Distribution and change of stresses, slippage, tension, and friction forces in wound rolls (Simulation of center winding without nip)

Abstract

Distribution and change of roll stresses, slippage, web tension, and friction forces during winding rolls are investigated using commercial FEM software. The model used here is two dimensional and consists of an isotropic web and a rigid winding core. The rolls are wound up to 70 or 80 layers by the center winder with a constant line tension and this winding process is numerically simulated. The results show that the roll stresses decrease when the front part of the web is tapered compared to the non-tapered case and approach the result of Catlow or Hakiel. The roll stresses and slippage increase as the line tension increases or an imaginary coefficient of friction or Young’s modulus decreases. The slippage occurs as the inner layers of the roll move faster than the outer layers. In case of large slippage, the tension of a point on the web gradually increases largely after entry into the roll. The friction forces acting between the web layers change violently in the inner layers of the roll and gradually decrease to zero in the outer layers. The friction forces acting on the inner surface of the web layer mainly direct to the direction of winding. A few local areas with extremely high friction forces occur and disappear abruptly and some concentric circles with relatively large friction force are observed constantly in the inner layers of the roll. The friction forces acting on the inner surface of the previous turn largely change in areas where the friction forces of the new turn are significant.

Keywords

• simulation
• fem
• web handling
• center winding
• roll stress
• slippage
• tension
• friction