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Note on the beginnings of sinusoidal testing methods
Tanner, R.I. The Korean Society of Rheology 2002 Korea-Australia rheology journal Vol.14 No.2
The measurement of the storage and loss moduli (G' and G" respectively) of materials as functions of frequency is now commonplace and is of wide utility. Yet il is not easy to trace the history of such measurements. and so this article discusses the genesis of this important experimental technique. We find that the technique grew out of a parallel technique for dielectric measurements (ca. 1900) and was developed in the mid-1930s by Philippoff and others. Important breakthroughs due to digital circuitry have occurred only in the last 20 years or so.r so.
Study of shear and elongational flow of solidifying polypropylene melt for low deformation rates
Tanner, R.I.,Kitoko, V.,Keentok, M. The Korean Society of Rheology 2003 Korea-Australia rheology journal Vol.15 No.2
An experimental technique was developed to determine the strain-rate in a tensile specimen. Then one can calculate the transient isothermal elongational viscosity. Both shear and elongational viscosities were measured to study the effect of shear and elongational fields on the flow properties. The comparison between these viscosities shows that the onset of rapid viscosity growth as crystallization solidification proceeds occurs at about the same value of time at very small deformation rates (0.0028 and 0.0047 $s^{-1}$). The comparison of these measured viscosities as functions of shear and elongational Hencky strains also reveals that the onset of rapid viscosity growths starts at critical Hencky strain values. The behaviour of steady shear viscosity as function of temperature sweep was also explored at three different low shear rates. Finally, the influence of changing oscillatory frequencies and strain rates was also investigated.
A phenomenological approach to suspensions with viscoelastic matrices
Tanner Roger I.,Qi Fuzhong The Korean Society of Rheology 2005 Korea-Australia rheology journal Vol.17 No.4
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.
On the congruence of some network and pom-pom models
Tanner, Roger I. The Korean Society of Rheology 2006 Korea-Australia rheology journal Vol.18 No.1
We show that some network and pom-pom constitutive models are essentially the same. Instead of the usual confrontation, we suggest that the two approaches can offer useful mutual support: vital information about network destruction rates found from detailed pom-pom calculations can be used to improve the network models, while deductions about network creation rates can pinpoint areas needing further attention in the tube modelling area. A new form of the PTT model, the PTT-X model, results in improved shear and elongational flow descriptions, plus an improved recoil behaviour. The remaining problems of strain-time separation, second normal stress difference description, and reduction of parameters are also discussed and some suggestions for progress are offered.
Effect of pH on Successive Foam and Sonic Droplet Fractionation of a Bromelain-invertase Mixture
Robert D. Tanner,Samuel Ko,Ales Prokop 한국생물공학회 2002 Biotechnology and Bioprocess Engineering Vol.7 No.1
A droplet fractionation method was previously developed to concentrate a dilute non-foaming protein solution. In that earlier study with invertase, it was demonstrated that droplets created by ultrasonic energy waves could be enriched up to 8 times that of the initial dilute invertase solution. In this study, a mixture of bromelain (a foaming protein) and invertase (a non-foaming protein) is investigated as a preliminary step to determine if droplet fractionation can also be used to separate a non-foaming protein from foaming proteins. The foaming mixture containing bromelain is first removed by bubbling the binary mixture with air. After the foam is removed, the protein rich air-water interfacial layer is skimmed off (prior to droplet fractionation) so as not to interfere with the subsequent droplet production from the remaining bulk liquid, rich in non-foaming protein. Finally, sonic energy waves are then applied to this residual bulk liquid to recover droplets containing the non-foaming protein, presumed to be invertase. The primary control variable used in this droplet fractionation process is the pH, which ranged for separate experiments between 2 and 9. It was observed that the maximum overall protein partition coefficients of 5 and 4 were achieved at pH 2 and 4, respectively, for the initial foaming experiment followed by the post foaming droplet fractionation experiment.