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978-3-8439-0057-7, Reihe Ingenieurwissenschaften
Free-Surface Flows in Shape Optimization of Extrusion Dies
127 Seiten, Dissertation Rheinisch-Westfälische Technische Hochschule Aachen (2011), Softcover, A5
Extrusion is a manufacturing process used by the plastics industry to create continuous objects of a fixed cross-sectional profile. Plastics melt is pushed through a die, which reshapes the originally restiform melt to the desired profile shape. The key challenge is the design of the transition region between outflow and inflow. In industrial applications, extrusion is a large-scale process, financially attractive only for mass products. This is not so much due to the actual value of the die, but the construction and time-consuming running-in experiments that must precede each production cycle. In this work, a numerical die design concept has been developed with the intention to increasingly automate the design process, to consider non-intuitive designs and to significantly reduce the number of running-in trials.
The numerical design method is based on an existing flow solver and an optimization framework. The quality criteria considered are a homogeneous velocity distribution at the outflow and homogeneous die swell. For both criteria, an objective function has been developed. To model the flow through the extrusion die, the steady Stokes equations were used in connection with the following constitutive equations: Newtonian material model, Carreau model, Oldroyd-B model, and Giesekus model.