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Dissertations / Theses on the topic 'Elastohydrodynamical lubrication'
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Brhlík, Rostislav. "MKP simulace elastohydrodynamického kontaktu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231788.
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This diploma thesis deals with an application of the finite element method on elastohydrodynamic (EHD) lubrication simulations. Commercially available software COMSOL is used for the computation, while two different modules for modeling EHD lubrication are described in a detail. Firstly, a new approach using the module Thin-Film Flow is developed, considering and describing some limitations of this approach. This is the very first published work dealing complex with EHD simulation in Thin-Film Flow module. In the second part of the thesis, there was created a model of line contact using the module for the introduction of partial differential equations (PDE). The model is partially verified with available works for different values of the input parameters. Subsequently, the velocity effect of the contact surfaces on the pressure and the lubricant thickness in contact is analyzed. Finally, the last part is examines the influence of the values of some parameters on the final value of the contact pressure and the lubricant thickness, as well as on numerical stability of the entire model.
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Roberts, H. "Elastohydrodynamic lubrication." Thesis, University of Liverpool, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356293.
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Richmond, J. W. "Traction in elastohydrodynamic lubrication." Thesis, University of Reading, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356067.
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Björling, Marcus. "Friction in Elastohydrodynamic Lubrication." Doctoral thesis, Luleå tekniska universitet, Maskinelement, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17478.
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Today, with increasing demands on industry to reduce energy consumption and emissions, the strive to increase the efficiency of machine components is maybe bigger than ever. This PhD thesis focus on friction in elastohydrodynamic lubrication (EHL), found in, among others, gears, bearings and cam followers. Friction in such contacts is governed by a complex interaction of material, surface and lubricant parameters as well as operating conditions. In this work, experimental studies have been conducted that show how friction varies over a wide range of running conditions when changing parameters like lubricant viscosity, base oil type, surface roughness and lubricant temperature. These measurements have also been used to predict the friction behaviour in a real gear application. Numerical modeling of elastohydrodynamic (EHD) friction and film thickness are important for increased understanding of the field of EHL. Due to the high pressure and shear normally found in EHD contacts it is crucial that appropriate rheological models are used. An investigation has been carried out in order to assess the friction prediction capabilities of some of the most well founded rheological models. A numerical model was used to predict friction coefficients through the use of lubricant transport properties. Experiments were then performed that matches the predicted results rather well, and the deviations are discussed. The numerical model in combination with experimental measurements are used to investigate the friction reducing effect of diamond like carbon (DLC) coatings in EHL. A new mechanism of friction reduction through thermal insulation is proposed as an alternative to the current hypothesis of solid-liquid slip. These findings opens up for new families of coatings where thermal properties are in focus that may be both cheaper, and more effective in reducing friction in certain applications than DLC coatings of today.Godkänd; 2014; 20140825 (marbjo); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Marcus Björling Ämne: Maskinelement/Machine Elements Avhandling: Friction in Elastohydrodynamic Lubrication Opponent: Professor H P Evans, Cardiff School of Engineering, Cardiff University, Cardiff, Wales, UK Ordförande: Professor Roland Larsson, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Torsdag den 2 oktober 2014, kl 09.00 Plats: E231, Luleå tekniska universitet
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Hartinger, Markus. "CFD modelling of elastohydrodynamic lubrication." Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444143.
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Usually elastohydrodynamic lubrication (EHL) is modelled using the Reynolds equation for the fluid flow and the elastic deformation is calculated following the Hertzian contact theory. In this thesis a CFD approach for modelling EHL is established. The full Navier-Stokes equations are used which enables the entire flow domain to be modelled and which can resolve all gradients inside the contact. Liquid properties are introduced where the viscosity is piezo-viscous, shear-thinning and temperature dependent and where the density is a function of pressure. The phenomenon of cavitation is taken into account by two homogeneous equilibrium cavitation models which are compared with each other. For one cavitation model an energy equation is developed which considers the effects of heat conduction and convection, viscous heating and the heat of evaporation. The Hertzian contact theory is implemented and parallelised within the CFD method and validated against analytical solutions. Then, the cavitation models and the Hertzian contact theory are occupied together in a forward iterative manner. The developed method is applied to glass-on-steel and metal-on-metal line contacts and isothermal results are compared to the Reynolds theory. Very good agreement was found with the Reynolds theory in most cases. For high viscosity, high velocity and rolling conditions small differences to the Reynolds theory were found. The influence of temperature is studied for a series of test cases and the results are compared to their isothermal counterparts. All thermal calculations under sliding conditions developed a temperature-induced shear-band which is closer towards the slower, thus hotter, surface. The thermal, high viscosity calculations under sliding conditions showed significant pressure variation across the film thickness due to very large viscosity gradients. The impact of temperature on the friction force is very significant. Results of a three-dimensional, isothermal point contact are shown to demonstrate the feasibility of such calculations. The developed method is capable of giving new insights into the physics of elastohydrodynamic lubrication, especially in cases where the usual assumptions of the Reynolds theory break down.
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Shieh, Jinn-An. "Film collapse in elastohydrodynamic lubrication /." The Ohio State University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487760357820679.
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Košťál, David. "Studium utváření mazacích filmů za podmínek nedostatečného zásobování kontaktu mazivem." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229431.
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The purpose of this thesis is to reveal production mechanisms of lubrication films between non-conformal surfaces in situations, when is not possible to designate lubrication regime as fully flooded elastohydrodynamic contact. Under certain conditions of lubrication volume, rolling speeds, temperatures, lubrication properties or loads could lubrication film decrease under values determined by fully flooded formulas. This regime is designated as starvation at it includes risk of increased wear. In this thesis the methodology and the new simulator of starving contact are described. Obtained film thickness results are compared with existing numerical models.
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Kweh, C. C. "Elastohydrodynamic lubrication with fire-resistant fluids." Thesis, Bucks New University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375126.
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Elsharkawy, Abdallah A. "Elastohydrodynamic lubrication of multilayered elastic solids /." The Ohio State University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487779914825588.
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Larsson, Roland. "Elastohydrodynamic lubrication under non-steady conditions." Doctoral thesis, Luleå tekniska universitet, Maskinelement, 1996. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18564.
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The six papers presented in this thesis consider the effects on elastohydrodynamic lubrication (ehl) of non-steady conditions. The vast majority of ehl investigations, both experiemental and theoretical, utilise steady state conditions, i.e. constant load, velocity, geometry and temperature. The lubricant is, however, in conditions that are far from those of steady state. Many components operate with varying load, velocity and geometry. Some examples are gears, rolling element bearings, cams and follower mechanisms and reciprocating seals. To predict the operation of these components it is necessary to consider the transient effects. The theory of elastohydrodynamic lubrication under non-steady conditions is presented in this thesis and applied to some practical cases. Papers A and B deal with the simulation of the lubrication in the contact between an impacting ball and a lubricated surface. These investigations give understanding of lubrication under impact loading and also fundamental understanding of the dynamics of an ehl contact. Paper C is an experimental investigation of the impacting ball problem. The deformation of the surfaces in the contact region is studied for different combinations of lubricant viscosities and impact velocities. Paper D and E deal with the breakdown mechanisms of a lubricant film. It is shown that lubricant film failure occurs at high sliding velocities if the load is non-stationary. This contradicts elastohydrodynamic theory since increasing sliding velocity implies increasing entrainment of lubricant and thus thicker lubricant film and less risk for failure. It is, however, shown in Paper E that starvation can be the reason why film failure occurs even if the conjunction is lubricated by a thick layer of lubricant. Paper F is a transient simulation of a meshing involute spur gear. Film thickness, pressure, friction and subsurface stresses are computed at different positions along the line of action. Two different sets of lubricant properties are used, the first oneGodkänd; 1996; 20070219 (rola)
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Goodyer, Christopher Edward. "Adaptive numerical methods for elastohydrodynamic lubrication." Thesis, University of Leeds, 2001. http://etheses.whiterose.ac.uk/1294/.
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Numerical solutions to elastohydrodynamic lubrication problems have been computed for the last half century. Over the past decade multilevel techniques have been successfully applied in several solvers and significant speed-ups achieved. The aim of numerical research in this field is to develop techniques in order to calculate accurate solutions to demanding industrial problems as efficiently as possible. In this work the numerical solver, previously developed by Nurgat, is examined. Despite being successful in achieving converged results on a single grid, there were some unresolved issues relating to the multigrid performance. These problems are explained and the necessary modifications to the method used are detailed. There is much current interest in obtaining results to transient elastohydrodynamic lubrication problems. These are examined in detail and the justification for the methods used are discussed. Example results for industrially relevant cases, such as variation of lubricant entrainment, oscillation of the applied load and the presence of surface defects are considered. In many other fields, adaptation in both space and time is used to increase performance and accuracy. However, these techniques are not currently used for elastohydrodynamic lubrication problems. It is shown that they can be successfully applied and substantial benefits accrued. A method of variable timestepping has been introduced and results are presented showing that not only is it as accurate as fixed time stepping methods, but that the computational work required to obtain these solutions is significantly reduced. Local error control on each individual timestep is also implemented. Adaptation of the spatial mesh is also developed. By developing a hierarchy of refined meshes within the multigrid structure it is seen how significantly fewer computational points are used in the most expensive numerical calculations. This, in turn, means that the computational time required is reduced. Different criteria for adaptation are explained and results presented showing the relative levels of accuracy and speed-up achieved.
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Hart, Daniel Edward. "Adjoint error estimation for elastohydrodynamic lubrication." Thesis, University of Leeds, 2008. http://etheses.whiterose.ac.uk/1358/.
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In this thesis, adjoint error estimation techniques are applied to complex elastohydrodynamic lubrication (EHL) problems. A functional is introduced, namely the friction, and justification is provided as to why this quantity, and hence its accuracy, is important. An iterative approach has been taken to develop understanding of the mechanisms at work. A series of successively complex cases are proposed, each with adjoint error estimation techniques applied to them. The first step is built up from a model free boundary problem, where the cavitation condition is captured correctly using a sliding mesh. The next problem tackled is a hydrodynamic problem, where non-linear viscosity and density are introduced. Finally, a full EHL line contact problem is introduced, where the surface deforms elastically under pressure. For each case presented, an estimate of a finer mesh friction, calculated from solutions obtained only on a coarse mesh, is corrected according to the adjoint error estimation technique. At each stage, care is taken to ensure that the error estimate is computed accurately when compared against the measured error in the friction. Non-uniform meshes are introduced for the model free boundary problem. These nonuniform meshes are shown to give the same excellent predictions of the error as uniform meshes. Adaptive refinement is undertaken, with the mesh being refined using the adjoint error estimate. Results for this are presented for both the model free-boundary problem and the full EHL problem. This is shown to enable the accurate calculation of friction values using an order of magnitude fewer mesh points than with a uniform mesh. Throughout this thesis, standard numerical techniques for calculating EHL solutions have been used. That is, regular mesh finite difference approximations have been used to discretise the problem, with multigrid used to efficiently solve the equations, and spatial adaptivity added through multigrid patches. The adjoint problems have been solved using standard linear algebra packages.
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Hrdonka, Štěpán. "Simulace mazání bodových kontaktů metodou konečných prvků." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-377883.
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This diploma thesis is concerned with simulation of elastohydrodynamic lubrication of point contacts using the finite element method. The first part of the thesis focuses on the study of the issue and introduces equations for model creation and numerical methods which can be used for EHD calculation. The most suitable solution approach has been chosen from the overview, namely the Full system approach. The software we chose for applying the method was COMSOL Multyphysics. The following part of the thesis deals with model’s creation and gives its elaborate description. We introduce models for calculation of line and point EHD lubrication for newtonian lubricants and, last but not least, we also present a model for calculation of point contact EHD lubrication for non-newtonian lubricants. The next part of the thesis then verifies all the models. That is achieved by comparing the calculated results to results from different papers. The conclusive part of the thesis then examines the matches of acquired results to different prediction relationships and experiments.
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Bakman, Aleksandr Israel. "Elastohydrodynamic simulator." Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/19492.
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Sloetjes, Jan Willem. "Micro-elastohydrodynamic lubrication in concentrated sliding contacts." Enschede : University of Twente [Host], 2006. http://doc.utwente.nl/57640.
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Almqvist, Andreas. "Rough surface elastohydrodynamic lubrication and contact mechanics." Licentiate thesis, Luleå, 2004. http://epubl.luth.se/1402-1757/2004/035.
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Myers, Timothy Gerard. "Chebyshev series method for piezoviscous elastohydrodynamic lubrication." Thesis, University of Leeds, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277479.
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de, Boer Gregory Nicholas. "A two-scale approach to elastohydrodynamic lubrication." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/8318/.
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Derived from the Heterogeneous Multiscale Methods (HMM), a two-scale method is developed in this thesis for the analysis of Elastohydrodynamic Lubrication (EHL) and micro-EHL in tilted-pad bearings with three-dimensional topography. A relationship linking the pressure gradient to mass flow rate is derived and represented in the bearing domain through homogenisation of near-periodic simulations which describe the Fluid Structure Interaction (FSI) of topographical features. This relationship is approximated using Response Surface Methodology (RSM) which allows the scales to be coupled by a Moving Least Squares (MLS) metamodel at a reduced computational effort. For the parameters investigated the influence of compressibility and piezoviscosity was found to be more significant than that of non-Newtonian (shear-thinning) behaviour on textured bearing performance. As the size of topography increased two-scale solutions demonstrated that at constant load the coefficient of friction increased and the minimum film thickness decreased over a range of pad lengths and tilt angles. Through the two-scale method the micro-EHL effect on film thickness was quantified and shown to be at least an order of magnitude or less than that of the total EHL effect. Parameterisation of topography led to an optimisation procedure which aimed to reduce the coefficient of friction in textured bearings as to improve their performance under load. It was shown through this procedure that a transverse topography benefits the performance over a longitudinal one. The best performing topography was found to have a mix of both longitudinal and transverse components, and it was also shown that very different topographies can exhibit similar characteristics. Through the metamodelling process deviation from the smooth surface model was quantified by the constants associated with the MLS approximations.
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Morales, Espejel Guillermo Enrique. "Elastohydrodynamic lubrication of smooth and rough surfaces." Thesis, University of Cambridge, 1993. https://www.repository.cam.ac.uk/handle/1810/260244.
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Different aspects of Elastohydrodynamic Lubrication (EHL) are studied. For smooth surfaces, a novel approach which solves separately the inlet and outlet regions by using the fracture mechanics equations, is proposed to solve EHL line contacts for shape and pressure. For rough surfaces, the full EHL geometry is reduced to an infinitely long contact with known mean film thickness and pressure; so real-roughness steady state analyses are carried out by considering the separate Fourier components of roughness and pressures, transient analysis by applying general finite difference methods. The subsurface stresses under micro-EHL are also calculated and given in form of a probability rather than a specific value and location. Initially, full-geometry EHL line contacts of smooth surfaces are studied. The spike of pressures is assumed to be singular and the idea is to start with an original Hertzian pressure distribution, then the edges of this pressure are truncated and the effects calculated via linear fracture mechanics; after this, the removed pressures are replaced by the converged inlet and outlet pressures, previously obtained by iterating the Reynolds and fracture mechanics equations. It is found that the outlet pressures follow a modified logarithmic function and therefore the exit bump in the shape joins the parallel film zone with a finite value of slope, unlike the Greenwood extension of Grubin's theory. From a set of solutions, the behaviour of the pressure spike as a function of two dimensionless numbers is followed. Comparisons with results from full numerical solutions are shown, giving good agreement. The scheme is later extended to consider compressibility and the Roelands viscosity law. After reducing full EHL geometry, the effects of real and wavy roughness in microEHL of Newtonian and Eyring fluids with or without compressibility are studied. Steady state analyses of real roughness show that only the high frequency components remain after deformation. By linearizing the Reynolds- Eyring equation an analytical solution is obtained and a criterion for the deformation of the roughness in EHL is given; from this, it is shown that the deformation is very much dependent on the ratio λ/ħ, obtaining little deformation for low values of it. Transient analyses of roughness in lubrication are also carried out considering the infinitely long contact. It is found that the transient pressure and film distributions are made of two parts: a) the well known steady state solution, plus b) a complementary function depending only on the modulation of film and pressures from the inlet. It is shown that the conclusions outlined for some authors (e.g. Venner and Lubrecht) about pressures travelling with the velocity of the roughness but shape with the average velocity of the lubricant, are only a particular case of a more general understanding. It is now believed that there is no a real physical damping in the transient shape.
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Shirzadegan, Mohammad. "Elastohydrodynamic Lubrication of Cam and Roller Follower." Licentiate thesis, Luleå tekniska universitet, Maskinelement, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26291.
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Modelling and simulation of friction is a research issue that still requires an extensive amount of input from the scientific community. In a lubricated system, the dissipation of energy is connected to the direct contact between the surfaces, or more precisely the tribofilms, as well as of the shearing of the lubricant film. Elastohydrodynamic lubrication (EHL) is a lubrication regime which is characteristic for contacts found in machine components such as in roller bearings, gears and cam mechanisms. These contacts have in common that they carry load on a very small/concentrated area and exhibit elastic deformations that are much greater than the thickness of the hydrodynamically formed film. There are a vast number of parameters that affect the friction in EHL contacts and it is a challenge to include other than the most basic ones in the model. The most advanced and sophisticated models are very complex with millions of degrees of freedom and are, therefore, not yet feasible to conduct parametric studies with. The extreme conditions associated with EHL, i.e., nm thin films, with phase transition from liquid to solid, GPa pressure, temperature increase with considerable implications on lubricant flow and surface chemistry, etc., makes it even more difficult to model these systems. The shape of the contacting parts further complicates modeling of EHL. More precisely, an EHL contact can geometrically be either of a line, circular, elliptic or truncated contact type. Since the line contact appears between two cylindrical shaped bodies of infinite length, it permits a 2D-model for the flow and there are analytical solutions, in the most elementary cases. The circular and the elliptic contacts more are complicated. The case when the surfaces are fully separated by the lubricant film has, however, been addressed by many researchers, who also have presented numerical predictions validated by experimental data. The finite line contact appears to be the most challenging type, but it is also the only physically reasonable model for EHL contacts where the edge effects cannot be neglected. In this work, both steady state and time dependent, fully deterministic models are utilized and further developed to enable the study edge effects under variable operating conditions in cam and roller follower systems. The numerical investigations were specified so that generic knowledge about friction in these systems would be generated and also to provide validation data for the development of a semi-analytical, low degree freedom model, for rapid estimation of friction. The main objective was to design such a low degree of freedom model so that it can be employed in a multibody dynamic model, requiring friction estimation in milliseconds. The semi-analytical low degree of freedom model developed in this work, takes thermal effects into account and is built on an advanced and well-characterized rheological model, including lubricant shear thinning, in order to estimate the viscosity and volume of the lubricant. The model was utilized to perform friction prediction covering a range of operating conditions, which were also run in an experimental investigation using a ball-on-disk test device. The results turned out to compare well, suggesting that it constitutes a suitable foundation for further developments.Godkänd; 2015; 20151005 (mohshi); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Mohammad Shirzadegan Ämne: Maskinelement/Machine Elements Uppsats: Elastohydrodynamic Lubrication of Cam and Roller Follower Examinator: Biträdande professor Andreas Almqvist, Institutionen för teknikvetenskap och matematik, Avdelning: Maskinelement, Luleå tekniska universitet Diskutant: PhD – Senior Researcher Jonas Ståhl, SKF, Göteborg Tid: Fredag 6 november, 2015 kl 09.00 Plats: E632, Luleå tekniska universitet
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Sharma, Shashi Kant. "Transition from elastohydrodynamic to partial elastohydrodynamic lubrication in a point contact with asperity /." The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487948807585738.
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Jolkin, Alexei. "A hybrid technique for investigation of elastohydrodynamic lubrication /." Luleå, 2001. http://epubl.luth.se/1402-1544/2001/01/index.html.
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Hurley, Susan Rebecca. "Fundamental studies of grease lubrication in elastohydrodynamic contacts." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342330.
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Elcoate, Colin D. "Coupled solution methods for the elastohydrodynamic lubrication problem." Thesis, Cardiff University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299801.
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Schäfer, Christian Thomas. "Elastohydrodynamic lubrication based on the Navier-Stokes equations." Thesis, Liverpool John Moores University, 2005. http://researchonline.ljmu.ac.uk/5788/.
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Jamali, Hazim. "Analysis of helical gear performance under elastohydrodynamic lubrication." Thesis, Cardiff University, 2015. http://orca.cf.ac.uk/73975/.
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In this thesis an elastohydrodynamic lubrication (EHL) solution method has been developed for helical Gears. Helical gears mesh with each other and develop contact areas under load that are approximately elliptical in shape. The contact ellipses have aspect ratios which are large and lubricant entrainment takes place in the rolling / sliding direction which is along the minor axis of the contact ellipse. The contact between helical gear teeth is therefore considered as a point contact EHL problem and the EHL analysis has been developed to include all aspects of the correct gear geometry. This includes the variation in radius of relative curvature at the contact over the meshing cycle, the introduction of tooth tip relief to prevent premature tooth engagement under load, and axial profile relief to prevent edge contact at the face boundaries of the teeth. The EHL solution is first obtained as a quasi-steady state analysis at different positions in the meshing cycle and then developed into a transient analysis for the whole meshing cycle. The software developed has been used to assess the effects of geometrical modifications such as tip relief and axial crowning on the EHL performance of a gear, and different forms of these profile modifications are studied. The analysis shows that the transient squeeze film effect becomes significant when the contact reaches the tip relief zone. Thinning of the film thickness occurs in this region and is associated with high values of pressure which depend on the form of tip relief considered. A transient EHL analysis for helical gears having faceted tooth surfaces has also been developed. Such surface features arise from the manufacturing process and can have a significant effect on the predicted transient EHL behaviour. The EHL results have been found to depend significantly on the facet spacing and thus on the manufacturing process. The important effect of surface roughness is also considered by developing a three dimensional line contact model to include real surface roughness information by considering a finite length of the nominal contact in the transverse direction of the tooth. This model is based on the use of the fast Fourier transform method to provide the repetition of the solution space along the nominal contact line between the helical teeth with the inclusion of cyclic boundary conditions at the transverse boundaries of the solution space. In helical gears the lay of tooth roughness (direction of finishing) is generally inclined to the direction in which rolling (entrainment) and sliding take place, and this is found to have a significant effect on both film thickness and pressure distribution.
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Guangteng, Gao. "A study of squeeze and starvation in elastohydrodynamic lubrication." Thesis, Imperial College London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388292.
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Chimanpure, Amit S. "A Generalized Elastohydrodynamic Lubrication Model for Two-Dimensional Contacts." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595503685282483.
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Lee, Rong-Tsong. "Transient and rheological effects in elastohydrodynamic and microelastohydrodynamic lubrication /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487672245900119.
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Lu, Hongqiang. "High order finite element solution of elastohydrodynamic lubrication problems." Thesis, University of Leeds, 2006. http://etheses.whiterose.ac.uk/1341/.
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In this thesis, a high-order finite element scheme, based upon the Discontinuous Galerkin (DG) method, is introduced to solve one- and two-dimensional Elastohydrodynamic Lubrication (EHL) problems (line contact and point contact). This thesis provides an introduction to elastohydrodynamic lubrication, including some history, and a description of the underlying mathematical model which is based upon a thin film approximation and a linear elastic model. Following this, typical nondimensionalizations of the equations are discussed, along with boundary conditions. Two families of problems are considered: line and point contacts. Following a review of existing numerical methods for EHL problems, a different numerical technique, known as the Discontinuous Galerkin method is described. This is motivated by the high accuracy requirement for the numerical simulation of EHL problems. This method is successfully applied to steady-state line contact problems. The free boundary is captured accurately using the moving-grid method and the penalty method respectively. Highly accurate numerical results are obtained at a low expense through the use of h-adaptivity methods based on discontinuity and high-order components respectively. Combined with the Crank-Nicolson method and other implicit schemes for the temporal discretization, highly accurate solutions are also obtained for transient line contact problems using the high order DG method for the spatial discretization. In particular, an extra pressure spike is captured, which is difficult to resolve when using low order schemes for spatial discretization. The extension of this high order DG method to the two-dimensional case (point contact) is straightforward. However, the computation in the two-dimensional case is more expensive due to the extra dimension. Hence p-multigrid is employed to improve the efficiency. Since the free boundary in the two-dimensional case is more complicated, only the penalty method is used to handle the cavitation condition. This thesis is ended with the conclusions and a discussion of future work.
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Almqvist, Torbjörn. "Computational fluid dynamics in theoretical simulations of elastohydrodynamic lubrication." Doctoral thesis, Luleå, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26754.
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The work presented in this thesis concerns computer simulations of lubrication processes, and the main part deals with simulations in the elastohydrodynamic lubrication (EHL) regime. The thesis summarises the work performed in the five papers referred to as Paper A, B, C, D and E. The aim is to give the reader a more explanatory description of the investigations performed in the papers and of the physical processes present in EHL. Lubrication is a sub-area of tribology, which is the science of interacting bodies in relative motion, two other sub-areas being wear and friction. Lubrication is commonly referred to as a way of reducing friction and protecting the surfaces from wear. Typical devices where EHL is present are machine components. Examples of these are bearings, cams and gears. The lubricant can in such an application have many different tasks. The ultimate goal is that the surfaces in motion should be separated by a fluid film, thus reducing the friction and wear. That leads to low frictional losses and long operating life for the machine components. This goal is, however, not always fulfilled, and to protect the surfaces from wear when the lubricating film collapses, there are additives added to the lubricant. Commonly, lubricants contain of a number of additives, but these are not in focus in this thesis. Common to many EHL-applications, especially machine components, are thin lubricating films and high fluid pressures. The high pressures result in elastic deformation of the contacting bodies. The lubricating films in such applications are very thin, often in the range 0.1-1 10^-6m with pressures ranging from 0.5-3 GPa. The contact diameter is approximately 1 mm and the time a fluid element needs to pass through the contact is approximately 0.1 ms. The altering geometrical scales and rapid changes in the physical variables, such as pressure, viscosity and temperature etc., make numerical simulations to a challenging task. The variables of primary interest in the numerical simulations are: film thickness, pressure, temperature and friction. The film thickness is an important variable that gives information as to whether the surfaces are separated by the lubricating film. It is the lifting force generated by the hydrodynamic pressure that governs the separation of the surfaces in motion. However, even if a lubricating film is present, EHL machine components deteriorate when they have been in service for a long time. It is then that the cycling in pressure and temperature leads to fatigue of the surfaces, so that the level of these variables is also of importance. The friction that has developed in the EHL-contacts leads to a loss of energy, which increases the temperature in the conjunctions. Friction is therefore important not only for the efficiency, but also when thermal aspects have to be considered. The physical processes present in EHL are inter-disciplinary, closely related to other fields of science such as fluid mechanics, solid mechanics, and rheology. In almost all numerical simulations of lubrication performed today, the hydrodynamics are modelled by an equation referred to as the Reynolds equation. This equation is derived from a simplified form of the momentum equations, which are combined with the continuity equation; and the result is a Poisson equation for the fluid pressure. The assumptions made when deriving this equation limit the size of the computational or spatial domain, and the equation cannot predict pressure variations across the lubricating fluid film. In the work presented in this thesis, an extended approach, where the technique is based on CFD (computational fluid dynamics), is used to simulate the lubricant flow. The extended approach is here based on more complete forms of the equations of momentum, continuity and energy and the above degeneracy will be removed. That implies, if such an approach works, that it should now be possible to simulate the lubricant flow under conditions where the Reynolds equation is not valid. So far, only few attempts have been made to use the CFD-technique. From the preceding discussion of rapid changes in accordance with elastic deformation of the contacting surfaces, a great deal of work has been carried out to modify the numerical algorithm in the CFD-software to fit EHL-problems. The CFD- software used throughout the work in this thesis is CFX4 (2003).Godkänd; 2004; 20061030 (haneit)
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Chitta, Sudeendra. "Elastohydrodynamic lubrication in spur gear and helical gear contacts." Thesis, KTH, Maskinkonstruktion (Avd.), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-151246.
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The gears in a transmission are lubricated to prevent their premature failure as a result of pitting and wear on the tooth surfaces. Furthermore, the lubricant also limits the rise in surface temperature of the gears, which could otherwise lead to failure as a result of scuffing. The purpose of this thesis was to construct a fairly realistic theoretical lubrication model for spur and helical gears, the primary output parameters of this model being film thickness and flash temperatures, which would help in the identification of areas on the gear tooth surface prone to the aforementioned modes of failure. This thesis was carried out at the Gear Technology group in Scania CV AB in collaboration with the department of machine design at KTH. Gear lubrication is tricky as it entails the determination of parameters such as loads, curvatures, and velocities; which are different along the entire surface of the gear tooth. Primarily the loads are hard to obtain as they are dynamic in nature; the load is shared between different pairs of teeth during motion. The calculation of velocities and curvatures in an area of the gear surface called the tip relief can also not be done in a straightforward manner. These issues were simplified to a large extent with the assistance of a program called Helical 3D; owing to its powerful contact analysis algorithm, values of the film thickness and flash temperatures could be determined in almost every region where contact occurred between the gear teeth. The results of the lubrication model showed a reduction in film thickness in the tip relief area of the gear tooth surface; which meant that there were higher chances for the incidence of pitting and wear in this region. This was later confirmed when photographs from experimental tests illustrated a pitting line in the tip relief region of the helical gear. It was also inferred from the model that the occurrence of pitting could be greatly reduced if a quadratic tip relief modification were applied when compared to the existing linear modification used at Scania. Another important conclusion drawn was that thermal effects contributed to a significant decrease in the film thickness. Furthermore, the model showed higher flash temperatures close to the tip of the gear tooth surface, and photographs from experiments conducted showed the prescence of scuffing marks there.
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Matoušek, Kamil. "Vliv povrchových rýh na mazání bodových kontaktů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231945.
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This diploma thesis deals with experimental study of the effect of surface grooves on distribution of lubricant film in elastohydrodynamic lubricated point contact. Lubricant film thickness was measured by ball-on-disc apparatus using an optical interferometry technique - thin film colorimetric interferometry. The effects of groove geometry, lubricant and operating conditions were studied in this diploma thesis. The effects of these variables are evaluated based on newly suggested parameter Rgi (groove influence ratio). Groove influence ratio is defined as an influenced film thickness influenced by groove divided by film thickness for smooth surfaces.
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Zapletal, Lukáš. "Studium chování elastohydrodynamicky mazaných kontaktů strojních částí s nehladkými povrchy." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-229014.
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Master’s thesis deals with development of software application to calculate contact pressure in eleastohydrodynamic lubricated contact in order to use previously obtained data of the lubricating film thickness. The introduction contains a short overview of methods used for the study of film thickness and contact pressure. Custom work includes a contact pressure solution derived from a film thickness, a description of the developed software and analysis of algorithms used for its compilation. The last part deals with the verification of algorithm, application of software for calculating the contact pressure on the rough surface and analysis of the results. The conclusion includes a summary and possible application of software in practice.
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Jaffar, Mohammad Jawad. "Elastic strips in dry and lubricated contacts." Thesis, University of Leeds, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237097.
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Cioc, Carmen. "An elastohydrodynamic lubrication model for helicopter high-speed transmission components /." SeeFull Text at OhioLINK ETD Center (Requires Adobe Acrobat Reader for viewing), 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=toledo1100618919.
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Dissertation (Ph.D.)--University of Toledo, 2004.Typescript. "A dissertation [submitted] as partial fulfillment of the requirements of the Doctor of Philosophy degree in Engineering." Bibliography: leaves 220-247.
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Cioc, Carmen Ana Beatrice. "An Elastohydrodynamic Lubrication Model for Helicopter High-Speed Transmission Components." University of Toledo / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1100618919.
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Al-Hamood, Amjad. "Friction and thermal behaviour in elastohydrodynamic lubrication power transmission contacts." Thesis, Cardiff University, 2015. http://orca.cf.ac.uk/74240/.
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This thesis reports experimental and theoretical analyses to study the heat generation and partition between contacting bodies under rolling/sliding elastohydrodynamic (EHL) point contact. A twin disk test rig was re-commissioned and used for the experimental work. 76 mm diameter crowned, super-finished test disks, fixed on parallel shafts, were used in the experimental EHL tests. In each disk, 6 thermocouples were installed to measure the temperature during sliding/rolling contact under EHL conditions. In addition, ceramic washers were fixed on the plane sides of each disk to minimize heat transfer over those surfaces. A Labview data acquisition system was built for acquiring data from the sensors installed on the rig. The EHL experimental results show the fast disk has significantly higher bulk temperature than the slow disk. A transient two dimensional numerical model was constructed to calculate the average circumferential temperature distribution within the disks using three thermocouples as a boundary condition. The heat partition factor, , and convection heat transfer coefficient, h, were varied systematically in the model. A linear relationship between and hf for the fast disk and 1- and hs for the slow disk were obtained. These two linear relations were related together by the variation of h with the rotational speed. Over the approximately steady state condition, the calculated using this approach was in the range of 0.65 to 0.77 for 32 EHL tests at different loads and sliding speeds. This means that the majority of heat is conducted to the fast disk, which is compatible with the previous findings. In order to carry out transient modelling, the unloading mechanism was developed to ensure rapid disk separation. This improved the temperature trend in the cooling phase. In addition, a microswitch was used to give accurate monitoring of the disks contacting and separation. The thermocouple arrangement within the disks and their installation technique were assessed and developed. An immersion test in a hot oil bath was used to test the thermocouples dynamic response. This test was modelled, and the results showed significant lag in the measurements. It was concluded that a system identification method is required to identify the dynamic characteristics of the temperature measurement system in order to compensate for time lagging Extensive studies were carried out to determine the cause behind some of the experimental uncertainties. It was found that the most likely reason behind these uncertainties is the contact pressure variation along the disk-shaft interference fit, which would result in significant thermal conductance variation. The traction force measurement within the EHL contacts has shown broadly linear increase with increased load at constant sliding speed. This indicates a constant coefficient of friction at constant sliding speed. The results also showed that the coefficient of friction decreases as the sliding speed increases.
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Ahmed, Sarfraz. "Efficient finite element simulation of full-system elastohydrodynamic lubrication problems." Thesis, University of Leeds, 2012. http://etheses.whiterose.ac.uk/3347/.
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This thesis is concerned with the efficient numerical solution of problems of elastohydrodynamic lubrication (EHL). Our approach is to consider fully-coupled models in which the governing equations for the lubricating film, the elastic deformation and the force balance are each discretized and solved as a single monolithic nonlinear system of algebraic equations. The main contributions of this work are to propose, implement and analyse a novel, optimal, preconditioner for the Newton linearization of this algebraic system, and to assess the development of efficient finite element meshes through both manual tuning and the use of adaptive mesh refinement based upon a posteriori error estimation and control. Throughout this work, we employ first order finite element discretizations for both the Reynolds equation (for the lubricant) and for the linear elasticity model on a finite domain. The resulting nonlinear algebraic equations are then solved using a quasi-Newton algorithm. For each linear solve a Krylov subspace method is used and a new blockwise preconditioner is presented which is designed to exploit the specific structure that is present in this class of problem. This preconditioner combines the use of multigrid preconditioning for the elasticity block and a separate, efficient, approximation to precondition the Reynolds block. The solver developed in this work can be distinguished into two variants based upon the use of algebraic and geometric multigrid preconditioning of the elasticity block. Numerical results are presented both for line and point contact problems to validate the implementations and to allow a comparison of the performance and efficiency of the proposed solution strategies compared to the use of a state-of-the-art sparse direct solver at each Newton step. These results demonstrate that the preconditioned iterative approach is both computationally and memory superior to the sparse direct solver. Most importantly, both the computational and memory costs are seen to grow linearly with the number of unknowns. A locally adaptive solution scheme is also developed for fully-coupled EHL point contact problems. This automates the refinement process to the regions of the domain which exhibit large error in their solutions. Numerical results are presented which demonstrate the performance and effectiveness of the proposed procedure.
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Aitken, M. B. "Elastohydrodynamic lubrication of big end bearings under steady and cyclic loads." Thesis, University of Canterbury. Mechanical Engineering, 1989. http://hdl.handle.net/10092/6012.
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Lubrication of the big-end bearing is re-examined under elastohydrodynamic assumptions. All current models were found to be in someway deficient, motivating the development of a new consistent schema.
Uniform axial film-thickness assumptions and parabolic axial pressure profiles are combined with curved-beam and planar Finite Element housings to produce a single dimensional EHL model. Body-forces due to con-rod motion were found to be a necessary part of the elasticity implementation.
The role of discretisation and surface displacement interpolation errors are investigated under steady load conditions. Under dynamic load, ring, housing and previous experimental works are compared.
Increased dynamic journal action from housing distorsion was found to lead to film collapses not present in equivalent rigid bearing analyses; these collapses are likened to vapour cavitation. Correlation of dynamic film-thickness measurements with the elastic solutions are generally improved over rigid predictions.
With regard to minimum film thickness, inertial 'ring' solutions gave similar values to housing solutions with and without gas loading; this facilitates non-dimensionalisation. Two separate minimum-film regime were subsequently identified: one in the con-rod neck and a second, at higher load, in the cap. The first condition sees thicker minimum films than the rigid bearing; the second, thinner films with an increased sensitivity to load.
Non-dimensionalisation of this transition along with bearing flexibility and load enabled new tribological measures to be developed; the influence of elastic geometry on minimum film thickness is sufficiently well portrayed to make these useful design tools.
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Clarke, Alastair. "Heat partition in elastohydrodynamic sliding contacts under full film lubrication conditions." Thesis, Cardiff University, 2009. http://orca.cf.ac.uk/54814/.
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The principal aim of the work within this thesis was to investigate the fundamental problem of how the frictional heat generated by lubricant shearing at a rolling/sliding elastohydrodynamic contact is divided between the contacting bodies. In elastohydrodynamic lubrication (EHL), a knowledge of the temperatures of the contacting bodies is important due to the effects of temperature on lubricant viscosity in the inlet zone and hence on film thickness. A two-disc test rig previously used to study scuffing was subject to extensive modifications to allow the measurement of disk temperatures at six sub-surface locations in each disk using carefully calibrated embedded thermocouples. A series of experiments using a synthetic gas turbine engine oil was conducted at a range of sliding speeds from 10 ms"1 to 20 ms1 and loads equivalent to maximum Hertzian contact pressures between 1.0 GPa and 1.6 GPa. In each experiment, the speed was fixed and the load applied. Once the temperatures had reached steady-state conditions, the load was removed and the disks separated. The disks were run whilst they cooled until they returned to ambient temperatures. The data recorded dining these experiments were analysed using a transient two-dimensional conduction model of the outer region of the disks, which attempted to obtain an optimal agreement between calculated and measured temperatures. This was achieved by adjusting the partition of heat between the disks and the level of forced convection from the disk surface until the temperatures during the loaded phase of the test (governed by heat partition and cooling) and the cooling phase of the test (governed by the disk surface convection only) were in closest agreement with experimental measurements. Whilst the data recorded from the slow disk was found to be repeatable, there were some errors and lack of repeatability noted with the fast disk data. However, using the slow disk data, it was found that approximately 40% of the frictional heat flows into the slow disk, with the remaining 60% flowing into the fast disk. A series of thermal EHL analyses was performed, using a range of viscosity and rheological models. It was found that the heat partition predicted by the thermal EHL analysis only approached that measured during experiment when the majority of the heat was dissipated by slip at or near to the fast surface. These conditions only occurred when using a limiting shear stress rheological model in conjunction with the Bams viscosity model. The thesis also contains details of finite-element modelling carried out to study elastic-plastic deformation of asperities during the running-in process. It was found that the residual deformation following loading beyond the elastic regime always followed the same shape, with characteristic "piling up" of material around the boundary of the contact. A series of non-dimensional relations for the shape and magnitude of the residual deformation were developed, and their potential for use in an EHL rough surface solver in order to take into account plastic deformation was noted.
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Akchurin, Aydar. "Lubrication and Wear at Metal/HDPE Contacts." Thesis, North Dakota State University, 2012. https://hdl.handle.net/10365/26503.
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In the thesis lubrication and wear at metal/HDPE contacts was addressed. In particular this type of contact occurs in artificial joint replacements. Wear of HDPE was recognized as a major factor limiting device performance.
In the thesis, fully implicit fully coupled numerical approach was developed to simulate lubrication and wear. Approach allows solving stationary and transient problems for rough surfaces in a wide range of parameters. Wear coefficients were estimated from experimental data.
Wear particles formed in wear process were investigated. Particles were found to be approximately 100 nm in diameter and spherical in shape. Considering theoretical solutions, it was concluded that debris may play a role of third-body abrasive wear particles.
In the summary section, some discussion was provided on the topic of theoretical modeling of friction and wear and recommendations for future research were formulated.
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Mitchell, M. C. "An experimental and analytical investigation of screen printing process fundamentals." Thesis, Nottingham Trent University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266912.
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Wilson, Lance Jon. "Performance measurements of rail curve lubricants." Queensland University of Technology, 2006. http://eprints.qut.edu.au/16344/.
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Wear of railroad rolling stock and rails costs millions of dollars annually in all rail systems throughout the world. The rail industry has attempted to address flange wear using rail curve lubricants and presently use a variety of lubricants and lubricant applicators. The choice of lubricant and applicator is currently based on considerations that do not address the wear problem directly. This research quantified rail curve lubricant performance through laboratory simulation. The effects of lubricants in the wheel/rail contact were investigated. Rail curve lubricant performance was measured with a laboratory rail/wheel simulator for the purpose of optimising the choice of lubricant. New methods for measurement of rail curve lubricant performance have been presented. These performance measurements are total absorbed energy, the energy absorbed in the lubricant film instead of being utilised for wear processes; total distance slid, the sliding distance or accumulated strain achieved prior to development of a set tractive force limit; half life of lubricant, the time taken for a lubricant to lose half of its sliding performance; and apparent viscosity, a measure of the lubricity presented with respect to accumulated strain. The rail/wheel simulator used in this research consists of two dissimilar wheels (disks) rotating in contact with one another simulating a conformal gauge corner contact. The first wheel, a simulated rail, is driven by an electric motor which then drives the second wheel, a simulated railroad wheel, through the contact. Hydraulic braking on the railroad wheel is used to simulate the rolling/sliding conditions. The variables of the simulated contact that are controlled with this equipment are normal force, input wheel speed, slip ratio between samples, sample geometries and material properties, and lubricant types. Rail curve lubricants were laboratory tested to define their properties using the ASTM and other appropriate standards. The performance differences measured using ASTM standards based tests were susceptible to repeatability problems and did not represent the contact as accurately as the rail/wheel simulator. This laboratory simulator was used to gather data in lubricated and unlubricated conditions for the purpose of providing lubricant performance measurements. These measurements were presented and the tested lubricants were ranked conclusively using three industrially relevant performance criteria. Total sliding distance and total absorbed energy measurements of the rail curve lubricants displayed clear differences in lubricant performance for both of these criteria. Total sliding distance is equivalent to the number of axles in the field situation, while total absorbed energy is the energy unavailable for wear processes of rails and wheels. Lubricants designed using these measurements will increase lubricant performance with respect to these performance criteria which in turn will reduce wear to both rails and wheels. Measurement of the apparent viscosity of rail curve lubricants, using the rail/wheel simulator, displayed changes in rheological characteristics with respect to accumulated strain. Apparent viscosity is a measure of the shear stress transmitted from the wheels to the rails. Designing a rail curve lubricant after analysing measurements taken from the rail/wheel simulator will assist in identifying lubricant properties to reduce the wear producing shear stresses generated in a rail wheel contact. Decay of lubricant performance was measured for three different rail curve lubricants under simulated conditions. The research found appreciable and quantifiable differences between lubricants. Industrial application of the findings will improve positioning of lubrication systems, improve choice of lubricants and predict effective lubrication distance from the lubricant application point. Using the new methods of lubricant performance measurement developed in this thesis, the objective of this research, to quantify rail curve lubricant performance through laboratory simulation, has been achieved.
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Shi, Fanghui. "A deterministic mixed-elastohydrodynamic lubrication model and analysis of lip seal performance." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/17585.
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Davies, C. N. "Effects of non-Newtonian rheology on the line contact elastohydrodynamic lubrication problem." Thesis, Cardiff University, 2005. http://orca.cf.ac.uk/56028/.
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The Bair and Winer, Gecim and Winer, Circular and Cardiff limiting shear stress models are compared and contrasted under different load, viscosity, limiting shear stress, surface velocities, Young's modulus, relative radius of curvature and temperature. Isothermal comparisons show that limiting shear stress rheology reduces the pressure gradients in the centre of the contact. Also a localised increase in film thickness in the inlet and a reduction near the exit of the contact occur. The bulk oil temperature significantly influences the limiting shear stress features developed. As a result a full thermal approach was adopted that includes the heat generated, by slip, at the fluid-surface interface. Regions where limiting shear stress and temperature effects dominate are identified under optical interferometry operating conditions. The heat generated during contact was included in the thermal approach. Sinusoidal roughness features promoted contact and the temperature responses were compared using different coefficients of friction. Contact develops higher temperatures than those generated in full film regions, with much greater temperature rises for higher coefficients of friction. Thermal and isothermal gear meshes are simulated using equivalent roller and involute geometries with rough and smooth surfaces. Roughness data taken from gear teeth are linked to the numerical involute used in the simulation, allowing roughness features to be used in the correct part of the gear mesh. Smooth and rough surface results are obtained for three different meshes. 'Running in' was investigated by measuring the amount of surface modification and contact developed between two rotating disks using 'in situ' Talysurf profiles and contact resistance measurements respectively. 'Running in' occurred quickly, with temperature effects reducing the films prolonging the contact period. Comparisons using the software developed incorporating actual roughness profiles, bulk disk and bulk oil temperatures, gave good agreement between the numerical and experimental approaches.
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Jordán, Jakub. "Vliv cílené modifikace topografie na nedostatečně mazaný kontakt." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-229252.
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The diploma thesis deals with the analysis of the effects surface texturing on starved contact. Experimental verification was realized on apparatus simulating contact between a steel ball and glass disc using colorimetric interferometry and high-speed camera. The work deals with lubrication regimes, problems with starved contacts and surface texturing which can reduce effects of starvation on non-conformal surface contacts.
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Moraru, Laurentiu Eugen. "Numerical Predictions and Measurements in the Lubrication of Aeronautical Engine and Transmission Components." University of Toledo / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1125769629.
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Lord, John. "Thin lubricating films in elastohydrodynamic contacts : experimental techniques and applications /." Luleå, 2004. http://epubl.luth.se/1402-1544/2004/016.
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Holmes, Mark J. A. "Transient analysis of the point contact elastohydrodynamic lubrication problem using coupled solution methods." Thesis, Cardiff University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400222.
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