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Melt Flow (melt + flow)
Kinds of Melt Flow Terms modified by Melt Flow Selected AbstractsInfluence of internal radiation on the heat transfer during growth of YAG single crystals by the Czochralski methodCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2003Z. Galazka Abstract Heat and mass transfer taking place during growth of Y3Al5O12 (YAG) crystals by the Czochralski method, including inner radiation, is analyzed numerically using a Finite Element Method. For inner radiative heat transfer through the crystal the band approximation model and real transmission characteristics, measured from obtained crystals, are used. The results reveal significant differences in temperature and melt flow for YAG crystals doped with different dopands influencing the optical properties of the crystals. When radiative heat transport through the crystal is taken into account the melt-crystal interface shape is different from that when the radiative transport is not included. Its deflection remains constant over a wide range of crystal rotation rates until it finally rapidly changes in a narrow range of rotation rates. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Finite element and finite volume simulation and error assessment of polymer melt flow in closed channelsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 11 2006M. Vaz Jr. Abstract This work aims at evaluating the discretization errors associated to the finite volume and finite element methods of polymer melt flow in closed channels. Two strategies are discussed: (i) Richardson extrapolation and (ii) a posteriori error estimation based on projection/smoothing techniques. The numerical model accounts for the full interaction between the thermal effects caused by viscous heating and the momentum diffusion effects dictated by a shear rate and temperature-dependent constitutive model. The simulations have been performed for the commercial polymer Polyacetal POM-M90-44. Copyright © 2006 John Wiley & Sons, Ltd. [source] 3D computer simulation of melt flow and heat transfer in the lost foam casting processINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2003S. M. H. Mirbagheri Abstract A new mathematical model has been developed to simulate mould filling in the lost foam casting process, using the finite difference method. The simulation of molten flow and track of free surfaces is based on the SOLA-VOF numerical technique. An algorithm was developed to calculate the gas pressure of the evaporated foam during the mould filling. The effect of backpressure on the filling behaviour was modelled with an experimental function by adding three-dimensions 3DVOF functions. In order to verify the computational results, a thin grey iron plate was poured into a transparent mould. Cavity filling, foam depolymerization and gap formation were recorded with a 16mm high-speed camera. A good agreement was achieved for simulation results of filling sequences with those from experiments. Copyright © 2003 John Wiley & Sons, Ltd. [source] Inverse design of directional solidification processes in the presence of a strong external magnetic fieldINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 11 2001Rajiv Sampath Abstract A computational method for the design of directional alloy solidification processes is addressed such that a desired growth velocity ,f under stable growth conditions is achieved. An externally imposed magnetic field is introduced to facilitate the design process and to reduce macrosegregation by the damping of melt flow. The design problem is posed as a functional optimization problem. The unknowns of the design problem are the thermal boundary conditions. The cost functional is taken as the square of the L2 norm of an expression representing the deviation of the freezing interface thermal conditions from the conditions corresponding to local thermodynamic equilibrium. The adjoint method for the inverse design of continuum processes is adopted in this work. A continuum adjoint system is derived to calculate the adjoint temperature, concentration, velocity and electric potential fields such that the gradient of the L2 cost functional can be expressed analytically. The cost functional minimization process is realized by the conjugate gradient method via the FE solutions of the continuum direct, sensitivity and adjoint problems. The developed formulation is demonstrated with an example of designing the boundary thermal fluxes for the directional growth of a germanium melt with dopant impurities in the presence of an externally applied magnetic field. The design is shown to achieve a stable interface growth at a prescribed desired growth rate. Copyright © 2001 John Wiley & Sons, Ltd. [source] A comprehensive 3-D analysis of polymer melt flow in slit extrusion diesADVANCES IN POLYMER TECHNOLOGY, Issue 2 2004Yihan Huang Abstract An understanding of flow behaviour of polymer melts through a slit die is extremely important for optimizing die design and, consequently, for die performance in processing polymer sheets and films. In view of the complex nature and the physical properties of polymer melts as well as of die geometries, such as coat-hanger dies, no simple mathematical formulae can be used to compute the flow regimes within dies. This paper illustrates the development of a three-dimensional (3-D) computer model of an example of a coat-hanger die design using the computational fluid dynamics package, FIDAP, based on the finite element method. A difference of only 3.7% was found when comparing the velocity distribution at the die exit obtained from the 3-D simulation with that calculated using a two-dimensional analytical design procedure, indicating that full 3-D analysis seems to be unnecessary. However it has been shown that unwanted flow phenomena and production problems can be ameliorated by means of visualization and the detailed information obtained from computer simulations. Comparative simulation results with polymers of different rheological properties in the same die are also described. The comprehensive analyses provide a means of interpretation for flow behavior, which allows modification of the die geometry for optimal design. © 2004 Wiley Periodicals, Inc. Adv Polym Techn 23: 111,124, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20002 [source] Analysis of the fluid,structure interaction in the optimization-based design of polymer sheeting diesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Qi Wang Abstract A polymer-sheeting-die-design methodology is presented that integrates a simulation of the polymer melt flow and die-cavity deformation with numerical optimization to compute a die-cavity geometry capable of giving a nearly uniform exit flow rate. Both the polymer melt flow and sheeting-die deformation are analyzed with a general-purpose finite-element program. The approach includes a user-defined element that is used to evaluate the purely viscous non-Newtonian flow in a flat die. The flow analysis, which is simplified with the Hele,Shaw approximation, is coupled to a three-dimensional finite-element simulation for die deformation. In addition, shape optimization of a polymer sheeting die is performed by the incorporation of the coupled analyses in our constrained optimization algorithm. A sample problem is discussed to illustrate the die-design methodology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3994,4004, 2007 [source] Origin of migmatites by deformation-enhanced melt infiltration of orthogneiss: a new model based on quantitative microstructural analysisJOURNAL OF METAMORPHIC GEOLOGY, Issue 1 2008P. HASALOVÁ Abstract A detailed field study reveals a gradual transition from high-grade solid-state banded orthogneiss via stromatic migmatite and schlieren migmatite to irregular, foliation-parallel bodies of nebulitic migmatite within the eastern part of the Gföhl Unit (Moldanubian domain, Bohemian Massif). The orthogneiss to nebulitic migmatite sequence is characterized by progressive destruction of well-equilibrated banded microstructure by crystallization of new interstitial phases (Kfs, Pl and Qtz) along feldspar boundaries and by resorption of relict feldspar and biotite. The grain size of all felsic phases decreases continuously, whereas the population density of new phases increases. The new phases preferentially nucleate along high-energy like,like boundaries causing the development of a regular distribution of individual phases. This evolutionary trend is accompanied by a decrease in grain shape preferred orientation of all felsic phases. To explain these data, a new petrogenetic model is proposed for the origin of felsic migmatites by melt infiltration from an external source into banded orthogneiss during deformation. In this model, infiltrating melt passes pervasively along grain boundaries through the whole-rock volume and changes completely its macro- and microscopic appearance. It is suggested that the individual migmatite types represent different degrees of equilibration between the host rock and migrating melt during exhumation. The melt topology mimicked by feldspar in banded orthogneiss forms elongate pockets oriented at a high angle to the compositional banding, indicating that the melt distribution was controlled by the deformation of the solid framework. The microstructure exhibits features compatible with a combination of dislocation creep and grain boundary sliding deformation mechanisms. The migmatite microstructures developed by granular flow accompanied by melt-enhanced diffusion and/or melt flow. However, an AMS study and quartz microfabrics suggest that the amount of melt present did not exceed a critical threshold during the deformation to allow free movements of grains. [source] Preparation of extruded melt-mixed polypropylene/montmorillonite nanocomposites with inline monitoringPOLYMER ENGINEERING & SCIENCE, Issue 3 2010Marcelo K. Bertolino This article advances the use of an inline optical detector to monitor the disaggregation of the montmorillonite (MMT) clay tactoids during the preparation of polypropylene (PP)/MMT nanocomposites via polymer melt compounding. During the exfoliation of the tactoids their size are reduced below the minimum particle size to produce light extinction and so, the signal of the inline detector reduces as the nanosize composite is formed. The measurement is done at the transient state with the MMT clay added as a pulse with constant weight into the PP extrusion melt flow and followed by the optical detector. The data comes out as the common residence time distribution curves having its maximum intensity related to the tactoids average particle size, keeping all other variables constants. The light extinction was measured for composites with different clays (Cloisite® 15A, 30B, Na+, and Sintered 20A) using the same PP grafted with maleic anhydride compatibilizer. The dissaglomeration/exfoliation efficiency increases as: ,,Sintered 20A'' < ,,Na+ clay'' < ,,organo-modified clay'' < ,,organo-modified clay + compatibilizer''. The best result is obtained using Cloisite® 15A and Cloisite® 20A following the expected reduction of the particle size obtained during a nanocomposite melt processing. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source] Yield stress and rheological characterization of the low shear zone of an epoxy molding compound for encapsulation of semiconductor devicesPOLYMER ENGINEERING & SCIENCE, Issue 4 2008Masaki Yoshii In encapsulation molding of IC packages, the melt flow inside the cavity is generally controlled in a low shear to prevent wire sweep, and other molding defects. Therefore, it is important to evaluate the rheological properties of epoxy molding compounds (EMC) in a low shear zone including determining the yield stress. In this study, a newly specialized Parallel-Plate Plastometer for EMCs was built up. Using this plastometer, the yield stress and its temperature dependence were clarified, and the rheological properties in the low shear zone were evaluated. As a result, the rheological properties in a low shear zone of 0.1,10 s,1 were characterized using the Herschel,Bulkley viscosity model which introduced the yield stress, the Castro,Macosko equation as a dependency model of cure, and the WLF equation as a dependency model for temperature. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Nonisothermal comprehensive 3D analysis of polymer melt flow in a coat-hanger diePOLYMER ENGINEERING & SCIENCE, Issue 4 2006Tingqi Wu The nonisothermal flow of Carreau fluid in a coat-hanger die is studied. A general three-dimensional finite volume code is developed for the purpose of flow analysis. The isobars, the isotherms, and the velocity distribution are obtained. Simulation results illustrated that the highest temperature occurred by the center of manifold, rather than the die-lip region because of the combined effects of high shear rate and poor heat conduction, which is important for processing those heat-sensitive materials. In the regions where die gap is relatively small, the wall temperature plays a key role in deciding temperature distribution in the melt. The validity of simulation results is verified experimentally. POLYM. ENG. SCI., 46:406,415, 2006. © 2006 Society of Plastics Engineers. [source] Gas assisted injection molding of a handle: Three-dimensional simulation and experimental verificationPOLYMER ENGINEERING & SCIENCE, Issue 8 2005A. Polynkin Methods implemented in a three-dimensional finite element code for the simulation of gas assisted injection molding are described, and predictions compared with the results of molding trials. The emphasis is on prediction of primary gas penetration and plastic wall thickness, including the effects of cooling during a delay before gas injection. For the latter, time dependent heat transfer coefficients at the cavity surface are used, determined in a separate analysis of transient heat conduction through the plastic and the mold tool to the circulating coolant. This shows how the initial value of 25,000 W/m2K falls by about an order of magnitude during the first few seconds of cooling, and also how values vary from cycle to cycle as steady periodic conditions are approached. For a tubular handle molded in polystyrene, with melt flow modeled by a Cross WLF model, comparisons of simulations with sectioned parts show excellent prediction of wall thickness and its variation circumferentially and in bends. The increase in wall thickness due to cooling during a gas delay is accurately modeled, as is the occurrence of a blow out. POLYM. ENG. SCI. 45:1049,1058, 2005. © 2005 Society of Plastics Engineers [source] Numerical analysis of polymer melt flow in the nipping regionPOLYMER ENGINEERING & SCIENCE, Issue 4 2002M. Takase In the extrusion coating process, it has never been revealed how a polymer melt flows near the nipping region and how the cooling process occurs. We created a numerical simulation program for the polymer melt flow near the nipping region using the finite element method. Numerical results showed the effects of many individual factors (e.g. line speed, melt thickness, extrusion temperature, shear-thinning property, etc.) on the cooling process and polymer melt flow near the nipping region. It was found that a polymer melt buildup that can be observed between two calender rolls in the sheet forming process also formed in the extrusion coating process, and that the amount of polymer melt buildup (bank) depended upon the coating condition. It was found that not only line speed and melt thickness contribute to the extrusion coating process significantly, but also the rheological property has an effect on the process. [source] | |||||||||||||