Simulation of die filling for the wax injection process: Part II. Numerical simulation
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07/08/2004
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Simulation of Die Filling for the Wax Injection Process: Part II. Numerical Simulation J.-C. GEBELIN, M.R. JOLLY, A.M. CENDROWICZ, J. CIRRE, and S. BLACKBURN This article is the second of two articles dedicated to the modeling of wax injection for the investment casting (or lost wax) process. This article presents the experiments and numerical simulations carried out in order to validate the models developed and presented in a previous article.[1] Three different experiments have been used. The first was to characterize the flow of the wax during the filling and the capacity of the models developed to describe it accurately, in the liquid state. The second experiment was to test the capacity of the models to predict the apparition of filling defects. The third was to compare the predictions in liquid and paste or semisolid state. A good agreement between experiments and simulations has been found, showing that the models are able to represent the behavior of the wax used.
I. INTRODUCTION
THE prediction of defect formation during the wax injection stage of the investment casting process will enable the process engineer to reduce scrap by improving the die design through better positioning of the in-gates and the ability to tune the injection process parameters (mainly temperature and pressure) so that a defect free wax can be produced. In a previous article,[1] the modeling of the thermomechanical behavior of the wax was presented. A selection of models was given for describing the rheological behavior of the wax as a function of temperature and shear rate. The compressibility of the wax was also studied and modeled with two different approaches that can be used in different simulation packages. In this article, the simulation of the wax injection process using the models shown in the previous article[1] is presented. Three different experiments have been modeled and the results obtained have been compared with experimental results. II. FLOW VISUALIZATION EXPERIMENTS A transparent die was designed, which encompassed thick (35 mm) and thin (5 mm) sections similar to a simplified geometry of a turbine blade. Three different gate positions were selected. This allowed the visual recording of the filling front motion during the injection. Figure 1 presents a schematic of the patterns produced with the three different in-gate systems. The process parameters investigated in the experiments were 1. wax temperature, 2. injection pressure, and 3. in-gate location. J.-C. GEBELIN, Research Fellow, M.R. JOLLY, Senior Research Fellow, A.M. CENDROWICZ, Research Associate, and S. BLACKBURN, Head, are with the IRC in Materials Processing, University of Birmingham, Birmingham B15 2TT, United Kingdom. Contact e-mail: [email protected] J. CIRRE, Researcher, is with St Gobain Quartz plc, Neptune Road, PO Box 6, Wallsend Tyne & Wear, NE28 6DG, United Kingdom. Manuscript submitted April 15, 2003. METALLURGICAL AND MATERIALS TRANSACTIONS B
The simulations were carried out using Flow-3D* (Flow *For more
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