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  • 1. Bennett, A. I.
    et al.
    Harris, Kathryn L
    University of Florida, USA.
    Schulze, K. D.
    Urueña, J. M.
    McGhee, A. J.
    Pitenis, A. A.
    Müser, M. H.
    Angelini, T. E.
    Sawyer, W. G.
    Contact Measurements of Randomly Rough Surfaces2017In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 65, no 4, article id 134Article in journal (Refereed)
    Abstract [en]

    This manuscript presents an experimental effort to directly measure contact areas and the details behind these scaled experiments on a randomly rough model surface used in the “Contact Mechanics Challenge” (2017). For these experiments, the randomly rough surface model was scaled up by a factor of 1000× to give a 100 mm square sample that was 3D printed from opaque polymethylmethacrylate (PMMA). This sample was loaded against various optically smooth and transparent samples of PDMS that were approximately 15 mm thick and had a range in elastic modulus from 14 kPa to 2.1 MPa. During loading, a digital camera recorded contact locations by imaging the scattering of light that occurs off of the PMMA rough surface when it was in contact with the PDMS substrate. This method of illuminating contact areas is called frustrated total internal reflection and is performed by creating a condition of total internal reflection within the unperturbed PDMS samples. Contact or deformation of the surface results in light being diffusely transmitted from the PDMS and detected by the camera. For these experiments, a range of reduced pressure (nominal pressure/elastic modulus) from below 0.001 to over 1.0 was examined, and the resulting relative contact area (real area of contact/apparent area of contact) was found to increase from below 0.1% to over 60% at the highest pressures. The experimental uncertainties associated with experiments are discussed, and the results are compared to the numerical results from the simulation solution to the “Contact Mechanics Challenge.” The simulation results and experimental results of the relative contact areas as a function of reduced pressure are in agreement (within experimental uncertainties).

  • 2. Bennett, A. I.
    et al.
    Rohde, S.
    Harris, Kathryn L
    University of Florida, USA.
    Schulze, K. D.
    Urueña, J. M.
    Pitenis, A. A.
    Ifju, P. G.
    Angelini, T. E.
    Müser, M. H.
    Sawyer, W. G.
    Deformation Measurements of Randomly Rough Surfaces2017In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 65, no 4, article id 123Article in journal (Refereed)
    Abstract [en]

    Measurements of surface deformations as part of the “Contact Mechanics Challenge” were collected using digital image correlation (DIC). For these experiments, a scaled version (1000×) of the periodic and random roughness surface provided for the “Contact Mechanics Challenge” was used. A 100 mm × 100 mm scale replica of the surface, approximately 10 mm thick, was 3D-printed using an opaque polymethylmethacrylate and pressed into contact against flat, transparent polydimethylsiloxane (PDMS) sheets with dead weight loads. Four different formulations of PDMS were used, and the resulting elastic moduli ranged from 64 kPa to 2.1 MPa. The DIC technique was used in situ to measure the deformation of the PDMS surface at each load increment from 22.5 to 450 N. Surface deformations in and out of contact were measured across the entire apparent area of contact and overlaid with the measurements of contact area to provide a complete description of the surface profile during loading. A direct comparison between these experiments and the simulations regarding the gap within the contact at a reduced pressure of 0.164 agrees to within ±10% when normalized to the maximum gap. 

  • 3.
    Harris, Kathryn L
    et al.
    University of Florida, USA.
    Bennett, A. I.
    Rowe, K. G.
    Sawyer, W. G.
    Janus Blocks: A Binary System Wear Instability2016In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 63, no 1, article id 8Article in journal (Refereed)
    Abstract [en]

    In this manuscript, a simple binary model is devised that describes the wear behavior of two blocks coupled under a constant, dynamically partitioned normal load. In this simple system, the frictional force is reacted by two independent springs and the blocks are allowed to move and wear independently based on system dynamics and kinematics. The only coupling between the blocks occurs through the partitioning of the applied normal load, which uses a pair of springs in parallel to model elasticity. This system is found to preferentially wear one of the blocks until two disparately unique conditions of steady wear are reached in the system: (1) a condition in which the partitioning of the load between the blocks yields equal wear and thus steady partitioning of the load and (2) a condition in which the pair of blocks go to zero wear by having one block not sliding but carrying all of the load and the other block completely slipping but carrying none of the load. These “Janus blocks,” the simplest of binary spring–block systems, begin life in a nominally identical state and then their behavior bifurcates, producing runaway or irregular wear. The onset of this instability can initiate from any differences in load partitioning, spring constants, friction coefficient, or wear rates (no matter how small). 

  • 4.
    Harris, Kathryn L
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Collier, Elizabeth S
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Skedung, Lisa
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Rutland, Mark W.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design. KTH Royal Institute of Technology, Sweden.
    A Sticky Situation or Rough Going?: Influencing Haptic Perception of Wood Coatings Through Frictional and Topographical Design2021In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 69, no 3, article id 113Article in journal (Refereed)
    Abstract [en]

    Improving the tactile aesthetics of products that can be described as touch intensive is an increasing priority within many sectors, including the furniture industry. Understanding which physical characteristics contribute to the haptic experience of a surface, and how, is therefore highly topical. It has earlier been shown that both friction and topography affect tactile perception. Thus, two series of stimuli have been produced using standard coating techniques, with systematic variation in (physical) friction and roughness properties. This was achieved through appropriate selection of matting agents and resins. The stimuli sets were then evaluated perceptually to determine the extent to which discrimination between pairs of surfaces followed the systematic materials variation. In addition to investigating the role of the physical properties in discrimination of the surfaces, their influence on perceived pleasantness and naturalness was also studied. The results indicate that changes in tactile perception can be understood in terms of friction and roughness, and that varying the matting agents (topography) and resins (material properties) in the coatings provide the controlling factors for furniture applications. Perceived pleasantness is associated with low friction and smoother topography, whilst perceived naturalness is found to be described by an interaction between tactile friction and the average maximum peak height of the surface features. Graphic Abstract: [Figure not available: see fulltext.] © 2021, The Author(s).

  • 5.
    Harris, Kathryn L
    et al.
    University of Florida, USA.
    Curry, J. F.
    Pitenis, A. A.
    Rowe, K. G.
    Sidebottom, M. A.
    Sawyer, W. G.
    Krick, B. A.
    Wear Debris Mobility, Aligned Surface Roughness, and the Low Wear Behavior of Filled Polytetrafluoroethylene2015In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 60, no 1, article id 2Article in journal (Refereed)
    Abstract [en]

    PTFE/α-alumina composites are well known to exhibit very low wear rates compared to unfilled PTFE and various other PTFE-matrix composites. The improved wear life of these composites is attributed in part to the formation of a uniform protective transfer film on the metal countersurface. It is postulated that the retention of transferred material and the recirculation of third bodies between the transfer film and running surface of the polymer composite are necessary for the maintenance of low wear within this tribological system. The accumulation of these third bodies was observed in reciprocating sliding tests on countersamples prescribed with aligned roughness. Wear performance of the polymer composite was tested as a function of the between the sliding direction and the aligned roughness of the countersample, ranging from parallel to perpendicular to the sliding direction. The wear rate of roughness oriented with the sliding direction was 300 times higher than roughness perpendicular to the sliding direction, revealing the importance of surface morphology and third body retention.

  • 6. Lundgren, SM
    et al.
    Persson, K
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Kronberg, B
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Claesson, PM
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Adsorption of fatty acids from alkane solution studied with quartz crystal microbalance2006In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 22, no 1, p. 15-20Article in journal (Refereed)
    Abstract [en]

    This paper describes the adsorption of the unsaturated fatty acids, oleic-, linoleic-, and linolenic acid onto steel coated quartz crystal surfaces from 2,2,4,4,6,8,8-heptamethylnonane as monitored by the quartz crystal microbalance (QCM) technique. It is shown that addition of fatty acid to the oil results in changes in bulk density and viscosity and that these changes must be considered before the sensed mass can be evaluated. The change in viscosity of the solution is larger for oleic acid than for linoleic acid and linolenic acid, which results in a larger correction for oleic acid with respect to bulk effects. After considering the effects due to changes in bulk properties, the influence of the viscoelastic properties of the adsorbed layer on the sensed mass was evaluated. The correction for the viscoelastic properties of the adsorbed layer was found to be very small for the systems studied. The sensed mass, at 1.1 weight percent, ranged from 0.5 mg/m2 for oleic acid to 5 mg/m2 for linolenic acid.

  • 7. McGhee, A. J.
    et al.
    Pitenis, A. A.
    Bennett, A. I.
    Harris, Kathryn L
    University of Florida, USA.
    Schulze, K. D.
    Urueña, J. M.
    Ifju, P. G.
    Angelini, T. E.
    Müser, M. H.
    Sawyer, W. G.
    Contact and Deformation of Randomly Rough Surfaces with Varying Root-Mean-Square Gradient2017In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 65, no 4, article id 157Article in journal (Refereed)
    Abstract [en]

    The “Contact Mechanics Challenge” posed to the tribology community by Müser and Dapp in 2015 detailed a 100 µm × 100 µm randomly rough surface with a root-mean-square gradient of unity, g ¯ = 1. Many surfaces, both natural and synthetic, can be described as randomly rough, but rarely with a root-mean-square gradient as steep as g ¯ = 1. The selection of such a challenging surface parameter was intentional, but potentially limiting for broad comparisons across existing models and theories which may be limited by small-slope approximations. In this manuscript, the root-mean-square gradients (g ¯) of the “Contact Mechanics Challenge” surface were produced on 1000 × scaled models such that there were three different surfaces for study with g¯=0.2,0.5, and 1. In situ measurements of the real area of contact and contact area distributions were performed using frustrated total internal reflectance along with surface deformation measurements performed using digital image correlation. These optical in situ experiments used the scaled 3D-printed rough surfaces that were loaded into contact with smooth, flat, and elastic samples that were made from unfilled PDMS: (10:1) E* = 2.1 MPa Δγ = 4 mJ/m2; (20:1) E* = 0.75 MPa Δγ = 3 mJ/m2; (30:1) E* = 0.24 MPa Δγ = 2 mJ/m2. All of the loading was performed using a uniaxial load frame under force control. A Green’s function molecular dynamics simulation assuming the small-slope approximation was compared to all experimental data. These measurements reveal that decreasing root-mean-square gradient noticeably increases real area of contact area under conditions of “equal” applied load, but variations in the root-mean-square gradient did not significantly alter the contact patch geometry under conditions of nearly equal real area of contact. Including g ¯ in the reduced pressure (p= P/ (E∗ g ¯)) reduced the root-mean-square error between the simulation (g ¯ = 1) and all experimental data for the relative area of contact as a function of reduced pressure over the entire range of surfaces, materials, and loads tested.

  • 8.
    Meurk, A
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Microscopic stick-slip in friction force microscopy2000In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 8, p. 161-169Article in journal (Refereed)
    Abstract [en]

    Friction force measurements were performed on 2-hydroxy stearic acid (2-HSA) and 12-hydroxy stearic acid (12-HSA) coated silica surfaces in air using an atomic force microscope. The 2-HSA displayed viscoelastic behaviour with a yield point as the static–dynamic friction transition. Steady sliding motion was replaced by microscopic stick–slip at lower velocities and higher loads. Stick–slip motion was successfully described and fitted to a phenomenological model ascribed to interfacial material melting and freezing in periodic cycles. The stick–slip periodicity is of the same order as the contact diameter. The 12-HSA did not experience a yield point and exhibited steady sliding over the entire load and velocity regime. We attribute these observations to the difference in molecular configuration, shear strength and adsorption density of the stearic acid layers.

  • 9. Müser, M. H.
    et al.
    Dapp, W. B.
    Bugnicourt, R.
    Sainsot, P.
    Lesaffre, N.
    Lubrecht, T. A.
    Persson, B. N. J.
    Harris, Kathryn L
    University of Florida, USA.
    Bennett, A.
    Schulze, K.
    Rohde, S.
    Ifju, P.
    Sawyer, W. G.
    Angelini, T.
    Ashtari Esfahani, H.
    Kadkhodaei, M.
    Akbarzadeh, S.
    Wu, J. -J
    Vorlaufer, G.
    Vernes, A.
    Solhjoo, S.
    Vakis, A. I.
    Jackson, R. L.
    Xu, Y.
    Streator, J.
    Rostami, A.
    Dini, D.
    Medina, S.
    Carbone, G.
    Bottiglione, F.
    Afferrante, L.
    Monti, J.
    Pastewka, L.
    Robbins, M. O.
    Greenwood, J. A.
    Meeting the Contact-Mechanics Challenge2017In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 65, no 4, article id 118Article in journal (Refereed)
    Abstract [en]

    This paper summarizes the submissions to a recently announced contact-mechanics modeling challenge. The task was to solve a typical, albeit mathematically fully defined problem on the adhesion between nominally flat surfaces. The surface topography of the rough, rigid substrate, the elastic properties of the indenter, as well as the short-range adhesion between indenter and substrate, were specified so that diverse quantities of interest, e.g., the distribution of interfacial stresses at a given load or the mean gap as a function of load, could be computed and compared to a reference solution. Many different solution strategies were pursued, ranging from traditional asperity-based models via Persson theory and brute-force computational approaches, to real-laboratory experiments and all-atom molecular dynamics simulations of a model, in which the original assignment was scaled down to the atomistic scale. While each submission contained satisfying answers for at least a subset of the posed questions, efficiency, versatility, and accuracy differed between methods, the more precise methods being, in general, computationally more complex. The aim of this paper is to provide both theorists and experimentalists with benchmarks to decide which method is the most appropriate for a particular application and to gauge the errors associated with each one..

  • 10. Pitenis, A. A.
    et al.
    Ewin, J. J.
    Harris, Kathryn L
    University of Florida, USA.
    Sawyer, W. G.
    Krick, B. A.
    In vacuo tribological behavior of polytetrafluoroethylene (ptfe) and alumina nanocomposites: The importance of water for ultralow wear2014In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 53, no 1, p. 189-197Article in journal (Refereed)
    Abstract [en]

    Polytetrafluoroethylene (PTFE) is widely regarded as an excellent candidate for solid lubrication in vacuum. However, it is often precluded from many practical applications due to its intrinsically high wear rate. Over the past decade, it has been discovered that small loading fractions of alumina nanofillers can increase the wear resistance of PTFE by three to four orders of magnitude. This dramatic increase in wear resistance has in turn prompted numerous tribological studies to examine the robustness of this performance. In this study, the wear and friction behavior of unfilled PTFE and PTFE and alumina nanocomposites were evaluated under a broad range of vacuum environments from 760 to 4 9 10-6 Torr. The nanocomposites of PTFE/alumina showed a dramatic increase in wear of over two orders of magnitude at the highest vacuum conditions. There appears to be an optimal vacuum environment around 1-10 Torr, in which these samples achieved the lowest wear rates of approximately 2.5 9 10-7 mm3/(Nm)

  • 11. Pitenis, A. A.
    et al.
    Harris, Kathryn L
    University of Florida, USA.
    Junk, C. P.
    Blackman, G. S.
    Sawyer, W. G.
    Krick, B. A.
    Ultralow wear PTFE and alumina composites: It is all about tribochemistry2015In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 57, no 2, article id 4Article in journal (Refereed)
    Abstract [en]

    Over the last decade, researchers have explored an intriguing polymer composite composed of granular polytetrafluoroethylene (PTFE) 7C and alumina particles. This material is extraordinary because a very small amount of alumina additive (<5 wt%) decreased the wear rate of the PTFE composite by over four orders of magnitude. Previous studies have shown that this wear resistance was initiated and maintained by the formation of a stable, robust, and uniform polymeric transfer film on the surface of the countersample. Although its importance to this tribological system is clear, the transfer film itself has not been well understood. Careful spectroscopic analysis throughout the stages of transfer film development revealed that tribochemistry plays a major role in the significant wear rate reductions achieved in PTFE and alumina composites. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy reveal that PTFE chains break due to the mechanical stresses at the wear surface and, in the presence of oxygen and water in the ambient environment, produce carboxylic acid end groups. These carboxylic acid end groups can chelate to the exposed metal on the steel surface and nucleate the formation of the transfer film. The resulting thin and robust fluoropolymer transfer film protects the surface of the steel and changes the sliding interface from polymer on steel to polymer on polymer transfer film. These effects keep friction coefficients and wear rates low and stable. Ultimately, the real mechanisms responsible for the exceptional wear performance of these materials are all about the tribochemistry. 

  • 12. Rowe, K. G.
    et al.
    Harris, Kathryn L
    University of Florida, USA.
    Schulze, K. D.
    Marshall, S. L.
    Pitenis, A. A.
    Urueña, J. M.
    Niemi, S. R.
    Bennett, A. I.
    Dunn, A. C.
    Angelini, T. E.
    Sawyer, W. G.
    Lessons from the lollipop: Biotribology, tribocorrosion, and irregular surfaces2014In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 56, no 2, p. 273-280Article in journal (Refereed)
    Abstract [en]

    Biotribology and tribocorrosion are often not included in numerical or computational modeling efforts to predict wear because of the apparent complexity in the geometry, the variability in removal rates, and the challenge associated with mixing time-dependent removal processes such as corrosion with cyclic material removal from wear. The lollipop is an accessible bio-tribocorrosion problem that is well known but underexplored scientifically as a tribocorrosion process. Stress-assisted dissolution was found to be the dominant tribocorrosion process driving material removal in this system. A model of material removal was described and approached by lumping the intrinsically time-dependent process with a mechanically driven process into a single cyclic volumetric material removal rate. This required the collection of self-reported wear data from 58 participants that were used in conjunction with statistical analysis of actual lollipop cross-sectional information. Thousands of repeated numerical simulations of material removal and shape evolution were conducted using a simple Monte Carlo process that varied the input parameters and geometries to match the measured variability. The resulting computations were analyzed to calculate both the average number of licks required to reach the Tootsie Roll® center of a Tootsie Roll® pop, as well as the expected variation thereof.

  • 13.
    Skedung, Lisa
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Danerlöv, Katrin
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Olofsson, Ulf
    Aikala, Maiju
    Niemi, Kari
    Kettle, John
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Finger friction measurements on coated and uncoated printing papers2010In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 37, no 2, p. 389-399Article in journal (Refereed)
    Abstract [en]

    A macroscopic finger friction device consisting of a piezoelectric force sensor was evaluated on 21 printing papers of different paper grades and grammage. Friction between a human finger and the 21 papers was measured and showed that measurements with the device can be used to discriminate a set of similar surfaces in terms of finger friction. When comparing the friction coefficients, the papers group according to paper grade and the emerging trend is that the rougher papers have a lower friction coefficient than smoother papers. This is interpreted in terms of a larger contact area in the latter case. Furthermore, a decrease in friction coefficient is noted for all papers on repeated stroking (15 cycles back and forth with the finger). Complementary experiments indicate that both mechanical and chemical modifications of the surface are responsible for this decrease: (1) X-ray photoelectron spectroscopy measurements show that lipid material is transferred from the finger to the paper surface, (2) repeated finger friction measurements on the same paper sample reveal that only partial recovery of the frictional behaviour occurs and (3) profilometry measurements before and after stroking indicate small topographical changes associated with repeated frictional contacts.

  • 14.
    Skedung, Lisa
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Harris, Kathryn L
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Collier, Elizabeth S
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Arvidsson, Martin
    RISE - Research Institutes of Sweden (2017-2019).
    Wäckerlin, Aneliia
    Glas Trösch AG, Switzerland.
    Haag, Walter
    Glas Trösch AG, Switzerland.
    Bieri, Marco
    Glas Trösch AG, Switzerland.
    Romanyuk, Andriy
    Glas Trösch AG, Switzerland.
    Rutland, Mark W.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design. KTH Royal Institute of Technology, Sweden.
    Feeling smooth: Psychotribological probing of molecular composition2018In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 66, no 4, p. 1-10, article id 138Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to evaluate whether smooth surfaces varying in surface chemistry could be perceptually distinguished with the sense of touch. A set of ten glass surfaces was prepared which varied systematically in terms of the molecular composition of a thin coating of low topography. The contact angle, contact angle hysteresis, and surface energy were evaluated as objective physical parameters characterizing each coating. Additionally, the interaction forces between a human finger and the different coatings were quantified and compared in terms of tactile friction coefficients. The surfaces were evaluated psychophysically in terms of perceived similarities and were then ranked according to pleasantness. The participants could perceptually distinguish between surfaces varying in surface chemistry and a primary and secondary perceptual dimension were identified as sufficient to distinguish them. The primary dimension correlates with surface free energy, but both tactile friction and surface energy contribute to this dimension depending on whether the coatings are organic or inorganic. The secondary dimension could not be identified explicitly in terms of a physical quantity but is discussed in terms of recent developments in the literature. Coated glass is characterized by high friction coefficient upon interaction with a human finger as well as significant hysteresis in the stroking directions (lower applied load and higher friction in the backward stroke). Despite the complexity of the tribology, pleasantness can be clearly linked to it, where low friction (high contact angle) materials receive a higher ranking. © The Author(s) 2018.

  • 15. Urueã, J. M.
    et al.
    Pitenis, A. A.
    Harris, Kathryn L
    University of Florida, USA.
    Sawyer, W. G.
    Evolution and wear of fluoropolymer transfer films2015In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 57, no 2, article id 9Article in journal (Refereed)
    Abstract [en]

    Polytetrafluoroethylene (PTFE) is a solid lubricant known for its low friction coefficient and high wear rate. When filled with a low volume percent of alumina particles (5 wt%), its wear rate is decreased over four orders of magnitude. The development of a thin, uniform and well adhered transfer film during sliding is partially responsible for this decrease in wear rate by creating a low shear interface and forming a protective layer between the PTFE/alumina sample and metal countersample. In this work, a ''striped'' transfer film was generated by sliding up to one million reversals over a gradually decreasing stroke length. Wear and friction experiments were performed on a microtribometer to determine the robustness of the transfer film. Interferometry and profilometry were used to measure the height and wear of the film. Microscopy was used to investigate the morphology of the transfer film over sliding distance. 

  • 16.
    Álvarez-Asencio, Rubén
    et al.
    KTH Royal Institute of Technology, Sweden.
    Pan, Jinshan
    KTH Royal Institute of Technology, Sweden.
    Thormann, Esben
    KTH Royal Institute of Technology, Sweden.
    Rutland, Mark
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Tribological Properties Mapping: Local Variation in Friction Coefficient and Adhesion2013In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 50, no 3, p. 387-395Article in journal (Refereed)
    Abstract [en]

    Tribological properties mapping is a new technique that extracts friction coefficient and adhesion maps obtained from lateral atomic force microscope (LAFM) images. By imaging the surface systematically as a function of load, a series of images can be tiled, and pixelwise fitted to a modified Amontons' Law to obtain friction coefficient and adhesion maps. This removes the ambiguity of friction contrast in LAFM imaging which can be a function of the load used for imaging. In ambient laboratory, air and tetradecane, a sample of Vancron ®40, commercial powder metallurgical tool alloy containing nitrogen, have been scanned using a standard silicon cantilever in order to obtain tribological data. The tribological properties mapping provides unique information regarding the heterogeneous alloy microstructure as well as shedding light on the tribological behavior of the alloy.

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