Explicit analysis of the lateral mechanics of web spans

Abstract

All previous analyses of webs being steered through process equipment have required enforcement of assumed boundary conditions. An example is the normal entry boundary condition which has been employed in many web/roller analyses.

Explicit finite element analyses show much promise for studying all types of web handling problems. The primary benefit of this type of analysis is that only very basic assumptions are required, average web velocity and tension for example. Beyond this the interaction of webs with rollers are governed entirely by forces of contact and friction that develop between the web and rollers. Conditions of stick and slip are possible. Additional benefits include the ability to study web deformations and stresses which may result in the development of boundary conditions that can be employed in models that are computationally less expensive.

This paper will focus on a study of the lateral behavior of a web transiting a set of rollers in a process machine, one of which will be misaligned. The misalignment will be increased until there is interaction with an upstream span, a phenomena that has been previously called moment interaction. Any steering of a web laterally in a process machine produces reactions that must be resolved as frictional forces between the web and rollers. Thus the slightest misalignment of a roller will induce some slippage between the web and an upstream roller. That slippage will become gross as the degree of misalignment increases until it migrates around the upstream roller and induces lateral deformation in the upstream span. These phenomena will be studied and results will be compared to experiments. Finally an assessment of potential boundary conditions will be made.