Trough and Wrinkling Analysis of Non-Uniform Webs

Abstract

Depending on the final product requirements webs may have thickness non-uniformities across the web width. Some products require layers of different materials to be bonded together (i.e. laminated) to meet the desired characteristics of the final product. Also there are many limitations associated with the production of webs that prevent the web from being perfectly uniform in length and thickness. This research study focuses on how non-uniform webs differ from uniform webs in terms of instability when travelling through process machinery. Much of the research to date has focused on instabilities of uniform webs. Little is known regarding whether non-uniform webs are more or less stable than uniform webs which will be examined herein. The non-uniform web approaching tapered roller and a misaligned roller were modeled using finite element techniques in COSMOS. The results from Finite Element Analysis (FEA) models were compared with closed form solutions that were developed using a structural stiffness matrix approach. Linear FEA was more accurate than the closed form expressions in predicting the onset of troughs in non-uniform webs approaching tapered or misaligned roller. These closed form solutions still have value for web line engineers who lack the ability or time to employ FEA. The closed form solutions typically yield conservative results that can safely be used by design engineers. Non-linear FEA can be used to predict the onset of wrinkles in uniform and non-uniform webs approaching tapered or misaligned rollers. It has been shown herein that the non-uniform web studied is more unstable than a similar uniform web. The non-uniform web was shown to be more susceptible to troughs and wrinkles.