Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2001-02-13
2003-08-26
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C428S402000, C428S403000, C428S634000, C252S062520, C252S062540, C188S267000, C267S140140, C267S140150
Reexamination Certificate
active
06610404
ABSTRACT:
BACKGROUND
1. Technical Field
The present invention relates generally to magnetorheological materials for use in space applications and, more particularly, to the use of controlled-shaped particles in magnetorheological materials to increase yield-stress of the material.
2. Discussion
Magnetorheological materials are magnetic field responsive materials which are a subdivision of the family of materials known as smart or actively controllable materials. Smart materials use feedback information to dynamically alter the material behavior in order to enhance device and component performance to levels otherwise unachievable using traditional materials and devices.
Magnetorheological materials are particularly unique smart materials because they provide millisecond response time, may be used in both small and large displacement devices, and generate very large forces and torque independent of the velocity of operation. Magnetorheological materials and devices utilizing such materials have been used extensively in earth-based applications. The flexibility and performance has proved useful in vibration isolation systems such as building seismic isolators, mechanical clutches, torque/tension controllers, brakes, damping devices, fluid flow controllers, precision surface shaping/polishing machines, and gripping/latching devices.
Magnetorheological materials, however, have not been thus far particularly attractive for space applications due to size, weight, and power restrictions. For example, for a given magnetic field strength, magnetorheological device size and weight varies approximately between the square and the cubic power of the material yield stress. For example, a doubling or tripling of a material's yield stress results in between a 10-30 times reduction in the device size and weight. Although the doubling and tripling of the magnetorheological property performance appears to be a modest goal, existing formulations for magnetorheological materials do not allow such improvements.
The design of high performance magnetorheological materials for space and other high performance applications necessarily requires high forces between particles at moderate magnetic fields. Existing particles for magnetorheological fluids are typically embodied as spherical particles. Such particles, however, do not provide the requisite packing density and interaction area for yielding the necessary attractive forces between particles at moderate magnetic fields.
Because existing magnetorheological materials do not provide the requisite particle interaction, the basic yield stress properties of components utilizing magnetorheological material devices have been undesirable for space applications because of the desired size, weight, and power requirements that such materials present. Thus it is desirable to provide magnetorheological materials for devices that can be utilized in space applications including actively-controlled launch vibration isolators, large-appendage deployment mechanisms, vibration dampeners for suppression of spacecraft attitude control systems and station keeping operation disturbances, and low-impulse, more accurate release and latch mechanisms.
SUMMARY OF THE INVENTION
The present invention is directed to a magnetorheological medium including a carrier medium and a plurality of magnetizable particles suspended in the carrier medium. The particles are formed in a selected non-spherical shape. The plurality of particles has an inducible interactive force defining an attraction between a selected two of the plurality of particles. When the plurality of particles are subjected to a magnetic field, the particles align to increase the interactive force.
For a more complete understanding of the invention, its objects and advantages, reference should be made to the following specification and to the accompanying drawings.
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Shtarkman Emil M.
Starkovich John A.
Harness & Dickey & Pierce P.L.C.
Kiliman Leszek
TRW Inc.
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