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Characterization and Modeling of Ferromagnetic Shape Memory NiMnGa Actuators

Wang, Xiang
http://rave.ohiolink.edu/etdc/view?acc_num=osu1213185504

Abstract Details

2008, Doctor of Philosophy, Ohio State University, Mechanical Engineering.
It has been shown that a magnetic field induced strain (MFIS) up to 10% can be obtained when Ferromagnetic Shape Memory Alloys (FSMAs) in the NiMnGa system are driven by perpendicular magnetic field and mechanical stresses. Prior experiments on single crystal NiMnGa have demonstrated the existence of reversible strains along the [001] crystallographic axis of a cylindrical rod under the application of collinear magnetic fields and stresses. This unusual behavior is used in this paper to develop a dynamic model for NiMnGa as operated in a solenoid transducer consisting of a driving coil and an external mass-spring-damper loading. A constitutive model to describe the motion of twin boundaries in the presence of energetically strong pinning sites is presented. The effective pinning strength is represented by an internal bias stress oriented transversely. This also explains the reduced maximum MFIS of -0.41% compared to possible -6% obtained from its variant structure. Stochastic homogenization is then used to account for variability in the bias stresses throughout the material and inhomogeneity in the interaction field intensity. Finally, the internal rod dynamics are modeled through force balancing with boundary conditions dictated by the constructive details of the transducer and mechanical load. The model is formulated in variational form, resulting in a second-order temporal system with magnetic field induced strain as the driving mechanism. Model results are compared with experimental measurements for validation and parameter identification. To provide a theoretical understanding of the frequency-dependent power losses in NiMnGa, this dissertation also extends the constitutive hysteresis model by incorporating eddy current and magnetic domain configuration(anomalous) losses; the analytical solutions are compared with finite element simulations. Finally, a parametric analysis of NiMnGa actuator performance based on energy delivery efficiency and the energy conversion efficiency is provided. The optimal stiffness ratios from the classical linear constitutive model and our nonlinear model are experimentally validated. The approach presented is useful for designing a control system, especially for the purpose of designing an energy efficient control system.
Marcelo Dapino (Advisor)
Stephen Bechtel (Committee Member)
Mark Walter (Committee Member)
Gregory Washington (Committee Member)

Recommended Citations

Citations

  • Wang, X. (2008). Characterization and Modeling of Ferromagnetic Shape Memory NiMnGa Actuators [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1213185504

    APA Style (7th edition)

  • Wang, Xiang. Characterization and Modeling of Ferromagnetic Shape Memory NiMnGa Actuators. 2008. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1213185504.

    MLA Style (8th edition)

  • Wang, Xiang. "Characterization and Modeling of Ferromagnetic Shape Memory NiMnGa Actuators." Doctoral dissertation, Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1213185504

    Chicago Manual of Style (17th edition)

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© 2008, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.