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Proceedings Paper

Magnetic shape memory fatigue
Author(s): Oleg Heczko; Ladislav Straka; Outi Soderberg; Simo-Pekka Hannula
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Paper Abstract

Single crystal specimens of having compositions close to Ni2MnGa and exhibiting magnetic shape memory effect (MSME) were tested in a rotating magnetic field at a frequency of 5.7 Hz. The applied magnetic field, about 0.7 T was strong enough to induce the MSME. Test of one specimen was discontinued because of the structural failure of the specimens after 0.5 million cycles. Second specimen was tested up to 37 millions cycles. The evolution of the martensitic morphology and crack propagation were observed by optical microscopy. To characterize the magnetic shape memory behavior the simultaneous measurements of the field-induced strain and magnetization as a function of the magnetic field and external load was used. The full MSM effect, about 6% obtained prior the test, decreased to about 3% during the first million cycles. This value stayed then approximately constant up to 37 millions cycles of rotating magnetic field. The magnetic field needed to initiate the MSME increased. The observed behavior is discussed within the framework of observed martensitic band structure in the specimens and the existence of initial cracks and other obstacles for martensitic twin boundary motion.

Paper Details

Date Published: 16 May 2005
PDF: 8 pages
Proc. SPIE 5761, Smart Structures and Materials 2005: Active Materials: Behavior and Mechanics, (16 May 2005); doi: 10.1117/12.599814
Show Author Affiliations
Oleg Heczko, Helsinki Univ. of Technology (Finland)
Ladislav Straka, Helsinki Univ. of Technology (Finland)
Outi Soderberg, Helsinki Univ. of Technology (Finland)
Simo-Pekka Hannula, Helsinki Univ. of Technology (Finland)

Published in SPIE Proceedings Vol. 5761:
Smart Structures and Materials 2005: Active Materials: Behavior and Mechanics
William D. Armstrong, Editor(s)

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