| Calendering is the name of a forming process in the polymer industry, of a finishing operation in papermaking, and of a post-coating smoothing step. Common to all three is flow of a solid-like material between two counter-rotating rolls. Experiments of paper calendering reveal the effects of nip loading and roll surface temperature on the surface roughness, gloss, and elastic properties of paper, as well as on the porosity reduction of the surface layers of paper handsheets from images of a two-photon confocal microscope.; Lamination refers to pressing together two substrates with adhesive between. It also is commonly done between two counter-rotating rolls. A simple theoretical model and experiments of lamination of three-layer composites show the effects of web tensions, nip loading and roll speed on the curl and hang of the laminate, air entrapment and delamination.; The deformation in calendering commonly spans viscous, elastic, plastic, and various combinations of these. A constitutive theory of poro-elasto-viscoplastic materials for finite deformations is developed based on thermodynamics of internal variables and the principle of maximum dissipation. Internal variables represent changes of deviatoric and total elastic stress-free states, i.e. deviatoric and isotropic yielding. Two scalar potentials, the free energy and the yield or dissipation function, describe the evolution of the elastic stress-free states.; Indentation is commonly used to estimate material properties, like modulus and hardness, and visualize the deformation of the surface zones. A spherical cavity model for finite elasto-poro-plastic materials predicts the effect of isotropic yielding or change of total elastic stress-free state on indentation load and the size of plastic region.; A calendering model of slab analysis for plastic and poro-plastic materials reveals the effects of the friction coefficient and of isotropic yielding on the stress distribution and densification in the calendering nip. Two-dimensional modeling of calendering elasto-visco-plastic materials with a slight modification of the discrete elasto-viscous split stress, independent velocity gradient interpolation, streamline upwind Petrov-Galerkin (DEVSS-G/SUPG) method, predicts distributions of the departure of the current material state in the nip from the elastic stress-free state in a warped material space and of stresses in the calendering nip. |
