Effect of surface structure, composition and texture on friction under boundary conditions

1952 ◽  
Vol 212 (1111) ◽  
pp. 508-512
Keyword(s):  
Oxide Film ◽  
Boundary Conditions ◽  
Coefficient Of Friction ◽  
Substrate Material ◽  
Pure Aluminium ◽  
Surface Layers ◽  
The Coefficient Of Friction ◽  
The Difference ◽  
Frictional Behaviour ◽  
Effect Of Surface

The coefficient of friction of surfaces lubricated under boundary conditions may be profoundly affected by such factors as the degree of working of the substrate material, the nature of the oxide film and the degree of roughness of the surface. Experiments are described wherein the frictional behaviour of surfaces of stainless steel specimens prepared in various ways was compared. The worked surface layers in these particular experiments appear to increase the value of the coefficient of friction, but the effect of surface texture is of predominant importance. The effect of different oxide films is best illustrated by reference to pure aluminium, the surface of which has been oxidized under different environmental conditions. The constitution of the oxide film formed is modified with a consequent effect on boundary friction. When the friction of rough and smooth surfaces is compared, the difference in behaviour appears to be qualitative rather than quantitative.

The friction of clean crystal surfaces

1966 ◽  
Vol 295 (1442) ◽  
pp. 233-243 ◽  
Keyword(s):  
Coefficient Of Friction ◽  
High Surface ◽  
High Vacuum ◽  
Surface Films ◽  
Surface Adhesion ◽  
Crystal Surfaces ◽  
Deformation And Fracture ◽  
The Coefficient Of Friction ◽  
Molecular Layers ◽  
Frictional Behaviour

A study is made of the frictional behaviour of crystals (diamond, magnesium oxide, sapphire) sliding on themselves in high vacuum (10 -10 torr). The surface films normally present on these crystals are very tenacious but they may be worn away by repeated sliding in the same track. Under these conditions the friction of the clean crystals may increase by a factor of ten so that the coefficient of friction may rise to μ ≈ 1. The frictional rise is limited because of the elastic and brittle behaviour of the contact regions. Under these conditions subsurface deformation and fracture of the crystal occurs and this, combined with the high surface adhesion, causes pronounced wear. Adsorption of a few molecular layers of gas can again reduce the friction to a low value. The results are relevant to the operation of bearings and to the wear of surfaces in space.

scholarly journals The Effect of Surface Texture on Lubricated Fretting

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4886
Author(s):  
Agnieszka Lenart ◽  
Pawel Pawlus ◽  
Andrzej Dzierwa ◽  
Slawomir Wos ◽  
Rafal Reizer
Keyword(s):  
Coefficient Of Friction ◽  
Surface Texture ◽  
Friction And Wear ◽  
Normal Load ◽  
Disc Surface ◽  
The Coefficient Of Friction ◽  
42Crmo4 Steel ◽  
Ball Diameter ◽  
Steel Balls ◽  
Effect Of Surface

Experiments were conducted using an Optimol SRV5 tester in lubricated friction conditions. Steel balls from 100Cr6 material of 60 HRC hardness were placed in contact with 42CrMo4 steel discs of 47 HRC hardness and diversified surface textures. Tests were carried out at a 25–40% relative humidity. The ball diameter was 10 mm, the amplitude of oscillations was set to 0.1 mm, and the frequency was set to 80 Hz. Tests were performed at smaller (45 N) and higher (100 N) normal loads and at smaller (30 °C) and higher (90 °C) temperatures. During each test, the normal load and temperature were kept constant. We found that the disc surface texture had significant effects on the friction and wear under lubricated conditions. When a lower normal load was applied, the coefficient of friction and wear volumes were smaller for bigger disc surface heights. However, for a larger normal load a higher roughness corresponded to a larger coefficient of friction.

scholarly journals The Influence of Surface Texturing on the Frictional Behaviour in Starved Lubricated Parallel Sliding Contacts

Lubricants ◽  
2019 ◽  
Vol 7 (8) ◽  
pp. 68 ◽  
Author(s):  
Bijani ◽  
Deladi ◽  
Rooij ◽  
Schipper
Keyword(s):  
Coefficient Of Friction ◽  
Surface Texturing ◽  
Geometrical Parameters ◽  
Textured Surfaces ◽  
Tribological Behaviour ◽  
Sliding Contacts ◽  
Cavitation Effect ◽  
The Coefficient Of Friction ◽  
Starved Lubrication ◽  
Frictional Behaviour

Starvation occurs when the lubricated contact uses up the lubricant supply, and there is not enough lubricant in the contact to support the separation between solid surfaces. On the other hand, the use of textures on surfaces in lubricated contacts can result in a higher film thickness. In addition, a modification of the surface’s geometrical parameters can benefit the tribological behaviour of the contacts. In this article, for parallel sliding surfaces in starved lubricated conditions, the effect of surface texturing upon the coefficient of friction is investigated. It is shown that surface texturing may improve film formation under the conditions of starvation, and as a result, the frictional behaviour of the parallel sliding contact. Furthermore, the effect of starved lubrication on textured surfaces with different patterns in the presence of a cavitation effect, and its influence on frictional behaviour, is investigated. It is shown that surface texturing can reduce the coefficient of friction, and that under certain conditions, the texturing parameter could have an influence on the frictional behaviour of parallel sliding contacts in the starved lubrication regime.

The Full Journal Bearing

1949 ◽  
Vol 161 (1) ◽  
pp. 59-72 ◽  
Author(s):  
A. Cameron ◽  
W. L. Wood
Keyword(s):  
Boundary Conditions ◽  
Coefficient Of Friction ◽  
Journal Bearing ◽  
Complete Solution ◽  
Radial Clearance ◽  
Eccentricity Ratio ◽  
Relaxation Methods ◽  
The Coefficient Of Friction ◽  
Final Answer ◽  
Detailed Application

The basic mathematics of the full journal bearing have been known since 1904 when Sommerfeld‡ made the complete solution, for the infinite journal, of Reynolds theory of 1886. The detailed application of the theory has not been possible owing to the uncertainty in the choice of boundary conditions. In this paper the Reynolds condition that p = 0 at θ = 0 and p = ∂ p/∂θ = 0 at θ = π + α is shown to follow for the infinite bearing from a consideration of continuity of flow and, equally important, from the shaft stability condition, first put forward by Swift in 1933. It is claimed that this is the final answer to the question of correct boundary conditions. The Reynolds equation for the infinitely wide bearing was solved using these conditions. Assuming the viscosity is constant all round the bearing, the coefficient of friction-load criterion curve has the same slope as experimentally determined curves. The Mathematics Division, N.P.L., computed, by Southwell's relaxation methods (1946), the figures for finite bearings of diameter length ratios of 4, 2, and 1. The theoretical figures for eccentricity ratio-load criterion are satisfactorily compared with some of Nücker's experimental results, and the coefficient of friction, load criterion, figures explain the apparent intercept found by McKee and McKee. A diagram is given allowing the eccentricity ratio c, to be obtained from the load criterion for any bearing of diameter/length ratio from 0 to 4, and this enables the minimum film thickness, which equals (1 — c) x radial clearance, to be calculated.

Fine Motor Control with CBR Protective Gloves

1987 ◽  
Vol 31 (11) ◽  
pp. 1206-1210 ◽  
Author(s):  
Demetrios Karis
Keyword(s):  
Motor Control ◽  
Coefficient Of Friction ◽  
Ring Finger ◽  
Fine Motor ◽  
Control Task ◽  
Trial Time ◽  
Cursor Control ◽  
The Coefficient Of Friction ◽  
Within Subjects ◽  
The Difference

Using a within-subjects design, performance on a continuous cursor control task was measured in three conditions: no gloves, flight gloves, and a combination of three gloves worn simultaneously for chemical, biological, or radiological (CBR) protection. Twelve subjects used their left ring finger on a two-axis force controller to move a cursor on a CRT. After centering it over one of eight possible targets, they depressed the controller to designate the target and end a trial. Time to acquire the target and accuracy in centering the cursor over the target were recorded. Subjects had faster acquisition times in the two glove conditions with no increase in errors, although only the difference between the CBR gloves and no-gloves was statistically significant. My explanation for these findings is that the thickness of the gloves may have improved the fit of the fingertip in the force controller, which was concave, and also prevented the finger from slipping by increasing the coefficient of friction between the finger and the controller.

Brush Dynamics: Models and Characteristics

2006 ◽  
Author(s):  
Libardo V. Vanegas Useche ◽  
Magd M. Abdel Wahab ◽  
Graham A. Parker
Keyword(s):  
Surface Roughness ◽  
Coefficient Of Friction ◽  
Rotational Speed ◽  
Surface Finishing ◽  
Stick Slip ◽  
Street Sweeping ◽  
The Coefficient Of Friction ◽  
Dynamics Models ◽  
Frictional Behaviour ◽  
Duct Cleaning

This paper reviews investigations into the dynamics and modelling of brushes. They include brushes for surface finishing operations, removal of fouling, post-CMP brushing processes, air duct cleaning, and street sweeping. The methods that have been proposed to model brush dynamics are described, and the results of the research into brush mechanics are presented and discussed. Some conclusions of the paper are as follows: brush dynamics is very complex, as it depends on the interaction among many phenomena and variables. The bristle oscillations that occur in some brushes constitute a complexity for modelling brush behaviour and are not normally addressed. Additionally, the literature reveals that the coefficient of friction is not a constant value that depends only on the materials and surface roughness of the two contacting bodies. Frictional behaviour strongly depends on many variables, such as brush setup angles and rotational speed, which play a part in the development of stick-slip friction cycles. Finally, it is concluded that brush behaviour and the phenomena involved in brushing have not been fully studied or understood and more research into this field is needed.

EXTRINSIC SYMMETRY-BREAKING EFFECT ON ELECTRO-OPTICS OF LIQUID CRYSTALS

1990 ◽  
Vol 04 (17) ◽  
pp. 1071-1076 ◽  
Author(s):  
SIN-DOO LEE ◽  
J.S. PATEL
Keyword(s):  
Liquid Crystals ◽  
Symmetry Breaking ◽  
Boundary Conditions ◽  
Surface Layers ◽  
Interfacial Interactions ◽  
Breaking Effect ◽  
Simple Geometry ◽  
Electro Optic ◽  
The Difference ◽  
Anchoring Strength

It is demonstrated that the symmetry-breaking of interfacial interactions between two surface layers in liquid crystals can produce a polar electro-optic effect. In a simple geometry with homogeneous boundary conditions, it is found that the magnitude of this polar effect is directly proportional to the difference in the anchoring strength between two aligning surface layers.

Friction Characteristics of Porous Rubber Under Wet Conditions

2009 ◽  
Author(s):  
Yutaro Kosugi ◽  
Tomoaki Iwai ◽  
Yutaka Shokaku ◽  
Naoya Amino
Keyword(s):  
Friction Force ◽  
Coefficient Of Friction ◽  
Contact Surface ◽  
Road Surface ◽  
Water Removal ◽  
The Road ◽  
Rubber Specimen ◽  
The Coefficient Of Friction ◽  
The Difference ◽  
Tread Rubber

In recent years, porous rubber has been used as a tread matrix for studless tires. It is said that the pores in the tread rubber remove water between the tire and the wet road surface; however, the water removal is not sufficiently well understood. In this study, a rotating rubber specimen was rubbed against a mating prism to observe the contact surface. The friction force was also measured simultaneously with observation of contact surface. The water entering the pores was distinguished by the continuity method. As the result of these experiments, the coefficient of friction for rubber having pores on the surface was found to be larger than that of rubber without pores. Moreover, the difference in the coefficient of friction for rubber specimens with and without pores tended to be larger at lower sliding speeds. No water entered pores 3mm or less in diameter at any sliding speed in this experiment. An experiment to make the rubber specimen collide with the mating prism was conducted since actual tires seem to be deformed by the vehicle weight, such that the tire surface might contact the road collisionally. In the resulting collision experiment, the water did enter pores 3mm in diameter.

scholarly journals The influence of temperature on boundary lubrication

1942 ◽  
Vol 181 (984) ◽  
pp. 23-42 ◽  
Keyword(s):  
Oleic Acid ◽  
Coefficient Of Friction ◽  
Boundary Lubrication ◽  
Surface Film ◽  
Adsorbed Layer ◽  
Surface Measurement ◽  
Polar Group ◽  
The Coefficient Of Friction ◽  
Low Speeds ◽  
Frictional Behaviour

The frictional behaviour between mild steel surfaces lubricated with excess of pure hydrocarbons, ketones, alcohols, amides, acids and esters has been investigated at low speeds and under high loads. In all cases a transition from smooth sliding to irregular stick and slip motion takes place at a temperature characteristic of the lubricant employed. Experiments in which lubricant films one or more molecules thick were built up by the Langmuir-Blodgett technique have shown that the transition from smooth sliding to stickslips occurs when the adsorbed surface film of lubricant breaks down and becomes disoriented. Acids and esters are shown to be strongly adsorbed, while hydrocarbons, ketones, alcohols and amides are not appreciably adsorbed. It is shown that adsorption of acids and esters occurs by the interaction of the dipoles in their polar group with the metal atoms in the surface. The results also suggest that molecules of long-chain compounds are oriented on a metal surface in the same way as they have been shown to be arranged on an aqueous surface. Measurement of the coefficient of friction between surfaces lubricated with films one and many molecules thick has shown that under conditions of ‘ boundary lubrication ’ prevailing at high loads and low speeds, excess of lubricant is squeezed out, and lubrication is effected by a unimolecular film adsorbed on each surface. The variation of the coefficient of friction with load in the case of oleic acid shows that orientation with this lubricant extends beyond the primary adsorbed layer. This result accounts for the low values of the coefficient of friction obtained by previous workers, and explains the good lubricating properties of oleic acid. These experiments show that a study of the frictional behaviour provides a m ethod of investigating the properties of surface films on metals.

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