In:
The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 109, No. 5_Supplement ( 2001-05-01), p. 2435-2435
Abstract:
Very large field-induced strains (e=6%) have been reported for Ni–Mn–Ga single-crystal ferromagnetic shape memory alloys (FSMAs) at room temperature. While these materials show the conventional thermoelastic shape memory effect upon transformation to the high-temperature phase, the magnetic field-induced strain occurs fully within the low-temperature, martensitic phase by twin-boundary motion. Fields of 320–400 kA/m (4–5 kOe) are sufficient to produce the maximum strain under opposing stresses of order 1 MPa. The blocking stress observed here is approximately 2 MPa but can be up to 10 MPa. An ac test system is described that applies an axial load to the sample via a spring. A magnetic field applied transverse to the load causes axial extension. Result indicate that the effective magnetostrictivity, d31 (output strain per unit field), is little changed over the actuation-frequency range accessible with our present power supplies, namely 320 Hz. The hysteresis in the strain-versus-field curves can be as large as 100 kA/m but in some samples is much less. The field dependence and stress dependence of the strain are well accounted for by the simple thermodynamic model. All parameters for the model can be measured from stress-versus-strain curves and magnetization-versus-field curves.
Type of Medium:
Online Resource
ISSN:
0001-4966
,
1520-8524
Language:
English
Publisher:
Acoustical Society of America (ASA)
Publication Date:
2001
detail.hit.zdb_id:
1461063-2
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