The Experts below are selected from a list of 4716 Experts worldwide ranked by ideXlab platform
Michael R. Lovell - One of the best experts on this subject based on the ideXlab platform.
-
Analysis of the Contribution of Adhesion and Hysteresis to Shoe–Floor Lubricated Friction in the Boundary Lubrication Regime
Tribology Letters, 2012Co-Authors: Caitlin Moore Strobel, Pradeep L. Menezes, Michael R. Lovell, Kurt E. BeschornerAbstract:Slip and fall accidents cause frequent occupational injuries. Despite recent evidence that boundary Lubrication is relevant to slipping, few studies have examined the mechanisms that contribute to shoe–floor friction in this Lubrication Regime. This study aims to identify the contributions of adhesion and hysteresis to friction in boundary Lubrication. Three shoe materials (40 Shore A hardness polyurethane, 60 Shore A hardness rubber, and 70 Shore A hardness rubber), two floor materials (vinyl and marble), and six lubricants (water, 1.5 % detergent, 25 % glycerol–75 % water, 50 % glycerol–50 % water, 75 % glycerol–25 % water, and canola oil) were tested at a single sliding speed (0.01 m s^−1). Dry adhesion and hysteresis were quantified for each of the shoe–floor combinations and lubricated adhesion was quantified for all shoe–floor-fluid combinations. The contribution of adhesion and hysteresis to shoe–floor-lubricant friction was affected by both the shoe and floor material due to differences in hardness and roughness. Lubricated adhesion was complex and multifactorial with contributions from the shoe, fluid, shoe–floor interaction, floor-lubricant interaction, and shoe-lubricant interactions. A simple regression model including two fluid coefficients and the dry adhesion friction force was able to predict 49 % of the lubricated adhesion friction variability.
-
analysis of the contribution of adhesion and hysteresis to shoe floor lubricated friction in the boundary Lubrication Regime
Tribology Letters, 2012Co-Authors: Caitlin T Strobel, Pradeep L. Menezes, Michael R. Lovell, Kurt E. BeschornerAbstract:Slip and fall accidents cause frequent occupational injuries. Despite recent evidence that boundary Lubrication is relevant to slipping, few studies have examined the mechanisms that contribute to shoe–floor friction in this Lubrication Regime. This study aims to identify the contributions of adhesion and hysteresis to friction in boundary Lubrication. Three shoe materials (40 Shore A hardness polyurethane, 60 Shore A hardness rubber, and 70 Shore A hardness rubber), two floor materials (vinyl and marble), and six lubricants (water, 1.5 % detergent, 25 % glycerol–75 % water, 50 % glycerol–50 % water, 75 % glycerol–25 % water, and canola oil) were tested at a single sliding speed (0.01 m s−1). Dry adhesion and hysteresis were quantified for each of the shoe–floor combinations and lubricated adhesion was quantified for all shoe–floor-fluid combinations. The contribution of adhesion and hysteresis to shoe–floor-lubricant friction was affected by both the shoe and floor material due to differences in hardness and roughness. Lubricated adhesion was complex and multifactorial with contributions from the shoe, fluid, shoe–floor interaction, floor-lubricant interaction, and shoe-lubricant interactions. A simple regression model including two fluid coefficients and the dry adhesion friction force was able to predict 49 % of the lubricated adhesion friction variability.
-
Analysis of the Contribution of Adhesion and Ploughing to Shoe-Floor Lubricated Friction in the Boundary Lubrication Regime
ASME STLE 2011 Joint Tribology Conference, 2011Co-Authors: Caitlin Moore, Pradeep L. Menezes, Kurt E. Beschorner, Michael R. LovellAbstract:Slip and fall accidents cause frequent occupational injuries. Despite recent evidence that boundary Lubrication is relevant to slipping, few studies have examined the mechanisms that contribute to shoe–floor friction in this Lubrication Regime. This study aims to identify the contributions of adhesion and hysteresis to friction in boundary Lubrication. Three shoe materials (40 Shore A hardness polyurethane, 60 Shore A hardness rubber, and 70 Shore A hardness rubber), two floor materials (vinyl and marble), and six lubricants (water, 1.5 % detergent, 25 % glycerol–75 % water, 50 % glycerol–50 % water, 75 % glycerol–25 % water, and canola oil) were tested at a single sliding speed (0.01 m s−1). Dry adhesion and hysteresis were quantified for each of the shoe–floor combinations and lubricated adhesion was quantified for all shoe–floor-fluid combinations. The contribution of adhesion and hysteresis to shoe–floor-lubricant friction was affected by both the shoe and floor material due to differences in hardness and roughness. Lubricated adhesion was complex and multifactorial with contributions from the shoe, fluid, shoe–floor interaction, floor-lubricant interaction, and shoe-lubricant interactions. A simple regression model including two fluid coefficients and the dry adhesion friction force was able to predict 49 % of the lubricated adhesion friction variability.
-
Analysis of the Contribution of Adhesion and Ploughing to Shoe-Floor Lubricated Friction in the Boundary Lubrication Regime
ASME STLE 2011 Joint Tribology Conference, 2011Co-Authors: Caitlin Moore, Pradeep L. Menezes, Kurt E. Beschorner, Michael R. LovellAbstract:Slip and fall accidents cost billions of dollars each year. Shoe-floor-lubricant friction has been shown to follow the Stribeck effect, operating primarily in the boundary and mixed-Lubrication Regimes. Two of the most important factors believed to significantly contribute to shoe-floor-lubricant friction in the boundary Lubrication Regime are adhesion and ploughing. Experiments were conducted using a pin-on-disk tribometer to quantify adhesion and ploughing contributions to shoe-floor friction in dry and lubricated conditions. The coefficient of friction between three shoe materials and two floor materials of different hardness and roughness were considered. Experiments were conducted under six lubricants for a sliding speed of 0.01 m/sec at ambient conditions. It was found that the contribution of adhesion and ploughing to shoe-floor-lubricant friction was significantly affected by material hardness, roughness, and lubricant properties. Material hardness and roughness are known to affect adhesion, with increased hardness or increased roughness typically resulting in decreased adhesion. The smoothest shoe material, while also being the hardest, resulted in the greatest adhesional contribution to friction. The roughest material, while also being the softest, resulted in the lowest adhesional contributions under dry conditions. Canola oil consistently resulted in the lowest percent of full adhesion and water consistently resulted in the highest percent of full adhesion, presumably due to the thickness, of the boundary Lubrication layer. Ploughing contribution was dependent upon the hardness of the shoe and floor materials. A positive correlation was found between the shoe and floor hardness ratio and ploughing coefficient of friction.Copyright © 2011 by ASME
-
The Response of Balls Undergoing Oscillatory Motion: Crossing From Boundary to Mixed Lubrication Regimes
Journal of Tribology, 1993Co-Authors: Michael R. Lovell, Michael M. Khonsari, R. D. MarangoniAbstract:There are many applications where determining the response of a slowly oscillating ball bearing becomes crucial. Many instrument pointing mechanisms, in particular those used for aerospace applications, contain ball bearings which sinusoidally oscillate at very slow rates over small angles. Prediction of the frictional response of these bearings is essential to designers, as the friction torque which they develop is an important factor for controlling space instruments. The friction torque associated with the motion of sinusoidally oscillating ball bearings has been found to trace out hysteresis loops. These loops can be separated into two regions: the steady rolling region and the pre-rolling region. The steady rolling friction torque, Ts , characterizes the steady rolling region, while the rest slope, σ, characterizes the pre-rolling region. The speed of a ball bearing in sinusoidal motion varies from rest to a maximum velocity, changing velocity at instantaneous increments. It is found that while moving toward this maximum velocity, a bearing may cross from boundary to mixed Lubrication Regimes. As a result, the prediction and interpretation of σ and Ts in sinusoidal oscillating systems becomes more difficult than their counterparts in constant rate systems, which ordinarily operate in only one Lubrication Regime. To establish the velocity boundaries associated with the onset of different Lubrication Regimes, a series of experiments were conducted at a constant rotation rate. Starting at the ultra-low-speed of .01 deg/s, the angular velocity was gradually increased to 72 deg/s. In this velocity range, the balls traveled from boundary Lubrication, crossing the mixed Lubrication Regime, into the elastohydrodynamic Lubrication Regime. Sinusoidal hysteresis curves were also generated experimentally and characterized. The rest slope and steady rolling friction torque were investigated in both rolling regions using two different lubricants.
Jürgen Rühe - One of the best experts on this subject based on the ideXlab platform.
-
Ultralow Friction of Steel Surfaces Using a 1,3-Diketone Lubricant in the Thin Film Lubrication Regime
Langmuir, 2015Co-Authors: Ke Li, Tobias Amann, Mathias List, Andreas Kailer, Michael Walter, Michael Moseler, Jürgen RüheAbstract:Ultralow friction (coefficient of friction μ ≈ 0.005) is observed when two steel surfaces are brought into sliding contact in the presence of a particular 1,3-diketone lubricant (1-(4-ethyl phenyl) nonane-1,3-dione). We investigate the friction process of such a system both experimentally and theoretically and show that the superlubricity is caused by a novel, unique mechanism: The formation of iron-1,3-diketonato complexes during frictional contact leads to a self-limiting, tribochemical polishing process while at the same time a self-assembled monolayer of the diketone is formed on the employed steel surfaces. This polishing process reduces the contact pressure and at the same time leads to formation of a boundary lubricant layer. During sliding the system transits from the original boundary Lubrication Regime toward hydrodynamic Lubrication. Conductivity measurements across the friction gap during sliding show that the lubricant layer present in the gap between the two shearing surfaces is a only few 1...
-
Ultralow Friction of Steel Surfaces Using a 1,3-Diketone Lubricant in the Thin Film Lubrication Regime
Langmuir, 2015Co-Authors: Ke Li, Tobias Amann, Mathias List, Andreas Kailer, Michael Walter, Michael Moseler, Jürgen RüheAbstract:Ultralow friction (coefficient of friction μ ≈ 0.005) is observed when two steel surfaces are brought into sliding contact in the presence of a particular 1,3-diketone lubricant (1-(4-ethyl phenyl) nonane-1,3-dione). We investigate the friction process of such a system both experimentally and theoretically and show that the superlubricity is caused by a novel, unique mechanism: The formation of iron-1,3-diketonato complexes during frictional contact leads to a self-limiting, tribochemical polishing process while at the same time a self-assembled monolayer of the diketone is formed on the employed steel surfaces. This polishing process reduces the contact pressure and at the same time leads to formation of a boundary lubricant layer. During sliding the system transits from the original boundary Lubrication Regime toward hydrodynamic Lubrication. Conductivity measurements across the friction gap during sliding show that the lubricant layer present in the gap between the two shearing surfaces is a only few 10 nanometers thick, so that the molecules experience under typical sliding conditions shear rates of a few 10(6) s(-1). Simulations show that under such strong shear the molecules become strongly oriented in the friction gap and the effective viscosity in sliding direction is significantly reduced so that the system is in the thin film Lubrication Regime and superlubricity is observed. The results of the experiments suggest that such diketones are promising lubricants to achieve a decrease of energy loss and frictional damage in steel based mechanical devices.
Ke Li - One of the best experts on this subject based on the ideXlab platform.
-
Ultralow Friction of Steel Surfaces Using a 1,3-Diketone Lubricant in the Thin Film Lubrication Regime
Langmuir, 2015Co-Authors: Ke Li, Tobias Amann, Mathias List, Andreas Kailer, Michael Walter, Michael Moseler, Jürgen RüheAbstract:Ultralow friction (coefficient of friction μ ≈ 0.005) is observed when two steel surfaces are brought into sliding contact in the presence of a particular 1,3-diketone lubricant (1-(4-ethyl phenyl) nonane-1,3-dione). We investigate the friction process of such a system both experimentally and theoretically and show that the superlubricity is caused by a novel, unique mechanism: The formation of iron-1,3-diketonato complexes during frictional contact leads to a self-limiting, tribochemical polishing process while at the same time a self-assembled monolayer of the diketone is formed on the employed steel surfaces. This polishing process reduces the contact pressure and at the same time leads to formation of a boundary lubricant layer. During sliding the system transits from the original boundary Lubrication Regime toward hydrodynamic Lubrication. Conductivity measurements across the friction gap during sliding show that the lubricant layer present in the gap between the two shearing surfaces is a only few 1...
-
Ultralow Friction of Steel Surfaces Using a 1,3-Diketone Lubricant in the Thin Film Lubrication Regime
Langmuir, 2015Co-Authors: Ke Li, Tobias Amann, Mathias List, Andreas Kailer, Michael Walter, Michael Moseler, Jürgen RüheAbstract:Ultralow friction (coefficient of friction μ ≈ 0.005) is observed when two steel surfaces are brought into sliding contact in the presence of a particular 1,3-diketone lubricant (1-(4-ethyl phenyl) nonane-1,3-dione). We investigate the friction process of such a system both experimentally and theoretically and show that the superlubricity is caused by a novel, unique mechanism: The formation of iron-1,3-diketonato complexes during frictional contact leads to a self-limiting, tribochemical polishing process while at the same time a self-assembled monolayer of the diketone is formed on the employed steel surfaces. This polishing process reduces the contact pressure and at the same time leads to formation of a boundary lubricant layer. During sliding the system transits from the original boundary Lubrication Regime toward hydrodynamic Lubrication. Conductivity measurements across the friction gap during sliding show that the lubricant layer present in the gap between the two shearing surfaces is a only few 10 nanometers thick, so that the molecules experience under typical sliding conditions shear rates of a few 10(6) s(-1). Simulations show that under such strong shear the molecules become strongly oriented in the friction gap and the effective viscosity in sliding direction is significantly reduced so that the system is in the thin film Lubrication Regime and superlubricity is observed. The results of the experiments suggest that such diketones are promising lubricants to achieve a decrease of energy loss and frictional damage in steel based mechanical devices.
Anne Neville - One of the best experts on this subject based on the ideXlab platform.
-
Modelling tribochemistry in the mixed Lubrication Regime
Tribology International, 2019Co-Authors: Abdullah Azam, Ali Ghanbarzadeh, Ardian Morina, Anne Neville, Mark C. T. WilsonAbstract:Mixed Lubrication is a contact condition when the total load is carried by both the fluid lubricant and the solid contacting asperities. The aim of this study is to couple tribochemistry with Lubrication. A recent semi-deterministic tribochemical model of tribofilm growth is integrated in a deterministic mixed Lubrication model. The model considers the variable hardness of the tribofilm and enables the study of Lubrication and tribochemistry and their mutual interaction. Results from the current model are compared against the previously published results. The model can be easily adapted to actual experimental conditions and geometries. The model can be used beyond pure boundary Lubrication conditions to monitor tribofilm growth under mixed Lubrication conditions.
-
corrosive abrasive wear induced by soot in boundary Lubrication Regime
Tribology Letters, 2016Co-Authors: Motamen F Salehi, Ardian Morina, D. N. Khaemba, Anne NevilleAbstract:Soot is known to induce high wear in engine components. The mechanism by which soot induces wear is not well understood. Although several mechanisms have been suggested, there is still no consensus. This study aims to investigate the most likely mechanism responsible for soot-induced wear in the boundary Lubrication Regime. Results from this study have shown that previously suggested mechanisms such as abrasion and additive adsorption do not fully explain the high wear observed when soot is present. Based on the results obtained from tests conducted at varying temperature and soot levels, it has been proven that the corrosive–abrasive mechanism was responsible for high wear that occurred in boundary Lubrication conditions.
-
Designing new lubricant additives using biomimetics
Design and Nature III: Comparing Design in Nature with Science and Engineering, 2006Co-Authors: Ardian Morina, Tomasz Liskiewicz, Anne NevilleAbstract:Nature produces some complex nanocomposite structures having the following properties, self-healing capability, functional gradation and smartness. These properties are all required of tribofilms in the field of Lubrication technology where their structure, formation and removal rate and smartness are key to their ability to maintain fuel economy and durability. In this paper the potential for using biomimetic principles in the field of tribology and specifically as a means of improving tribological performance in the boundary Lubrication Regime is investigated. The paper initially describes the challenges associated with operating tribological contacts in the boundary Lubrication Regime, assesses the need for new approaches to Lubrication and gives a preliminary appraisal of biomimetic principles applied to this engineering problem.
Patrick Maspeyrot - One of the best experts on this subject based on the ideXlab platform.
-
influence of surface texturing on the hydrodynamic performance of a thrust bearing operating in steady state and transient Lubrication Regime
Tribology International, 2016Co-Authors: A Gherca, Aurelian Fatu, M Hajjam, Patrick MaspeyrotAbstract:Abstract This paper presents a finite element modeling of hydrodynamic thrust bearings operating both in steady-state and transient Lubrication Regime. The presented numerical algorithm is conservative and makes it possible to determine, with a high degree of accuracy, the operating characteristics such as the friction torque, the film pressure, the film thickness and the oil flow. For different operating conditions, it was shown that the behavior of the thrust bearing is not the same when textures are applied on the rotor or on the stator. Thus, the difference in behavior between the stationary and non-stationary case was revealed. Lastly, it was predicted that placing the textures on the rotor could, under certain conditions, improve the hydrodynamic performance of the thrust bearing.
