Viscoelasticity in thermoforming

This analysis for thermoforming cones from a viscoelastic melt gives the speed of the stresses in the deforming melt. We follow the mechanics of Kershner and Giacomin developed for thermoforming cones from a Newtonian melt, deriving an analytical solution for the corotational Maxwell (CM) model. We have distinguished what happens before and after the melt touches the conical mold (free vs. constrained forming). The CM reduces to the Newtonian solution of Kershner and Giacomin. The upper convected Maxwell (UCM) model is also investigated, but does not yield an analytical solution for conical thermoforming. Our results are confined to forming with a conical mold, the simplest relevant problem in thermoforming, using the simplest relevant constitutive equation, the CM model.