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Characterization and modeling of ferromagnetic shape memory Ni-Mn-Ga in a collinear stress-field configuration

Faidley, LeAnn Elizabeth
http://rave.ohiolink.edu/etdc/view?acc_num=osu1149085270

Abstract Details

2006, Doctor of Philosophy, Ohio State University, Mechanical Engineering.
Ferromagnetic Shape Memory Alloys (FSMAs) in the Nickel-Manganese-Gallium system have been shown to exhibit large magnetically induced strains of up to 9.5% due to magnetically driven twin variant reorientation. In order for these strains to be reversible, restoring stresses or magnetic fields need to be applied orthogonal to the drive field. This leads to a typical implementation of Ni Mn-Ga in applications involving the use of electromagnets, which tend to be heavy, bulky and narrowband. This dissertation presents the investigation of the behavior of Ni[50]Mn[28.7]Ga[21.3] in a unique configuration in which a magnetic field produced by a solenoid is applied along the axis of a cylindrical rod and the strain is measured collinearly to the field while axial loads are applied. A strain mechanism is proposed where imperfections and inclusions in the sample create internal stresses that provide the restoring forces while also limiting the maximum strain from the sample by limiting the motion of the twin boundaries. This mechanism explains the presence and reduced magnitude of the -0.41% quasi-static strain that has been measured in this sample in the collinear configuration. This dissertation also expands the experimental testing of Ni-Mn-Ga into the dynamic domain most usually found in applications through a set of swept-sine tests. These tests demonstrate a 250% shift of elastic modulus with applied dc bias field that makes these materials extremely promising for variable stiffness applications. Finally, this document presents a model for the strain of Ni-Mn-Ga. A Gibb's Free Energy approach is used to describe an idealized hysteresis kernel that does not account for the inhomogeneities in pinning site strength and internal field. A stochastic homogenization method is then implemented that estimates the inhomogeneities as probability distributions. The implementation and testing of this model is discussed in detail and results showing simulations that fall within 3% of the data are presented demonstrating the power of this method for future design and control of applications for Ni-Mn-Ga in solenoid based transducers.
Marcelo Dapino (Advisor)
Gregory Washington (Advisor)
Stephen Bechtel (Other)
C.H. Menq (Other)
152 p.
Engineering, Mechanical
Ferromagnetic Shape Memory Alloys; Ni-Mn-Ga; collinear configuration

Recommended Citations

Citations

  • Faidley, L. E. (2006). Characterization and modeling of ferromagnetic shape memory Ni-Mn-Ga in a collinear stress-field configuration [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1149085270

    APA Style (7th edition)

  • Faidley, LeAnn. Characterization and modeling of ferromagnetic shape memory Ni-Mn-Ga in a collinear stress-field configuration. 2006. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1149085270.

    MLA Style (8th edition)

  • Faidley, LeAnn. "Characterization and modeling of ferromagnetic shape memory Ni-Mn-Ga in a collinear stress-field configuration." Doctoral dissertation, Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1149085270

    Chicago Manual of Style (17th edition)

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© 2006, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.