A mechanical model for felt in impulse drying: A cellular materials approach. I. Model development and simulation

This paper presents a physically based model of the densification of a felt in the press nip of a paper machine, running at operating conditions similar to those used in impulse drying. The model incorporates the observed features of wet felts compression such as non-linear elasticity and non-recoverable strains that are rate-dependent. A viscoelastoplastic model, based on the cellular solids theory, was developed to describe this behavior. The governing differential equations of the model were established bearing in mind an assembly of modified Maxwell elements combined in series and then arranged in parallel. This approach resulted in a three-dimensional unsteady-state problem, solved by means of an integrator based in the Gear method. The model was used to predict the evolution of thickness, elastic and viscous moduli and apparent density of the material.