Magneto-mechanical properties and applications of Ni-Mn-Ga ferromagnetic shape memory alloy
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2000.
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| Format: | Thesis |
| Language: | eng |
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Massachusetts Institute of Technology
2005
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| Online Access: | http://hdl.handle.net/1721.1/9163 |
| _version_ | 1826199706191003648 |
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| author | Murray, Steven J. (Steven James), 1974- |
| author2 | Samuel M. Allen and Robert C. O'Handley. |
| author_facet | Samuel M. Allen and Robert C. O'Handley. Murray, Steven J. (Steven James), 1974- |
| author_sort | Murray, Steven J. (Steven James), 1974- |
| collection | MIT |
| description | Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2000. |
| first_indexed | 2024-09-23T11:24:46Z |
| format | Thesis |
| id | mit-1721.1/9163 |
| institution | Massachusetts Institute of Technology |
| language | eng |
| last_indexed | 2024-09-23T11:24:46Z |
| publishDate | 2005 |
| publisher | Massachusetts Institute of Technology |
| record_format | dspace |
| spelling | mit-1721.1/91632019-04-12T09:35:24Z Magneto-mechanical properties and applications of Ni-Mn-Ga ferromagnetic shape memory alloy Murray, Steven J. (Steven James), 1974- Samuel M. Allen and Robert C. O'Handley. Massachusetts Institute of Technology. Dept. of Materials Science and Engineering. Massachusetts Institute of Technology. Dept. of Materials Science and Engineering. Materials Science and Engineering. Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2000. Vita. Includes bibliographical references (p. 151-155). Ferromagnetic shape memory alloys (FSMA's) have shown large strains under magnetic field as magnetic variants in the rnartensite rearrange to accommodate the applied field. The theoretical maximum field-induced strain is 6.3% in Ni-Mn-Ga FSMA, and results of 6.1% are presented. These strain establish FSMA's as a new class of active materials with strains much larger than piezoelectric or magnetostrictive actuators. This work looks at Ni-Mn-Ga FSMA and explores the correlation between structure and properties, field induced strain at various stresses, and devices based on this new class of active materials. Martensitic Ni-Mn-Ga was found to have a tetragonal 14/mmm crystal structure with a cla ratio of 1.3 3. Twinning can occur on the { 112} planes. A twin boundary in such a crystal should cause a change of direction in the crystal axes of 7 .1 degrees. This angle was measured at 6.5 degrees in a single crystal of Ni-Mn-Ga. Twin angles and strains in the material are dependent on c/a. Surface magnetization measurements show that for this sample each variant is dominated by a single direction of magnetization, with a change in magnetization at the twin boundary. Using a constrained sample technique, the rnagnetocrystalline anisotropy was measured at 0.16 MJ/m3, and the permeability was measured at 22 along the easy axis of the crystal and 2.1 along the hard axis. A model is proposed which predicts a threshold type strain behavior both with internal field at constant stress, and with stress at constant internal field. An experimental apparatus was built to test these conditions. The predictions of the model were largely verified in experiment and field-induced strains up to 6.1 % are measured. Blocking stress matched that predicts at about 1. 7 MP a A prototype magnetic actuator based on Ni-Mn-Ga was built to demonstrate the feasibility of the technology. lbis actuator applied fields of up to 600 kNm to a slender sample in the transverse direction. A maximum deflection of 1.6 mm is achieved for an active material length of 41 mm. AC testing shows the response degrades at frequencies above a few Hz. by Steven J. Murray. Ph.D. 2005-08-22T23:12:28Z 2005-08-22T23:12:28Z 2000 2000 Thesis http://hdl.handle.net/1721.1/9163 45278002 eng M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582 182 p. 10548393 bytes 10548149 bytes application/pdf application/pdf application/pdf Massachusetts Institute of Technology |
| spellingShingle | Materials Science and Engineering. Murray, Steven J. (Steven James), 1974- Magneto-mechanical properties and applications of Ni-Mn-Ga ferromagnetic shape memory alloy |
| title | Magneto-mechanical properties and applications of Ni-Mn-Ga ferromagnetic shape memory alloy |
| title_full | Magneto-mechanical properties and applications of Ni-Mn-Ga ferromagnetic shape memory alloy |
| title_fullStr | Magneto-mechanical properties and applications of Ni-Mn-Ga ferromagnetic shape memory alloy |
| title_full_unstemmed | Magneto-mechanical properties and applications of Ni-Mn-Ga ferromagnetic shape memory alloy |
| title_short | Magneto-mechanical properties and applications of Ni-Mn-Ga ferromagnetic shape memory alloy |
| title_sort | magneto mechanical properties and applications of ni mn ga ferromagnetic shape memory alloy |
| topic | Materials Science and Engineering. |
| url | http://hdl.handle.net/1721.1/9163 |
| work_keys_str_mv | AT murraystevenjstevenjames1974 magnetomechanicalpropertiesandapplicationsofnimngaferromagneticshapememoryalloy |