensional measured rough surfaces moving at different velocities. Many different engineering surfaces are measured and analyzed in the present study, demonstrating that the numerical analysis is practical for real surfaces of bearings, cams, gears and other components, as long as a significant EHL film still exists. In addition, discussions are given in this paper for the effects of three-dimensional rough surface topography, which is related to machining process. It appears that, for the circular contact cases analyzed, surface roughness texture and orientation do not have a significant effect on the average film thickness, but they do affect the maximum pressure peak height and asperity deformation in the contact zone considerably.

Reduced Rough-Surface Parametrization for Use With the Discrete-Element Model

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Stephen T. McClain ◽  
Jason M. Brown
Keyword(s):  
Heat Transfer ◽  
Rough Surface ◽  
Surface Characterization ◽  
Rough Surfaces ◽  
Roughness Element ◽  
Three Dimensional ◽  
Element Model ◽  
Discrete Element ◽  
Diameter Distribution ◽  
Discrete Element Model

The discrete-element model for flows over rough surfaces was recently modified to predict drag and heat transfer for flow over randomly rough surfaces. However, the current form of the discrete-element model requires a blockage fraction and a roughness-element diameter distribution as a function of height to predict the drag and heat transfer of flow over a randomly rough surface. The requirement for a roughness-element diameter distribution at each height from the reference elevation has hindered the usefulness of the discrete-element model and inhibited its incorporation into a computational fluid dynamics (CFD) solver. To incorporate the discrete-element model into a CFD solver and to enable the discrete-element model to become a more useful engineering tool, the randomly rough surface characterization must be simplified. Methods for determining characteristic diameters for drag and heat transfer using complete three-dimensional surface measurements are presented. Drag and heat transfer predictions made using the model simplifications are compared to predictions made using the complete surface characterization and to experimental measurements for two randomly rough surfaces. Methods to use statistical surface information, as opposed to the complete three-dimensional surface measurements, to evaluate the characteristic dimensions of the roughness are also explored.

Reduced Rough-Surface Parameterization for Use With the Discrete-Element Model

2007 ◽  
Author(s):  
Stephen T. McClain ◽  
Jason M. Brown
Keyword(s):  
Heat Transfer ◽  
Rough Surface ◽  
Surface Characterization ◽  
Rough Surfaces ◽  
Roughness Element ◽  
Three Dimensional ◽  
Element Model ◽  
Discrete Element ◽  
Diameter Distribution ◽  
Discrete Element Model

The discrete-element model for flows over rough surfaces was recently modified to predict drag and heat transfer for flow over randomly-rough surfaces. However, the current form of the discrete-element model requires a blockage fraction and a roughness-element diameter distribution as a function of height to predict the drag and heat transfer of flow over a randomly-rough surface. The requirement for a roughness element-diameter distribution at each height from the reference elevation has hindered the usefulness of the discrete-element model and inhibited its incorporation into a computational fluid dynamics (CFD) solver. To incorporate the discrete-element model into a CFD solver and to enable the discrete-element model to become a more useful engineering tool, the randomly-rough surface characterization must be simplified. Methods for determining characteristic diameters for drag and heat transfer using complete three-dimensional surface measurements are presented. Drag and heat transfer predictions made using the model simplifications are compared to predictions made using the complete surface characterization and to experimental measurements for two randomly-rough surfaces. Methods to use statistical surface information, as opposed to the complete three-dimensional surface measurements, to evaluate the characteristic dimensions of the roughness are also explored.

Plasto-Elastohydrodynamic Lubrication in Point Contacts for Surfaces With Three-Dimensional Sinusoidal Waviness and Real Machined Roughness

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Tao He ◽  
Ning Ren ◽  
Dong Zhu ◽  
Jiaxu Wang
Keyword(s):  
Plastic Deformation ◽  
Rough Surface ◽  
Mechanical Design ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Von Mises Stress ◽  
Asperity Contacts ◽  
Lubrication Characteristics ◽  
Von Mises

Efficiency and durability are among the top concerns in mechanical design to minimize environmental impact and conserve natural resources while fulfilling performance requirements. Today mechanical systems are more compact, lightweight, and transmit more power than ever before, which imposes great challenges to designers. Under the circumstances, some simplified analyses may no longer be satisfactory, and in-depth studies on mixed lubrication characteristics, taking into account the effects of 3D surface roughness and possible plastic deformation, are certainly needed. In this paper, the recently developed plasto-elastohydrodynamic lubrication (PEHL) model is employed, and numerous cases with both sinusoidal waviness and real machined roughness are analyzed. It is observed that plastic deformation may occur due to localized high pressure peaks caused by the rough surface asperity contacts, even though the external load is still considerably below the critical load determined at the onset of plastic deformation in the corresponding smooth surface contact. It is also found, based on a series of cases analyzed, that the roughness height, wavelength, material hardening property, and operating conditions may all have significant influences on the PEHL performance, subsurface von Mises stress field, residual stresses, and plastic strains. Generally, the presence of plastic deformation may significantly reduce some of the pressure spikes and peak values of subsurface stresses and make the load support more evenly distributed among all the rough surface asperities in contact.

scholarly journals Transient elastohydrodynamic point contact analysis using a new coupled differential deflection method Part 2: Results

2003 ◽  
Vol 217 (4) ◽  
pp. 305-322 ◽  
Author(s):  
M. J. A. Holmes ◽  
H. P. Evans ◽  
T. G. Hughes ◽  
R. W. Snidle
Keyword(s):  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Contact Analysis ◽  
Asperity Contact ◽  
Lubrication Equation ◽  
Analysis Technique ◽  
Elliptical Contact ◽  
Surface Profiles ◽  
Film Thinning ◽  
Film Collapse

The paper presents results obtained using a transient analysis technique for point contact elastohydrodynamic lubrication (EHL) problems based on a formulation that effectively couples the elastic and hydrodynamic equations. Results are presented for transverse ground surfaces in an elliptical contact that show severe film thinning at the transverse limits of the contact area. This thinning is caused by transverse (side) leakage of the lubricant from the contact in the remaining deep valley features. Comparison is made between the elliptical contact results on the entrainment centreline and the equivalent line contact analysis. This confirms the importance of edge effects as a likely cause of film collapse and scuffing failure. The surface profiles used in the analysis are taken from test discs used in scuffing experiments and from gears used in micropitting tests. Side leakage is found to be sufficiently severe to cause microasperity contact in the numerical examples presented. This contact mainly occurs close to the edges of the corresponding Hertzian area and correlates in position with the location at which scuffing is found to first occur in the earlier experiments. Comparisons are made with other numerical results for point contact configurations with sinusoidally varying surface features obtained by Zhu (2000) and considerable differences are seen in the calculated extent of asperity contact. The differences are thought to be due to the simplified treatment of the lubrication equation adopted by Zhu.

scholarly journals Principles of discrete-event modeling of physical processes during technical surfaces contact interaction

2021 ◽  
Vol 2094 (2) ◽  
pp. 022019
Author(s):  
A A Rachishkin
Keyword(s):  
Rough Surface ◽  
Data Storage ◽  
Contact Interaction ◽  
Rough Surfaces ◽  
Discrete Event ◽  
Three Dimensional ◽  
Advantages And Disadvantages ◽  
Event Modeling ◽  
Physical Experiments ◽  
Rough Surface Contact

Abstract The article discusses the advantages and disadvantages of computer modeling used in physical experiments field on rough surfaces contact interaction. Methods for constructing the software model are given. The description of a single irregularity in the form of revolution ellipsoid segment is presented and an algorithm for rough surface three-dimensional modeling based on it is proposed. Some assumptions made for generating surface topography do not significantly affect the simulation validity. Taking into account the individual parameters of each irregularity and the algorithm for their distribution make it possible to create inhomogeneous rough surfaces that are close to real ones relative to the physical experiments being carried out. The general principles of the software architecture and the data storage model of discrete-event modeling system of rough surface contact interaction are described. The developed software can be used for modeling the rough surfaces contact interaction, for researching of tribo-interface units’ parameters, predicting the characteristics of frictional interaction and tribotechnical tests computer simulation.

Calculation of Gear Meshing Stiffness Considering Lubrication

2019 ◽  
Vol 142 (3) ◽  
Author(s):  
Gong Cheng ◽  
Ke Xiao ◽  
Jiaxu Wang ◽  
Wei Pu ◽  
Yanfeng Han
Keyword(s):  
Rough Surface ◽  
Calculation Method ◽  
Contact Stiffness ◽  
Dynamic Performance ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Mixed Lubrication ◽  
Meshing Stiffness ◽  
Roughness Amplitude ◽  
Meshing Process

Abstract Gear meshing stiffness is the key parameter to study the gear dynamic performance. However, the study on the calculation of gear meshing stiffness considering lubrication, especially mixed lubrication, is still insufficient. Based on the three-dimensional linear contact mixed elastohydrodynamic lubrication model and the contact stiffness calculation method of rough surface, a method for calculating the gear meshing stiffness under mixed lubrication is proposed in this paper. According to the proposed calculation method, the effects of speed, external load, and roughness amplitude on gear meshing stiffness are further explored. The method can take into account the real rough surface topography and lubrication in the meshing process, so it may be more advantageous than the conventional method to some extent.

Predicting Skin Friction for Turbulent Flow Over Randomly-Rough Surfaces Using the Discrete-Element Method: Part I — Surface Characterization

2003 ◽  
Author(s):  
Stephen T. McClain ◽  
B. Keith Hodge ◽  
Jeffrey P. Bons
Keyword(s):  
Discrete Element Method ◽  
Turbulent Flow ◽  
Skin Friction ◽  
Rough Surface ◽  
Rough Surfaces ◽  
Three Dimensional ◽  
Discrete Element ◽  
Randomly Rough Surfaces ◽  
Randomly Rough Surface ◽  
Element Method

The discrete-element method for predicting skin friction for turbulent flow over rough surfaces considers the drag on the surface to result from the combination of the skin friction on the flat part of the surface and the drag on the individual roughness elements that protrude into the boundary layer. To adequately analyze flow over a randomly-rough surface using the discrete-element method, the blockage fraction and the roughness element cross-section area distributions as a function of height must be measured. Taylor, in 1983, proposed a method for evaluating the blockage fraction and cross-sectional areas distributions, assuming circular cross sections, using two-dimensional profilometer traces. With the advent of three-dimensional profilometery, the geometry of a randomly-rough surface can be completely characterized. Two randomly-rough surfaces found on high-hour gas-turbine blades were characterized using a Taylor-Hobson Form Talysurf Series 2 profilometer. A method for using the three-dimensional profilometer output to determine the geometry input required in the discrete-element method for randomly-rough surfaces is presented in this paper, Part 1. Part 2 extends the validation of the discrete-element roughness method to closely-packed, randomly-rough surfaces. The procedure for handling randomly-rough surfaces is described, and the characterizations for the surfaces used to validate the discrete element model in Part 2 are presented.

A Three-Dimensional Thermomechanical Model of Contact Between Non-Conforming Rough Surfaces

2000 ◽  
Vol 123 (1) ◽  
pp. 17-26 ◽  
Author(s):  
Shuangbiao Liu ◽  
Qian Wang
Keyword(s):  
Rough Surfaces ◽  
Frictional Heating ◽  
Three Dimensional ◽  
Point Contact ◽  
Numerical Algorithms ◽  
Normal Surface ◽  
Thermomechanical Model ◽  
Influence Coefficients ◽  
Surface Displacements ◽  
Thermomechanical Contact

A necessary step in understanding failure problems of tribological elements is to investigate the contact performance of rough surfaces subjected to frictional heating. It is essential that the interfacial variables are obtained through solving the interactive thermomechanical contact problem. This paper studies the three dimensional thermomechanical contact of non-conforming rough surfaces, the model of which includes the normal surface displacements caused by the contact pressure, frictional shear, and frictional heating. Influence coefficients and frequency response functions for elastic and thermoelastic displacements, as well as those for temperature rises, are investigated for model construction. In order to develop an accurate and efficient solver, the numerical algorithms with the discrete convolution and fast Fourier transform techniques and the single-loop conjugated gradient method are used. The model modules are numerically verified and the thermomechanical performance of the rough surfaces in a point contact is studied.

Three-Dimensional Temperature Distribution in EHD Lubrication: Part II—Point Contact and Numerical Formulation

1993 ◽  
Vol 115 (1) ◽  
pp. 36-45 ◽  
Author(s):  
Kyung-Hoon Kim ◽  
Farshid Sadeghi
Keyword(s):  
Temperature Distribution ◽  
Film Thickness ◽  
Numerical Study ◽  
Control Volume ◽  
Three Dimensional ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Numerical Formulation ◽  
Energy Equations

A numerical study of Newtonian thermal elastohydrodynamic lubrication (EHD) of rolling/sliding point contacts has been conducted. The two-dimensional Reynolds, elasticity and the three-dimensional energy equations were solved simultaneously to obtain the pressure, film thickness and temperature distribution within the lubricant film. The control volume approach was employed to discretize the differential equations and the multi-level multi-grid technique was used to simultaneously solve them. The discretized equations, as well as the nonorthogonal coordinate transformation used for the solution of the energy equation, are described. The pressure, film thickness and the temperature distributions, within the lubricant film at different loads, slip conditions and ellipticity parameters are presented.

Sliding Contact Analysis of Layered Elastic/Plastic Solids With Rough Surfaces

2001 ◽  
Vol 124 (1) ◽  
pp. 46-61 ◽  
Author(s):  
Wei Peng ◽  
Bharat Bhushan
Keyword(s):  
Surface Deformation ◽  
Rough Surfaces ◽  
Normal Load ◽  
Three Dimensional ◽  
Sliding Contact ◽  
Fast Fourier Transformation ◽  
Maximum Pressure ◽  
Asperity Contact ◽  
Elastic Plastic ◽  
Von Mises

A three-dimensional numerical model is presented to investigate the quasi-static sliding contact behavior of layered elastic/plastic solids with rough surfaces. The model is applicable for both single-asperity contact and multiple-asperity contacts. The surface deformation is obtained based on a variational principle. The surface and subsurface stresses in the layer and the substrate are determined with a Fast Fourier transformation (FFT) based scheme and von Mises and principal tensile stresses are computed accordingly. Contact statistics, such as fractional contact area, maximum pressure/E2 and relative meniscus force are predicted. The results are used to investigate the effect of the contact statistics on friction, stiction, and wear problems such as debris generation, brittle failure, and delamination of layered media. Optimum layer parameters are identified. It allows the specification of layer properties, according to the contact statistics, to reduce friction, stiction, and wear of materials. A normalization procedure is presented to apply the results on various combinations of surface roughness, material properties, and normal load.

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