VISCOELASTIC MODELING OF PAPER IN A CALENDER NIP

Paper is subjected to a compressive pressure pulse in a calender nip. After the nip, there is time-dependent partial recovery of the initial thickness. The material bahaviour is viscoelastic; recovery depends o n the pulse magnitude and duration. Measurements of paper strain in th e nip, within a few hundred milliseconds after the nip and after condi tioning for 24 h, have been made for an eastern Canadian newsprint mad e from These measurements lead to new perceptions regarding viscoelast ic properties of paper in a rolling nip. Linear viscoelastic models ar e examined and found to be inadequate. As paper is a rough, structured material characterized by substantial local nonuniformity in both thi ckness and density, models for smooth, continuous, locally uniform mat erials should not be affected to apply.