The Experts below are selected from a list of 11346 Experts worldwide ranked by ideXlab platform
David L Burris - One of the best experts on this subject based on the ideXlab platform.
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Transfer Film Tenacity: A Case Study Using Ultra-Low-Wear Alumina–PTFE
Tribology Letters, 2015Co-Authors: J. Ye, A. C. Moore, David L BurrisAbstract:The transfer film, a protective barrier that forms when a solid lubricant slides against a hard and high-surface-energy counterface, plays an important role in friction and Wear reduction. The transfer films of many solid lubricants are removed and replenished during sliding. However, one particularly Low Wear Rate solid lubricant has been shown to produce persistent transfer films that thicken and homogenize over the course of a test. Based on a mass balance of the system, transfer film growth can only occur if its Wear Rate is less than that of the parent polymer. However, recent measurements of the Wear Rates of these transfer films show that they are likely orders of magnitude higher than those of the parent polymer. The goal of this paper is to elucidate the origins of this apparent contradiction. In this study, a high-density polyethylene (HDPE) probe was used in an effort to approximate the contact conditions under which the film originally formed. Transfer films formed during run-in of the parent solid lubricant were removed immediately by the HDPE pin (k ~ 100 mm3/Nm). However, transfer films formed after the solid lubricant had transitioned to ultra-Low Wear Rates themselves exhibited ultra-Low Wear Rates in the range from 10−8 to 10−10 mm3/Nm; to our knowledge, this is the first direct observation of ultra-Low Wear Rate transfer films, a condition that was previously assumed necessary for ultra-Low Wear Rates of the solid lubricant system. FolLow-up measurements showed that the Wear Rate of the transfer film was extremely sensitive to the surface energy of the probe; the Wear Rate increased by orders of magnitude when the surface energy of the probe exceeded a critical value near ~35 mJ/mm2. These results provide fresh insights into the Wear behaviors of transfer films and the processes governing ultra-Low Wear of solid lubricant materials.
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a Low friction and ultra Low Wear Rate peek ptfe composite
Wear, 2006Co-Authors: David L Burris, Gregory W SawyerAbstract:This paper presents a PEEK filled PTFE composite that exhibits Low friction and ultra-Low Wear. It is hypothesized that a synergistic effect shuts down the dominant Wear mechanism of each constituent. The friction coefficient and Wear Rate of this composite material on lapped stainless steel were evaluated for samples with PEEK wt.% of 0, 5, 10, 20, 30, 40, 50, 70 and 100 using a linear reciprocating tribometer. Tests were performed in filtered, standard laboratory conditions with a nominal contact pressure of 6.35 MPa, a speed of 50 mm/s and total sliding distances ranging from 0.5 km for the unfilled PTFE to 140 km for a 20 wt.% PEEK filled sample. The friction coefficients, averaged over an entire test, ranged from ¯ µ = 0.111 for a 50 wt.% composite to ¯ µ = 0.363 for unfilled PEEK. Wear Rates ranged from K = 2.3 × 10 −9 mm 3 /(Nm) for a 20 wt.% PEEK sample to K =6 × 10 −4 mm 3 /(Nm) for unfilled PTFE. Scanning electron microscopy revealed a unique interfacial connection between the PTFE
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A Low friction and ultra Low Wear Rate PEEK/PTFE composite
Wear, 2006Co-Authors: David L Burris, W. Gregory SawyerAbstract:This paper presents a PEEK filled PTFE composite that exhibits Low friction and ultra-Low Wear. It is hypothesized that a synergistic effect shuts down the dominant Wear mechanism of each constituent. The friction coefficient and Wear Rate of this composite material on lapped stainless steel were evaluated for samples with PEEK wt.% of 0, 5, 10, 20, 30, 40, 50, 70 and 100 using a linear reciprocating tribometer. Tests were performed in filtered, standard laboratory conditions with a nominal contact pressure of 6.35 MPa, a speed of 50 mm/s and total sliding distances ranging from 0.5 km for the unfilled PTFE to 140 km for a 20 wt.% PEEK filled sample. The friction coefficients, averaged over an entire test, ranged from ¯ µ = 0.111 for a 50 wt.% composite to ¯ µ = 0.363 for unfilled PEEK. Wear Rates ranged from K = 2.3 × 10 −9 mm 3 /(Nm) for a 20 wt.% PEEK sample to K =6 × 10 −4 mm 3 /(Nm) for unfilled PTFE. Scanning electron microscopy revealed a unique interfacial connection between the PTFE
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A Low friction and ultra Low Wear Rate PEEK/PTFE composite
Wear, 2006Co-Authors: David L Burris, W. Gregory SawyerAbstract:2016-12-26T15:11:00
Bikramjit Basu - One of the best experts on this subject based on the ideXlab platform.
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Tribological Properties of WC–ZrO2 Nanocomposites
Journal of the American Ceramic Society, 2005Co-Authors: T. Venkateswaran, Debasish Sarkar, Bikramjit BasuAbstract:In the present work, the fretting Wear (mode I, linear relative tangential displacement, constant normal load) of a newly developed nanocomposite is investigated with varying load (2-10 N) and test duration (10000-100000 cycles). A detailed morphological investigation of worn surface is carried out using a Stylus surface profilometer, optical microscope, SEM, and electron probe microanalyser (EPMA). A clear transition in friction and Wear behavior with load is observed. Based on the worn surface topography and Wear debris analysis, the Wear mechanisms are proposed. The extremely Low Wear Rate (10 -8 mm 3 /N . m) along with Low Wear depth (< 1 μm) indicates high Wear resistance of nanoceramic composites. The high fretting Wear resistance of the nanocomposites as well as the observed tribological properties are discussed in terms of material properties, abrasion, and tribochemical Wear phenomenon.
Yoshihiko Kotoura - One of the best experts on this subject based on the ideXlab platform.
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Low Wear Rate of UHMWPE against zirconia ceramic (Y-PSZ) in comparison to alumina ceramic and SUS 316L alloy.
Journal of biomedical materials research, 1991Co-Authors: P. Kumar, Masanori Oka, Ken Ikeuchi, Koichiro Shimizu, Takao Yamamuro, Hideo Okumura, Yoshihiko KotouraAbstract:Partially stabilized zirconia ceramic is being recognized among ceramics for its high strength and toughness. With this ceramic, is possible to manufacture a 22-mm-size femoral head for Low friction arthroplasty of the hip joint in association with an ultra-high-molecular-weight polyethylene socket. Wear-resistant properties of zirconia ceramic were screened on two principally different Wear devices. Sterile calf bovine serum, physiological saline, and distilled water were chosen as the lubricant fluid media. Depending on the lubricant medium, the Wear factor of polyethylene against zirconia ceramic counterfaces was 40 to 60% less than that against alumina ceramic counterfaces, and 5 to 10 times Lower than with the SUS316L metal counterfaces. Polyethylene Wear against metal was more susceptible in saline in which it had 2 to 3 times higher Wear Rate than with serum. On the other hand, different fluid media had little effect on polyethylene Wear against ceramic counterfaces. In each set of tests, the Wear factor obtained on an unidirectional Wear device showed 10 to 15 times higher values, in comparison to the Wear factor estimated on a reciprocating Wear device.
Jun Yang - One of the best experts on this subject based on the ideXlab platform.
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effects of temperature and microstructure on the triblogical properties of cocrfeninbx eutectic high entropy alloys
Journal of Alloys and Compounds, 2019Co-Authors: Zhuhui Qiao, Zhijun Wang, Weimin Liu, Jun YangAbstract:Abstract This paper is aimed to evaluate the high temperature tribological behaviors of CoCrFeNiNbx eutectic high entropy alloys which would be highly-promising candidates for high-temperature applications. The effects of testing temperature and material structure on the friction and Wear properties are investigated. The CoCrFeNiNbx alloys display a Low harness decrement Rate about 35% from room temperature to 1000 °C, indicating good softening resistance. The main Wear mechanisms are abrasion Wear at room temperature, change to adhesion Wear at 400 °C, and translate into oxidation Wear and mechanical Wear over 600 °C. The Wear Rates increase from room temperature to 400 °C and decrease afterwards. The effects of material structure are dominated by the hardness of alloy, the content of chemically active Nb element and the structure of oxidized tribo-layer. The compact oxidized tribo-layers with excellent anti-Wear properties are formed on the worn surface of CoCrFeNiNb0.65 and CoCrFeNiNb0.8 alloys at 800 °C, leading to extremely Low Wear Rate.
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effect of particle size on tribological behavior of ni3al matrix high temperature self lubricating composites
Tribology International, 2011Co-Authors: Qinling Bi, Jun YangAbstract:Abstract The Ni 3 Al matrix high temperature self-lubricating composites with different particle size were fabricated by the powder metallurgy technique. The effect of particle size on the mechanical and tribological properties of the composites was investigated in this paper. The results showed that the coarse particle composite exhibited the Lowest friction coefficient and Wear Rate compared to the fine particle ones at a wide temperature range from room temperature to 1000 °C. The reason for the Low Wear Rate was that the coarse bulk phase could provide better deformation resistance and higher load bearing capacity than the fine microstructure.
Staffan Jacobson - One of the best experts on this subject based on the ideXlab platform.
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Wear mechanism differences of intake valves within heavy duty combustion engines
2015Co-Authors: Staffan JacobsonAbstract:Today, there is an increasing demand on higher efficiency and Lower emissions for heavy duty combustion engines. This puts a lot of strain on the different components of the engine. This work is focused on the intake valve system: the valve and valve seat insert. They need to have a Low Wear Rate to survive for an increased operating time but the design of them is a compromise between high efficiency and Low Wear Rate. At the same time they see less and less particulates in the fuel and emissions due to harder legislation that differs around the world, which may hinder the formation of protective tribofilms.To deal with the challenge this puts on the developers of the valve system, knowledge is needed about how the tribofilms form and protect the sealing surfaces of the valve and valve seat insert. In an earlier study it was shown that the tribofilms and their Wear protecting abilities of the intake valve system vary with different operating conditions regarding alLowed emissions from the engine. However, observations from the developers tell not only about differences between engines regarding the Wear of the valve system but also sometimes visually large differences of valves coming from the same engine.In this study, differences within the same engine are analyzed. Valves have been taken from three different engines. The set of valves from each engine differ in visual appearance and Wear. The valves have been examined with scanning electron microscopy and energy dispersive x-ray analysis to see the coverage and composition of tribofilms.The results will be presented and discussed regarding the differences within an engine and how these differences compare to the ones between different engines.
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Wear mechanism study of intake valve system in modern heavy duty combustion engines
2015Co-Authors: Staffan JacobsonAbstract:At the present time, there is an increasing demand on higher efficiency, a longer operational life, and Lower amounts of emissions for heavy duty combustion engines. This puts a lot of strain on the different components of the engine, not least the valve and valve seat insert, which opeRate in direct contact with the combustion chamber. A Low Wear Rate is needed to maintain their sealing and performance abilities, but the design is often a compromise in between high efficiency and Low Wear Rate. At the same time, the sealing surfaces see less and less particulates geneRated in the engine due to harder environmental legislations which may hinder the formation of protective tribofilms. these changes are expected to change the Wear Rates of the valve sealing interfaces rapidly.In this study, intake valves and valve seat inserts from three different engines have been analyzed. The samples come from two field engines and a cell test and differ in effect, operating time, fuel, and environmental legislation class. The valve sealing surfaces have been examined with high resolution electron microscopy and surface analysis in order to analyze and establish the possible Wear mechanisms and presence of protective tribofilms. The results will be presented and their implication with regard to future valve systems will be discussed.
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Influence from humidity on the alumina friction drive system of an ultrasonic motor
Tribology International, 2009Co-Authors: Johanna Olofsson, Stefan Johansson, Staffan JacobsonAbstract:Abstract Miniaturized ultrasonic motors, based on piezoelectric movement, are rapidly developing and the number of commercial applications is steadily growing. The details of the friction drive system of these motors still need systematic studies to fully utilize the potential of the technique. The friction drive system transfers the high frequency oscillatory movement from the stator to a drive rail. The friction force should be maximized and stabilized to achieve the best motor performance, while maintaining a Low Wear Rate. The mating parts of a friction drive system typically consist of alumina which is selected due to its relatively Low Wear Rate and relatively high coefficient of friction. With increasing relative humidity, the friction coefficients of alumina ceramics generally decrease. This work examines how water and humidity affect a friction drive system with respect to coefficient of friction and Wear of the mating surfaces. Ball-on-disc experiments were used to evaluate the tribological properties. The worn surfaces were studied by scanning electron microscopy. The coefficient of friction was found to be relatively Low but stable with water on the surface but higher and more fluctuating in dryer conditions. The character of the worn surfaces did not clearly correlate to the friction behaviour.
