Capillary and Viscoelastic Effects on Elastohydrodynamic Lubrication in Roller Nips

Abstract

A viscocapillary model of liquid movement and film-splitting in deformable nips between an elatomer-covered roll and a hard roll is presented here. This “soft” elastohydrodynamic regime is described by Reynolds’ equation of lubrication flow and a simple set of spring-and-dashpot elements for the viscoelastic behavior of elastomeric roll covers. Capillary effects around the film-split are accounted for with an augmented Young-Laplace equation from film-flow theory. Effects of the liquid’s surface tension (via capillary number) and the elastomeric cover’s relaxation time (via Deborah number) are predicted and compared with available experiments. Application to the flows through the multiple roller nips of printing press systems is discussed.