Transfer of material between rolling and sliding surfaces

Many industrial processes involve the passage of material through the nip between rollers: printing, paper manufacture, rubber processing and metal rolling. During an investigation of wear of involute gear teeth it was observed that the wear debris tended to accumulate on the tips of the mating teeth. This behaviour was reproduced by passing small pieces of plasticine between rollers pressed into contact, which had a difference in peripheral speeds. The plasticine was observed to transfer from the slower to the faster surface. Similar behaviour was found with a granular paste and in the processing of uncured rubber. The paper reports an investigation in depth into this phenomenon. Transfer was found to depend on the ratio of surface speeds and the amount of compression through the nip. For small reductions in thickness of the billet it always emerged adhering to the slower surface, but for large reductions the opposite was true. Simple kinematic models of the deformation in the nip have been proposed which reflect the observations qualitatively and point the way to more complete finite-element analysis.