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Dimitri Merger, Mahdi Abbasi, Juri Merger, A. Jeffrey Giacomin, Chaimongkol Saengow, Manfred Wilhelm
Simple Scalar Model and Analysis for Large Amplitude Oscillatory Shear

Appl. Rheol. 26:5 (2016) 53809 (15 pages)

This work presents a simple, scalar model for predicting a nonlinear shear stress response of a viscoelastic fluid in Large Amplitude Oscillatory Shear (LAOS) experiments. The model is constructed by replacing the viscosity in the well-known Maxwell model by a shear rate dependent viscosity function. By assuming the empirical Cox-Merz rule to be valid, this shear rate dependent viscosity function is specified based on the Maxwell expression for the complex viscosity. We thus construct a particular case of the White-Metzner constitutive equation. Numerical solutions as well as an asymptotic analytical solution of the model are presented. The results, analyzed for higher harmonic content by Fourier transform, are compared to experimental data of a viscoelastic solution of wormlike micelles based on cetyltrimethylammonium bromide. Good agreement is found for low frequencies, where viscous properties dominate.

Cite this publication as follows:
Merger D, Abbasi M, Merger J, Giacomin AJ, Saengow C, Wilhelm M: Simple Scalar Model and Analysis for Large Amplitude Oscillatory Shear, Appl. Rheol. 26 (2016) 53809.

Antony Beris, A. Jeffrey Giacomin
πάντα ῥεῖ: Everything flows

Appl. Rheol. 24:5 (2014) 52918 (13 pages)

This historical study deepens the rheologist.s understanding of the motto of The Society of Rheology, of its history, and of its many typographies. The motto "παντα ῥει" is not verbatim something written or said by the ancient Greek Ionian philosopher Heraclitus, ca. 540 - 480 BCE. Rather it is first encountered much later, in the writings of the Roman Simplicius ca. 490 - 560 CE. Thus, although it is uniformly agreed by Greek scholars that it correctly and concisely distills Heraclitian philosophy, that of constant change, and although this is appropriately used as the motto of The Society of Rheology, there is little point in trying to rewrite it into another form (for example to capitalize it) in an effort to be more faithful to an ancient prototype. Rather, we suggest simply reinstating the two missing diacritical marks, and thus, to express it as "πάντα ῥεῖ" which is the form in which the motto was introduced in 1929. This is also consistent with current typography of ancient Greek writings, in use since the ninth century CE, following the byzantine scholars. We provide Table 1 to facilitate accurate typesetting of the motto.

Cite this publication as follows:
Beris A, Giacomin AJ: πάντα ῥεῖ: Everything flows, Appl. Rheol. 24 (2014) 52918.

Y.-C. Wang, S. Gunasekaran, A.J. Giacomin
The Lodge Rubberlike Liquid Behavior for Cheese in Large Amplitude Oscillatory Shear

Appl. Rheol. 11:6 (2001) 312-319

The viscoelasticity of reduced-fat Cheddar and Mozzarella cheeses was characterized in small (parallel disk rheometer, go = 0.01) and large (sliding plate rheometer, 0.2< go <7) amplitude oscillatory shear at 40 and 60 C. We deduced the linear relaxation spectrum from the small strain measurements. At large strain amplitudes, we found sinusoidal stress responses whose amplitudes are well below those predicted from the linear relaxation spectrum, and yet remarkably linear with strain amplitude. We call this the large strain linear regime. We discovered that the Lodge rubberlike liquid can quantitatively explain the large strain linear regime if we scale down the relaxation moduli in the linear spectrum by a constant. This large strain linear regime persists to much higher strain amplitudes for Cheddar (go <= 4) than for Mozzarella (go <= 1). This is perhaps due to oriented structure of the protein matrix in the Mozzarella cheese.

Cite this publication as follows:
Wand YC, Gunasekaran S, Giacomin AJ: The Lodge Rubberlike Liquid Behavior for Cheese in Large Amplitude Oscillatory Shear, Appl. Rheol. 11 (2001) 312.

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