• Korea-Australia Rheology Journal
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• v.19 no.3
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• pp.117-123
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• 2007

There has been considerable interest in recent years in field-responsive suspensions, which are of some importance in industry in many different applications. The microstructure of these materials is a significant issue which can be probed by rheological measurements. In this study, measurements were made of a magnetorheological fluid (MRF) under steady and oscillatory shear flow, with and without a magnetic field. Mathematical inversion was used to derive the relaxation time spectrum of the MRF from oscillatory shear data. Experimental evidence is presented of the gel-like properties of this MRF.

• Proceedings of the Korean Society of Rheology Conference
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• 2001.09a
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• pp.154.1-154
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• 2001

(No abstract, see full-text)

• Proceedings of the Korean Society of Rheology Conference
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• 2001.09a
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• pp.154.3-154
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• 2001

(No abstract, see full-text)

• Proceedings of the Korean Society of Rheology Conference
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• 2000.11a
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• pp.21-24
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• 2000

• Proceedings of the Korean Society of Rheology Conference
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• 2001.09a
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• pp.152.2-152
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• 2001

(No abstract, see full-text)

• Proceedings of the Korean Society of Rheology Conference
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• 2000.11a
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• pp.17-20
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• 2000

• Korea-Australia Rheology Journal
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• v.18 no.1
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• pp.15-24
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• 2006

The first international inter-laboratory study, involving six laboratories, has been conducted to examine issues associated with yield stress measurements in suspensions. The initial focus of the project was to evaluate the reliability and reproducibility of several common yield stress measuring techniques employed in different laboratories and with different instruments. Aqueous suspensions of colloidal $TiO_2$ at concentrations of 40-70 wt% solids were used as the test fluids. A wide range of instruments and techniques employing both direct and indirect methods were used to determine the yield stress of the samples prepared according to a prescribed procedure. The results obtained indicated that although variations of results existed among different techniques, direct yield stress measurements using static methods produced more reliable and repeatable results than other methods. Variability of the yield stress measured using different techniques within any laboratory however was less significant than variability of the results among different laboratories. The nature and condition of the test suspensions was identified as the most likely factor responsible for the poor reproducibility of yield stress measurements from different laboratories.

• Journal of computational fluids engineering
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• v.14 no.4
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• pp.101-108
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• 2009

We present a new finite-element scheme for direct numerical simulation of particle suspensions in simple shear flow of a viscoelastic fluid in 3D. The sliding tri-periodic representative cell concept has been combined with DEVSS/DG finite element scheme by introducing constraint equations along the domain boundary. Rigid body motion of the freely suspended particle is described by the rigid-shell description and implemented by Lagrangian multipliers on particle boundaries. We present the bulk rheology of suspensions through the numerical examples of single-, two- and many-particle problems, which represent a large number of such systems in simple shear flow. We report the steady bulk viscosity and the first normal stress coefficient, which show shear-thickening behavior for both properties.

• Korea-Australia Rheology Journal
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• v.17 no.4
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• pp.149-156
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• 2005

A simple constitutive model for viscoelastic suspensions is discussed in this paper. The model can be used to predict the rheological properties (relative viscosity and all stresses) for viscoelastic suspensions in shear and elongational flow, and the constitutive equations combine a 'viscoelastic' behaviour component and a 'Newtonian' behaviour component. As expected, the model gives a prediction of positive first normal stress difference and negative second normal stress difference; the dimensionless first normal stress difference strongly depends on the shear rate and decreases with the volume fraction of solid phase, but the dimensionless second normal stress difference (in magnitude) is nearly independent of the shear rate and increases with the volume fraction. The relative viscosities and all the stresses have been tested against available experimental measurements.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 2000.06a
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• pp.215-232
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• 2000

The Valence(Z) of positively and negatively charged alumina particles in the dilute suspensions was analyzed with the electrical conductivity of the suspensions. The mobility of negative particles was lower than that of positive particles at a similar Z value because of the stronger effect of chemical bonding over the hydrated particle surfaces. The apparent viscosity of acidic suspensions of 1-40 vol % solid was lower than that of basic suspensions. This result was discussed based on the three important effects of the valence, concentration and nature of hydrated surface of alumina particles. The density of alumina compacts consolidated by filtration through gypsum molds became lower for the basic suspensions than for the acidic suspensions. This result was correlated to the properties of the colloidal alumina suspensions.