Rheology of Magnetorheological Fluids: Models and Measurements

Abstract

Numerical and analytical models of magnetorheological fluid phenomena that account explicitly for the effects of magnetic nonlinearity and saturation are described. Finite-element analysis was used to calculate the field distribution in chains of magnetizable particles. The field-dependent stress required to shear the chains was then obtained using the Maxwell stress tensor. Three regimes are identified: at low applied fields, the stress increase quadratically, as expected from linear magnetostatics. In intermediate fields, the contact or polar regions of each particle saturate, reducing the rate of increase of the stress with increasing field. At high fields, the particles saturate completely, and the stress reaches its limiting value. Approximate analytical expressions for the yield stress and shear modulus in these regimes are also derived. The predictions of these models are compared to magnetorheological experiments in the literature and from our laboratory. These models predict successfully the magnitude of the stresses as well as their field dependence. They also suggest that particles comprised of materials with higher saturation magnetizations will exhibit the largest magnetorheological effects.

Effect of Particle Characteristics and Temperature on Shear Yield Stress of Magnetorheological Fluid

“…Tang calculated the static shear yield stress by theoretical analysis method [10]. Ginder analyzed the effect of magnetic saturation [11,12]. Han investigated the field-dependent characteristics of MR fluids containing corroded iron particles [13].…”

Microrheology of magnetorheological silicone elastomers during curing process under the presence of magnetic field

“…The equilibrium EI values at long times exhibit the increasing tendency at high magnetic field intensity and SiCIPs content, demonstrating the effect of magnetic field-induced formation of chain-like structure that couples with the jamming effect of MREs in the cured silicone matrix. [21][22][23][24][25]35 The MVI profiles are depicted in Fig. 4(b).…”

“…[11][12][13][14][15][16][17][18][19][20][21] Thus far, their rheological characteristics have been extensively studied. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] However, the structural evolution during the process of elastomer curing under magnetic field is not yet illuminated.…”

On the direct employment of dipolar particle interaction in microfluidic systems

“…On the other hand, the magnetic colloids themselves introduce a magnetic gradient on the microscale. These field contributions and the entailed magnetic interplay may strongly influence the fluid velocity as it can be seen in the example of ferrofluids or magnetorheological liquids (Shliomis and Morozov 1994;Love et al 2005;Rosensweig 1996;Zahn and Pioch 1999;Moskowitz and Rosensweig 1967;Ginder et al 1996;Ginder and Davis 1994;Mao et al 2011;Kose et al 2009). In fact, this is only the case if a high concentration of magnetic particles is present within the suspension.…”