High-energy absorption in bulk ferromagnetic shape memory alloys (Ni 50 Mn 29 Ga 21 )

Gans, Eric; Henry, Christopher P.; Carman, Greg P.

doi:10.1117/12.540124

Cited by 10 publications

(9 citation statements)

References 6 publications

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“…look very similar to the loops reported for single crystals of Ni-Mn-Ga subjected a cycle of tension and compression [36]. The slope of the nearly vertical regions corresponds to the un-twinned modulus, and the nearly horizontal regions correspond to the modulus when twins are mobile.…”

Section: Cyclic Stress-strain Modelingsupporting

confidence: 63%

Section: Magnetic Materialsmentioning

confidence: 99%

“…More recently full tension and compression loops were measured in Ni-Mn-Ga single crystals, and show a large hysteresis [36,37]. The large hysteresis was not the most desir-able feature for an actuator material, but could be a useful feature for a damping material.…”

Section: Ni-mn-gamentioning

confidence: 99%

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Energy absorption in Ni-Mn-Ga-polymer composites

Feuchtwanger

Michael

Juang

et al. 2003

Journal of Applied Physics

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In recent years Ni-Mn-Ga has attracted considerable attention as a new kind of actuator material. Off-stoichiometric single crystals of Ni 2 MnGa can regularly exhibit 6% strain in tetragonal martensites and orthorhombic martensites have shown up to 10% strain when subjected to a magnetic field. These crystals are brittle and the production of single crystals can be quite costly. Terfenol-D, a commercially available giant-magnetostrictive material, suffers from some of the same drawbacks. It was found that composite materials made from Terfenol-D particles in a polymeric matrix could solve the issue of the brittleness while retaining a large fraction of the strain output of the alloy. At first glance a similar approach could be used to solve the brittleness issue of Ni-Mn-Ga, but the low blocking force of these alloys reduces the chances of achieving a Ni-Mn-Ga/polymer composite actuator. However, the stress-strain loops for Ni-Mn-Ga show a large mechanical hysteresis. This ability to dissipate energy makes this alloys very desirable for damping applications, and by putting particles of Ni-Mn-Ga in a composite, their brittleness becomes less of an issue.It is shown that by curing Ni-Mn-Ga/polymer composites under a magnetic field it is possible to align the particles in chains and to orient them so they will respond to a uniaxial load. The magnetic measurements show that there are twin boundaries in the particles that can be moved by an external stress. Stress-induced twin boundary motion in the particles is confirmed more directly by x-ray diffraction measurements, transmission electron microscope micrographs, and scanning electron microscope micrographs. Finally we demonstrate the ability of the Ni-Mn-Ga/polymer composites to dissipate mechanical energy when subjected to cyclic loads. The Ni-Mn-Ga/polymer composites can dissipate more than 70% of the energy they are given in every cycle, while pure polymer, Fe-filled and Terfenol-filled control samples dissipate less than 50% of the input energy in every cycle. The additional loss in these composites is shown to be due to the motion of twin boundaries. Simple numerical models reproduce the cyclic stress-strain behavior of the composites and explain non-conventional features observed in the Ni-Mn-Ga composites.

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Section: Cyclic Stress-strain Modelingsupporting

confidence: 63%

Section: Magnetic Materialsmentioning

confidence: 99%

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Energy absorption in Ni-Mn-Ga-polymer composites

Feuchtwanger

Michael

Juang

et al. 2003

Journal of Applied Physics

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“…The tan δ reported for the FSMA single crystals showed a loss that was dependent on the strain amplitude imposed on the crystals. The tan δ of the materials increased from 0.6 to 1.1 as the strain level went from 1% to 3.7% [36]. The first studies on the use of Ni-Mn-Ga/polymer composites as energy absorbers were published by the author and they predate the work on single crystals and polycrystals mentioned above.…”

Section: Magnetic Materialsmentioning

confidence: 99%

Large energy absorption in Ni–Mn–Ga/polymer composites

Feuchtwanger

Richard

Tang

et al. 2005

Journal of Applied Physics

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In recent years Ni-Mn-Ga has attracted considerable attention as a new kind of actuator material. Off-stoichiometric single crystals of Ni 2 MnGa can regularly exhibit 6% strain in tetragonal martensites and orthorhombic martensites have shown up to 10% strain when subjected to a magnetic field. These crystals are brittle and the production of single crystals can be quite costly. Terfenol-D, a commercially available giant-magnetostrictive material, suffers from some of the same drawbacks. It was found that composite materials made from Terfenol-D particles in a polymeric matrix could solve the issue of the brittleness while retaining a large fraction of the strain output of the alloy. At first glance a similar approach could be used to solve the brittleness issue of Ni-Mn-Ga, but the low blocking force of these alloys reduces the chances of achieving a Ni-Mn-Ga/polymer composite actuator. However, the stress-strain loops for Ni-Mn-Ga show a large mechanical hysteresis. This ability to dissipate energy makes this alloys very desirable for damping applications, and by putting particles of Ni-Mn-Ga in a composite, their brittleness becomes less of an issue. It is shown that by curing Ni-Mn-Ga/polymer composites under a magnetic field it is possible to align the particles in chains and to orient them so they will respond to a uniaxial load. The magnetic measurements show that there are twin boundaries in the particles that can be moved by an external stress. Stress-induced twin boundary motion in the particles is confirmed more directly by x-ray diffraction measurements, transmission electron microscope micrographs, and scanning electron microscope micrographs. Finally we demonstrate the ability of the Ni-Mn-Ga/polymer composites to dissipate mechanical energy when subjected to cyclic loads. The Ni-Mn-Ga/polymer composites can dissipate more than 70% of the energy they are given in every cycle, while pure polymer, Fe-filled and Terfenol-filled control samples dissipate less than 50% of the input energy in every cycle. The additional loss in these composites is shown to be due to the motion of twin boundaries. Simple numerical models reproduce the cyclic stress-strain behavior of the composites and explain non-conventional features observed in the Ni-Mn-Ga composites.

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“…The slight rise and drop in the damping can be attributed to the presence of twin boundaries. 10 With increasing field, the field-preferred twin variants are initiated with the introduction of the twin boundaries between the two variants. With increasing fields, the twin boundaries continue to exist, resulting in constant or increased damping.…”

Section: Transverse Field Testsmentioning

confidence: 99%

Electrical stiffness tuning in ferromagnetic shape memory Ni-Mn-Ga

Sarawate

Dapino

2007

SPIE Proceedings

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This paper is focused on the dynamic characterization of field-induced mechanical stiffness changes under varied bias magnetic fields in commercial-quality, single-crystal ferromagnetic shape memory Ni-Mn-Ga. Prior to the dynamic measurements, a specified variant configuration is created in a prismatic Ni-Mn-Ga sample through the application and subsequent removal of collinear or transverse bias magnetic fields. Base excitation is used to measure the acceleration transmissibility across the sample, from where the resonance frequency is directly identified. These measurements are repeated for various collinear and transverse bias magnetic fields ranging from 0 to 575 kA/m, which are applied by a solenoid and an electromagnet, respectively. A 1-DOF model for the Ni-Mn-Ga sample is used to calculate the mechanical stiffness from resonance frequency measurements. A resonance frequency increase of 21% and a stiffness increase of 52% are observed in the collinear field tests. In the transverse field tests, a resonance frequency decrease of -36% is observed along with a stiffness decrease of -61%. The damping exhibited by this material is low in all cases (≈ 0.03). The measured dynamic behaviors make Ni-Mn-Ga well suited for vibration absorbers with electrically-tunable stiffness.

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High-energy absorption in bulk ferromagnetic shape memory alloys (Ni 50 Mn 29 Ga 21 )

Cited by 10 publications

References 6 publications

Energy absorption in Ni-Mn-Ga-polymer composites

Energy absorption in Ni-Mn-Ga-polymer composites

Large energy absorption in Ni–Mn–Ga/polymer composites

Electrical stiffness tuning in ferromagnetic shape memory Ni-Mn-Ga

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