Effect on friction

As is known, microscale friction and wear is important in microtribology. However, it is not easy to get real friction force on micro/nano scale during the tests. The surface morphology at nanometer scale, the scanning direction of the FFM, etc., have significant effects on friction force measurement. Even nowadays for commercial SPM we are not quite sure if the friction force we get is a real one or not. 

Should have no adverse effects on frictional characteristics of wool fibres or yarns. 

Tribochemical reactions may be assessed to have the most diverse effects on friction, lubrication, and wear processes in the formation of the tribofllm in surface protection. 

Friction is the tangential resistance offered to the sliding of one solid over another, due to dry friction. Friction is an apparently simple phenomenon with very complex mechanisms that take place on a variety of length scales, from atomic to nano and up. The study of friction is part of the engineering-scientific discipline of tribology,3 which is the scientific study of friction, wear, and lubrication (6). It was Leonardo da Vinci (1452-1519) who discovered the first two laws of friction, namely, that the area of contact has no effect on friction and that friction is proportional to the load. These two laws were rediscovered later by Guillaume Amontons (1663-1705), and later Charles-Augustin Coulomb (1736-1806), added the third law ... 

Spalvins ° attributed the poor performance in air to the presence of water, and Roberts further showed that the effect on friction occurs at two different levels and is reversible when testing alternates between moist air and high vacuum. It is significant that the coefficient of friction in moist air of the ultra-pure films produced by Donnet et al ° 0.15, is almost identical with that of the less-rigidly contaminant-free films of Roberts, 0.16. This suggests that the high friction in moist air is almost entirely due to the water present, and is not significantly affected by any other contaminants which may have been present. 

Mizutani, Y., Imada, Y and Nakajima, K., Formation of Molybdenum Sulfide in Fe-Mo-S Alloys and its Effect on Frictional Property, Proc. JSLE-ASLE Inti. Lub. Conf., Tokyo, (9-11 June, 1975), p. 161. 

Kelsall, G.H., Zhu, Y., and Spikes, H.A., Electrochemical effects on friction between metal oxide surfaces in aqueous solutions, J. Chem. Soc. Faraday Trans., 89, 267, 1993. 

Another factor which complicates the matching of theoretical deductions with observed behavior in the study of contact adhesion is the influence of surface films. The effect on friction of adsorbed gas films, metal oxide films and additive reaction films has been discussed in detail in Chapters 9 and 10. Since the major frictional mode is adhesive, it follows that the factors which influence lubricated friction in such instances ultimately resolve back to their influence on adhesion. The interactions among surface films, surface topography, contact and adhesion are discussed in detail in Section 12.6. 

Gas flow in lagged process pipes will be essentially adiabatic, and some drop in temperature may occur. The drop in temperature will lead to a decrease in viscosity, but the decrease in viscosity will usually be rather small. For example, a drop in temperature of methane from 200°C to 100°C causes the viscosity to drop by 25%, and from equation (4.25), this will lead to an increase of Reynolds number of a similar percentage. This increase in Reynolds number will have no effect on friction factor for Reynolds numbers above 100000 because of the flatness of the Moody curve in this region. We may evaluate the effect for Reynolds numbers below 100000 by differentiating equation (4.28) to give ... 

For friction loss of slurries Cooper et al. (38) presented the friction correction factor shown in Figure 14. The authors claim that it is based on a theoretical method of predicting friction pressures of non-Newtonian fluids. The method assumes vertical flow, no hold-up effect, and pseudohomogeneous characteristics. However, the details of the method are not presented in open literature. It is shown in their article that the modeled effect on friction pressures is consistent with a field study conducted by Swanson and Meeken (39). 

A.P. Reynolds and W. Tang, Alloy, Tool Geometry, and Process Parameter Effects on Friction Stir Welding Energies and Resultant ESW Joint Properties, Friction Stir Welding and Processing, K.V. Jata, M.W. Mahoney, R.S. Mishra, S.L. Semi-atin, and D.P. Eield, Ed., TMS, 2001, p15-23... 

TANAKA AND YAMADA Temperature Effects on Friction and Wear... 

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