Rheological Characterization of a New Alloy for Thixoforming

2008 ◽  
Vol 141-143 ◽  
pp. 301-306 ◽  
Author(s):  
Annalisa Pola ◽  
Roberto Roberti ◽  
Michael Modigell ◽  
Lars Pape
Keyword(s):  
Flow Behavior ◽  
Thermodynamic Simulation ◽  
Semisolid State ◽  
Rheological Characterization ◽  
Scanning Calorimetry ◽  
Globule Size ◽  
Semisolid Alloy ◽  
Dependent Flow ◽  
Mechanical Performances

A new aluminum alloy (AlSi5Mg0.5Cu0.3Ag) for semisolid die-casting applications was designed, starting from computational thermodynamics calculations by Computherm Database. The goal was to obtain a combination of good castability and proper concentration of hardening elements for strengthening precipitation treatment. The predicted thixotropic properties were verified by measuring the microstructural conventional parameters, such as globule size and shape factor, and the solidification range, by means of differential scanning calorimetry. To complete the characterization of this new alloy and to evaluate its applicability in industrial production, the shear rate and time-dependent flow behavior of the alloy in the semisolid state was studied in a Searle-type rheometer. A future aim of the present research is to try to use rheology testing as the tool to optimize the chemical composition, in order to design an alloy characterized by good mechanical performances and easy processability. Considering the strong influence of the solid fraction content on semisolid alloy viscosity, the rheology tests were interrupted after a certain time and the alloy was deeply freezed using vaporized liquid nitrogen, in order to fix the microstructure and verify the correctness of the thermodynamic simulation.

scholarly journals Rheological Characterization of a Concentrated Phosphate Slurry

Fluids ◽  
2021 ◽  
Vol 6 (5) ◽  
pp. 178
Author(s):  
Souhail Maazioui ◽  
Abderrahim Maazouz ◽  
Fayssal Benkhaldoun ◽  
Driss Ouazar ◽  
Khalid Lamnawar
Keyword(s):  
Flow Behavior ◽  
Continuous Phase ◽  
Raw Material ◽  
Rheological Characterization ◽  
Phosphate Ore ◽  
Insoluble Particles ◽  
Experimental Protocols ◽  
Solid Liquid

Phosphate ore slurry is a suspension of insoluble particles of phosphate rock, the primary raw material for fertilizer and phosphoric acid, in a continuous phase of water. This suspension has a non-Newtonian flow behavior and exhibits yield stress as the shear rate tends toward zero. The suspended particles in the present study were assumed to be noncolloidal. Various grades and phosphate ore concentrations were chosen for this rheological investigation. We created some experimental protocols to determine the main characteristics of these complex fluids and established relevant rheological models with a view to simulate the numerical flow in a cylindrical pipeline. Rheograms of these slurries were obtained using a rotational rheometer and were accurately modeled with commonly used yield-pseudoplastic models. The results show that the concentration of solids in a solid–liquid mixture could be increased while maintaining a desired apparent viscosity. Finally, the design equations for the laminar pipe flow of yield pseudoplastics were investigated to highlight the role of rheological studies in this context.

scholarly journals Development of a Rheology Die and Flow Characterization of Gas-Containing Polymer Melts

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3305
Author(s):  
Clemens Kastner ◽  
Dominik Altmann ◽  
Eva Kobler ◽  
Georg Steinbichler
Keyword(s):  
Polymer Melts ◽  
Flow Behavior ◽  
Volumetric Flow Rate ◽  
Thermal Characterization ◽  
Polymer Processing ◽  
Rheological Characterization ◽  
Process Measurement ◽  
Flow Characterization ◽  
Chemical Blowing Agents

We present a novel measurement die for characterizing the flow behavior of gas-containing polymer melts. The die is mounted directly on the injection-molding cylinder in place of the mold cavity and thus enables near-process measurement of viscosity (i.e., under the conditions that would be present were a mold attached). This integration also resolves the issue of keeping gas-containing polymer melts under pressure during measurement to prevent desorption. After thermal characterization of the die, various correction approaches were compared against each other to identify the most suitable one for our case. We conducted measurements using polypropylene in combination with two different chemical blowing agents. Increasing the blowing-agent content to up to 6% revealed an interestingly low influence of gases on melt viscosity, which was confirmed by elongational viscosity measurements. For verification, we compared our results to corresponding measurements taken on a high-pressure capillary rheometer and found that they were in excellent agreement. Our die cannot only be used for rheological characterization. Combined with ultrasound sensors, it provides an innovative way of measuring the volumetric flow rate. This development represents an important step in improving the sustainability of gas-containing polymer processing.

scholarly journals Printing of Zirconia Parts via Fused Filament Fabrication

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5467
Author(s):  
Dorit Nötzel ◽  
Ralf Eickhoff ◽  
Christoph Pfeifer ◽  
Thomas Hanemann
Keyword(s):  
Flow Behavior ◽  
Special Focus ◽  
Fused Filament Fabrication ◽  
Rheological Characterization ◽  
Structural Details ◽  
Low Shear Stress ◽  
Flow Situation ◽  
The Individual ◽  
Low Shear

In this work, a process chain for the fabrication of dense zirconia parts will be presented covering the individual steps feedstock compounding, 3D printing via Fused Filament Fabrication (FFF) and thermal postprocessing including debinding and sintering. A special focus was set on the comprehensive rheological characterization of the feedstock systems applying high-pressure capillary and oscillation rheometry. The latter allowed the representation of the flow situation especially in the nozzle of the print head with the occurring low-shear stress. Oscillation rheometry enabled the clarification of the surfactant’s concentration, here stearic acid, or more general, the feedstocks composition influence on the resulting feedstock flow behavior. Finally, dense ceramic parts (best values around 99 % of theory) were realized with structural details smaller than 100 µm.

Rheological Characterization of Emulsified Bitumen from Industrial Waste

2021 ◽  
Vol 1163 ◽  
pp. 148-157
Author(s):  
Mohd Najib Razali ◽  
Thanushiya A.P. Asaithamby ◽  
Najmuddin Mohd Ramli ◽  
Mohd Khairul Nizam Mohd Zuhan ◽  
Musfafikri Musa ◽  
...  
Keyword(s):  
Industrial Waste ◽  
Abietic Acid ◽  
High Viscosity ◽  
Rheological Characterization ◽  
Scanning Calorimetry ◽  
Bitumen Emulsion ◽  
Emulsion Formulation ◽  
Aqueous Mixture ◽  
Temperature Susceptibility

Emulsified bitumen is an aqueous mixture of bitumen and can be used in insulation and coating applications. In this study, used automotive oil was utilized as a component in bitumen emulsion formulation. Five formulations of bitumen emulsion comprising different ratios of neat bitumen and recycled automotive oil were formulated, namely EMB01–EMB05. The formulation utilized 1 g of abietic acid (C20H30O2) as an emulsifier. The formulated bitumen was characterized for penetration, softening point, differential scanning calorimetry, viscosity, and oscillatory test, and the results were compared to commercial bitumen emulsion (ATLAS bitumen emulsion). The results show that EMB05 has softer consistency, high viscosity, temperature susceptibility, higher thermal stability, and an adaptable viscoelastic range compared to other formulations that provide suitable properties for coating and insulation of wall waterproof material.

Rheological and microstructural characterization of WPI-stabilized O/W emulsions exhibiting time-dependent flow behavior

LWT ◽  
2012 ◽  
Vol 46 (2) ◽  
pp. 375-381 ◽  
Author(s):  
Pablo Bellalta ◽  
Elizabeth Troncoso ◽  
Rommy N. Zúñiga ◽  
José M. Aguilera
Keyword(s):  
Flow Behavior ◽  
Microstructural Characterization ◽  
Time Dependent ◽  
Dependent Flow

scholarly journals Physicochemical, Microstructural, and Rheological Characterization of Tigernut (Cyperus esculentus) Starch

2019 ◽  
Vol 2019 ◽  
pp. 1-7
Author(s):  
P. T. Akonor ◽  
C. Tortoe ◽  
C. Oduro-Yeboah ◽  
E. A. Saka ◽  
J. Ewool
Keyword(s):  
Physicochemical Properties ◽  
Amylose Content ◽  
Flow Behavior ◽  
Pasting Properties ◽  
Cyperus Esculentus ◽  
Rheological Characterization ◽  
Freeze Thaw ◽  
Starch Gels

The aim of this study was to characterize the physicochemical properties of starch isolated from two varieties of tigernuts. The results showed wide variations between the two types of tigernuts. Mean granule sizes were 11.1 and 6.1 μm, respectively, for starch from the yellow and black while amylose content ranged from 19 to 21%. Starch gels from the yellow variety were more stable to freeze-thaw and recorded 37.1% syneresis, compared to 56.5% after the first storage cycle. Pasting properties were significantly different (p < 0.05) among starch from the two tigernut varieties, with black recording higher peak viscosity, lower breakdown, and higher setback viscosity. Gels made from the yellow variety were clearer, softer, more adhesive, and more cohesive. Both gels showed a pseudoplastic flow behavior without thixotropy.

Experimental Studies and Thermodynamic Simulation of Phase Transformations in γ-TiAl Based Alloys

2004 ◽  
Vol 842 ◽  
Author(s):  
Harald F. Chladil ◽  
Helmut Clemens ◽  
Harald Leitner ◽  
Arno Bartels ◽  
Rainer Gerling ◽  
...  
Keyword(s):  
Phase Transformations ◽  
Thermodynamic Simulation ◽  
Experimental Studies ◽  
Transition Temperatures ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Thermodynamic Simulations ◽  
Simulation Based ◽  
Phase Transition Temperatures

ABSTRACTPhase transformations and phase transition temperatures in several Nb-rich γ-TiAl based alloys were investigated experimentally and compared to thermodynamic simulations. The present study combines light-optical and scanning electron microscopy, X-ray diffraction and differential-scanning-calorimetry for the characterization of the prevailing phases and phase transformations. Thermodynamic simulation based on the CALPHAD method was used for predict phase stabilities. The results from experiments on a variety of γ-TiAl based alloys are compared to thermodynamic calculations. Finally, the influence of carbon on the transition temperatures is presented.

Light-cured dental composites characterization by Electron Microscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 428-429
Author(s):  
B. M. Culbertson ◽  
M. L. Devinev ◽  
E. C. Kao
Keyword(s):  
Electron Microscopy ◽  
Mechanical Analysis ◽  
Service Performance ◽  
Dental Composite ◽  
Dental Composites ◽  
Neat Resin ◽  
Scanning Calorimetry ◽  
Research Meeting ◽  
Formulation Variables

The service performance of current dental composite materials, such as anterior and posterior restoratives and/or veneer cements, needs to be improved. As part of a comprehensive effort to find ways to improve such materials, we have launched a broad spectrum study of the physicochemical and mechanical properties of photopolymerizable or visible light cured (VLC) dental composites. The commercially available VLC materials being studied are shown in Table 1. A generic or neat resin VLC system is also being characterized by SEM and TEM, to more fully understand formulation variables and their effects on properties.At a recent dental research meeting, we reported on the differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) characterization of the materials in Table 1. It was shown by DSC and DMA that the materials are substantially undercured by commonly used VLC techniques. Post curing in an oral cavity or a dry environment at 37 to 50°C for 7 or more hours substantially enhances the cure of the materials.

Rheological characterization of tack and viscoelasticity of compositions of crepe coating used in the Yankee dryer

TAPPI Journal ◽  
2019 ◽  
Vol 18 (11) ◽  
pp. 641-649
Author(s):  
JOSHUA OMAMBALA ◽  
CARL MCINTYRE
Keyword(s):  
Normal Force ◽  
Weight Ratio ◽  
Good Combination ◽  
Rheological Characterization ◽  
Nonlinear Viscoelastic ◽  
Coating Composition ◽  
Linear And Nonlinear ◽  
Work Done ◽  
Tissue Production

The vast majority of tissue production uses creping to achieve the required set of properties on the base sheet. The Yankee coating helps to develop the desired crepe that in turn determines properties such as bulk and softness. The adhesion of the sheet to the Yankee surface is a very important characteristic to consider in achieving the desired crepe. The coating mix usually consists of the adhesive, modifier, and release. A good combination of these components is essential to achieving the desired properties of the tissue or towel, which often are determined by trials on the machine that can be time consuming and lead to costly rejects. In this paper, five compositions of an industrial Yankee coating adhesive, modifier, and release were examined rheologically. The weight ratio of the adhesive was kept constant at 30% in all five compositions and the modifier and release ratios were varied. The normal force and work done by the different compositions have been shown at various temperatures simulating that of the Yankee surface, and the oscillatory test was carried out to explain the linear and nonlinear viscoelastic characteristic of the optimal coating composition.

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