VISCOELASTIC EFFECTS IN MODELING WEB HANDLING SYSTEMS - UNSTEADY-STATE ANALYSIS

A model to predict the tension in open spans of web handling systems d uring transient operations has been developed. Governing equations wer e developed by rising the White-Metzner equation to describe the mater ial response in conjunction with mass and force balances. The governin g equations were nondimensionalized and solved via the MacCormack pred ictor/corrector technique. Two dimensionless parameters emerged from t he analyses, the Deborah number, De, and the ratio of the viscous stre ss to the steady state stress, N. The resulting model is the companion to a previously reported model for steady-state operations (Guan et a l., 1995). The model was used to predict the behavior of a web handlin g system during start-up, transition between steady states, and a peri odic disturbance. During start-up and transition, systems responded mo re vapidly at low De. The system response during a periodic disturbanc e was correlated to De, the frequency, and the magnitude of the distur bance.