Hysteresis reduction in giant magnetostrictive materials

Details Hysteresis reduction in giant magnetostrictive materials Hysteresis reduction in giant magnetostrictive materials

1998-12-21

2001-10-09

Barrera, Ramon M. (Department: 2832)

Electricity: magnetically operated switches, magnets, and electr

Magnets and electromagnets

Magnetostrictive-type device

C310S026000

Reexamination Certificate

active

06300855

ABSTRACT:

BACKGROUND
This invention relates to magnetostrictive materials and more particularly to rare earth-iron magnetostrictive materials.
It has recently become apparent that the primary loss mechanism in high power devices employing giant magnetostrictive materials is hysteresis losses. Even at low audio frequencies, this loss far exceeds the sum of all other losses, which include Cu-coil loss, Terfenol eddy current losses, and eddy current loses in the Cu and in d. c. biasing magnets. While the lowered efficiency may be a significant drawback, the most deleterious effect of the loss is often excessive heating, requiring increased complexity with associated increased costs to cool the device.
The desired new magnetostrictive transducer element should combine a very low magnetization hysteresis with a giant magnetostrictive effect. Moreover the transducer element should not be more expensive to make or operate than prior art transducer elements.
SUMMARY
Accordingly, an object of this invention is to provide a new method of converting magnetic energy into mechanical energy.
Another object of this invention is to provide a more efficient high powered conversion of electrical or magnetic energy into mechanical energy using a magnetostrictive transducer.
A further object of this invention is to prove a new method of converting magnetic energy into mechanical energy using a magnetostrictive transducer element which has a low hysteresis loss but a large magnetostriction.
Still another object of this invention is to provide a new magnetostrictive material which can be used to producer powerful sound projectors and actuators which do not require cooling mechanisms.
These and other objects of this invention are achieved by providing a transducer for converting magnetic energy into mechanical energy comprising:
A. a magnetostrictive element comprising a magnetostrictive material of the formula Tb
x
Dy
y
Ho
z
Fe
2−w
wherein 0.24≦x≦0.28, 0.52≦y≦0.56, 0.13≦z≦0.22, x+y+z=1, and 0≦w≦0.20 and wherein the magnetostrictive element is prestressed by applying a compressive force of from about 5 to about 100 MPa to it; and B. conductive means for generating a magnetic field in the magnetostrictive element.


REFERENCES:
patent: 4308474 (1981-12-01), Savage et al.
patent: 5792284 (1998-08-01), Cedell et al.
Article entitled “Anisotrophy of Single Crystal HoxDyTb1−x−yFe2Laves Phase Compounds,” Physics 86-88B, 147-148 (1977).

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