Mechanisms of formation of polymeric transfer films

Rhee, Sang Hoon; Ludema, Kenneth C.

doi:10.1016/0043-1648(78)90124-2

Cited by 70 publications

(31 citation statements)

References 2 publications

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“…Extrapolation of friction coefficients reveals zero friction at temperatures above 200°C, corresponding to a degradation temperature of e.g. 220°C as reported by Rhee and Ludema [43]. The hypothetical formation of a supplementary crystalline structure with high temperature resistance due to orientation effects should then explain this high-temperature behaviour, however, this should be ascertained by further research in the second part of this project.…”

Section: Influence Of Temperature On Frictionmentioning

confidence: 81%

Friction of polyoxymethylene homopolymer in highly loaded applications extrapolated from small-scale testing

Samyn

Baets

2005

Tribol Lett

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Most studies on tribology of polymer materials are traditionally performed on small-scale test specimens. However, to obtain data relevant for practical design of polymer parts in highly loaded bearings or sliding systems one must simulate real working conditions as close as possible on laboratory scale. In present work, a large-scale test rig has been used for determinating friction of a commercial polyoxymethylene homopolymer (POM-H). Test samples with contact area 22500 mm 2 are submitted to a reciprocating motion with stroke 230 mm under different contact pressures from 8 to 150 MPa and sliding velocity of 5 mm/s. Test results are compared to those obtained on a traditional cylinder-on-plate configuration and reveal lower friction on large-scale tests. However, general laws predicting the coefficient of friction as a function of normal loads cannot be used for extrapolation. Bulk and flash temperatures are calculated to explain transitions in friction mechanisms on both testing scales. Local surface temperatures are higher under large-scale sliding and allow for surface melting, which is not observed on small-scale tests. Although, sliding conditions implying an identical flash temperature induce polymer transfer only on large-scale tests, while no transfer occurs on small-scale tests. Even an artificial increase in small-scale bulk temperatures allowing for polymer transfer, is not able to provide low friction as observed on large-scale. An appropriate combination of load and sliding velocity is used for linear extrapolation of friction values, indicating the additional importance of bulk temperatures. When the polymer softening point is exceeded, creep at the polymer surface contributes to low friction.

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Section: Influence Of Temperature On Frictionmentioning

confidence: 81%

Friction of polyoxymethylene homopolymer in highly loaded applications extrapolated from small-scale testing

Samyn

Baets

2005

Tribol Lett

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“…Some reactions are controlled by radical formation. Rhee et al [87] reported that the friction and wear processes at high temperatures are rather controlled by pyrolysis. Thermal and oxidative reactions cause degraded wear particles to incorporate in the transfer film and change its stability.…”

Section: Theoretical Considerationsmentioning

confidence: 99%

Friction and Wear Mechanisms of Sintered and Thermoplastic Polyimides under Adhesive Sliding

Samyn

Schoukens

Verpoort

et al. 2007

Macro Materials & Eng

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Polyimides function under high‐temperature sliding. The available literature explains transitions in friction and wear mainly by mechanical effects, such as influences of normal load, sliding velocity and humidity on polymer transfer to steel counterfaces. Theoretical models are evaluated for sintered and thermoplastic polyimides. Tribologists have been interested in tribochemical and tribophysical reactions in the sliding interface for about 25 years. Reactions such as hydrolysis, imidisation and/or degradation occur as a function of sliding temperature and are reviewed in this paper. An overview of polyimide synthesis and degradation is presented, while new insights in sliding mechanisms are obtained from a detailed study of Raman spectroscopy on worn polymer surfaces.magnified image

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“…To give a perspective on the tenacity of oxides, some tests were done by sliding various polymers over 440C stainless steel. It was found that the polymers that had a shear strength less than 9200 lbf in-* (63.4 MPa) did not remove oxide from the stainless steel, whereas polymers with a shear strength over 9500 lbf in-* (65.5 MPa) did remove oxide from stainless steel [64]. It would, therefore, seem that the tenacity or shear strength of oxide on stainless steel is of the order of 9500 lbf in-* (65.5 MPa) and perhaps this property should be the focus of research attention rather than the properties of the substrates.…”

Section: Research Topics On Oxidesmentioning

confidence: 99%

“…asperity height, skewness, kurtosis and bearing area. It is interesting to see how often the surface finish (or roughness) is specified numerically in the geometric progression 1, 2, 4, 8, 16,32,64 etc. It would appear that specification in intermediate numbers is either unnecessary, or perhaps designers do not really know what roughness is needed.…”

Section: Effect Of Surface Finishmentioning

confidence: 99%

A review of scuffing and running-in of lubricated surfaces, with asperities and oxides in perspective

Ludema

1984

Wear

238

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SummaryThe slow progress in the understanding of scuffing (scoring) and runningin of most lubricated surfaces is probably due to an inadequate understanding of the details of asperity deformation and oxide formation. The thickness and properties of oxides influence the stress states imposed on asperities as much as does the liquid lubricant, but the oxides are ignored in theories. Present theories also focus on adhesion as the cause of scuffing and they usually do not take account of the changing surface roughness during sliding. There may indeed be some evidence of adhesion in the later stages of damage but adhesion has not been demonstrated to be the initiating mechanism of scuffing. Plastic fatigue is the more likely explanation, and this can occur without atomic contact between the sliding surfaces.

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Mechanisms of formation of polymeric transfer films

Cited by 70 publications

References 2 publications

Friction of polyoxymethylene homopolymer in highly loaded applications extrapolated from small-scale testing

Friction of polyoxymethylene homopolymer in highly loaded applications extrapolated from small-scale testing

Friction and Wear Mechanisms of Sintered and Thermoplastic Polyimides under Adhesive Sliding

A review of scuffing and running-in of lubricated surfaces, with asperities and oxides in perspective

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