The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
David Moens - One of the best experts on this subject based on the ideXlab platform.
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the influence of external dynamic loads on the lifetime of rolling element bearings experimental analysis of the Lubricant Film and surface wear
Mechanical Systems and Signal Processing, 2016Co-Authors: William Jacobs, Rene Boonen, Paul Sas, Brecht Van Hooreweder, David MoensAbstract:Abstract Precise prediction of the lifetime of rolling element bearings is a crucial step towards a reliable design of many rotating machines. For bearings subjected to highly varying loads, recent research emphasises a strong reduction of the actual bearing lifetime w.r.t. the classically calculated bearing lifetime. This paper experimentally analyses the influence of external dynamic loads on the lifetime of rolling element bearings. A novel bearing test rig is introduced. The test rig is able to apply a fully controlled multi-axial static and dynamic load on a single test bearing. Also, different types and sizes of bearings can be tested. Two separate investigations are conducted. First, the behaviour of the Lubricant Film between the rolling elements and raceways is analysed. Increased metallic contact or breakdown of the Film during dynamic excitation is investigated based on the measured electrical resistance through the bearing. The study shows that the Lubricant Film thickness follows the imposed variations of the load. Variations of the Lubricant Film thickness are similar to the variations when the magnitude of the static bearing load is changed. Second, wear of the raceway surfaces is analysed. Surface wear is investigated after a series of accelerated lifetime tests under high dynamic load. Due to sliding motion between asperities of the contacting surfaces in the bearing, polishing of the raceway honing structure occurs. This polishing is clearly observed on SEM images of the inner raceway after a test duration of only 0.5% of the calculated L10 life. Polishing wear of the surfaces, such as surface induced cracks and material delamination, is expected when the bearing is further exposed to the high dynamic load.
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the influence of the Lubricant Film on the stiffness and damping characteristics of a deep groove ball bearing
Mechanical Systems and Signal Processing, 2014Co-Authors: William Jacobs, Rene Boonen, Paul Sas, David MoensAbstract:Abstract This paper experimentally investigates the formation of a Lubricant Film in a deep groove ball bearing and its effect on the bearing dynamics. A novel test rig is introduced, which allows testing different types and sizes of bearings in real-life conditions. The test rig dynamics are optimised such that the dynamic properties of the bearing are measured in a frequency range below the resonances of the flexible modes. Two properties of the bearing, both its stiffness and damping value in the direction of the static bearing load, are identified. The behaviour of the Lubricant Film between the rolling elements and raceways is measured based on the electrical resistance through the bearing. For this purpose, the bearing housing is electrically isolated from the surrounding structure. The electrical resistance, stiffness and damping of the test bearing are identified during a speed run-up. The influence of the bearing temperature is analysed as well. During a run-up at constant bearing temperature, the measurement of the electrical resistance describes the formation of the Lubricant Film. Due to the formation of the Lubricant Film, the bearing stiffness increases by 3.2% while the damping increases by 24%. During a warm-up of the bearing, the viscosity of the Lubricant Film decreases strongly. A resulting decrease in electrical resistance, stiffness and damping is measured. Finally, the electrical resistance, stiffness and damping are identified at different speeds, after the bearing has reached a stable temperature at each speed. A combined effect of both rotation and temperature is observed and discussed.
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The influence of the Lubricant Film on the stiffness and damping characteristics of a deep groove ball bearing
Mechanical Systems and Signal Processing, 2014Co-Authors: William Jacobs, Rene Boonen, Paul Sas, David MoensAbstract:This paper experimentally investigates the formation of a Lubricant Film in a deep groove ball bearing and its effect on the bearing dynamics. A novel test rig is introduced, which allows testing different types and sizes of bearings in real-life conditions. The test rig dynamics are optimised such that the dynamic properties of the bearing are measured in a frequency range below the resonances of the flexible modes. Two properties of the bearing, both its stiffness and damping value in the direction of the static bearing load, are identified. The behaviour of the Lubricant Film between the rolling elements and raceways is measured based on the electrical resistance through the bearing. For this purpose, the bearing housing is electrically isolated from the surrounding structure. The electrical resistance, stiffness and damping of the test bearing are identified during a speed run-up. The influence of the bearing temperature is analysed as well. During a run-up at constant bearing temperature, the measurement of the electrical resistance describes the formation of the Lubricant Film. Due to the formation of the Lubricant Film, the bearing stiffness increases by 3.2% while the damping increases by 24%. During a warm-up of the bearing, the viscosity of the Lubricant Film decreases strongly. A resulting decrease in electrical resistance, stiffness and damping is measured. Finally, the electrical resistance, stiffness and damping are identified at different speeds, after the bearing has reached a stable temperature at each speed. A combined effect of both rotation and temperature is observed and discussed. © 2013 Elsevier Ltd. All rights reserved.status: publishe
A V Khomenko - One of the best experts on this subject based on the ideXlab platform.
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phenomenological theory for the melting of a thin Lubricant Film between two atomically smooth solid surfaces
Technical Physics, 2010Co-Authors: I A Lyashenko, A V Khomenko, L S MetlovAbstract:A thermodynamic model is developed for the melting of an ultrathin Lubricant Film squeezed between two atomically smooth solid surfaces. To describe the state of Lubricant, an excess volume parameter is introduced; it appears due to the chaos in the structure of a solid body induced by melting. This parameter increases with the total internal energy upon melting. Thermodynamic melting and shear melting are described. The dependences of the friction force on the Lubricant temperature and the shear rate of friction surfaces are analyzed. The calculated results are compared to the experimental data.
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Hysteresis Phenomena during Melting of an Ultrathin Lubricant Film
Physics of the Solid State, 2007Co-Authors: A V Khomenko, Iakov A. LyashenkoAbstract:The influence of a deformational defect of the shear modulus on the melting of an ultrathin Lubricant Film was investigated in the framework of the Lorenz model used for describing a viscoelastic medium. It was established that the Film can undergo both stepwise and continuous melting. Analysis of the Lubricant behavior revealed that there are three modes corresponding to a zero shear stress, a Hookean portion in the loading dia- gram, and a plastic-flow portion. The hysteresis in the dependences of the stationary shear stress on the strain and the friction surface temperature is examined.
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noise influence on solid liquid transition of ultrathin Lubricant Film
Physics Letters A, 2004Co-Authors: A V KhomenkoAbstract:The melting of ultrathin Lubricant Film by friction between atomically flat surfaces is studied. The additive noises of the elastic shear stress and strain, and the temperature are introduced for building the phase diagrams with the domains of sliding, stick-slip, and dry friction. It is shown that increase of the strain noise intensity causes the Lubricant Film melting even at low temperatures of the friction surfaces.
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Noise influence on solid–liquid transition of ultrathin Lubricant Film
Physics Letters A, 2004Co-Authors: A V KhomenkoAbstract:The melting of ultrathin Lubricant Film by friction between atomically flat surfaces is studied. The additive noises of the elastic shear stress and strain, and the temperature are introduced for building the phase diagrams with the domains of sliding, stick-slip, and dry friction. It is shown that increase of the strain noise intensity causes the Lubricant Film melting even at low temperatures of the friction surfaces.
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Noise influence on solid–liquid transition of ultrathin Lubricant Film
Physics Letters A, 2004Co-Authors: A V KhomenkoAbstract:The melting of ultrathin Lubricant Film by friction between atomically flat surfaces is studied. The additive noises of the elastic shear stress and strain, and the temperature are introduced for building a phase diagram with the domains of sliding, stick-slip, and dry friction. It is shown that increase of the strain noise intensity causes the Lubricant Film melting even at low temperatures of the friction surfaces.Comment: 10 pages, 2 figures, LaTe
Olga V Yushchenko - One of the best experts on this subject based on the ideXlab platform.
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solid liquid transition of ultrathin Lubricant Film
Physical Review E, 2003Co-Authors: A V Khomenko, Olga V YushchenkoAbstract:We represent a melting of ultrathin Lubricant Film by friction between atomically flat surfaces as a result of action of spontaneously appearing elastic field of stress shear component caused by the external supercriticalheating. The kinetics of this solid-liquid transition is described by the Maxwell-type and Voigt-Kelvin equations for viscoelastic matter as well as by the relaxation equation for temperature. We show that these equations coincide formally with the synergetic Lorenz system, where the stress acts as the order parameter, the conjugate field is reduced to the elastic shear strain, and the temperature is the control parameter. Using the adiabatic approximation we find the steady-state values of these quantities. Taking into account the deformational defect of the shear modulus, we show that Lubricant melting is realized according to mechanism of the first-order transition. The critical temperature of the friction surfaces increases with growth of the characteristic value of shear viscosity and decreases with growth of the shear modulus value linearly.
William Jacobs - One of the best experts on this subject based on the ideXlab platform.
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the influence of external dynamic loads on the lifetime of rolling element bearings experimental analysis of the Lubricant Film and surface wear
Mechanical Systems and Signal Processing, 2016Co-Authors: William Jacobs, Rene Boonen, Paul Sas, Brecht Van Hooreweder, David MoensAbstract:Abstract Precise prediction of the lifetime of rolling element bearings is a crucial step towards a reliable design of many rotating machines. For bearings subjected to highly varying loads, recent research emphasises a strong reduction of the actual bearing lifetime w.r.t. the classically calculated bearing lifetime. This paper experimentally analyses the influence of external dynamic loads on the lifetime of rolling element bearings. A novel bearing test rig is introduced. The test rig is able to apply a fully controlled multi-axial static and dynamic load on a single test bearing. Also, different types and sizes of bearings can be tested. Two separate investigations are conducted. First, the behaviour of the Lubricant Film between the rolling elements and raceways is analysed. Increased metallic contact or breakdown of the Film during dynamic excitation is investigated based on the measured electrical resistance through the bearing. The study shows that the Lubricant Film thickness follows the imposed variations of the load. Variations of the Lubricant Film thickness are similar to the variations when the magnitude of the static bearing load is changed. Second, wear of the raceway surfaces is analysed. Surface wear is investigated after a series of accelerated lifetime tests under high dynamic load. Due to sliding motion between asperities of the contacting surfaces in the bearing, polishing of the raceway honing structure occurs. This polishing is clearly observed on SEM images of the inner raceway after a test duration of only 0.5% of the calculated L10 life. Polishing wear of the surfaces, such as surface induced cracks and material delamination, is expected when the bearing is further exposed to the high dynamic load.
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the influence of the Lubricant Film on the stiffness and damping characteristics of a deep groove ball bearing
Mechanical Systems and Signal Processing, 2014Co-Authors: William Jacobs, Rene Boonen, Paul Sas, David MoensAbstract:Abstract This paper experimentally investigates the formation of a Lubricant Film in a deep groove ball bearing and its effect on the bearing dynamics. A novel test rig is introduced, which allows testing different types and sizes of bearings in real-life conditions. The test rig dynamics are optimised such that the dynamic properties of the bearing are measured in a frequency range below the resonances of the flexible modes. Two properties of the bearing, both its stiffness and damping value in the direction of the static bearing load, are identified. The behaviour of the Lubricant Film between the rolling elements and raceways is measured based on the electrical resistance through the bearing. For this purpose, the bearing housing is electrically isolated from the surrounding structure. The electrical resistance, stiffness and damping of the test bearing are identified during a speed run-up. The influence of the bearing temperature is analysed as well. During a run-up at constant bearing temperature, the measurement of the electrical resistance describes the formation of the Lubricant Film. Due to the formation of the Lubricant Film, the bearing stiffness increases by 3.2% while the damping increases by 24%. During a warm-up of the bearing, the viscosity of the Lubricant Film decreases strongly. A resulting decrease in electrical resistance, stiffness and damping is measured. Finally, the electrical resistance, stiffness and damping are identified at different speeds, after the bearing has reached a stable temperature at each speed. A combined effect of both rotation and temperature is observed and discussed.
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The influence of the Lubricant Film on the stiffness and damping characteristics of a deep groove ball bearing
Mechanical Systems and Signal Processing, 2014Co-Authors: William Jacobs, Rene Boonen, Paul Sas, David MoensAbstract:This paper experimentally investigates the formation of a Lubricant Film in a deep groove ball bearing and its effect on the bearing dynamics. A novel test rig is introduced, which allows testing different types and sizes of bearings in real-life conditions. The test rig dynamics are optimised such that the dynamic properties of the bearing are measured in a frequency range below the resonances of the flexible modes. Two properties of the bearing, both its stiffness and damping value in the direction of the static bearing load, are identified. The behaviour of the Lubricant Film between the rolling elements and raceways is measured based on the electrical resistance through the bearing. For this purpose, the bearing housing is electrically isolated from the surrounding structure. The electrical resistance, stiffness and damping of the test bearing are identified during a speed run-up. The influence of the bearing temperature is analysed as well. During a run-up at constant bearing temperature, the measurement of the electrical resistance describes the formation of the Lubricant Film. Due to the formation of the Lubricant Film, the bearing stiffness increases by 3.2% while the damping increases by 24%. During a warm-up of the bearing, the viscosity of the Lubricant Film decreases strongly. A resulting decrease in electrical resistance, stiffness and damping is measured. Finally, the electrical resistance, stiffness and damping are identified at different speeds, after the bearing has reached a stable temperature at each speed. A combined effect of both rotation and temperature is observed and discussed. © 2013 Elsevier Ltd. All rights reserved.status: publishe
Martin Hartl - One of the best experts on this subject based on the ideXlab platform.
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On the Temperature and Lubricant Film Thickness Distribution in EHL Contacts with Arbitrary Entrainment
Lubricants, 2018Co-Authors: Milan Omasta, Petr Sperka, Jakub Adam, Ivan Krupka, Martin HartlAbstract:An understanding of mechanisms which are responsible for elastohydrodynamic Lubricant Film formation under high sliding conditions is necessary to increase durability of machine parts. This work combines thin-Film colorimetric interferometry for Lubricant Film thickness measurement and infrared microscopy for in-depth temperature mapping through the contact. The results describe the effect of operating conditions such as speed, slide-to-roll ratio, ambient temperature, and sliding direction on Lubricant Film thickness and temperature distribution. Film thickness data shows how much the Film shape is sensitive to operating conditions when thermal effects are significant, while the temperature profiles provides an explanation of this behavior.
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effect of surface roughness on Lubricant Film breakdown and transition from ehl to mixed lubrication
Tribology International, 2016Co-Authors: Ivan Krupka, Petr Sperka, Martin HartlAbstract:Abstract The ability of elastohydrodynamically lubricated (EHL) contacts to separate surfaces represents essential design requirement ensuring long life and low friction of machine components. Nevertheless, it is strongly affected by surface roughness that tends to decrease formed Lubricant Film. Surface roughness related effects are highly scales dependent. Dimensions in longitudinal and transverse directions influence roughness deformation while dimensions in roughness height can have significant effects on lubrication process. The prediction of the roughness features effect on Lubricant Film in the case of possible Lubricant Film breakdown still represents the challenge even for nowadays power full numerical simulation tools. At the same time some simple measures as the lambda ratio does not provides realistic estimation of lubrication regimes. However, there is a strong demand for such a prediction especially close to the transition to the mixed lubrication regime. In this paper possible approach based on the combination of experimental and numerical data is discussed. It is suggested that quantified experimental data could bridge possible gaps in the ability of the theory to provide the sufficient fast estimation of lubrication capabilities of engineering surfaces in the transition region between EHL and mixed lubrication.
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including the method of Lubricant Film thickness measurement with the use of the monochromatic interferometry to the education of tribology
2016Co-Authors: David Kostal, I Křupka, Martin HartlAbstract:Measuring of distance as presented at the universities is usually limited to dimension down to microns. This orders of distance are sufficient for common engineer’s application. However dimension are a lot smaller when engineers deal with the tribology research. One of the most important progresses in the field of tribology in last century is without doubts the elastohydrodynamic lubrication (EHL). This lubrication regime can be found for example in rolling bearings or gears. Common thickness of the Lubricant Film in the EHD contact is in order of tens or hundreds of nanometers. Optical method which enables measurements of such distances was developed by Gohar and Cameron in 1960s. This method is based on interference of monochromatic light and provides possibility of obtaining Lubricant Film thickness from known wavelength of used light and its intensity in the lubricated contact. Students can create central Film thickness prediction with use of the analytical formulae of the Hamrock and Dowson. This prediction is then confirmed by hands-on experiment in laboratory. Contact simulator with microscope and red light is used to record sequence of the interferograms. These interferograms are then processed in Matlab® software in order to obtain Film thickness.
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Elastohydrodynamic Lubricant Film shape - comparison between experimental and theoretical results
Tribology Series, 1998Co-Authors: Ivan Křupka, Martin Hartl, J. Čermák, Miroslav LiškaAbstract:A newly developed experimental technique enabled the determination of Lubricant Film thickness distribution in elastohydrodynamic (EHD) point contacts with high accuracy and spatial resolution. This technique uses a computer-aided system developed for this purpose, which with the help of differential colorimetry makes the reconstruction of the Lubricant Film shape possible. Chromatic interferograms were obtained with the use of a conventional optical test rig. Obtained results were compared with a numerical solution of Newtonian isothermal compressible EHD lubrication of point contacts. Experimental and numerical three-dimensional representations of a Lubricant Film thickness and shape for various operating conditions are shown. Comparisons of obtained central and minimum Film thickness values with Hamrock and Dowson equations are presented.
