scholarly journals A Multi-Rheology Design Method of Sheeting Polymer Extrusion Dies Based on Flow Network and the Winter–Fritz Design Equation

Polymers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1924
Author(s):  
Amin Razeghiyadaki ◽  
Dongming Wei ◽  
Asma Perveen ◽  
Dichuan Zhang
Keyword(s):  
Velocity Distribution ◽  
Power Law ◽  
Die Design ◽  
Rheological Parameters ◽  
Process Conditions ◽  
Geometrical Parameters ◽  
Polymer Extrusion ◽  
Flow Network ◽  
Extrusion Dies ◽  
Percent Improvement

In the polymer sheet processing industry, the primary objective when designing a coat-hanger die is to achieve a uniform velocity distribution at the exit of the extrusion die outlet. This velocity distribution depends on the internal flow channels of the die, rheological parameters and extrusion process conditions. As a result, coat-hanger dies are often designed for each polymer based on its individual rheological data and other conditions. A multi-rheology method based on a flow network model and the Winter–Fritz equation is proposed and implemented for the calculation, design and optimization of flat sheeting polymer extrusion dies. This method provides a fast and accurate algorithm to obtain die design geometries with constant wall-shear rates and optimal outlet velocity distributions. The geometric design when complemented and validated with fluid flow simulations could be applied for multi-rheological fluid models such as the power-law, Carreau–Yasuda and Cross. This method is applied to sheet dies with both circular- and rectangular-shaped manifolds for several rheological fluids. The designed geometrical parameters are obtained, and the associated fluid simulations are performed to demonstrate its favorable applicability without being limited to only the power-law rheology. The two such designed dies exhibit 32.9 and 21.5 percent improvement in flow uniformity compared to the previous methods for dies with circular and rectangular manifolds, respectively.

scholarly journals Internal Flow Optimization in a Complex Profile Extrusion Die Using Flow Restrictors and Flow Separators

2021 ◽  
Author(s):  
Jingyang Xing ◽  
Majed Alsarheed ◽  
Animesh Kundu ◽  
John P. Coulter
Keyword(s):  
Velocity Distribution ◽  
Cross Flow ◽  
Internal Flow ◽  
Outer Wall ◽  
Die Design ◽  
Cross Sectional ◽  
Polymer Flow ◽  
Extrusion Dies ◽  
Flow Imbalance ◽  
Distinct Features

Abstract The control of flow balance at the die exit is the key for successful extrusion of polymers. The complex cross-sectional variation in real-world hollow extrusion profiles intrinsically promotes flow imbalance in the die cavity. Special considerations are required for designing extrusion dies for such profiles. The die design for a complex door frame profile was computationally optimized in this study with the aid of a commercially available software package. The velocity distribution at the die exit, post-die extrudate deformation, temperature distribution, and pressure distribution of a traditional die was investigated in detail and found to be inadequate. A modified die incorporated three distinct features, flow restrictors, flow separators and approach angle of the torpedoes, to achieve a balanced and uniform velocity at the die exit. The flow restrictors and flow separators were added in the pre-parallel zone. Flow restrictors were added on top and bottom of the torpedoes to increase the restriction on polymer flow. A unique inclined flow restrictor was introduced to achieve uniform internal melt flow. Flow separators were added at junctions of outer wall and inner vertical walls to separate the polymer flow into different sections and minimize cross flow between these sections. The addition of these features proved to be highly effective for balancing the velocity distribution at the die exit. The combination of 3-D modeling and simulation is an effective cost and time efficient approach for optimizing complex die designs before manufacturing.

Thermorheological Characterization of Elastoviscoplastic Carbopol Ultrez 20 Gel

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
M. A. Hassan ◽  
Manabendra Pathak ◽  
Mohd. Kaleem Khan
Keyword(s):  
Experimental Investigation ◽  
Yield Stress ◽  
Elastic Properties ◽  
Viscous Dissipation ◽  
Power Law ◽  
Effect Of Temperature ◽  
Rheological Parameters ◽  
Frequency Range ◽  
Power Law Index

The temperature and concentration play an important role on rheological parameters of the gel. In this work, an experimental investigation of thermorheological properties of aqueous gel Carbopol Ultrez 20 for various concentrations and temperatures has been presented. Both controlled stress ramps and controlled stress oscillatory sweeps were performed for obtaining the rheological data to find out the effect of temperature and concentration. The hysteresis or thixotropic seemed to have negligible effect. Yield stress, consistency factor, and power law index were found to vary with temperature as well as concentration. With gel concentration, the elastic effect was found to increase whereas viscous dissipation effect was found to decrease. Further, the change in elastic properties was insignificant with temperature in higher frequency range of oscillatory stress sweeps.

On the Extraction of Milling Tools Out of Shrink Fit Chucks

2012 ◽  
Vol 523-524 ◽  
pp. 445-450 ◽  
Author(s):  
Berend Denkena ◽  
Dennis Heinisch
Keyword(s):  
High Performance ◽  
Experimental Investigations ◽  
Process Conditions ◽  
Geometrical Parameters ◽  
Dynamic Force ◽  
Unique Type ◽  
Milling Operations ◽  
Torque Transmission ◽  
Shrink Fit ◽  
Milling Tools

Thermal shrink fit chucks are widely used in high performance machining where excellent concentricity and high torque transmission are required. It was reported that in those milling operations, severe damage of tools, workpieces, and also machine tools occurs due to an extraction of the milling tool out of the shrink fit chuck during the process. Although, theoretically the interference fit assembly should withstand certain process forces, milling tools are apparently pulled out under special process conditions. The resulting increase of the cutting depth often leads to tool overload and breakage. So far, the phenomenon of tool extraction could not be explained. This paper presents an experimental approach of the investigation of the phenomenon of axial tool extraction. Therefore, a unique type of test rig for main spindles and tool interfaces is used. Experimental investigations on dynamic force and torque combinations leading to tool extraction are described. Results show, that the holding force is not only affected by geometrical parameters of the shrink fit chuck, but also by the applied dynamic load.

scholarly journals Inversion of flow Measurements for Stress and Rheological Parameters in a Valley Glacier

1973 ◽  
Vol 12 (64) ◽  
pp. 19-44
Author(s):  
Charles F. Raymond
Keyword(s):  
Shear Stress ◽  
Power Law ◽  
Measurement Errors ◽  
Effective Viscosity ◽  
Three Dimensional ◽  
Rheological Parameters ◽  
Mean Stress ◽  
Flow Measurements ◽  
Anomalous Zone ◽  
Flow Law

AbstractMethods are developed for determining the distributions of stress and effective viscosity in a glacier, under the assumptions: the ice is quasi-viscous, the flow is time independent, and acceleration forces are negligible. Measurements of the three-dimensional distribution of velocity are needed for their application. The differential equations of mechanical equilibrium, expressed in terms of viscosity, strain-rate components, mean stress, and their gradients, are viewed as equations to be solved for viscosity and mean stress subject to boundary conditions at the free upper surface. For certain rectilinear flow patterns, unique distributions of stress and effective viscosity can always be derived. For more complicated flow this is not necessarily so. However, it is still possible to choose the best values of rheological parameters in any trial flow law based on the requirement that the residuals to the equations of equilibrium be minimized in a mean-square sense. The techniques are applied to measurements of internal deformation made in nine bore holes on the Athabasca Glacier. At the center line the magnitude of the surface-parallel shear stress increases with depth more slowly than would be expected from a standard shape factor correction or the theoretical distribution of Nye. Correspondingly the lateral distribution of lateral shear stress shows the opposite relationships. In the lower one- to two-thirds of the depth corresponding to a range in effective stress from about 0.5 to 1.2 bars, the gross rheology of the ice is not distinguishably different from the experimentally determined flow law of Glen (n = 4.2, T = 0.02° C) as generalized by Nye. The results do not support the conclusion that the effective viscosity is higher than would be expected from Glen’s experiments as indicated by the more limited measurements of Paterson and Savage. Power-law parameters derived for the different bore holes considered separately show a spread, which suggests some rheological inhomogeneity. However, no definite conclusions can be drawn, because of direct measurement errors at the bore holes and less definable uncertainty in the interpolated distribution of velocity between the holes. The upper one- to two-thirds of the glacier constitutes an anomalous zone in which there is either a strong effect from a complex distribution of stress arising from longitudinal stress gradients or more complicated rheology than in a homogeneous power-law material.

Viscoelastic Effects in Multilayer Polymer Extrusion

2006 ◽  
Vol 16 (4) ◽  
pp. 198-205 ◽  
Author(s):  
Patrick D. Anderson ◽  
Joseph Dooley ◽  
Han E.H. Meijer
Keyword(s):  
Design Optimization ◽  
Normal Stress ◽  
Mapping Method ◽  
Computational Method ◽  
Die Design ◽  
Polymer Extrusion ◽  
Viscoelastic Effects ◽  
Normal Stress Differences

Abstract The effect of viscoelasticity on multilayer polymer extrusion is discussed. In these coextrusion processes predetermined patterns are created with a remarkable breadth of complexity even in geometrically simple dies via elastic rearrangements caused by the second-normal stress differences. A computational method is offered, based on the mapping method, which quantitatively describes the flow-induced patterns. Besides that the results are esthetically beautiful, they are also relevant for practice, since process and die design optimization is now possible. Not only to minimize interface distortion, but potentially also to deliberately create new processes and products based on this flow-induced patterning of polymers.

3D FEM Study of the Flow Uniformity of Flat Polypropylene Film/Sheet Extrusion Dies

2020 ◽  
Vol 841 ◽  
pp. 375-380
Author(s):  
Dastan Igali ◽  
Asma Perveen ◽  
Dong Ming Wei ◽  
Di Chuan Zhang ◽  
Almagul Mentbayeva
Keyword(s):  
Polymer Melt ◽  
Die Design ◽  
Manufacturing Companies ◽  
Flow Uniformity ◽  
3D Fem ◽  
Extrusion Dies ◽  
Polypropylene Sheet ◽  
Flat Film ◽  
Extrusion Die Design ◽  
Sheet Extrusion

Coat-hanger dies are widely used in the extrusion of polymer sheets and films. However, when designing the flat film/sheet extrusion dies manufacturing companies still facing difficulties in achieving the flow uniformity of the polymer melt. This affects the product quality and tool life. This study examines the existing extrusion die design which is used in in the industry in Kazakhstan for polypropylene sheet production and proposes better geometry of a die. These die geometries will be tested for flow uniformity in terms of velocity and pressure at the outlet.

Cantalever Protection Aluminum Profiles Extrusion Die Design Method and Numerical Simulation

2012 ◽  
Vol 152-154 ◽  
pp. 301-305
Author(s):  
Jian Yi Pan ◽  
Yao Wang ◽  
Zhao Yao Zhou ◽  
Shou Bin Dong
Keyword(s):  
Numerical Simulation ◽  
Material Flow ◽  
Design Method ◽  
Simulation Method ◽  
Die Design ◽  
Design Scheme ◽  
Extrusion Dies ◽  
Cantilever Structure ◽  
Extrusion Die Design ◽  
Stress And Deformation

In order to improve the service life of extrusion dies with long cantilever structure, a design scheme of porthole die for half-hollow profiles with long cantilever was introduced. Using numerical simulation method, compared with conventional method for the half-hollow porthole design method of a typical profile die model, the equilibrium of the material flow at the outlet, the stress and deformation of the die were analyzed in detail. With selection of the cantilever thickness shrinkage as the objective function, experiment was done to verify the result of simulating analysis. The results indicated that there was only little difference for the equilibrium of material flow between the two design schemes, but the stress load and deformation of the design scheme were greatly improved.

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