Plasticating single screw extrusion involves the progressive compaction and heating of loose solid
pellets that eventually melt, form a relatively homogenous stream and are subsequently pumped through a
shaping tool. Traditional analyses of the solids conveying stage assume the sliding of an elastic solid plug due
to differential wall friction coefficients. However, not only the corresponding predictions may fail
considerably, but it is also well known that, at least in the initial screw turns, pellets are far from compact.
This work follows previous efforts to model the flow of solids in the hopper and initial screw turns using the
Discrete Element Method (DEM). The model considers the development of normal and tangential forces
resulting from the inelastic collisions between the pellets and between them and the neighbouring metallic
surfaces. As an example of the capability of the model to capture detailed features of granular flow, the effect
of pellet size on flow is discussed.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BPD/39381/2007
