Boundary lubrication.—Further consideration of the influence of the composition of the solid face

Abstract

It has been shown in previous papers (Hardy and Doubleday, ‘Roy. Soc. oc.,' A, vol. 100, p. 550 (1921); A, vol. 101, p. 487 (1922)) that the curves obtained by plotting the coefficient of static friction against the molecular weight of the lubricant, in the case of homologous series of normal paraffins ad their related primary and secondary alcohols and acids, satisfy the equations μ = b – a M, (1) when the slider has a curved face and the plate is plane and both are of the some material. When they are of different materials, 1 and 2, the equation becomes: μ = b 1 – b 2 / 2 – a M, (2) where M is molecular weight of lubricant; a is a parameter independent of the nature of the solid face and dependent only on chemical type, varying from one homologous series to another; and b is dependent on the nature of the solid face, as well as on the chemical series. Hitherto the only solids tested have been glass, a mild carbon steel, bismuth and quartz, and it was found that on changing from one to another the curve or a chemical series was merely moved parallel to itself. The investigations have now been extended to include various specimens of alloy steels and phosphor bronze.