Magnetorheological suspensions

There are also complex fluids that change from solid-like to liquid-like, or vice versa, when subjected to a modest deformation. Complex fluids of this type include particulate and polymeric gels. Some fluids change to solids when an electric or magnetic field is applied these are electrorheological and magnetorheological suspensions. A classical liquid or solid, on the other hand, does not change character in response to a weak field unless it is extremely close to a phase transition temperature. 

A. Kawai, K. Uchida, F. Ikazaki, Effects of shape and size of dispersoid on electrorheology. In Proceedings of 8th International Conference, Electrorheological Fluids and Magnetorheological Suspensions. Edited by G. Bossis Singapore, World Scientific 2002, 626-632. 

It determines the influence of the external magnetic field on the superparamagnetic filament. The number Bj compares dipolar to bending forces and it is proportional to the magnetoelastic number introduced in Refs [4, 73, 74]. An alternative dimensionless number for characterizing the influence of the magnetic field is the Mason number introduced in the literature on magnetorheological suspensions [75, 88],... 

Fig. 5 Magnetorheological effect of carbonyl iron particles in uniform magnetic field, a Magnetite suspension in the absence of external field, b The same suspension in the presence of 100 mT uniform magnetic field. The direction of forming chains is parallel to the field direction, as shown by the arrow [78]...

P. Kuzhir, M.T. Lopez-Lopez, G. Bossis, Magnetorheology of fiber suspensions. II. Theory, /. Rheol, 2009, 53, 127. 

Magnetorheological fluid production levels in 2005 are of the order of hundreds of metric tons per year (or tens of thousands of liters) such that commercial applications on several automotive platforms are supported. A factor of ten or more increase in volume over the next decade is anticipated. It is estimated that there are presently more than one hundred thousand MR dampers, shock absorbers, brakes and clutches in use worldwide. This number is expected to rise into the millions as more automotive platforms adopt smart MR fluid suspensions and clutch systems. 

A typical magnetorheological fluid consists of 20... 40% by volume of relatively pure, elemental iron particles suspended in a carrier liquid such as mineral oil, synthetic oil, water and/or glycol. A variety of proprietary additives, similar to those found in commercial lubricants, that inhibit gravitational settling and promote particle suspension, enhance lubricity, modify viscosity, and inhibit wear are commonly added. 

Cinder, J.M. Davis, L.C. and Elie, L.D. Rheology of Magnetorheological Fluids Models and Measurements. Proc. 5th Int. Conf. on ER Fluids, MR Suspensions and Assoc. Tech., Sheffield (July 1995), W.A. Bullough, ed.. World Scientific, Singapore (1996), pp. 504-514... 

Yanyo, L.C. Magnetorheological (MR) Fluid for Automotive Damping Sys-tems. Proc. HR Suspension and Damping Conf, Germany (2004)... 

Electro- and magnetorheological fluids are mainly used in semi-active damping devices, current car suspension systems in premimn class vehicles based on MRF [139]. Furthermore, shape memory alloys are imder investigation, especially for active pre-crash systems [141]. 

This Corvette ZRl uses magnetorheological fluid in its suspension system. 

L6pez-L6pez, M.T., Kuzhir, R, Lacis, S., Bossis, G., Gonzalez-CahaUero, R, and Duran, J.D.G. 2006. Magnetorheology for suspensions of sohd particles dispersed in ferrofluids. J. Phys. Condens. Matter 18 S2803-S2813. 

Viota, J.L., Duran, J.D.G., and Delgado, A.V. 2009. Study of the magnetorheology of aqueous suspensions of extremely bimodal magnetite particles. Eur. Phys. J. E. in press. 

---