The contact behaviour in a coating roller or printing press roller nip is investigated in this paper by using soft elastohydrodynamic lubrication (EHL) theory. Film thickness, roller deformation and pressure profiles are evaluated for a range of possible dimensionless speed, load, elastomer thickness, Poisson's ratio and fluid inlet positions. To achieve the simultaneous iterative solution of the describing equations, the Reynolds equation is transformed into a form of boundary integral equation which is solved by Simpson's rule and surface distortion is obtained by a boundary element method. The numerical scheme proved to be very effective for such layered soft EHL problems. Results show that relatively thick fluid films exist in the nip because of the large deformation of the elastomer under normal working conditions. The dimensionless speed parameter has more influence on film formation at a fully flooded condition than any of the other parameters. Because the layer is easily deformable, film thickness may increase when load increases. The shape and thickness of the film and pressure profile are also controlled by the degree of starvation. At severely starved fluid supply, speed and load parameters have the most significant effect on the minimum film thickness. Larger Poisson's ratios produce a little smaller film thicknesses and larger surface displacements than the small values, and small elastomer thickness gives small indentation and large pressures in the nip.
SUMMARYThis paper presents a numerical routine to compute the contact characteristics of elastomer layered cylinders lubricated by isoviscous liquids. The indentation of the elastic layer is calculated from boundary integral equations which are solved by linear and quadratic boundary element methods for a finite plane model and a circular representation of the junction. The hydrodynamic equation is also transformed into a boundary integral equation and solved by Simpson's rule. Some factors which possibly affect numerical accuracy are examined. Examples for finite plane and circular layer are analysed with reference to parameters for printing press roller contact, in which results are obtained for the indentation, film thickness and liquid pressure, as well as internal stresses through the simultaneous solution of the elasticity and hydrodynamic equations. The results show that high precision is easily achieved and the method is efficient for such layered problems.
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