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Flows in Complex Systems

Effect of Pressure on the Flow Properties of Magnetorheological Fluids

[+] Author and Article Information
A. Spaggiari1

Department of Engineering Sciences and Methods,  University of Modena and Reggio Emilia, via Amendola, 2, Padiglione Morselli, Reggio Emilia, 42122, Italyandrea.spaggiari@unimore.it

E. Dragoni

Department of Engineering Sciences and Methods,  University of Modena and Reggio Emilia, via Amendola, 2, Padiglione Morselli, Reggio Emilia, 42122, Italy

1

Corresponding author

J. Fluids Eng. 134(9), 091103 (Aug 22, 2012) (9 pages) doi:10.1115/1.4007257 History: Received May 11, 2012; Revised July 24, 2012; Published August 22, 2012; Online August 22, 2012

Magnetorheological (MR) fluids are widely used in the industrial world; however, sometimes their properties fail to meet system requirements. In shear mode, MR fluids have been found to exhibit a pressure dependency called squeeze strengthen effect. Since a lot of MR fluid based devices work in flow mode (i.e., dampers), this paper investigates the behavior in flow mode under pressure. The system design consists of three steps: the hydraulic system, the magnetic circuit, and the design of experiment method. The experimental apparatus is a cylinder in which a piston displaces the fluid without the use of standard gear pumps, which are incompatible with MR fluids. The experimental apparatus measures the yield stress of the MR fluid as a function of the pressure and magnetic field, thus, enabling the yield shear stress to be calculated. A statistical analysis of the results shows that the squeeze strengthen effect is also present in flow mode, and that the internal pressure enhances the performance of MR fluids by nearly five times.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Experimental properties of MRF-140-CG from Lord Corp. [2]. Yield stress-field correlation (a) and B-H curve (b).

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Figure 2

Cross section of the hydraulic system

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Figure 3

Bingham model, suitable for MR fluids and the classical viscous Newton model

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Figure 4

Flux density inside the hydromagnetic system for a current of 2 amp (a), scale 0–1 T, and flux distribution along the diametral section of the inner channel (b) with μr  = 5

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Figure 5

Magnetic system (a) and complete hydromagnetic setup for the experimental test of MR fluids under internal pressure (b)

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Figure 6

Experimental curves (black lines), four levels of applied magnetic field, and p = 0, 10, 20, and 30 bars, reported in (a), (b), (c), and (d), respectively. Bingham regression curve (gray lines) used to retrieve the pull-out force.

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Figure 7

Half normal plot of the effects on τTOT

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Figure 8

Surface response (grid) and experimental points (black dots) for the total stress τTOT

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Figure 9

Half normal plot of the effects on τy

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Figure 10

Surface response (grid) and experimental points (single dots) for total stress τy

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Figure 11

Bypass magnetorheological damper [24]

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