Magnetic Field-Induced Phase Transformation in Magnetic Shape Memory Alloys with High Actuation Stress and Work Output

2010 ◽  
Author(s):  
Ibrahim Karaman ◽  
Dimitris C. Lagoudas
Keyword(s):  
Magnetic Field ◽  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Work Output ◽  
Magnetic Shape Memory ◽  
Magnetic Shape Memory Alloys

Constitutive Modeling of Magnetic Field-Induced Phase Transformation in NiMnCoIn Magnetic Shape Memory Alloys

2009 ◽  
Author(s):  
Dimitris C. Lagoudas ◽  
Krishnendu Haldar ◽  
Burak Basaran ◽  
Ibrahim Karaman
Keyword(s):  
Magnetic Field ◽  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Constitutive Modeling ◽  
Model Calibration ◽  
Magnetic Shape Memory ◽  
Magnetic Shape Memory Alloys ◽  
Working Principle ◽  
The Magnetic Field

In this work we model the magnetic field induced phase transformation (FIPT) of magnetic shape memory alloys (MSMAs). The working principle of such materials is described by the deformation of continua due to mechanical and magnetic forces. The cross coupling of mechanical and magnetic variables is captured by introducing nonlinear kinematics. The mechanical and magnetic constitutive equations are derived by a thermodynamic consistent way. Finally, the model prediction followed by model calibration is compared with the experimental results.

Stress-assisted reversible magnetic field-induced phase transformation in Ni2MnGa magnetic shape memory alloys

2006 ◽  
Vol 55 (4) ◽  
pp. 403-406 ◽  
Author(s):  
I. Karaman ◽  
H.E. Karaca ◽  
B. Basaran ◽  
D.C. Lagoudas ◽  
Y.I. Chumlyakov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Magnetic Shape Memory ◽  
Magnetic Shape Memory Alloys

Effects of Surface Pinning, Locking and Adaption of Twins on the Performance of Magnetic Shape-Memory Alloys

2011 ◽  
Vol 684 ◽  
pp. 177-201 ◽  
Author(s):  
Markus Chmielus ◽  
Peter Müllner
Keyword(s):  
Magnetic Field ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Surface Damage ◽  
Magnetic Shape Memory ◽  
Magnetic Shape Memory Alloys ◽  
Fatigue Lifetime ◽  
Twin Density ◽  
External Constraints ◽  
The Magnetic Field

We study the effect of surface modifications and constraints on the mechanical properties of Ni-Mn- Ga single crystals, which are imposed by (i) structural modifications near the surface, (ii) mounting to a solid surface, and (iii) guiding the stroke. Spark eroded samples were electropolished and characterized before and after each polishing treatment. Surface damage was then produced with spark erosion and abrasive wearing. Surface damage stabilizes and pins a dense twin-microstructure and prevents twins from coarsening. The density of twins increases with increasing degree of surface deformation. Twinning stress and hardening rate during mechanical loading increase with increasing surface damage and twin density. In contrast, when a damaged surface layer is removed, twinning stresses, hardening rate, and twin density decrease. Constraining the sample by mounting and guiding reduces the magnetic-field-induced strain by locking twins at the constrained surfaces. . For single-domain crystals and for hard magnetic shape-memory alloys, external constraints strongly reduce the magnetic-field-induced strain and the fatigue lifetime is short. In contrast, for selfaccommodated martensite and for soft magnetic shape-memory alloys, the twin-microstructure adapts well to external constraints and the fatigue lifetime is long. The performance of devices with MSMA transducers requires managing stress distributions through design and control of surface properties, microstructure, and constraints.

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