Publication: Determining the collision properties of semi-crystalline and amorphous thermoplastics for DEM simulations of solids transport in extruders
All || By Area || By Year| Title | Determining the collision properties of semi-crystalline and amorphous thermoplastics for DEM simulations of solids transport in extruders | Authors/Editors* | P.A. Moysey, M.R. Thompson |
|---|---|
| Where published* | Chemical Engineering Science |
| How published* | Journal |
| Year* | 2007 |
| Volume | 62 |
| Number | 14 |
| Pages | 3699-3709 |
| Publisher | Elsevier |
| Keywords | Contact mechanics, Granular materials, Polymers, Polymer processing, DEM, Extrusion |
| Link | doi:10.1016/j.ces.2007.03.033 |
| Abstract |
To improve application of the Discrete Element Method (DEM) to polymer processing applications it was necessary to evaluate the contact mechanics of a selection of commonly used polymers. The contact behaviours of high-density polyethylene (HDPE), polystyrene (PS) and polycarbonate (PC) were revealed in this paper from a series of impact studies where spherical polymeric particles struck a steel anvil at various angles of incidence and impact velocity. The coefficients of restitution and friction were calculated from high-speed video analysis of individual impacts. The collected data was used to evaluate the relevance of several popular normal contact forceâdisplacement models to determine their suitability for the tested semi-crystalline and glassy polymers. The models considered were those proposed by Walton and Braun [1986. Viscosity, granular-temperature, and stress calculations for shearing assemblies of inelastic, frictional disks. Journal of Rheology 30, 949â980], with constant (WBCE) and variable (WBVE) normal restitution coefficient, and Thornton [1997. Coefficient of restitution for collinear collisions of elastic-perfectly plastic spheres. Journal of Applied Mechanics 64, 383â386], based on elasticâplastic collisions. Comparison of the impact data with DEM simulations using the various contact forceâdisplacement models revealed that the WBVE model provides the best overall agreement with the viscoelastic-fully plastic behaviour of HDPE, while the almost purely elastic nature of PC and PS agreed well with all three models studied in this paper. The influence of the normal forceâdisplacement models on the solids transport zone of an extruder was subsequently discussed based on the findings from the impact study. |
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