Magnetoelastic dampers have been proposed for use in suppressing vibrations of large motors and transformers that operate at temperatures below 100 K. [Also see "Progress in Magnetoelastic Vibration Dampers," (NPO-20887) on page 57 of this issue.] These dampers would be made of magnetostrictive materials - specifically, Tb/Dy alloys. It would not be necessary to use the rare and expensive high-purity grades of Tb/ Dy; the commercial grade would suffice and may in fact be preferable.
Conventional dampers for such applications are based on viscoelasticity. Because viscoelastic damping involves movements of atoms and these movements become very small at low temperatures, viscoelastic dampers become ineffective at low temperatures.
In magnetostrictive materials, vibrational energy becomes damped through the movement of magnetic domains and the consequent dissipation of vibrational energy as heat. Because this effect is not diminished at low temperatures, magnetostrictive materials can be expected to be effective in damping vibrations at low temperatures. In a recent quasi-static experiment, a Tb/Dy alloy specimen was found to dissipate 30 percent of vibrational energy per stress-and-strain cycle at a temperature of 77 K. Moreover, it may be possible to increase the dissipation factor through the addition of small amounts of N, Ta, and/or other elements to Tb/ Dy alloys and through changes in the processing conditions.
This work was done by Jennifer Dooley, Brent Fultz, John Voccio, and Robert Chave of Caltech for NASA's Jet Propulsion Laboratory.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to
Intellectual Property group
JPL
Mail Stop 202-233
4800 Oak Grove Drive
Pasadena, CA 91109
(818) 354-2240
Refer to NPO-20988.
This Brief includes a Technical Support Package (TSP).
Magnetoelastic Vibration Dampers
(reference NPO20988) is currently available for download from the TSP library.
Don't have an account?
Overview
The document discusses the development and application of magnetoelastic vibration dampers, specifically utilizing magnetostrictive materials such as terbium-dysprosium (Tb/Dy) alloys. This technology was developed by a team at NASA's Jet Propulsion Laboratory (JPL) and is particularly aimed at addressing the challenges of vibration damping in environments with low temperatures, specifically below 100 K.
Traditional vibration dampers rely on viscoelastic materials, which become ineffective at low temperatures due to the reduced atomic movements that are essential for their damping mechanism. In contrast, magnetoelastic dampers operate on the principle of magnetic domain movement, allowing them to dissipate vibrational energy as heat without losing effectiveness in cold conditions. This unique property makes them suitable for applications in large motors and transformers that operate in cryogenic environments.
Recent experiments have demonstrated that a Tb/Dy alloy specimen can dissipate approximately 30% of vibrational energy per stress-and-strain cycle at a temperature of 77 K. The document also suggests that the damping characteristics of these materials could be further enhanced by incorporating small amounts of other elements, such as nitrogen (N) or tantalum (Ta), and by modifying processing conditions.
The work is presented as a significant advancement in the field of low-temperature vibration damping, offering a fundamentally different approach compared to conventional methods. The document emphasizes the novelty of using Tb/Dy materials for this purpose, highlighting the potential for improved performance in various industrial applications.
In terms of intellectual property, the document notes that the contractor has retained title to the invention, and inquiries regarding commercial use should be directed to the JPL Intellectual Property group.
Overall, the document serves as a technical brief on the innovative use of magnetoelastic materials for vibration damping, showcasing the research conducted by the JPL team and its implications for future applications in cryogenic technology.
