An elastoplastic continuum model for a wound roll with interlayer slippage

In paper industry the nip rollers used in the winding process and the clamping devices used to lift rolls during transport cause interlayer slippage in the rolls. A certain amount of slippage is acceptable, and sometimes even desired, but excess slippage can, in the worst case, render the roll useless. Numerical analysis of the stresses and strains in the roll can aid in the design process of winders and clamps. Since the number of layers in a roll may be several thousands, a full contact mechanical model of the layered structure is not feasible. The computational cost is significantly reduced by using a continuum approach and considering the layered structure as a continuum with slip surfaces. In this paper a model for rolls wound of orthotropic material is developed. The elastoplastic jointed material model with shear limits based on Coulomb friction is extended to orthotropic materials. The model is implemented into the FE-program ABAQUS and used to study the stresses, layer-to-layer slippage and J-line formation in a paper roll in rolling contact against a winding drum. The deformation of a roll due to compressive clamping forces is also calculated. It is found that the plastic flow (i.e., slippage) significantly affects the stress distribution in the roll.