Effects of average lubricant velocity and sliding velocity on friction behavior in mild steel sheet forming

A series of experiments was carried out using a rolling-type tribometer to investigate the frictional dependence on the average velocity of the lubricant V at the contact zone inlet and the relative sliding velocity Delta V between the roll and workpiece during deformation. Experiments using mild steel strips with a drill surface of 0.63 mu m Ra showed that the friction coefficient decreases with increasing forming velocity, especially at high forming velocity. This variation in the friction coefficient may be due to the increase in Delta V derived from the increase of the forming velocity, because the friction coefficient decreases with increasing Delta V but varies little with increasing V. It was also confirmed that an increase of Delta V or a decrease in V promotes flattening of the workpiece asperities.