Simulation of a Ferromagnetic Shape Memory Actuator in a Magnetic Field

2005 ◽  
Vol 881 ◽  
Author(s):  
B. Krevet ◽  
M. Kohl
Keyword(s):  
Magnetic Field ◽  
Mechanical Properties ◽  
Shape Memory ◽  
Permanent Magnet ◽  
Mechanical Performance ◽  
Inhomogeneous Field ◽  
Static Behavior ◽  
Two Phase ◽  
Magnetic Forces ◽  
Ferromagnetic Shape Memory

AbstractIn this work, we present simulations of the thermo-magneto-mechanical performance of a ferromagnetic SMA microactuator in the inhomogeneous field of a CoSm permanent magnet and compare it with experimental results. For the simulations, a combination of different finite element (FEM) programs is used allowing the coupling of electrical, thermal, magnetic and mechanical properties. The field of a permanent magnet is calculated along the trajectory of the microactuator, from which the magnetic forces Fmag and their gradients are derived. Shape memory forces FSME are calculated based on a two-phase macromodel. Both forces, Fmag and FSME, determine the quasi-static behavior of a NiMnGa microscanner, which has been proposed recently.

Modeling Smart Materials Using Hysteretic Recurrent Neural Networks

2009 ◽  
Author(s):  
Arun Veeramani ◽  
John Crews ◽  
Gregory D. Buckner
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Smart Materials ◽  
Real Time Control ◽  
Ferromagnetic Shape Memory Alloys ◽  
Two Phase ◽  
Time Control ◽  
Novel Approach ◽  
Three Phase ◽  
Ferromagnetic Shape Memory

This paper describes a novel approach to modeling hysteresis using a Hysteretic Recurrent Neural Network (HRNN). The HRNN utilizes weighted recurrent neurons, each composed of conjoined sigmoid activation functions to capture the directional dependencies typical of hysteretic smart materials (piezoelectrics, ferromagnetic, shape memory alloys, etc.) Network weights are included on the output layer to facilitate training and provide statistical model information such as phase fraction probabilities. This paper demonstrates HRNN-based modeling of two- and three-phase transformations in hysteretic materials (shape memory alloys) with experimental validation. A two-phase network is constructed to model the displacement characteristics of a shape memory alloy (SMA) wire under constant stress. To capture the more general thermo-mechanical behavior of SMAs, a three-phase HRNN model (which accounts for detwinned Martensite, twinned Martensite, and Austensite phases) is developed and experimentally validated. The HRNN modeling approach described in this paper readily lends itself to other hysteretic materials and may be used for developing real-time control algorithms.

Modulus Increase with Magnetic Field in Ferromagnetic Shape Memory Ni–Mn–Ga

2006 ◽  
Vol 17 (2) ◽  
pp. 123-131 ◽  
Author(s):  
Leann E. Faidley ◽  
Marcelo J. Dapino ◽  
Gregory N. Washington ◽  
Thomas A. Lograsso
Keyword(s):  
Magnetic Field ◽  
Shape Memory ◽  
Ferromagnetic Shape Memory

Structural Characterization of Co70-xNixGa30 Ferromagnetic Shape Memory Alloys

2008 ◽  
Vol 52 ◽  
pp. 103-108 ◽  
Author(s):  
Sidananda Sarma ◽  
A. Srinivasan
Keyword(s):  
Magnetic Susceptibility ◽  
Shape Memory ◽  
Room Temperature ◽  
Structural Parameters ◽  
Ac Magnetic Susceptibility ◽  
X Ray Diffraction ◽  
Ferromagnetic Shape Memory Alloys ◽  
Two Phase ◽  
X Ray ◽  
Ferromagnetic Shape Memory

Polycrystalline ingots of Co70–xNixGa30 (20 ≤ x ≤ 26) ferromagnetic shape memory alloy (FSMA) were prepared by arc melting elemental powders followed by homogenization at 1230 °C for 24 hrs and quenching in liquid nitrogen. Room temperature X-Ray diffraction (XRD) patterns of as-quenched samples exhibited single-phase tetragonal structure for alloy compositions with x = 21 to 26, and a two-phase structure (cubic A2-phase along with weak tetragonal phase) for the alloy with x = 20. Rietveld refinement was performed on the X-ray diffraction patterns to obtain the refined structural parameters. Differential Scanning Calorimeter (DSC) curves recorded from 30 °C to 250 °C revealed martensite-austenite and austenite-martensite transformations in all alloys except the alloy with composition x = 20. Low temperature ac magnetic susceptibility measurements confirmed the existence of martensitic transformations in the alloy with x = 20. The structural transformation temperatures show a linear variation with e/a ratio. All the alloys were ferromagnetic at room temperature. Curie temperature was determined using a high temperature ac magnetic susceptibility measurement set-up.

scholarly journals Nanoscale Mechanical Properties of Nanoindented Ni48.8Mn27.2Ga24 Ferromagnetic Shape Memory Thin Film

Scanning ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-5
Author(s):  
Xiaofei Fu ◽  
Chao Liu ◽  
Xili Lu ◽  
Xianli Li ◽  
Jingwei Lv ◽  
...  
Keyword(s):  
Thin Film ◽  
Mechanical Properties ◽  
Martensitic Transformation ◽  
Magnetron Sputtering ◽  
Shape Memory ◽  
Room Temperature ◽  
Shape Recovery ◽  
Recovery Ratio ◽  
Dc Magnetron Sputtering ◽  
Ferromagnetic Shape Memory

The structure and nanoscale mechanical properties of Ni48.8Mn27.2Ga24 thin film fabricated by DC magnetron sputtering are investigated systematically. The thin film has the austenite state at room temperature with the L21 Hesuler structure. During nanoindentation, stress-induced martensitic transformation occurs on the nanoscale for the film annealed at 823 K for 1 hour and the shape recovery ratio is up to 85.3%. The associated mechanism is discussed.

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