Pub Date : 2019-06-21DOI: 10.3389/fmech.2019.00039
Leila Pashazanusi, K. Kristiansen, Shaowei Li, Yu Tian, N. Pesika
The tribological properties between an AFM tip and a Au(111) surface in an aqueous environment is influenced by an applied electrical potential. Using lateral force microscopy, we measure the resulting friction force, while simultaneously applying a predetermined electrical potential on the Au surface via a three-electrode setup. Applying a positive potential to the Au surface forms an interfacial water layer at the Au/electrolyte interface, which sharply increases friction. However, when an anodic potential is applied, lower friction forces are measured. The potential dependent friction is observed on ultra-smooth gold surfaces as well as Au surfaces with larger roughness. An increase in the ionic strength of the electrolyte is found to lower friction. The use of an aqueous NaOH solution is found to lower the critical potential at which the friction sharply increases. Normal force curves are also measured as a function of approach velocity. The normal force linearly increases as the approach velocity increases in agreement with a drainage model. These results provide valuable insight into the effect of applied electrical potentials on the properties of water at charged surfaces and can potentially impact a wide range of fields including tribology, micro-electro-mechanical systems (MEMS), energy storage devices, fuel cells and catalysis.
{"title":"Role of Interfacial Water and Applied Potential on Friction at Au(111) Surfaces","authors":"Leila Pashazanusi, K. Kristiansen, Shaowei Li, Yu Tian, N. Pesika","doi":"10.3389/fmech.2019.00039","DOIUrl":"https://doi.org/10.3389/fmech.2019.00039","url":null,"abstract":"The tribological properties between an AFM tip and a Au(111) surface in an aqueous environment is influenced by an applied electrical potential. Using lateral force microscopy, we measure the resulting friction force, while simultaneously applying a predetermined electrical potential on the Au surface via a three-electrode setup. Applying a positive potential to the Au surface forms an interfacial water layer at the Au/electrolyte interface, which sharply increases friction. However, when an anodic potential is applied, lower friction forces are measured. The potential dependent friction is observed on ultra-smooth gold surfaces as well as Au surfaces with larger roughness. An increase in the ionic strength of the electrolyte is found to lower friction. The use of an aqueous NaOH solution is found to lower the critical potential at which the friction sharply increases. Normal force curves are also measured as a function of approach velocity. The normal force linearly increases as the approach velocity increases in agreement with a drainage model. These results provide valuable insight into the effect of applied electrical potentials on the properties of water at charged surfaces and can potentially impact a wide range of fields including tribology, micro-electro-mechanical systems (MEMS), energy storage devices, fuel cells and catalysis.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"1 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83136030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-20DOI: 10.3389/fmech.2019.00034
Wei Tang, M. Finney, S. McAllister, M. Gollner
An experimental study was conducted to understand the intermittent heating behavior downstream of a gaseous line burner under forced flow conditions. While previous studies have addressed time-averaged properties, here measurements of the flame location and intermittent heat flux profile help to give a time-dependent picture of downstream heating from the flame, useful for understanding wind-driven flame spread. Two frequencies are extracted from experiments, the maximum flame forward pulsation frequency in the direction of the wind, which helps describe the motion of the flame, and the local flame-fuel contact frequency in the flame region, which is useful in calculating the actual heat flux that can be received by the unburnt fuel via direct flame contact. The forward pulsation frequency is obtained through video analysis using a variable interval time average (VITA) method. Scaling analysis indicates that the flame forward pulsation frequency varies as a power-law function of the Froude number and fire heat-release rate, . For the local flame-fuel contact frequency, it is found that the non-dimensional flame-fuel contact frequency remains approximately constant before the local Rix reaches 1, e.g., attached flames. When Rix>1, decreases with local as Rix flames lift up. A piece-wise function was proposed to predict the local flame-fuel contact frequency including the two Rix scenarios. Information from this study helps to shed light on the intermittent behavior of flames under wind, which may be a critical factor in explaining the mechanisms of forward flame spread in wildland and other similar wind-driven fires.
{"title":"An Experimental Study of Intermittent Heating Frequencies From Wind-Driven Flames","authors":"Wei Tang, M. Finney, S. McAllister, M. Gollner","doi":"10.3389/fmech.2019.00034","DOIUrl":"https://doi.org/10.3389/fmech.2019.00034","url":null,"abstract":"An experimental study was conducted to understand the intermittent heating behavior downstream of a gaseous line burner under forced flow conditions. While previous studies have addressed time-averaged properties, here measurements of the flame location and intermittent heat flux profile help to give a time-dependent picture of downstream heating from the flame, useful for understanding wind-driven flame spread. Two frequencies are extracted from experiments, the maximum flame forward pulsation frequency in the direction of the wind, which helps describe the motion of the flame, and the local flame-fuel contact frequency in the flame region, which is useful in calculating the actual heat flux that can be received by the unburnt fuel via direct flame contact. The forward pulsation frequency is obtained through video analysis using a variable interval time average (VITA) method. Scaling analysis indicates that the flame forward pulsation frequency varies as a power-law function of the Froude number and fire heat-release rate, . For the local flame-fuel contact frequency, it is found that the non-dimensional flame-fuel contact frequency remains approximately constant before the local Rix reaches 1, e.g., attached flames. When Rix>1, decreases with local as Rix flames lift up. A piece-wise function was proposed to predict the local flame-fuel contact frequency including the two Rix scenarios. Information from this study helps to shed light on the intermittent behavior of flames under wind, which may be a critical factor in explaining the mechanisms of forward flame spread in wildland and other similar wind-driven fires.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"4 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78423437","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-20DOI: 10.3389/fmech.2019.00033
Suresh Jadhav, G. D. Thakre, Satish C. Sharma
The present numerical study investigates the combined effect of micro-texture and magneto hydrodynamic lubrication behaviour on the performance of EHL line contact. Micro-textures are provided in the inlet zone of contacting surface has been studied. Modified Reynolds equation, elasticity equation and load balance equation has been solved using FEA and Generalized Minimal Residual Method (GMRES). A parametric study has been performed to optimize the micro-texture shapes in the contacting surfaces for different values of magneto hydrodynamic lubricant parameters The numerical results show that increasing externally applied magnetic field and micro- texture shapes enhances the values of performance parameter of EHL line contact. Finally, the variation in the steady-state EHL characteristics pertaining to unidirectional pure sliding contacts due to an artificially produced IZMTS is investigated numerically. The enhancement in central and minimum film thickness is found to be upto 38% and 28% respectively along with 33.28% reduction in coefficient of friction.
{"title":"Influence of MHD Lubrication and Textured Surface in EHL Line Contact","authors":"Suresh Jadhav, G. D. Thakre, Satish C. Sharma","doi":"10.3389/fmech.2019.00033","DOIUrl":"https://doi.org/10.3389/fmech.2019.00033","url":null,"abstract":"The present numerical study investigates the combined effect of micro-texture and magneto hydrodynamic lubrication behaviour on the performance of EHL line contact. Micro-textures are provided in the inlet zone of contacting surface has been studied. Modified Reynolds equation, elasticity equation and load balance equation has been solved using FEA and Generalized Minimal Residual Method (GMRES). A parametric study has been performed to optimize the micro-texture shapes in the contacting surfaces for different values of magneto hydrodynamic lubricant parameters The numerical results show that increasing externally applied magnetic field and micro- texture shapes enhances the values of performance parameter of EHL line contact. Finally, the variation in the steady-state EHL characteristics pertaining to unidirectional pure sliding contacts due to an artificially produced IZMTS is investigated numerically. The enhancement in central and minimum film thickness is found to be upto 38% and 28% respectively along with 33.28% reduction in coefficient of friction.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"21 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78589404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-20DOI: 10.3389/fmech.2019.00036
S. Eswaramoorthi, M. Bhuvaneswari
The present article addresses the impact of passive control (PC) and active control(AC) on 3D flow of a viscoelastic nanofluid upon a stretching plate including heat generation and convective heating. The system of appearing non-linear PDE’s are converted into a couple of ODE’s by using suitable similarity transformations. Convergent series solutions are derived using homotopy analysis method (HAM). Graphical results of velocity, nanoparticle volume fraction and temperature of different pertinent physical parameters with notable discussions are pointed with their physical significance
{"title":"Passive and Active Control on 3D Convective Flow of Viscoelastic Nanofluid With Heat Generation and Convective Heating","authors":"S. Eswaramoorthi, M. Bhuvaneswari","doi":"10.3389/fmech.2019.00036","DOIUrl":"https://doi.org/10.3389/fmech.2019.00036","url":null,"abstract":"The present article addresses the impact of passive control (PC) and active control(AC) on 3D flow of a viscoelastic nanofluid upon a stretching plate including heat generation and convective heating. The system of appearing non-linear PDE’s are converted into a couple of ODE’s by using suitable similarity transformations. Convergent series solutions are derived using homotopy analysis method (HAM). Graphical results of velocity, nanoparticle volume fraction and temperature of different pertinent physical parameters with notable discussions are pointed with their physical significance","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"24 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89039074","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-14DOI: 10.3389/fmech.2019.00032
Sara E. Caton-Kerr, A. Tohidi, M. Gollner
During wildland fires, firebrands form once they break off of burning vegetation or structures. Many are then lofted into the fire plume where they are transported long distances ahead of the fire front, igniting new “spot” fires as they land. To date, very few studies have been conducted on the breakage mechanism of thermally-degraded vegetative elements. Knowledge of these mechanisms is needed to feed mathematical models of firebrand transport from traditional wildfires as well as those that spread into communities. First, a framework to understand the behavior of thermally-degraded wooden elements under simultaneous external loading is presented. A set of experiments were designed such that cylindrical wooden dowels of different species are exposed to different heating conditions similar to wildland fires, in order to model the breakage mechanisms of these elements in the absence of wind. The thermally-degraded elements are subjected to the three-point bending test to obtain the mechanical response of the materials after combustion. Assuming Hookean Orthotropic behavior for combusted dowels, dimensional analysis of the results reveals that the ultimate strength of the dowels is affected by the recoverable elastic strain during loading, which is found to occur under two distinct regimes. These results are not only important for better understanding of the breakage mechanisms but also are advantageous for developing a failure theory of thermally degrading wooden elements under simultaneous wind loading conditions.
{"title":"Firebrand Generation From Thermally-Degraded Cylindrical Wooden Dowels","authors":"Sara E. Caton-Kerr, A. Tohidi, M. Gollner","doi":"10.3389/fmech.2019.00032","DOIUrl":"https://doi.org/10.3389/fmech.2019.00032","url":null,"abstract":"During wildland fires, firebrands form once they break off of burning vegetation or structures. Many are then lofted into the fire plume where they are transported long distances ahead of the fire front, igniting new “spot” fires as they land. To date, very few studies have been conducted on the breakage mechanism of thermally-degraded vegetative elements. Knowledge of these mechanisms is needed to feed mathematical models of firebrand transport from traditional wildfires as well as those that spread into communities. First, a framework to understand the behavior of thermally-degraded wooden elements under simultaneous external loading is presented. A set of experiments were designed such that cylindrical wooden dowels of different species are exposed to different heating conditions similar to wildland fires, in order to model the breakage mechanisms of these elements in the absence of wind. The thermally-degraded elements are subjected to the three-point bending test to obtain the mechanical response of the materials after combustion. Assuming Hookean Orthotropic behavior for combusted dowels, dimensional analysis of the results reveals that the ultimate strength of the dowels is affected by the recoverable elastic strain during loading, which is found to occur under two distinct regimes. These results are not only important for better understanding of the breakage mechanisms but also are advantageous for developing a failure theory of thermally degrading wooden elements under simultaneous wind loading conditions.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"6 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80005873","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-06DOI: 10.3389/fmech.2019.00031
A. Kovalev, Yazhao Zhang, Cao Hui, Y. Meng
A new concept of the effective surface profile is proposed to facilitate the prediction of the wear texture on a surface under linear sliding conditions. The effective surface profile is a 2D phenomenological height characteristic that consist of the asperities of surface superimposed on a plane perpendicular both to the mean surface plane and to the direction of sliding. We hope to present a clear and compelling argument favoring the use of the effective surface profile as a versatile tool for characterization of rough surface subjected to an abrasive wear, calculation of contact characteristic at the sliding friction and for prediction of evolution of roughness parameters from virgin to the worn surfaces that being formed due to the mechanical wear. The effective surface profile can be successfully applied as for investigations of sliding abrasive wear under dry or lubricated conditions.
{"title":"A Concept of the Effective Surface Profile to Predict the Roughness Parameters of Worn Surface","authors":"A. Kovalev, Yazhao Zhang, Cao Hui, Y. Meng","doi":"10.3389/fmech.2019.00031","DOIUrl":"https://doi.org/10.3389/fmech.2019.00031","url":null,"abstract":"A new concept of the effective surface profile is proposed to facilitate the prediction of the wear texture on a surface under linear sliding conditions. The effective surface profile is a 2D phenomenological height characteristic that consist of the asperities of surface superimposed on a plane perpendicular both to the mean surface plane and to the direction of sliding. We hope to present a clear and compelling argument favoring the use of the effective surface profile as a versatile tool for characterization of rough surface subjected to an abrasive wear, calculation of contact characteristic at the sliding friction and for prediction of evolution of roughness parameters from virgin to the worn surfaces that being formed due to the mechanical wear. The effective surface profile can be successfully applied as for investigations of sliding abrasive wear under dry or lubricated conditions.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"4 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74313380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-04DOI: 10.3389/fmech.2019.00029
K. Yazawa, P. Shamberger, T. Fisher
The Ragone relation is a facile approach to assess and compare electro-chemical battery performance in terms of two critical performance parameters: power density and energy density. This power and energy nexus is equally relevant for thermal energy storage materials for thermal management applications that require a balance between energy storage capacity and on-demand cooling or heating rates. Here, thermal energy storage is evaluated for sensible heating and for phase-change materials (PCMs). We propose an analytic expression using a lumped mass model for thermal storage through an analogy with heat diffusion that allows for intuitive mapping of materials and components in power-energy space. In addition, a previously proposed figure-of-merit, $eta_q$, describing the intrinsic capability of PCMs to rapidly absorb or discharge heat is placed in the context of the thermal Ragone (power-energy) relation. This figure of merit serves as a proxy for the cooling power of PCMs and single-phase materials to store thermal energy. Thus, $eta_q$ plotted against energy density can serve graphically to illustrate performance tradeoffs between different thermal storage materials, as well as composites composed of different materials.
{"title":"Ragone Relations for Thermal Energy Storage Technologies","authors":"K. Yazawa, P. Shamberger, T. Fisher","doi":"10.3389/fmech.2019.00029","DOIUrl":"https://doi.org/10.3389/fmech.2019.00029","url":null,"abstract":"The Ragone relation is a facile approach to assess and compare electro-chemical battery performance in terms of two critical performance parameters: power density and energy density. This power and energy nexus is equally relevant for thermal energy storage materials for thermal management applications that require a balance between energy storage capacity and on-demand cooling or heating rates. Here, thermal energy storage is evaluated for sensible heating and for phase-change materials (PCMs). We propose an analytic expression using a lumped mass model for thermal storage through an analogy with heat diffusion that allows for intuitive mapping of materials and components in power-energy space. In addition, a previously proposed figure-of-merit, $eta_q$, describing the intrinsic capability of PCMs to rapidly absorb or discharge heat is placed in the context of the thermal Ragone (power-energy) relation. This figure of merit serves as a proxy for the cooling power of PCMs and single-phase materials to store thermal energy. Thus, $eta_q$ plotted against energy density can serve graphically to illustrate performance tradeoffs between different thermal storage materials, as well as composites composed of different materials.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"1 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83668243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-05-29DOI: 10.3389/fmech.2019.00030
I. Argatov
In the present paper, artificial neural networks (ANNs) are considered from a mathematical modelling point of view. A short introduction to feedforward neural networks is outlined, including multilayer perceptrons (MLPs) and radial basis function (RBF) networks. Examples of their applications in tribological studies are given, and important features of the data-driven modelling paradigm are discussed.
{"title":"Artificial Neural Networks (ANNs) as a Novel Modeling Technique in Tribology","authors":"I. Argatov","doi":"10.3389/fmech.2019.00030","DOIUrl":"https://doi.org/10.3389/fmech.2019.00030","url":null,"abstract":"In the present paper, artificial neural networks (ANNs) are considered from a mathematical modelling point of view. A short introduction to feedforward neural networks is outlined, including multilayer perceptrons (MLPs) and radial basis function (RBF) networks. Examples of their applications in tribological studies are given, and important features of the data-driven modelling paradigm are discussed.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"2014 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73289461","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-05-22DOI: 10.3389/fmech.2019.00028
M. Müser
Yes, there are. They result from the splitting of a large correlated contact into many small patches. When the lubricant consists of thin solid sheets, like graphene, the patches are expected to act independently from each other. Crude estimates for the friction forces between hard, stiff solids with randomly rough surfaces are given, which apply to surfaces with Hurst roughness exponents H > 0.5. The estimates are obtained by combining realistic contact-patch-size distributions with friction-load relations deduced for isolated contact patches. The analysis reveals that load is carried predominantly by large patches, while most frictional forces stem from small contact patches. Low friction is favored when the root-mean-square height gradients are small, while a large roll-off wavelength and thus large root-mean-square roughness is predicted to lead to small friction. Moreover, friction is found to increase sublinearly with load in a nominally flat, structurally lubric contact.
{"title":"Are There Limits to Superlubricity of Graphene in Hard, Rough Contacts?","authors":"M. Müser","doi":"10.3389/fmech.2019.00028","DOIUrl":"https://doi.org/10.3389/fmech.2019.00028","url":null,"abstract":"Yes, there are. They result from the splitting of a large correlated contact into many small patches. When the lubricant consists of thin solid sheets, like graphene, the patches are expected to act independently from each other. Crude estimates for the friction forces between hard, stiff solids with randomly rough surfaces are given, which apply to surfaces with Hurst roughness exponents H > 0.5. The estimates are obtained by combining realistic contact-patch-size distributions with friction-load relations deduced for isolated contact patches. The analysis reveals that load is carried predominantly by large patches, while most frictional forces stem from small contact patches. Low friction is favored when the root-mean-square height gradients are small, while a large roll-off wavelength and thus large root-mean-square roughness is predicted to lead to small friction. Moreover, friction is found to increase sublinearly with load in a nominally flat, structurally lubric contact.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"08 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86023170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-05-21DOI: 10.3389/fmech.2019.00022
J. Krim
Studies of the fundamental origins of friction have undergone rapid progress in recent years, providing valuable information on the relative contributions of electronic, magnetic, electrostatic and phononic dissipative mechanisms. They are now evolving into methods that allow active control of nano and/or meso scale friction through tuning of magnetic and electric fields external to the contact. These methods constitute an area of rapidly growing interest, as they address one of tribology’s present day grand challenges: achieving in situ control of friction levels without removing and replacing lubricant materials situated within inaccessible confines of a contact. In this minireview, 25 examples of electromagnetic tuning of friction are overviewed, with examples spanning atomic to macro scale systems to demonstrate the variety and versatility of approaches that have been reported in the literature. Applications include, but are not limited to triboelectric generators, geological drilling, automotive braking and efficiency, spacecraft systems, biological systems and magnetic spintronics. Experimental methods for measuring the impact of electric or magnetic fields on friction include AFM, SFA, QCM, pin-on-disk, hard disk head- substrate, MEMS and NEMS based tribometers, and optical spectroscopies. Computational and theoretical approaches include analytic, equilibrium and nonequilbrium Monte Carlo simulations.
{"title":"Controlling Friction With External Electric or Magnetic Fields: 25 Examples","authors":"J. Krim","doi":"10.3389/fmech.2019.00022","DOIUrl":"https://doi.org/10.3389/fmech.2019.00022","url":null,"abstract":"Studies of the fundamental origins of friction have undergone rapid progress in recent years, providing valuable information on the relative contributions of electronic, magnetic, electrostatic and phononic dissipative mechanisms. They are now evolving into methods that allow active control of nano and/or meso scale friction through tuning of magnetic and electric fields external to the contact. These methods constitute an area of rapidly growing interest, as they address one of tribology’s present day grand challenges: achieving in situ control of friction levels without removing and replacing lubricant materials situated within inaccessible confines of a contact. In this minireview, 25 examples of electromagnetic tuning of friction are overviewed, with examples spanning atomic to macro scale systems to demonstrate the variety and versatility of approaches that have been reported in the literature. Applications include, but are not limited to triboelectric generators, geological drilling, automotive braking and efficiency, spacecraft systems, biological systems and magnetic spintronics. Experimental methods for measuring the impact of electric or magnetic fields on friction include AFM, SFA, QCM, pin-on-disk, hard disk head- substrate, MEMS and NEMS based tribometers, and optical spectroscopies. Computational and theoretical approaches include analytic, equilibrium and nonequilbrium Monte Carlo simulations.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"1 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80161350","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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