Surface Roughness and Normal Force Effects on the Sliding and Rolling Behavior of POM-H Rolls

Polymer bearings are increasingly used due to their simple mass production and good tribological properties. The current contribution presents a macroscopic study of the effects of surface roughness and normal force on the sliding and rolling behavior of POM-H rolls. The counter-face roughness Ra was varied from 0.01 to 0.5 µm and the normal force from 150 up to 350 N. A polynomial regression model was used to analyze the effects of the two parameters and their interaction. The experiments showed that the coefficient of sliding friction depends strongly on the roughness with a distinct minimum at around 0.1 µm and only slightly on the normal force. In contrast, the coefficient of rolling resistance increases strongly with higher normal forces. From 150 to 350 N the coefficient of rolling resistance doubles in value. The roughness has a minor influence in rolling. The difference between sliding and rolling expresses also in the opposite interaction effects of the roughness and normal forces.