The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Peter J. Blau - One of the best experts on this subject based on the ideXlab platform.
-
Four great challenges confronting our understanding and modeling of sliding Friction
Tribology Series, 1998Co-Authors: Peter J. BlauAbstract:This paper addresses four challenges whose solutions may together enable significant progress in the predication and control of Friction for energy conservation. Posed as questions these are: (1) how can materials with greatly different properties and compositions produce similar Kinetic Friction Coefficients when tested under comparable conditions; (2) how is it possible that the Kinetic Friction Coefficient for the same materials pair can differ greatly when it is slid in different tribosystems; (3) how can Frictional phenomena at different size scales be reconciled; and (4) how can the effects of the machine, the materials (including lubricants) and the environment be successfully incorporated into quantitative and predictive Friction models? Examples related to these four challenges are provided, as are possible approaches for attacking them in future research efforts.
-
Nanoscale hardness and microFriction of titanium nitride films deposited from the reaction of tetrakis (dimethylamino) titanium with ammonia
Applied Physics Letters, 1995Co-Authors: Y. W. Bae, Woo Y. Lee, Theodore M. Besmann, Peter J. BlauAbstract:Nanocrystalline titanium nitride films with very low carbon and oxygen content were deposited on single‐crystal silicon substrates from the reaction of tetrakis (dimethylamino) titanium, Ti[(CH3)2N]4, with ammonia at 633 K and a pressure of 665 Pa. The film consisted of ∼10 nm grains. The hardness of the film, measured by nanoindentation, was 12.7±0.6 GPa. The average Kinetic Friction Coefficient, against type 440C stainless steel, was determined using a Friction microprobe to be 0.43.
-
Synthesis and selected micro-mechanical properties of titanium nitride thin films by the pyrolysis of tetrakis titanium in ammonia
MRS Proceedings, 1994Co-Authors: Y. W. Bae, Woo Y. Lee, Theodore M. Besmann, Peter J. Blau, L. RiesterAbstract:Thin films of titanium nitride were chemical vapor deposited on (100)-oriented single-crystal silicon substrates from tetrakis (dimethylamino) titanium, Ti((CH{sub 3}){sub 2}N){sub 4}, and ammonia gas mixtures in a cold-wall reactor at 623 K and 655 Pa. The films were characterized by Auger electron spectroscopy, X-ray diffraction, and transmission electron spectroscopy. The nano-scale hardness of the film, measured by nanoindentation, was 12.7 {plus_minus} 0.6 GPa. The average Kinetic Friction Coefficient against unlubricated, type 440C stainless steel was determined using a computer-controlled Friction microprobe to be {approximately}0.43.
Erland M. Schulson - One of the best experts on this subject based on the ideXlab platform.
-
Friction Along Coulombic Shear Faults in First-Year Arctic Sea Ice
2005Co-Authors: A. L. Fortt, Erland M. SchulsonAbstract:Coulombic shear faults mark brittle terminal failure of virgin S2 ice when rapidly loaded in across-the-column compression under a moderate degree of confinement, as described by Schulson (2004). Previous experiments (Fortt & Schulson, 2004) have described Friction Coefficients along Coulombic shear faults in fresh-water S2 ice. This paper compares those fresh-water Coefficients to Coefficients determined from faults in first-year arctic sea ice. The ice was collected from the Beaufort Sea during April 2003, and Coulombic shear faults were introduced as described by Fortt & Schulson (2004). Biaxial sliding experiments were performed at –10° C at five sliding velocities (4 × 10⁻³, 8 × 10⁻⁴, 8 × 10⁻⁵, 8 × 10⁻⁶ and 8 × 10⁻⁷ m/s). It was found that Kinetic Friction Coefficients follow a trend similar to that seen by Fortt & Schulson (2004) in fresh-water ice. Coefficients range from 0.69 ± 0.08 at the lowest velocity, rising to a peak value of 0.79 ± 0.09 at 8 × 10⁻⁵ m/s and then decreasing to 0.37 ± 0.15 at 4 × 10⁻³ m/s. In comparison, fresh-water Coefficients vary from 1.00 at the lowest velocity, rising to 1.04 at 8 × 10⁻⁶m/s and then decreasing to 0.39 at 4 × 10⁻³ m/s. Roughness measurements of melted, sanded and faulted surfaces, for both saline and fresh-water ice, revealed that for all velocities, as the roughness increases, so does the Kinetic Friction Coefficient.
-
The Kinetic Friction of saline ice against itself at low sliding velocities
Annals of Glaciology, 1991Co-Authors: D. E. Jones, F. E. Kennedy, Erland M. SchulsonAbstract:An experimental investigation was performed on the Kinetic Friction Coefficient of laboratory-grown, columnar saline ice sliding against itself. Tests were performed on a dual-opposing load apparatus specially manufactured for attachment to an MTS testing system. The mean Kinetic Friction Coefficient, μ, was measured for sliding velocities from 10−6 to 5 × 10−2 m s−1 at temperatures from —3° to —40°C under a contact pressure of about 20 kPa. The ice specimens were oriented with grain columns perpendicular to the sliding interface. At -3°C and at —10°C, three distinct regions were observed: from 10−6 to about 10−5ms−1, μwas nearly constant at 0.5; at velocities from 10−5 to 10−3 m s−1, μ began to drop rapidly to about 0.1; and, above 10−3 m s−1, μ began to level off at ~0.05. The velocity at which μ began to decline increased with decreasing temperature. At temperatures below —10°C, μ increased from ~0.5 at v =10−6ms−1 to a peak value of ~0.7 near a velocity of 5 × 10−5ms−1 and then fell rapidly to about 0.1 at 10−2ms−1. In general, μ increased with decreasing temperature and sliding velocity.
Y. W. Bae - One of the best experts on this subject based on the ideXlab platform.
-
Nanoscale hardness and microFriction of titanium nitride films deposited from the reaction of tetrakis (dimethylamino) titanium with ammonia
Applied Physics Letters, 1995Co-Authors: Y. W. Bae, Woo Y. Lee, Theodore M. Besmann, Peter J. BlauAbstract:Nanocrystalline titanium nitride films with very low carbon and oxygen content were deposited on single‐crystal silicon substrates from the reaction of tetrakis (dimethylamino) titanium, Ti[(CH3)2N]4, with ammonia at 633 K and a pressure of 665 Pa. The film consisted of ∼10 nm grains. The hardness of the film, measured by nanoindentation, was 12.7±0.6 GPa. The average Kinetic Friction Coefficient, against type 440C stainless steel, was determined using a Friction microprobe to be 0.43.
-
Synthesis and selected micro-mechanical properties of titanium nitride thin films by the pyrolysis of tetrakis titanium in ammonia
MRS Proceedings, 1994Co-Authors: Y. W. Bae, Woo Y. Lee, Theodore M. Besmann, Peter J. Blau, L. RiesterAbstract:Thin films of titanium nitride were chemical vapor deposited on (100)-oriented single-crystal silicon substrates from tetrakis (dimethylamino) titanium, Ti((CH{sub 3}){sub 2}N){sub 4}, and ammonia gas mixtures in a cold-wall reactor at 623 K and 655 Pa. The films were characterized by Auger electron spectroscopy, X-ray diffraction, and transmission electron spectroscopy. The nano-scale hardness of the film, measured by nanoindentation, was 12.7 {plus_minus} 0.6 GPa. The average Kinetic Friction Coefficient against unlubricated, type 440C stainless steel was determined using a computer-controlled Friction microprobe to be {approximately}0.43.
Bo N. J. Persson - One of the best experts on this subject based on the ideXlab platform.
-
On the dependency of Friction on load: Theory and experiment
EPL (Europhysics Letters), 2016Co-Authors: O. M. Braun, B. Steenwyk, A. Warhadpande, Bo N. J. PerssonAbstract:In rubber Friction studies it is often observed that the Kinetic Friction Coefficient depends on the nominal contact pressure. This is usually due to Frictional heating, which softens the rubber, increases the area of contact, and (in most cases) reduces the viscoelastic contribution to the Friction. In this paper we present experimental results showing that the rubber Friction also depends on the nominal contact pressure at such low sliding speed that Frictional heating is negligible. This effect has important implications for rubber sliding dynamics, e.g., in the context of the tire-road grip. We attribute this effect to the viscoelastic coupling between the macroasperity contact regions, and present a simple earthquakelike model and numerical simulations supporting this picture. The mechanism for the dependency of the Friction Coefficient on the load considered is very general, and is relevant for non-rubber materials as well.
-
On the nature of the static Friction, Kinetic Friction and creep
Wear, 2003Co-Authors: Bo N. J. Persson, O. Albohr, F. Mancosu, V. Peveri, V. N. Samoilov, Ion Marius SivebækAbstract:Abstract In this paper, we discuss the nature of the static and Kinetic Friction, and of (thermally activated) creep. We focus on boundary lubrication at high confining pressure (∼1 GPa), as is typical for hard solids, where one or at most two layers of confined molecules separates the sliding surfaces. We find in most of our Molecular Dynamics (MD) simulations (at low sliding velocity), that the lubricant molecules are permanently attached or pinned to one of the solid walls. We describe the (flexible) lubricant-wall bonds as springs with bending elasticity. If the springs are elastically stiff, the system exhibits a very small static Friction, and a (low velocity) Kinetic Friction which increases with increasing sliding velocity. On the other hand, if the springs are soft enough, strong elastic instabilities occur during sliding, resulting in a large static Friction force F s , and a Kinetic Friction force F k equal to the static Friction force at low sliding velocities. In this case rapid slip events occur at the interface, characterized by velocities much higher and independent of the drive velocity v . In the MD simulations we observe that, for incommensurate systems (at low temperature), only when the lubrication film undergoes a phase transformation at the onset of slip do we observe a static Friction Coefficient which is appreciately larger than the Kinetic Friction Coefficient . We give arguments for why, at very low sliding velocity (where thermally activated creep occurs), the Kinetic Friction force may depend linearly on ln (v/v 0 ) , as usually observed experimentally, rather than non-linearly [− ln (v/v 0 )] 2/3 as predicted by a simple theory of activated processes. We also discuss the role of elasticity at stop and start. We show that for “simple” rubber (at low start velocity), the static Friction Coefficient ( μ s ) is equal to the Kinetic Friction Coefficient ( μ k ). In general, at non-zero temperature, the static Friction Coefficient is higher than the Kinetic Friction Coefficient because of various thermally activated relaxation processes, e.g. chain interdiffusion or (thermally activated) formation of capillary bridges. However, there is no single value of the static Friction Coefficient, since it depends upon the initial dwell time and on rate of starting . We argue that the correct basis for the Coulomb Friction law, which states that the Friction force is proportional to the normal load, is not the approximate independence of the Friction Coefficient on the normal pressure (which often does not hold accurately anyhow), but rather it follows from the fact that for rough surfaces the area of real contact is proportional to the load, and the pressure distribution in the contact areas is independent of the load.
Kyungmok Kim - One of the best experts on this subject based on the ideXlab platform.
-
Measurement and analysis of Friction and wear on electrodeposited coatings against a high carbon chrome steel ball
Journal of Materials Research, 2016Co-Authors: Kyungmok KimAbstract:This paper investigates Friction and wear between an electro-deposited coating and high carbon chrome steel. A ball-on-flat plate tribometer was developed, measuring tangential and normal displacements of a high carbon chrome steel ball. For the purpose of measuring displacements of a ball, laser displacement sensors were used. An electro-deposited coating was applied to a cold-rolled high strength steel plate. Displacement amplitudes of 0.2 and 1.0 mm were imposed to produce fretting and reciprocal sliding at contact. A steady-state value of the Kinetic Friction Coefficient between an electro-deposited coating and high carbon chrome steel was found to be about 0.28. It was identified that wear volume on a coated specimen increased with the number of cycles. Correlation between the wear volume and a normal displacement of a ball was found to be linear. It was demonstrated that the proposed method is useful for understanding Friction and wear of an electro-deposited coating.
-
Reciprocal Sliding Friction Model for an Electro-Deposited Coating and Its Parameter Estimation Using Markov Chain Monte Carlo Method
Materials (Basel Switzerland), 2016Co-Authors: Kyungmok Kim, Jaewook LeeAbstract:This paper describes a sliding Friction model for an electro-deposited coating. Reciprocating sliding tests using ball-on-flat plate test apparatus are performed to determine an evolution of the Kinetic Friction Coefficient. The evolution of the Friction Coefficient is classified into the initial running-in period, steady-state sliding, and transition to higher Friction. The Friction Coefficient during the initial running-in period and steady-state sliding is expressed as a simple linear function. The Friction Coefficient in the transition to higher Friction is described with a mathematical model derived from Kachanov-type damage law. The model parameters are then estimated using the Markov Chain Monte Carlo (MCMC) approach. It is identified that estimated Friction Coefficients obtained by MCMC approach are in good agreement with measured ones.
-
Measurement and analysis of the Kinetic Friction Coefficient of AISI 52100 and ceramic balls on cold-rolled high strength steel
International Journal of Surface Science and Engineering, 2016Co-Authors: Kyungmok Kim, Kilho EomAbstract:In this paper, a ball-on-flat plate test is performed under dry condition. A cold-rolled high strength steel plate is used for a flat specimen, and AISI52100, ZrO2, Al2O3, and Si3N4 balls are selected as a counterpart. The Kinetic Friction Coefficient is determined and one-way analysis of variance (ANOVA) is employed. Experimental results show that the steady-state Friction Coefficient of AISI52100 balls ranges from 0.56 to 0.58 on a cold-rolled high strength steel plate. The Friction Coefficient of ZrO2 balls is lower than those of AISI52100, Al2O3, and Si3N4 balls. Results of ANOVA show that counterpart material plays a statistically significant role in determining the steady-state Friction Coefficient, whereas normal force does not make a critical impact on the steady-state Friction Coefficient within the range of 12 N and 50 N. Finally, we found the linear relation between the steady-state Friction Coefficient and the maximum contact pressure.
-
Influence of load on the Friction Coefficient of fretted electro-deposited coatings against steel and zirconia balls
International Journal of Surface Science and Engineering, 2016Co-Authors: Tea-sung Jun, Kyungmok KimAbstract:This paper investigates the influence of load on the evolution of the Kinetic Friction Coefficient of electro-deposited coatings against steel and zirconia balls. Fretting wear tests are performed with epoxy-based electro-deposited coating and three types of balls (AISI 52100, SUS316L and ZrO2). Loads of 20, 30, 40, and 50 N are induced normal to the contact surface between the electro-deposited coating and a ball. The evolution of the Kinetic Friction Coefficient is determined at various loads. Direct comparison among measured Friction Coefficient evolutions is carried out. Results show that when testing the coating against AISI 52100 balls at 20 N and 30 N, it wore off after higher fretting cycles than SUS316L and ZrO2 balls. Meanwhile, the coating tested against ZrO2 balls at 40 N and 50 N failed after higher fretting cycles than against SUS316L and AISI52100 balls. Finally, it is identified that the relation between the number of cycles to coating failure and load is expressed with an inverse power law.
