The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform

Yonggang Meng - One of the best experts on this subject based on the ideXlab platform.

  • Spatiotemporal manipulation of Boundary Lubrication by electro-charging and electrochemical methods
    Superlubricity, 2021
    Co-Authors: Yonggang Meng, Chenxu Liu
    Abstract:

    Abstract Active tribology is an emerging technology that enables in-process fine-tuning of adhesion, friction, wear, and Lubrication of interfaces by providing supplementary external stimuli. This chapter presents a survey on the progress in manipulation of Boundary Lubrication by electro-charging and electrochemical methods in liquid Lubrication systems, which is a subset of the active tribology researches. Achievements of the researches on potential control of Boundary Lubrication in pure water, acids, aqueous surfactant solutions, and polar base oils with different kinds of additives, including ionic liquids, nanoparticles, and ZDDP, are reviewed consequently. The mechanisms of the observed effects of potential controlled Boundary Lubrication in various test conditions are discussed in the viewpoint of multiscale and multidisciplinary approaches. A summary of the findings and prospects for industrial application are provided.

  • Boundary Lubrication by adsorption film
    Friction, 2015
    Co-Authors: Jun Zhang, Yonggang Meng
    Abstract:

    A complete understanding of the mechanism of Boundary Lubrication is a goal that scientists have been striving to achieve over the past century. Although this complicated process has been far from fully revealed, a general picture and its influencing factors have been elucidated, not only at the macroscopic scale but also at the nanoscale, which is sufficiently clear to provide effective instructions for a Lubrication design in engineering and even to efficiently control the Boundary Lubrication properties. Herein, we provide a review on the main advances, especially the breakthroughs in uncovering the mysterious but useful process of Boundary Lubrication by adsorption film. Despite the existence of an enormous amount of knowledge, albeit unsystematic, acquired in this area, in the present review, an effort was made to clarify the mainline of leading perspectives and methodologies in revealing the fundamental problems inherent to Boundary Lubrication. The main content of this review includes the formation of Boundary film, the effects of Boundary film on the adhesion and friction of rough surfaces, the behavior of adsorption film in Boundary Lubrication, Boundary Lubrication at the nanoscale, and the active control of Boundary Lubrication, generally sequenced based on the real history of our understanding of this process over the past century, incorporated by related modern concepts and prospects.

  • Stick–Slip Friction of Stainless Steel in Sodium Dodecyl Sulfate Aqueous Solution in the Boundary Lubrication Regime
    Tribology Letters, 2014
    Co-Authors: Jun Zhang, Yonggang Meng
    Abstract:

    The objective of this study is to correlate the mass and structure of the adsorbed sodium dodecyl sulfate (SDS) on stainless steel surface in aqueous solution with the Boundary Lubrication behavior, especially the stick–slip phenomenon of the ZrO2/stainless steel friction pair. Surface tension measurement, quartz crystal microbalance (QCM) technique and ball-on-flat friction test were performed in this study. The adsorption isotherm of SDS on stainless steel surface in SDS aqueous solution was measured by QCM, and four-stage adsorption behavior was found at the solid/liquid interface. As the SDS concentration increases, the mass of the adsorbed SDS molecules increases, while the structure of the adsorbed layer changes from monomers to hemimicelles. Tribological properties of ZrO2/stainless steel friction pair in SDS aqueous solution were verified with an UMT-3 tester. Boundary Lubrication was emphasized as water-based Lubrication easily fails in hydrodynamic Lubrication due to its low viscosity. Stick–slip phenomenon was observed in the Boundary Lubrication of the adsorbed SDS film under certain loading and sliding conditions. Both the static and kinetic friction coefficients were analyzed with respect to the SDS concentration and sliding velocity. The stick–slip phenomenon is related to both of the adsorbed mass and adsorption structure of the SDS Boundary film.

  • stick slip friction of stainless steel in sodium dodecyl sulfate aqueous solution in the Boundary Lubrication regime
    Tribology Letters, 2014
    Co-Authors: Jun Zhang, Yonggang Meng
    Abstract:

    The objective of this study is to correlate the mass and structure of the adsorbed sodium dodecyl sulfate (SDS) on stainless steel surface in aqueous solution with the Boundary Lubrication behavior, especially the stick–slip phenomenon of the ZrO2/stainless steel friction pair. Surface tension measurement, quartz crystal microbalance (QCM) technique and ball-on-flat friction test were performed in this study. The adsorption isotherm of SDS on stainless steel surface in SDS aqueous solution was measured by QCM, and four-stage adsorption behavior was found at the solid/liquid interface. As the SDS concentration increases, the mass of the adsorbed SDS molecules increases, while the structure of the adsorbed layer changes from monomers to hemimicelles. Tribological properties of ZrO2/stainless steel friction pair in SDS aqueous solution were verified with an UMT-3 tester. Boundary Lubrication was emphasized as water-based Lubrication easily fails in hydrodynamic Lubrication due to its low viscosity. Stick–slip phenomenon was observed in the Boundary Lubrication of the adsorbed SDS film under certain loading and sliding conditions. Both the static and kinetic friction coefficients were analyzed with respect to the SDS concentration and sliding velocity. The stick–slip phenomenon is related to both of the adsorbed mass and adsorption structure of the SDS Boundary film.

Anne Neville - One of the best experts on this subject based on the ideXlab platform.

  • corrosive abrasive wear induced by soot in Boundary Lubrication regime
    Tribology Letters, 2016
    Co-Authors: Motamen F Salehi, Ardian Morina, D. N. Khaemba, Anne Neville
    Abstract:

    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.

  • development of a new mechano chemical model in Boundary Lubrication
    Tribology International, 2016
    Co-Authors: Ali Ghanbarzadeh, Ardian Morina, M C T Wilson, D Dowson, Anne Neville
    Abstract:

    A newly developed tribochemical model based on thermodynamics of interfaces and kinetics of tribochemical reactions is implemented in a contact mechanics simulation and the results are validated against experimental results. The model considers both mechanical and thermal activation of tribochemical reactions instead of former thermal activation theories. The model considers tribofilm removal and is able to capture the tribofilm behaviour during the experiment. The aim of this work is to implement tribochemistry into deterministic modelling of Boundary Lubrication and study the effect of tribofilms in reducing friction or wear. A new contact mechanics model considering normal and tangential forces in Boundary Lubrication is developed for two real rough steel surfaces. The model is developed for real tribological systems and is flexible to different laboratory experiments. Tribochemistry (e.g. tribofilm formation and removal) and also mechanical properties are considered in this model. The amount of wear is calculated using a modified Archard’s wear equation accounting for local tribofilm thickness and its mechanical properties. This model can be used for monitoring the tribofilm growth on rough surfaces and also the real time surface roughness as well as changes in the λ ratio. This model enables the observation of in-situ tribofilm thickness and surface coverage and helps in better understanding the real mechanisms of wear.

  • Effect of Lubricant Additives on the WDLC Coating Structure When Tested in Boundary Lubrication Regime
    Tribology Letters, 2015
    Co-Authors: Liuquan Yang, Anne Neville, Alisdair Brown, Paul Ransom, Ardian Morina
    Abstract:

    Improvements in coating deposition technology enable the mass production of high-quality diamond-like carbon (DLC) coatings at an industrial scale and also increase their use in lubricated contacts. However, the understanding of the interactions of different lubricant additives with this material is not yet fully developed. This study focuses on several fundamental aspects of the tungsten-doped DLC coating (denoted as WDLC) behaviour under Boundary Lubrication conditions with model lubricants. The effect of lubricant additives on the coating structure change is discussed in terms of carbon structure and the tungsten dopant. Electron energy-loss spectroscopy, XPS and Raman spectroscopy characterization for the upper carbon layers indicate that the WDLC coating interacts chemically with selected lubricant additives. The study provides information on both coating and additive optimization under Boundary Lubrication.

  • Subscale Tribofilm Tribological Modelling in Boundary Lubrication Using Multivariate Analysis
    Proceedings of the Institution of Mechanical Engineers Part J: Journal of Engineering Tribology, 2011
    Co-Authors: R Roshan, Ardian Morina, Anne Neville, Martin Priest, X Xia, C P Warrens, M J Payne
    Abstract:

    A subscale tribofilm tribological performance model has been developed to investigate the sensitivity of the model to lubricant chemistries and tribological factors in Boundary Lubrication conditions. Tribological modelling of tribofilm performance in Boundary Lubrication deals with a large number of variables. Thus, multivariate techniques were used to obtain the subscale tribofilm friction and wear models in terms of additive concentration in the oil and tribological factors. Soft Independent Modelling of Class Analogy classification techniques such as principal component analysis and partial least squares regression were used to correlate the outputs friction, wear, and lambda ratio with additive concentration in a model oil and tribological factors. The results show that Boundary Lubrication can be divided into three ‘subscale’ Lubrication regimes which can be defined as (a) severe, (b) moderate, and (c) mild Boundary Lubrication conditions. The predictions from the friction and wear models showed var...

  • Friction Modelling in Boundary Lubrication Considering the Effect of MoDTC and ZDDP in Engine Oils
    Tribology Online, 2011
    Co-Authors: R Roshan, Ardian Morina, Anne Neville, Martin Priest, X Xia, C P Warrens, M J Payne
    Abstract:

    A predictive friction model has been developed in Boundary Lubrication conditions to understand the sensitivity of the model to molybdenum dithiocarbamate (MoDTC), a friction modifying additive and zinc dialkyldithiophosphate (ZDDP), an antiwear additive in engine oil. Controlled experiments were performed on a block-on-ring tribometer to record the friction performance of the tribofilms produced by ZDDP and MoDTC additives under conditions representative of Boundary Lubrication conditions in the cam and follower interface. A statistical approach was used to develop an empirical friction model. The Boundary Lubrication friction model considers ZDDP and MoDTC additive concentration in an ester-containing polyalphaolefin (PAO) base oil, temperature and sliding speed as the factors affecting friction. The friction significantly depends on ZDDP, MoDTC, speed and temperature; showing a ZDDP/MoDTC synergetic effect on reducing friction. The results show good agreement between the measured and the predicted friction values, with a high correlation coefficient.

Jun Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Boundary Lubrication by adsorption film
    Friction, 2015
    Co-Authors: Jun Zhang, Yonggang Meng
    Abstract:

    A complete understanding of the mechanism of Boundary Lubrication is a goal that scientists have been striving to achieve over the past century. Although this complicated process has been far from fully revealed, a general picture and its influencing factors have been elucidated, not only at the macroscopic scale but also at the nanoscale, which is sufficiently clear to provide effective instructions for a Lubrication design in engineering and even to efficiently control the Boundary Lubrication properties. Herein, we provide a review on the main advances, especially the breakthroughs in uncovering the mysterious but useful process of Boundary Lubrication by adsorption film. Despite the existence of an enormous amount of knowledge, albeit unsystematic, acquired in this area, in the present review, an effort was made to clarify the mainline of leading perspectives and methodologies in revealing the fundamental problems inherent to Boundary Lubrication. The main content of this review includes the formation of Boundary film, the effects of Boundary film on the adhesion and friction of rough surfaces, the behavior of adsorption film in Boundary Lubrication, Boundary Lubrication at the nanoscale, and the active control of Boundary Lubrication, generally sequenced based on the real history of our understanding of this process over the past century, incorporated by related modern concepts and prospects.

  • Stick–Slip Friction of Stainless Steel in Sodium Dodecyl Sulfate Aqueous Solution in the Boundary Lubrication Regime
    Tribology Letters, 2014
    Co-Authors: Jun Zhang, Yonggang Meng
    Abstract:

    The objective of this study is to correlate the mass and structure of the adsorbed sodium dodecyl sulfate (SDS) on stainless steel surface in aqueous solution with the Boundary Lubrication behavior, especially the stick–slip phenomenon of the ZrO2/stainless steel friction pair. Surface tension measurement, quartz crystal microbalance (QCM) technique and ball-on-flat friction test were performed in this study. The adsorption isotherm of SDS on stainless steel surface in SDS aqueous solution was measured by QCM, and four-stage adsorption behavior was found at the solid/liquid interface. As the SDS concentration increases, the mass of the adsorbed SDS molecules increases, while the structure of the adsorbed layer changes from monomers to hemimicelles. Tribological properties of ZrO2/stainless steel friction pair in SDS aqueous solution were verified with an UMT-3 tester. Boundary Lubrication was emphasized as water-based Lubrication easily fails in hydrodynamic Lubrication due to its low viscosity. Stick–slip phenomenon was observed in the Boundary Lubrication of the adsorbed SDS film under certain loading and sliding conditions. Both the static and kinetic friction coefficients were analyzed with respect to the SDS concentration and sliding velocity. The stick–slip phenomenon is related to both of the adsorbed mass and adsorption structure of the SDS Boundary film.

  • stick slip friction of stainless steel in sodium dodecyl sulfate aqueous solution in the Boundary Lubrication regime
    Tribology Letters, 2014
    Co-Authors: Jun Zhang, Yonggang Meng
    Abstract:

    The objective of this study is to correlate the mass and structure of the adsorbed sodium dodecyl sulfate (SDS) on stainless steel surface in aqueous solution with the Boundary Lubrication behavior, especially the stick–slip phenomenon of the ZrO2/stainless steel friction pair. Surface tension measurement, quartz crystal microbalance (QCM) technique and ball-on-flat friction test were performed in this study. The adsorption isotherm of SDS on stainless steel surface in SDS aqueous solution was measured by QCM, and four-stage adsorption behavior was found at the solid/liquid interface. As the SDS concentration increases, the mass of the adsorbed SDS molecules increases, while the structure of the adsorbed layer changes from monomers to hemimicelles. Tribological properties of ZrO2/stainless steel friction pair in SDS aqueous solution were verified with an UMT-3 tester. Boundary Lubrication was emphasized as water-based Lubrication easily fails in hydrodynamic Lubrication due to its low viscosity. Stick–slip phenomenon was observed in the Boundary Lubrication of the adsorbed SDS film under certain loading and sliding conditions. Both the static and kinetic friction coefficients were analyzed with respect to the SDS concentration and sliding velocity. The stick–slip phenomenon is related to both of the adsorbed mass and adsorption structure of the SDS Boundary film.

Ardian Morina - One of the best experts on this subject based on the ideXlab platform.

  • Corrosive–Abrasive Wear Induced by Soot in Boundary Lubrication Regime
    Tribology Letters, 2016
    Co-Authors: F. Motamen Salehi, Ardian Morina, D. N. Khaemba, A. Neville
    Abstract:

    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.

  • corrosive abrasive wear induced by soot in Boundary Lubrication regime
    Tribology Letters, 2016
    Co-Authors: Motamen F Salehi, Ardian Morina, D. N. Khaemba, Anne Neville
    Abstract:

    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.

  • development of a new mechano chemical model in Boundary Lubrication
    Tribology International, 2016
    Co-Authors: Ali Ghanbarzadeh, Ardian Morina, M C T Wilson, D Dowson, Anne Neville
    Abstract:

    A newly developed tribochemical model based on thermodynamics of interfaces and kinetics of tribochemical reactions is implemented in a contact mechanics simulation and the results are validated against experimental results. The model considers both mechanical and thermal activation of tribochemical reactions instead of former thermal activation theories. The model considers tribofilm removal and is able to capture the tribofilm behaviour during the experiment. The aim of this work is to implement tribochemistry into deterministic modelling of Boundary Lubrication and study the effect of tribofilms in reducing friction or wear. A new contact mechanics model considering normal and tangential forces in Boundary Lubrication is developed for two real rough steel surfaces. The model is developed for real tribological systems and is flexible to different laboratory experiments. Tribochemistry (e.g. tribofilm formation and removal) and also mechanical properties are considered in this model. The amount of wear is calculated using a modified Archard’s wear equation accounting for local tribofilm thickness and its mechanical properties. This model can be used for monitoring the tribofilm growth on rough surfaces and also the real time surface roughness as well as changes in the λ ratio. This model enables the observation of in-situ tribofilm thickness and surface coverage and helps in better understanding the real mechanisms of wear.

  • Effect of Lubricant Additives on the WDLC Coating Structure When Tested in Boundary Lubrication Regime
    Tribology Letters, 2015
    Co-Authors: Liuquan Yang, Anne Neville, Alisdair Brown, Paul Ransom, Ardian Morina
    Abstract:

    Improvements in coating deposition technology enable the mass production of high-quality diamond-like carbon (DLC) coatings at an industrial scale and also increase their use in lubricated contacts. However, the understanding of the interactions of different lubricant additives with this material is not yet fully developed. This study focuses on several fundamental aspects of the tungsten-doped DLC coating (denoted as WDLC) behaviour under Boundary Lubrication conditions with model lubricants. The effect of lubricant additives on the coating structure change is discussed in terms of carbon structure and the tungsten dopant. Electron energy-loss spectroscopy, XPS and Raman spectroscopy characterization for the upper carbon layers indicate that the WDLC coating interacts chemically with selected lubricant additives. The study provides information on both coating and additive optimization under Boundary Lubrication.

  • Subscale Tribofilm Tribological Modelling in Boundary Lubrication Using Multivariate Analysis
    Proceedings of the Institution of Mechanical Engineers Part J: Journal of Engineering Tribology, 2011
    Co-Authors: R Roshan, Ardian Morina, Anne Neville, Martin Priest, X Xia, C P Warrens, M J Payne
    Abstract:

    A subscale tribofilm tribological performance model has been developed to investigate the sensitivity of the model to lubricant chemistries and tribological factors in Boundary Lubrication conditions. Tribological modelling of tribofilm performance in Boundary Lubrication deals with a large number of variables. Thus, multivariate techniques were used to obtain the subscale tribofilm friction and wear models in terms of additive concentration in the oil and tribological factors. Soft Independent Modelling of Class Analogy classification techniques such as principal component analysis and partial least squares regression were used to correlate the outputs friction, wear, and lambda ratio with additive concentration in a model oil and tribological factors. The results show that Boundary Lubrication can be divided into three ‘subscale’ Lubrication regimes which can be defined as (a) severe, (b) moderate, and (c) mild Boundary Lubrication conditions. The predictions from the friction and wear models showed var...

Wuge H. Briscoe - One of the best experts on this subject based on the ideXlab platform.

  • Aqueous Boundary Lubrication: Molecular mechanisms, design strategy, and terra incognita
    Current Opinion in Colloid and Interface Science, 2017
    Co-Authors: Wuge H. Briscoe
    Abstract:

    The molecular mechanisms for aqueous Boundary Lubrication are very different from those in the classic Boundary Lubrication, originating from the fluidity of the hydration shells surrounding the surfactant and lipid headgroups. We discuss the important molecular and structural criteria for effective aqueous Boundary lubricants, and highlight the strategy for reinforcing the interfacial structure for aqueous Boundary Lubrication via synergistic interactions between amphiphilic polymers and lipids/surfactants. It is proposed that the energetic considerations of different molecular elastic deformations in the stalk model of cell membrane fusion can be applied to guide our design of molecular architectures for surfactants and lipids to implement structural integrity in aqueous Boundary Lubrication. We discuss a controversy associated with the quiescent bilayer structure in the context of Boundary lubricant interfacial structures. We also highlight other effective aqueous Boundary Lubrication systems, including hydrated ions and biomimetic hierarchical constructs inspired by the enigmatic and extremely efficient biological Lubrication. Finally, we suggest that the Stribeck curve might be re-considered in light of recent advances in aqueous Boundary Lubrication, although the exact scope of this new aqueous Boundary Lubrication regime remains terra incognita.

  • Boundary Lubrication under water
    Nature, 2006
    Co-Authors: Wuge H. Briscoe, Simon Titmuss, Jacob Klein, Fredrik Tiberg, Duncan J Mcgillivray, Robert J Thomas
    Abstract:

    Classical Boundary Lubrication is widespread in engineering applications and is also thought to exist in biological systems. It minimizes friction and wear by ensuring that rubbing takes place between the 'Boundary' layers of surfactant molecules that coat each surface, rather than between the substrates themselves. Experiments with Boundary-lubricant coated sliding surfaces immersed in water now show that friction stress can be reduced by two orders of magnitude or more, relative to its value in dry air. The mechanism may involve the hydration of charged head groups that can then slide easily on the surfaces to which they are attached. This new type of Boundary Lubrication could be useful for developing better lubricated artificial implants and new medical treatments for joint problems. Boundary Lubrication, in which the rubbing surfaces are coated with molecular monolayers, has been studied extensively for over half a century1,2,3,4,5,6,7. Such monolayers generally consist of amphiphilic surfactants anchored by their polar headgroups; sliding occurs at the interface between the layers, greatly reducing friction and especially wear of the underlying substrates. This process, widespread in engineering applications, is also predicted to occur in biological Lubrication via phospholipid films8,9, though few systematic studies on friction between surfactant layers in aqueous environments have been carried out5,10. Here we show that the frictional stress between two sliding surfaces bearing surfactant monolayers may decrease, when immersed in water, to as little as one per cent or less of its value in air (or oil). We attribute this to the shift of the slip plane from between the surfactant layers, to the surfactant/substrate interface. The low friction would then be due to the fluid hydration layers surrounding the polar head groups attached to the substrate. These results may have implications for future technological and biomedical applications.