Effect of Surface Topography on Mixed Lubrication Film Under Transient Conditions

2009 ◽  
Author(s):  
Ivan Krupka ◽  
Martin Hartl ◽  
Petr Svoboda
Keyword(s):  
Surface Topography ◽  
Film Formation ◽  
Surface Damage ◽  
Mixed Lubrication ◽  
Real Surface ◽  
Transient Conditions ◽  
Lubrication Film ◽  
Lubricated Contacts ◽  
Start Up ◽  
Ball Surface

Surface topography plays an important role in the efficiency of lubricated contacts formed between highly loaded machine parts. Gears, rolling bearings, cam and followers etc. subjected to high loads and/or slow speeds are operated under mixed lubrication when lubrication film is not able to completely separate rubbing surfaces. Such an effect becomes even more serious under transient conditions that bring the risk of the surface damage because of asperities interactions. This paper focuses on the effects of both artificially produced and real roughness features on mixed lubrication film formation during start up motion of non-conformal contacts operated under rolling/sliding conditions. The observation of the effects of surface dents artificially produced on the ball surface helped to understand better the behavior of real surface topography. It was found that the presence of shallow surface features can help to separate mixed lubricated rubbing surfaces more efficiently than it could be suggested from the results obtained with smooth surfaces.

scholarly journals EXPERIMENTAL INVESTIGATION OF LUBRICATION FILM FORMATION AT START-UP OF SMOOTH SURFACES

2015 ◽  
Vol 2015 (04) ◽  
pp. 825-828 ◽  
Author(s):  
Petr Svoboda ◽  
David Kostal ◽  
Ivan Krupka ◽  
Martin Hartl
Keyword(s):  
Experimental Investigation ◽  
Film Formation ◽  
Smooth Surfaces ◽  
Lubrication Film ◽  
Start Up

scholarly journals The Influence of Surface Texturing on the Frictional Behaviour of Parallel Sliding Lubricated Surfaces under Conditions of Mixed Lubrication

Lubricants ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 91 ◽  
Author(s):  
Dariush Bijani ◽  
Elena L. Deladi ◽  
Aydar Akchurin ◽  
Matthijn B. de Rooij ◽  
Dirk J. Schipper
Keyword(s):  
Coefficient Of Friction ◽  
Film Formation ◽  
Surface Texturing ◽  
Industrial Applications ◽  
Mixed Lubrication ◽  
Tribological Behaviour ◽  
Surface Geometry ◽  
Lubricated Contacts ◽  
The Coefficient Of Friction ◽  
Frictional Behaviour

In many industrial applications, a modification of the surface geometry can enhance the tribological behaviour of lubricated sliding contacts. In this paper, the effect of surface texturing on the coefficient of friction in parallel sliding lubricated surfaces is investigated. It is shown that surface texturing can improve film formation and, as a result, the load-carrying capacity as well as a reduction in the coefficient of friction. With the numerical model developed, and by considering cavitation, the effects of shape, depth, size, and the textured area fraction on the frictional behaviour of parallel sliding lubricated contacts under conditions of mixed lubrication is studied. In this article it is shown that the surface texturing can have a beneficial effect, in order to decrease friction.

Surface Texturing Effect, Characterization and Optimization for Boundary and Mixed Lubrication

2011 ◽  
Author(s):  
B. Podgornik ◽  
M. Sedlacˇek
Keyword(s):  
Surface Topography ◽  
Research Work ◽  
Surface Texturing ◽  
Considerable Change ◽  
Mixed Lubrication ◽  
Design Parameters ◽  
Textured Surfaces ◽  
Tribological Behaviour ◽  
Cavity Depth ◽  
Lubricated Contacts

Under boundary and mixed lubrication surface roughness and topography have significant influence on the tribological behaviour of contact surfaces, where even a small change in surface topography can lead to a considerable change in tribological behaviour. In recent years an effort for better controlling friction and wear has been focused also on the surface topography modification, especially on surface texturing. The aim of the present research work was to investigate the possibility of using roughness parameters kurtosis and skewness as design parameters for optimizing texturing pattern in boundary and mixed lubricated contacts. Results of the investigation performed on groove and dimple textured surfaces under low load low sliding speed conditions confirm correlation between kurtosis and skewness parameters and coefficient of friction. For textured surfaces increase in kurtosis and more negative skewness, obtained by reducing cavity size, increasing cavity depth and decreasing texturing density were found to yield lower friction. Furthermore, kurtosis and skewness were recognized as suitable parameters for textured surfaces optimization. Through virtual texturing effect of different texturing parameters on kurtosis and skewness parameters can be identified and then optimized to result in reduced friction under boundary and mixed lubrication.

Bearing Performance Limits With Grease Lubrication

2005 ◽  
Author(s):  
P. M. Cann ◽  
A. A. Lubrecht
Keyword(s):  
Surface Damage ◽  
Design Parameters ◽  
Performance Limits ◽  
Grease Lubrication ◽  
Lubricated Contacts ◽  
System A ◽  
Operating Limits ◽  
Bearing Design ◽  
Cage Effects ◽  
Efficient Mechanisms

This paper has examined the influence of bearing design and operation in controlling lubricant supply to the contact zone. Grease lubricated contacts are liable to starvation and as a result the film thickness is reduced, this can result in surface damage or premature bearing failure. It is of obvious importance to know when starvation occurs and the effect of grease type, bearing design and operation on lubrication replenishment. The aim therefore is to develop a starvation parameter capable of predicting the operating limits for a particular bearing/grease system. A number of bearing design parameters are examined in the paper, these include cage design, ball spin and bearing size. Ball spin and cage effects can be efficient mechanisms for maintaining the lubricant supply to the track. Increased bearing size, line contact geometries and high load result in reduced lubricant replenishment of the contact. Using this analysis it will be possible to establish operating limits for families of bearings.

scholarly journals On the Two-Scale Modelling of Elastohydrodynamic Lubrication in Tilted-Pad Bearings

Lubricants ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 78 ◽  
Author(s):  
Gregory de Boer ◽  
Andreas Almqvist
Keyword(s):  
Surface Topography ◽  
Load Capacity ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Multiscale Methods ◽  
Operating Conditions ◽  
Real Surface ◽  
Micro Scale ◽  
Macro Scale ◽  
Heterogeneous Multiscale

A two-scale method for modelling the Elastohydrodynamic Lubrication (EHL) of tilted-pad bearings is derived and a range of solutions are presented. The method is developed from previous publications and is based on the Heterogeneous Multiscale Methods (HMM). It facilitates, by means of homogenization, incorporating the effects of surface topography in the analysis of tilted-pad bearings. New to this article is the investigation of three-dimensional bearings, including the effects of both ideal and real surface topographies, micro-cavitation, and the metamodeling procedure used in coupling the problem scales. Solutions for smooth bearing surfaces, and under pure hydrodynamic operating conditions, obtained with the present two-scale EHL model, demonstrate equivalence to those obtained from well-established homogenization methods. Solutions obtained for elastohydrodynamic operating conditions, show a dependency of the solution to the pad thickness and load capacity of the bearing. More precisely, the response for the real surface topography was found to be stiffer in comparison to the ideal. Micro-scale results demonstrate periodicity of the flow and surface topography and this is consistent with the requirements of the HMM. The means of selecting micro-scale simulations based on intermediate macro-scale solutions, in the metamodeling approach, was developed for larger dimensionality and subsequent calibration. An analysis of the present metamodeling approach indicates improved performance in comparison to previous studies.

scholarly journals An Assessment of Quantitative Predictions of Deterministic Mixed Lubrication Solvers

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Yuechang Wang ◽  
Abdel Dorgham ◽  
Ying Liu ◽  
Chun Wang ◽  
Mark C. T. Wilson ◽  
...  
Keyword(s):  
Reynolds Equation ◽  
Thickness Distribution ◽  
Computation Time ◽  
Simulation Method ◽  
Coefficient Matrix ◽  
Mixed Lubrication ◽  
Contact Ratio ◽  
Lubricated Contacts ◽  
Discretization Schemes ◽  
Parametric Studies

Abstract The ability to simulate mixed lubrication problems has greatly improved, especially in concentrated lubricated contacts. A mixed lubrication simulation method was developed by utilizing the semi-system approach which has been proven to be highly useful for improving stability and robustness of mixed lubrication simulations. Then different variants of the model were developed by varying the discretization schemes used to treat the Couette flow terms in the Reynolds equation, varying the evaluation of density derivatives and varying the contribution of terms in the coefficient matrix. The resulting pressure distribution, film thickness distribution, lambda ratio, contact ratio, and the computation time were compared and found to be strongly influenced by the choice of solution scheme. This indicates that the output from mixed lubrication solvers can be readily used for qualitative and parametric studies, but care should be taken when making quantitative predictions.

Mixed Lubrication Model for Cold Rolling Considering the Inlet and Deformation Zones

2012 ◽  
Author(s):  
Martin Bergmann ◽  
Klaus Zeman ◽  
Alexander Kainz ◽  
Konrad Krimpelstätter ◽  
Dieter Paesold ◽  
...  
Keyword(s):  
Cold Rolling ◽  
Film Formation ◽  
Mixed Lubrication ◽  
Bulk Deformation ◽  
Metallic Surfaces ◽  
Hydrodynamic Friction ◽  
Plastic Strip ◽  
Coupled Equations ◽  
Inlet Zone ◽  
Raphson Method

A mixed lubrication model for cold rolling was developed by separating, according to common concepts, the domain of calculation into two zones: the inlet zone and the zone of plastic strip bulk deformation. The analysis of the inlet zone mainly focuses on film formation from different lubricants based on the evolution of layers consisting of neat oil on the metallic surfaces. In the zone of plastic strip bulk deformation, contributions of boundary and hydrodynamic friction are modeled incorporating longitudinal and transversal roughness components. Lubricant pressure, which is influenced by the geometry of these roughness structures, is governed by hydrodynamic mechanisms. Additionally, lubricant temperature in the roll bite is predicted by an integrated thermodynamics sub-model. While coupling between the inlet and plastic deformation zones is performed iteratively, the highly non-linear and coupled equations for the latter zone are solved simultaneously by applying a variant of the well-known damped Newton-Raphson method.

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