CALENDERING OF PSEUDOPLASTIC AND VISCOPLASTIC FLUIDS
USING THE LUBRICATION APPROXIMATION
S. Sofou, E. Mitsoulis*
School of Mining Engineering and Metallurgy
National
Technical University of Athens
Zografou 15780, Athens
Greece
The
Lubrication Approximation Theory (LAT) is used to provide numerical results for
calendering a sheet from an infinite reservoir. The Herschel-Bulkley model of
viscoplasticity is used, which reduces with appropriate modifications to the
Bingham, power-law and Newtonian models. The results give the final sheet
thickness as a function of the dimensionless power-law index (in the case of
pseudoplasticity) and the dimensionless yield stress (in the case of
viscoplasticity). Integrated quantities of engineering interest are also
calculated. These include the maximum pressure, the roll-separating force, and
the power input to the rolls. Decreasing the power-law index n or increasing the Bingham number Bn lead to excess sheet thickness over
the thickness at the nip. All engineering quantities calculated in
dimensionless form increase substantially with the departure from the Newtonian
values.
calendering, pseudoplasticity, viscoplasticity, yield stress, Herschel-Bulkley model