Mechanical Characters And Experimental Research On Giant Magnetostrictive Thin Film

Giant magnetostrictive film (GMF) is a new kind of functional material. The properties of high energy density, good dynamic response characteristics, prone to be made integration and miniaturization make it one of the ideal materials for driving component of micro actuators. At present, manufacturing methods of GMF and basic research of magnetic-mechanical coupling theory are mature. However, research on application-oriented static/dynamic properties, resonant characteristics and mechanical features is insufficient, which limits their applications. Therefore, investigations are conducted in this paper from theory and experimental aspects for the purpose of design and application of GMF devices.A high-power, high uniformity of combination drive coil is designed by solving the design problems using nonlinear programming method and taking magnetic power coefficient, structure and magnetic field intensity into account. Dc and Ac drive characteristics of the designed coil are analyzed and calculated using MATLAB and simulated calculation of magnetic field distribution characteristics of the coil is conducted using ANSYS software.On basis of the solving results of monolayer GMF magnetostrictive coefficient and reasonable assumptions on deformation mechanism of GMF, calculation formula of positive & negative compound GMF magnetostrictive coefficient is obtained by mathematical derivation method. Furthermore, magnetostrictive coefficient of multilayer compound GMF is also gained through promoting this method. In addition, according to the basic principle of theoretical mechanics and vibration mechanics, approximate solutions to parameters of GMF cantilever beam are calculated by equivalent width method. Parameters of Cu substrate monolayer GMF, Cu substrate positive& negative compound GMF and polyimide substrate positive & negative compound GMF are calculated using the method proposed in this paper. The resonance and super harmonic resonance frequencies of GMF cantilever are obtained by substituting these parameters into the equations of super harmonic and resonance frequencies of GMF.Basic research of static and dynamic characteristics of GMF cantilever is undertaken in the easily magnetized axial orientation. Systematic experimental research of dynamic characteristics of the GMF cantilever in the direction hard to be magnetized is explored: firstly, impact of bias magnetic field on GMF resonant characteristics is investigated, then main resonance and other super harmonic resonance vibration characteristics in hard magnetized direction are studied under the best bias magnetic field, finally it gives a simple discussion on relationship of best bias magnetic field and cantilever beam size.The research shows that the designed compound coil has good uniformity and its radial evenness can reach 5%o within the scope of 100mm which satisfies the driving demand completely; As the solution of compound GMF magnetostrictive coefficient reflects relationship of the material properties, film size and deformation, it can be used as a parameter optimization mathematical model of GMF; The calculated and experimental results of GMF cantilever beam resonance frequencies are similar, which demonstrate that the mechanical parameters solving method is effective; Experiments in hard magnetized axial orientation of GMF show that there exists an optimal bias magnetic field and it can improve the dynamic characteristics significantly; GMF cantilever beam can produce high order super harmonic resonance under the optimal bias magnetic field and vibration efficiency of the first three or four super harmonic resonances can satisfy the practical device application demand. This provides new ideas for reducing the driving frequency of GMF device, then realizing the miniaturization and integration.