Axial velocity distribution imparted on thin media transported by layered rolls

An investigation of the axial velocity distribution along a thin media that is transported between flexible rubber-coated rolls is presented. First, a finite element analysis of plane strain static contact between rubber-coat ed rolls with thin media in the nip is conducted to determine the relations hip between coating indentation and normal load. The rubber coatings on eac h roll are modeled as incompressible, hyperelastic materials using a Neo-Ho okean model. Where bearing torque is negligible and the size and angular sp eed of the rolls is small enough that inertia may be neglected, the static load-indentation relation is a reasonable approximation of the dynamic load indentation relation. Second, a numerical analysis of roll core bending un der the applied pinching load is used to determine the axial distributions of load and coating indentation and the deformed shape of the roll axes. In this analysis, the roll cores are modeled as beams and the rubber coatings as springs using the relationship between spring load and rubber coating i ndentation that was determined in the previous analysis. Finally, assuming steady rolling and a negligibly small slip region in the contact interface, it is expected that the deformation resulting from static indentation at a ny cross-section is very similar to that for the dynamic loading condition. The deformation from static indentation solutions for various cross-sectio ns along the axis are then used with the known velocity in the undeformed s tate to determine the average nip velocity at these axial locations. Experi ments were used to determine the rolls' nominal speed ratio as a function o f skew angle, as well as to corroborate the numerical results of load and v elocity distribution in the nip. (C) 1999 Elsevier Science Ltd. All rights reserved.