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245
100 150 200 250 300
Magnetic Flux Density, (mT)
350 400
Figure 6. Comparisons of shear yield stress versus magnetic field for three MR
materials. Hollow marks are the dynamic shear yield stress and
solid marks are static shear yield stress.
The performance of the device is compared to a rotational shear-mode rheometer. The results indicate
that the measurements obtained by the flow-mode device are consistent with rotational shear-mode
rheometer. Three different MR materials are examined under various magnetic flux densities. The
apparent viscosities, dynamic and static shear yield stresses are determined. All materials examined
show a strong shear rnrnning effect. A power-law relationship was obtained for the apparent viscosity
versus shear strain rate. The dynamic shear yield stress exceeds the static shear yield stress over the
entire range of magnetic flux densities for all the three MR materials.
ACKNOWLEDGEMENT
This study in part is supported by the U.S. Army Research Office and Visteon Corporation, USA. The
authors at the University of Nevada, Reno are thankful for their support.
REFERENCE
Ginder, J. M. (1996). Rheology Controlled by Magnetic Fields. Encyclopedia of Applied
Physics, 16, 487-503.
Felt, D. W. 9 Hagenbuchle M., Liu J, and Richard, J. (1996). Rheology of a magnetorheological
fluid. /. Int. Mat Sys. Struct 7 :5, 589-593.
Gordaninejad, F. and Breese, D. G. (2000). "Magneto-rheological fluid dampers." U.S. Patent
No. 6,019,201.