Talk
Abstract:
Seminar
on Industrial Problems
Magnetorheological Fluids and Elastomers
May
5, 2000
Presented
by:
John M. Ginder
Physics Department
Research Laboratory
Ford Motor Company
P.O. Box 2053, SRL MD 3028
Dearborn, MI 48121-2053
jginder@ford.com
570
Vincent Hall
10:10 am
Magnetorheological (MR) fluids, which comprise magnetically
soft particles dispersed in liquids, possess rheological properties
that can be rapidly and reversibly altered by the application
of a magnetic field. These fluids have recently been used commercially
to provide controllable resistance in exercise equipment and
to generate controllable damping in shock absorbers. The commercial
potential of this technology, coupled with the fascinating behavior
of these materials, has motivated the development of fluids
with improved stability against particle sedimentation and irreversible
aggregation.
By
embedding the magnetic particles not in fluids, but in viscoelastic
solids, these stability problems may be eliminated. We have
developed a class of such materials termed MR elastomers consisting
of iron particles in natural rubber, the base polymer in most
elastomeric automotive mounting components, resulting in a compound
that can be mixed and molded using conventional techniques.
Chemical crosslinking of the elastomer in an applied magnetic
field locks in a chainlike particle structure aligned along
the direction of the field. The resulting viscoelastic solid
possesses stiffness and damping that is nonzero even in zero
magnetic field and that increases substantially as a field is
applied.
In this talk, I will present measurements of the field-dependent
mechanical and magnetic properties of MR fluids and elastomers.
These measurements will be compared with the predictions of
analytical and numerical models that we have developed to describe
them. I will also sketch some possible automotive applications
of these controllable materials.
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