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|Title:||Non-Linear Viscoelastic Response of Magnetic Fiber Suspensions in Oscillatory Shear|
López-López, M. T.
Zubarev, A. Y.
|Citation:||Non-Linear Viscoelastic Response of Magnetic Fiber Suspensions in Oscillatory Shear / P. Kuzhir, A. Gómez-Ramírez, M. T. López-López et al. // Journal of Non-Newtonian Fluid Mechanics. — 2011. — Vol. 166. — Iss. 7-8. — P. 373-385.|
|Abstract:||This paper reports the first study on the large amplitude oscillatory shear flow for magnetic fiber suspensions subject to a magnetic field perpendicular to the flow. The suspensions used in our experiments consisted of cobalt microfibers of the average length of 37μm and diameter of 4.9μm, dispersed in a silicon oil. Rheological measurements have been carried out at imposed stress using a controlled stress magnetorheometer. The stress dependence of the shear moduli presented a staircase-like decrease with, at least, two viscoelastic quasi-plateaus corresponding to the onset of microscopic and macroscopic scale rearrangement of the suspension structure, respectively. The frequency behavior of the shear moduli followed a power-law trend at low frequencies and the storage modulus showed a high-frequency plateau, typical for Maxwell behavior. Our simple single relaxation time model fitted reasonably well the rheological data. To explain a relatively high viscous response of the fiber suspension, we supposed a coexistence of percolating and pivoting aggregates. Our simulations revealed that the former became unstable beyond some critical stress and broke in their middle part. At high stresses, the free aggregates were progressively destroyed by shear forces that contributed to a drastic decrease of the moduli. We have also measured and predicted the output strain waveforms and stress-strain hysteresis loops. With the growing stress, the shape of the stress-strain loops changed progressively from near-ellipsoidal one to the rounded-end rectangular one due to a progressive transition from a linear viscoelastic to a viscoplastic Bingham-like behavior. © 2011 Elsevier B.V.|
HIGH FREQUENCY HF
LARGE AMPLITUDE OSCILLATORY SHEAR
SINGLE RELAXATION TIME MODELS
STRESS-STRAIN HYSTERESIS LOOPS
|metadata.dc.description.sponsorship:||Biomag (PACA), Eureka E! 3733 Hydrosmart project, Dynxperts project (ref. FP7-2010-NMP-ICT-FoF-260073), FIS2009-07321 (MICINN, Spain), P08-FQM-3993, P09-FQM-4787 (Junta de Andalucía, Spain) and Cooperation Program between CNRS and BRFFR (No 23178, France-Belarus) are acknowledged for the financial support. One of the authors (M.T.L.-L.) also acknowledges financial support by the University of Granada (Spain).|
|Appears in Collections:||Научные публикации, проиндексированные в SCOPUS и WoS CC|
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