Steady friction state and contact models of asperity interaction

Rapoport, L.

doi:10.1016/j.wear.2008.12.031

Cited by 13 publications

(3 citation statements)

References 41 publications

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“…It has been shown that the steady friction state is characterized by the balance between geometrical and structural parameters of the contact [25]. This balance implies equilibrium between deformation, relaxation, and fracture in the deformed layers on the one hand and a preservation of the sizes of the asperity contacts and the wear particles on the other hand.…”

Section: Discussionmentioning

confidence: 99%

The Effect of Grain Size on Stribeck Curve and Microstructure of Copper Under Friction in the Steady Friction State

et al. 2011

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In the present work, the effect of grain size on the friction and wear behavior of a copper (Cu) samples under different lubricant conditions was studied. The structural evolution of Cu subsurface layers under friction in different lubricant conditions was considered. All friction tests were conducted under laboratory conditions using a block-on-ring rig. The effects of sliding velocity and load on the friction coefficient and wear rate of Cu with different grain size (1, 30, and 60 lm) were analyzed. The Cu samples with the average grain size of 1 lm were obtained due to severe plastic deformation (SPD) by equal channel angular pressing (ECAP). The Stribeck curves for Cu samples with different virgin grain sizes were considered. Elasto-hydrodynamic lubrication (EHL) and boundary lubrication (BL) regions were mainly studied in the present work. Similar Stribeck curves were found out for Cu samples with different virgin grain size. A load of the transition from the EHL to BL region was increased with a decrease of the grain size. While the friction coefficients were similar in the EHL and BL regions for the samples with different grain sizes, the wear rate was increased remarkably with an increase the virgin grain size. Flow localization during friction in the BL region led to formation of the vortex structure in subsurface layers. Based on the dependence of the microhardness upon the depth, the degree of hardening (H) was evaluated. A correlation between the coefficient of wear and the deformation hardening of Cu samples with different virgin grain sizes was revealed. In order to take into account the effect of the grain size and to predict the Stribeck curve, a parameter, K, as the ratio between hardness of tested and annealed samples, was incorporated into the lubricant number. The theoretical values of the Stribeck curve calculated for preliminary deformed Cu samples (d = 1 lm) and annealed samples (d = 60 lm) were well coincided with the experimental results.

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Section: Discussionmentioning

confidence: 99%

The Effect of Grain Size on Stribeck Curve and Microstructure of Copper Under Friction in the Steady Friction State

et al. 2011

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“…It has been shown that the steady friction state is characterized by a balance between the geometrical and structural parameters of the contact [14]. This balance implies an equilibrium between deformation, relaxation and fracture in the deformed layers on one side and a preservation of the sizes of the asperity contacts and wear particles on the other.…”

Section: Discussionmentioning

confidence: 99%

Stribeck Curve Under Friction of Copper Samples in the Steady Friction State

et al. 2009

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The friction and wear of a pure copper block (99.98 wt% Cu) against a hardened steel disc were studied. The effect of sliding velocity and load on the friction coefficient and wear rate of Cu samples during steady tests was studied. Elasto-hydrodynamic (EHL), mixed (ML) and boundary lubrication (BL) regions were analyzed using the Stribeck curve. The lubrication number of Schipper, Z, was used in the analysis of the Stribeck curve. The transitions from one lubrication region to another are discussed. The mixed EHL region is characterized by stable low values of the friction coefficient, wear rate and temperature. Straight asperity contact is the dominant mechanism under friction of Cu-steel pair in the BL region. High-friction coefficients and wear rates, thin lubricant films and large wear grooves indicate straight asperity contact between rubbed surfaces in the BL region. Although the dominant mechanisms in the mixed EHL and BL regions are different in principle, a steady friction state is preserved in both cases. It is expected that the steady friction state in the BL and mixed EHL regions is associated with deformation and fracture of surface layers but these process occur at different scale levels. It was shown that under friction of Cu-steel pair, two types of ML regions are observed. The first is the stable steady friction of mixed EHL with low values of the friction coefficient and wear rate. The second type of the ML region is the region of unstable friction and wear when a decrease of lubricant film leads to a change of external (roughness, temperature, friction and wear) and internal (strain and stress) parameters. It was found out that a transition to the unstable ML region occurs within a narrow range of Z parameter under definite values of the load and sliding velocity.

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“…A variety of research methods, each with distinct features, have been utilized to address the contact issues of rough surfaces. Rapoport 18 used the contact model and a description of the dislocation structure to analyse the steady-state friction of a rough surface. Guo et al 19 developed a mixed-lubrication model of a rotary seal described by a Reynolds equation that took into account the surface roughness effect using flow factors.…”

Section: Introductionmentioning

confidence: 99%

Analytical and experimental study on the sliding contact of the sealing ring in the wet clutch

Gong

Zhou

Che

et al. 2015

Proceedings of the Institution of Mechanical Engineers, Part D:

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Sealing rings in the wet clutch of heavy vehicles are vulnerable and weak. A key issue in designing and applying sealing rings is predicting the state of the seal contact quickly and accurately. A mixed-lubrication model of the sealing ring is developed on the basis of the load-sharing concept. A theoretical model is proposed to estimate the hydrodynamic and asperity contact behaviour of the sealing ring. The friction coefficients are calculated and compared under different operating conditions. The results cover the entire lubrication regime, including full-film lubrication, mixed lubrication and boundary lubrication. Experiments are conducted on a special test rig for sealing rings. General agreement is observed between the experiments and the simulations. The proposed method is simple but realistic and significantly improves the simulation efficiency. Designing the sealing ring quickly and accurately benefits the transmission system of heavy vehicles.

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Steady friction state and contact models of asperity interaction

Cited by 13 publications

References 41 publications

The Effect of Grain Size on Stribeck Curve and Microstructure of Copper Under Friction in the Steady Friction State

The Effect of Grain Size on Stribeck Curve and Microstructure of Copper Under Friction in the Steady Friction State

Stribeck Curve Under Friction of Copper Samples in the Steady Friction State

Analytical and experimental study on the sliding contact of the sealing ring in the wet clutch

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