Prediction of friction coefficient in dry-lubricated polyoxymethylene spur gear pairs

Abstract

In this article, the authors have experimentally determined the friction coefficient in the polyoxymethylene gear pairs lubricated by a dry film lubricant. The obtained expression increases the precision of the frictional power loss calculation, which is essential when the frictional power loss is used as the optimization criterion. The friction coefficient was characterized for three influencing parameters: radius of relative curvature, sliding velocity, and normal load. The full factorial organization was used for the experiment design; five curvature radii levels, four sliding velocity levels, and three load levels were used. Each of the runs was recorded three times, which resulted in a total of 180 experimental runs. The resulting expression for the friction coefficient is valid for the gear modules between 1 and 4.5 mm and sliding speeds of up to 2.7 m/s. The normal load was found to have the greatest influence on the friction coefficient, while the sliding velocity influenced only the specimens running under lower load levels. A further increase in the values of radii of relative curvature above 5 mm had no effect on the friction coefficient. The experimental data is provided in full.