A report describes uniaxial-stress-versus-strain experiments that were performed on polycrystalline Tb76Dy24 alloy specimens. [Also see "Magnetoelastic Vibration Dampers" (NPO-20988) on page 56 of this issue.] The proposal is to use Tb-Dy alloys as vibration-damping materials at temperatures -100 K, exploiting the fact that in Tb-Dy alloys and other magnetostrictive materials, vibrations cause the movement of magnetic domains and the consequent dissipation of vibrational energy as heat.
This work was done by Jennifer Dooley, Robert Chave, Brent Fultz, Art Clark, Nathan Good, and Jason Graetz 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
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Refer to NPO-20887.
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Progress in Magnetoelastic Vibration Dampers
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Overview
The document discusses advancements in magnetoelastic vibration dampers, particularly focusing on the use of polycrystalline terbium-dysprosium (Tb-Dy) alloys. Conducted by a team from Caltech for NASA's Jet Propulsion Laboratory, the research aims to address the need for effective vibration damping in large space structures at low temperatures, specifically below 100 K.
The report highlights uniaxial stress versus strain experiments performed on Tb-Dy alloy specimens. These materials are notable for their magnetostrictive properties, which allow them to dissipate vibrational energy as heat through the movement of magnetic domains. This mechanism is particularly advantageous at cryogenic temperatures, where conventional viscoelastic damping methods become less effective due to reduced atomic movement.
Key findings from the experiments include a significant reduction in Young's modulus at 77 K, which is about one-fifth of its value at 300 K. This reduction is attributed to magnetoelastic strains that occur when magnetic domains reorient under applied stress. The research also observed substantial mechanical hysteresis, with the ability to dampen as much as 19.2% of mechanical energy during a single vibration cycle at 77 K.
Additionally, the document suggests that the performance of Tb-Dy alloy dampers can be fine-tuned by applying an external magnetic field, offering a novel approach to enhance their effectiveness in various applications. The work represents a significant step forward in the development of materials that can operate efficiently in extreme conditions, making them suitable for aerospace applications where vibration control is critical.
The document is part of a broader effort to innovate in the field of vibration damping, leveraging the unique properties of magnetostrictive materials. It emphasizes the potential for these materials to improve the stability and performance of large structures in space, where traditional damping methods may fall short. The research is documented under NASA's contract and is intended for further exploration and potential commercial use, with inquiries directed to the JPL Intellectual Property group.
Overall, this work showcases the intersection of materials science and engineering, highlighting how advanced materials can solve specific challenges in aerospace technology.
