bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Simulation of the Effect of Processing Parameters on the Flow Behavior and Break-through Phenomenon in Co-Injection Molding
Authors: Ilinca F. , Hétu J.-F. 
Published: December 2013

Abstract
In this work, a three-dimensional finite element flow analysis code is used to study the flow behavior during sequential co-injection molding. Non-Newtonian, non-isothermal flow solutions are obtained by solving the momentum, continuity and energy equations. Two additional transport equations are solved for tracking polymer/air and skin/core polymers interfaces. Solutions are presented for the filling of a spiral-flow mould for which experimental measurements are available. The numerical approach is shown to predict the core advance stage during which the core flow front catches up on the skin flow front and the core expansion phase when the flow fronts of core and skin materials advance together without breakthrough. The breakthrough phenomenon is also predicted and the numerical solution is in good agreement with the experiment. Those phenomena are hard to predict numerically and to our knowledge this is the first attempt at simulating the three-dimensional melt behavior during core expansion and core breakthrough. The predicted flow front behavior is compared to the experimental observations for various skin/core melt temperature, skin/core viscosity ratio, and core injection delay. Simulation results are in good agreement with experimental data and indicate correctly the trends in solution change when processing parameters are changing.
Study of Shrinkage and Warpage in Microcellular Co-Injection Molding
Authors: Shen C. , Kramschuster A. , Ermer D. , Turng L.-S. 
Published: December 2013

Abstract
This study investigated the effects of processing conditions on the shrinkage and warpage behavior of a box-shaped, polypropylene part created using a special microcellular co-injection molding process. Results were compared to the shrinkage and warpage of conventional and microcellular injection molded parts. A preliminary study was performed to determine processing condition limits and the steady state conditions for each combination of molding parameters. A 26-1 fractional factorial design of experiments (DOE) was performed utilizing the previously determined processing conditions. The molded parts were measured using an optical coordinate measuring machine (OCMM), which had previously been examined with a repeatability and reproducibility (R&R) study. These measurements were analyzed to determine the processing parameters that had the greatest effect on the shrinkage and warpage (S&W). The results of this analysis indicated that the supercritical fluid content and core-to-skin volume ratio had the greatest effect on the shrinkage and warpage of microcellular co-injection molded parts. The results of the experiment were that a considerable reduction in shrinkage and warpage could be achieved by utilizing microcellular co-injection molding.
Experimental/Numerical Analysis of Chaotic Advection in a Three-dimensional Cavity Flow
Authors: Anderson P. D. , Ternet D. , Peters G. W. M. , Meijer H. E. H. 
Published: December 2013

Abstract
Advection of material volumes in a three-dimensional cavity flow is analyzed by using an experimental setup and a collection of computational tools. The experimental setup for the lid-driven cavity flow makes it possible to study the advection of drops for a wide range of flow parameters. The location of unmixed regions for a specific mixing protocol is predicted by means of the mapping method, which are then used to determine the initial location of the dyed drops in the experiments. Finally, an adaptive front tracking method is used to computationally follow the drops during flow in a precise way. In most cases, a qualitative comparison between the experiments and the simulations is found. In addition, the mapping method proves to be well suited to quickly predict unmixed regions in mixers.
Analysis of Necking Deformation Behavior in High-Speed In-line Drawing Process of PET by On-line Diameter and Velocity Measurements
Authors: Hahm W.-G. , Ito H. , Kikutani T. 
Published: December 2013

Abstract
To clarify the characteristic behavior of filament deformation in high-speed in-line drawing process of poly(ethylene terephthalate) (PET), on-line measurements of filament velocity and diameter were performed. In the process, velocity of the first godet roller was fixed at 2 km/min and the draw ratio was varied from 1.75 to 2.25 by changing the velocity of the second godet roller from 3.5 to 4.5 km/min. For comparison, on-line measurements were also performed for the high-speed melt spinning process at take-up velocities of 2 to 5 km/min. Diameter and velocity profiles of PET filament in the high-speed in-line drawing process indicated that the filament started to deform immediately after passing through the first godet roller (GR-1), and finished its deformation at 40 ~ 60 cm from the GR-1. The region of deformation became narrower and shifted toward the GR-1 with an increase in the draw ratio. Detailed analysis of necking deformation through simultaneous diameter measurements at two positions of close distance revealed that the position of necking deformation fluctuates along the drawing-line and its shape varies significantly depending on the direction of its movement. When the position of necking deformation was shifting toward the upstream, its shape was steeper than the one shifting toward the downstream. Results of the simultaneous on-line measurements of diameter and velocity supported this conclusion qualitatively. The analyzed maximum strain rate at the draw ratio of 2.0 reached a high value of 510 s– 1.
Process Optimization of Thermoforming PP/CaCO3 Composites
Authors: Liu S.-J. 
Published: December 2013

Abstract
Thermoforming of polypropylene/CaCO3 composite sheets has become an important process in industry because of their low cost and good formability. However there are some unsolved problems that confound the overall success of this technique. Nonuniform thickness distribution caused by inappropriate mold design and processing condition is one of them. An L'18 experimental matrix design based on the Taguchi method was conducted to optimize the thermoforming process of CaCO3 filled polypropylene composites. For the factors selected in the main experiment, the assist plug's displacement and velocity were found to be the principal factors affecting the thickness distribution of thermoformed composites.
A Comparative Study of Residence Time Distributions in a Kneader, Continuous Mixer, and Modular Intermeshing Co-Rotating and Counter-Rotating Twin Screw Extruders
Authors: Shon K. , Chang D. , White J. L. 
Published: December 2013

Abstract
Residence time distributions were measured for a Buss Kneader, Kobelco Nex-T continuous mixer as well as intermeshing co-rotating and counter-rotating twin screw extruders using polypropylene with aluminum flakes as a marker. Various modular screw configurations, screw speeds and feed rates were considered. Increasing feed rate and increasing screw speed the mean residence to shorter values and narrows the residence time distribution. Generally, in comparison of the different machines, the intermeshing counter-rotating twin screw extruder has the shortest mean residence time and narrowest distribution of residence times, while the Buss Kneader has the longest mean residence time and broadest residence time distribution.
Screw Drive Power of Single Screw Plasticating Units With Smooth Barrels
Authors: Potente H. , Obermann C. 
Published: December 2013

Abstract
In this contribution the computation of the drive power of single screw machines with smooth feed sections for extruders and injection molding machines will be presented. The drive power will be determined by means of the shear stresses at the barrel wall for the completely melt-filled channels as well as for the polymer melting section of the screw. In order to determine the shear stress and thus the power consumption the correct velocity profiles in the screw channels must be known, taking into account the non-Newtonian flow behavior of the polymer melt. For analytical solutions of this problem extreme simplifications are necessary. For this reason approximation equations are set up, which are based on numerical tests and by means of which a reliable determination of the screwdrive power is possible, knowing the throughput, the temperature development across the screwas well as the melting proile.
Design of Dispersive Mixing Devices
Authors: Rauwendaal C. , Osswald T. , Gramann P. , Davis B. 
Published: December 2013

Abstract
Mixing is one of the main functions of screw extruders. In the analysis of mixing, there are two mixing mechanisms that need to be considered: distributive and dispersive mixing. It is well known that single screw extruders generally have poor dispersive mixing capability, even when dispersive mixing elements are incorporated into the screw design. This paper will discuss the requirements for dispersive mixing, current dispersive mixing elements used in single screw extruders will be analyzed, and the lack of efficient dispersive mixing will be explained. A new generation of dispersive mixing elements will be introduced for use in both single and twin screw extruders and internal mixers. A two and three dimensional flow simulation will be used to analyze the mixing performance of these new mixers. Experimental work on the new mixing elements will be presented in a follow-up paper; the results demonstrate that it is possible to achieve dispersive mixing on single screw extruders that is as good as what can be achieved on twin screw extruders. The implications of these results on the compounding industry will be briefly discussed.
Using Computational Fluid Dynamics to Investigate the Flow of a Viscous Fluid in a Cavity with Oscillating Boundaries
Authors: Overd M. M. , Generalis S. C. 
Published: December 2013

Abstract
Many everyday engineering applications crucially depend on the mixing efficiency of the appropriate hardware. Chaotic mixing is pertained to be an effective way of attaining high levels of mixing. In this work we report on viscous fluid flow in a cavity, with oscillating boundaries, that exhibits such chaotic motion.
Using computational fluid dynamics we explain the transition from order to chaos which can be observed by a cascade of the trajectory orbit of particles as the time period of oscillation is increased. As the system moves from order into chaos it is shown that a particle will be displaced from ordered streamlines to the point where it moves throughout the whole low domain thus showing that good mixing is present. An attempt is also made to characterise the transition to aperiodicity, for the studied configuration.
Optimization of the Weldline Strength in Gas-assist Injection Molded Thermoplastic
Authors: Liu S.-J. , Ho C.-Y. , Chang J.-H. , Hung S.-W. 
Published: December 2013

Abstract
Gas assist injection molding has increasingly become an important process in industry because of its tremendous flexibility in the design and manufacture of plastic parts. However, there are some unsolved problems that confound the overall success of this technique. Weldlines success of this technique. Weldlines form wherever polymer flow fronts meet is one of them. In this report, an L'18 experimental matrix design based on the Taguchi method was conducted to optimize the weldline strength of gas assist injection molded thermoplastics. Experiments were carried out on an 80-ton injection molding machine equipped with a high-pressure nitrogen-gas injection unit. A dumbbell-shape mold cavity was used. After molding, the weldline strength of the parts was measured by a tensile tester For the factors selected in the main experiments, melt temperature and mold temperature were found to be the principal factors affecting the weldline property of gas assist injection molded thermoplastics. Weld strength decreases with the length of gas penetration. In addition the weldline strength of gas assist injection molded parts was found to be generally weaker than that of conventional injection molded parts.
Wire Coating by Drawdown of an Extruded Annular Melt
Authors: Slattery J. C. , Giacomin A. J. , Ding F. 
Published: December 2013

Abstract
An analytical solution is presented for wire coating by drawdown of an extruded annular melt. The solution is developed with the assumption that the pressures inside and outside the film are equal; a process in which these pressures differ, such as a vacuum inside the film, is treated as a limiting case.
Simulation of Blown-Film Process Taking Account of Cooling-air Effect
Authors: Akaike O. , Tsuji T. , Nagano Y. 
Published: December 2013

Abstract
Numerical simulation of blown-film process of plastics provides a tool for air ring designs and suitable polymer properties. Although cooling-air plays a key role in the process ability and film properties, there have been few research works taking correct account of the cooling-air effect. Numerical analyses of heat transfer from the surface of molten polymer to cooling-air were conducted using precise turbulence models and then simulations of bubble shape of blown-film process were performed under the air pressure and the thermal boundary conditions estimated from the numerical analyses of cooling-air. The film bubble shape predicted has coincided well with experimental data and it is confirmed that the bubble stability is strongly dominated by characteristics of cooling-air flow and heat transfer near the bubble surface.
Fitting of K-BKZ Model Parameters for the Simulation of Thermoforming
Authors: Novotný P. , Sáha P. , Kouba K. 
Published: December 2013

Abstract
Thermoforming is characterized by large deformations of the polymeric material being processed. The simulation is complicated by the fact that an elastic material model cannot principally describe the thermoforming deformation precisely. In this respect non-linear and time-dependent viscoelastic behavior of the polymeric material has to be taken into account. In our research we used the K-BKZ model capable of describing viscoelasticity and large deformations. The parameters of this model were determined experimentally using a simple testing method. The method is derived from plug-assisted thermoforming. Computer analysis was used to evaluate the experiments: The tests performed were simulated using FEM (Finite Elements Method) repeatedly with different material parameters. The material parameters leading to a minimum sum of squares of differences between experimental and simulated values estimate the tested material behavior. It has been found that the final shape and the wall thickness distribution show a significant dependence on the material properties in case of deep thermoforming.
Weld Line Strength in PC/ABS Injection Moldings
Authors: Semba T. , Hamada H. 
Published: December 2013

Abstract
Polycarbonate(PC)/ABS is a very common immiscible polymer blend. The internal structure such as distribution of each component in the injection moldings of PC/ABS would be strongly affected by the processing parameters. Especially, the weld line formed by meeting two melt flows and the internal structure at the weld area would be a very complex form. By observing the etched samples of PC/ABS injection moldings using scanning electron microscopy, a weld part with fine dispersion of ABS was found in the area below V-notch. When tensile load was applied perpendicular to the weld line, the fracture initiated from the V-notch, but the crack propagated along the interface between the weld part with fine dispersion and the part behind the weld part. This leads to unique characteristics of the weld strength.
Capillary Flow of Hard-Metal Carbide Powder Compounds
Authors: Hausnerová B. , Sáha P. , Kubát J. 
Published: December 2013

Abstract
Experimental data relating to capillary flow of hard-metal carbide powders compounded with various polymeric binders are presented. Such powder—binder mixtures are used for the production of sintered hard-metal carbide components, mainly by injection moulding. In addition to measurements of their rheological behaviour in a capillary rheometer, the compounds were also subjected to thermo-gravimetric analysis in order to assess the ability of the binder to debind properly. The binder composition was varied from paraffin wax and its combinations with polyethyleneglycols to multi-component binders consisting of polyethyleneglycol, polyethylene, ethylene/vinyl acetate copolymer, and paraffin wax. Two kinds of hard-metal carbide powders differing in particle size distribution (uni-modal, bi-modal) were used. Although the compounds containing the simpler binder types had acceptable flow properties, their debinding behaviour was unsatisfactory. The multi-component compounds exhibited considerably better debinding; their flow was stable within a wide range of shear rates. Flow instabilities appearing at high solids loadings can limit the processability of the compounds used.
Computer Controlled Rotational Molding of a Hollow Femur for 3-D Photoelastic Analysis
Authors: Teoh S. H. , Lau C. Y. 
Published: December 2013

Abstract
The rotational molding technique was utilized in the fabrication of hollow femur models for the expressed purpose of photostress analysis. Advances in computer control coupled with the development of proper experimental protocols enabled the consistent and automated reproduction of the joint model. Such considerations proved to be critical in overcoming the limitations of prevailing rotational molding operations. The use of hollow rotation molded models was advantageous as it better represented the physiologic constitution of real bones, thereby, conferring a greater degree of accuracy in the photostress experiments. The fabrication of the hollow models entailed flow visualization studies, which assessed the variation in rotational speeds with time as well as the optimum relative rotation speeds to be adopted. The preferred mode of rotational motion was also determined through a series of simulated experiments to determine whether steady or repetitive cyclical rotational modes were more beneficial. The fabricated hip models were loaded and the stress profiles examined. Contour maps of the stress fringes manifested in the photoelastic analysis indicated several sites of stress concentrations. These sites coincided with physiologic patterns of hip fractures, verifying the validity of the hollow femoral models. Computer controlled rotational molding has proven to be a feasible manufacturing process in the development of hollow physiologically representative femur models.
Residual Stresses and Birefringence in Injection Molding of Semicrystalline Polymer
Authors: Guo X. , Isayev A.I. 
Published: December 2013

Abstract
The viscoelastic process simulation of the idealized injection molding process for various isotactic polypropylenes having different molecular weights are conducted by using the theoretical formulation developed in the first part of the present study. Molding experiments are performed under a variety of molding conditions, and birefringence measurements are carried out on the molded samples. Based upon the experimental and simulated results of the residual stresses and birefringence, the effects of molding conditions and molecular weights are studied. The influences of flow-induced crystallization kinetics on the buildup and relaxation of residual stresses and birefringence in the moldings are discussed. It has been found that, due to the absence of the flow-induced crystallization in the core region, the flow stresses and birefringence introduced in that region during the filling stage relax shortly after the cavity is filled. Moreover, the low stresses and birefringence get frozen-in due to the occurrence of the low-induced crystallization are relatively large and located within a very narrow region close to the mold wall. The main contribution to the overall residual stresses is found to be due by the residual thermal stresses that are introduced by the progression of crystallization during the postfilling stage. The distribution of the residual birefringence in the moldings is closely related to that of the crystalline microstructure pattern and less dependent upon the level of overall residual stresses.
Solidification Behaviour of PA6/iPP Blends at High Cooling Rates
Authors: Colletti C. , Piccarolo S. , Valenza A. 
Published: December 2013

Abstract
The non isothermal crystallization behaviour of two model blends of immiscible polymers (an isotactic polypropylene and a polyamide-6) was examined by a quenching procedure within a range of cooling rates from 0.1 to above 1000°C/s in order to emulate the solidification conditions arising during polymer processing. The final structure of the blends was analyzed by density and WAXD and the transition from stable to metastable phases in the blends and the pure homopolymers was compared examining their dependence on cooling rate. This shows that crystallization in the blends is always faster since the transitions move to larger cooling rates. Observation of morphological details suggests that this can be due to enhanced nucleation at the interface. The density variation in the case of the polyamide-6 rich blend is larger than expected from an additive volume contribution which may be ascribed to development of microvoids at the interface. In the case of the isotactic polypropylene rich blend the additive volume contribution is consistent with experimental observations.
A Network Analysis of a Screw Mixing Zone
Authors: Klason C. , Jinescu V. V. , Poştoacǎ I. 
Published: December 2013

Abstract
Starting from our previous results concerning the melt flow during the dispersive mixing zones of Maddock and Egan type, one establishes relations for the pressure variation, appropriate for incremental calculation. Because generally the melt flow along the mixing zone is non-isothermal, one establishes relations for the temperature variation along the mixing zone, namely: temperature variation caused by external heating, by internal friction, by external friction and due to melt compressibility.
By using the established relations one develops a network procedure for pressure and temperature variation calculation along the mixing zone. The computer program based on the network procedure was used to calculate a usual mixing zone for a 63.5 mm extruder-screw. The program gives the possibility to represent the pressure and temperature variation between the inlet and the outlet of the mixing zone. This is useful when we are interested in the optimum design of such mixing zones.
An Investigation of Venturi and Coanda Effects in Blown Film Cooling
Authors: Sidiropoulos V. , Vlachopoulos J. 
Published: December 2013

Abstract
Numerical simulation of turbulent air flow tangentially impinging on a blown film bubble has been carried out. The cooling air is assumed to originate from a dual orifice adjustable air-ring. The stream line pattern and heat flux are determined through a finite volume numerical technique using a version of the so called k-∊ modeling. It is shown that as the air flows through the air ring passage relatively large under-pressure is created (Venturi effect), which applies a suction to the bubble. Depending on the flow rates and geometrical configurations the air jet may attach itself (Coanda effect) to either the air ring surface and/or to the bubble. The Coanda effect has a significant influence on local heat flux. The numerical results suggest that the Venturi and Coanda effects influence significantly process stability, production rate and final film properties.