Prediction of friction coefficient for polymer-coated mechanical elements

• Published in: Surface & coatings technology 1992-12, Vol.56 (1), p.39-46
• Main Authors: El Mowafi, S.A., Khorshid, S.A.Y., Mokhtar, M.O.A.
• Format: Article
• Language: English
• Subjects: Applied sciences; Deformation; Exact sciences and technology; Friction; Fundamental areas of phenomenology (including applications); Joints (structural components); Mathematical models; Mechanical contact (friction...); Mechanical properties; Organic polymers; Physicochemistry of polymers; Physics; Polyamides; Polymers; Properties and characterization; Solid mechanics; Structural and continuum mechanics; Thermal effects; Tribology; Viscoelasticity
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/0257-8972(92)90193-E

The concept of polymer coating of mechanical elements to improve frictional properties has gained practical acceptance based on experimental evidence. However, application of this technique to tribological joints has remained limited to prototype experimental results. The present work aims to predict the friction coefficient at these joints through time-dependant mechanical properties of the coating polymer. A theoretical model based on linear viscoelastic relations, as well as simplified deformation functions of coating material, was used to determine the friction coefficient in sliding and rolling motion. It was found that the coefficient of friction decreases with increasing load following a power function of the form μ = aP n , where n is dependent on the type of motion between contacted surfaces (sliding or rolling). Experimental verification of the model is given for steel discs coated by polyamide 6. Experimental results gave the same power law where the value of n was −0.9 for sliding and −0.6 for rolling. It is also shown that the value of the constant a is temperature dependent.