Master of Science, The Ohio State University, 2005, Graduate School

Committee: Not Provided (Other) Subjects:

Doctor of Philosophy, The Ohio State University, 2015, Mechanical Engineering

Magnetostrictive materials transfer energy between the magnetic and mechanical domains as they magnetize in response to applied stresses and deform in response to applied magnetic fields. The deformation that arises from this coupling directly causes the material's effective elastic moduli to depend on stress and magnetic field. This phenomenon, known as the Delta E effect, can be electrically modulated using electromagnets. Devices having an electrically-tunable stiffness can be developed by harnessing this effect. Such devices have broad application to the field of vibration control, particularly in instances where the vibration source or operating regime change over time. Although the static Delta E effect has been extensively measured in many man-made magnetostrictive materials, such as Galfenol (FeGa) and Terfenol-D (TbDyFe), this tunability has been seldom applied to the development of vibration control devices. Real-time tuning of the elastic moduli (i.e., the dynamic Delta E effect) has not been studied. Further, the effects of dynamic stress on the constitutive behavior of magnetostrictive materials are largely unknown, despite their critical importance to the modeling and design of many magnetostrictive systems, including dynamic sensors, energy harvesters, vibration dampers, and stiffness tuning devices. This work analytically, numerically, and experimentally explores the effects of dynamic stress on magnetostrictive materials and the use of the static and dynamic Delta E effect in the development of novel vibration control devices. Measurements of the quasi-static elastic response of Galfenol reveal that the Young's modulus and Delta E effect are stiffer and smaller, respectively, for small amplitude applied stresses than for large amplitude applied stresses. The static Delta E effect in Galfenol-based composite beams that are applied as adaptive vibration absorbers is studied by constructing nonlinear, dynamic models of their vibratory response. The (open full item for complete abstract)

Committee: Professor Marcelo Dapino (Advisor); Professor Giorgio Rizzoni (Committee Member); Professor Krishnaswamy Srinivasan (Committee Member); Professor Junmin Wang (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2009, Mechanical Engineering

Magnetostrictive materials have the ability to transfer energy between the magnetic and mechanical domains. They deform in response to magnetic fields and magnetize in response to stresses. Further, their stiffness and permeability depend on both magnetic field and stress. Galfenol, an alloy of iron and gallium, is an emerging magnetostrictive material which is unique for its combination of high magnetomechanical coupling and steel-like structural properties. Unique among smart materials, Galfenol can serve both as a structural element and as an actuator or sensor. This work presents nonlinear characterization and modeling of magnetization and strain of Galfenol, and a 3-D system-level model for Galfenol-based transducers. Magnetomechanical measurements are presented which reveal that Galfenol constitutive behavior is kinematically reversible and thermodynamically irreversible. Magnetic hysteresis resulting from thermodynamic irreversibilities is shown to arise from a common mechanism for both magnetic field and stress application. Linear regions in constant-stress magnetization curves are identified as promising for force sensing applications. It is shown that the slope of these linear regions, or the magnetic susceptibility, is highly sensitive to stress. This observation can be used for force sensing; the 19-22 at. % Ga range is identified as a favorable Galfenol composition for sensing, due to its low anisotropy with moderate magnetostriction and saturation magnetization. A thermodynamic framework is constructed to describe the magnetization and strain. An elementary hysteron, derived from the first and second laws, describes the underlying nonlinearities and hysteresis. Minimization of the energy of a single magnetic domain gives expressions for the hysteron states and accurately describes features of the constitutive behavior, including the stress dependence in the magnetization regions and the stress dependence of the location of the burst magnetization regio (open full item for complete abstract)

Committee: Marcelo Dapino PhD (Advisor); Joseph Heremans PhD (Committee Member); Ahmet Kahraman PhD (Committee Member); Menq Chia-Hsiang PhD (Committee Member) Subjects: Engineering; Materials Science; Mechanical Engineering