| Giant magnetostrictive/piezoelectric laminate composites (MPLC) have remarkable magnetoelectric effect and they can interconvert energies between the magnetic field and electric field. The promising applications include microwave device, transducer, magnetic field sensors, and so on. They have received an increasing attention. The affecting factors of magnetoelectric conversion should be investigated, the coupling relation among each component should be analyzed and the theoretical model of conversion should be established, in order to design and develop the device effectively. This paper take the laminate magnetoelectric composites as the research object, the nonlinear magneto-elastic characteristic of giant magnetostrictive material, the magnetoelectric effect and its converse effect of MPLC have been investigated in detail and the main work is as follows.1. The nonlinear theoretical model is established, based on the Gibbs free energy and Jiles-Atherton model. The effective magnetic field He is introduced by considering the influences of the pre-stress on the magnetic properties of magnetostrictive material. The calculation results show that the model can predict the relation between the magnetostrictive strain and applied magnetic field under various compressive pre-stress levels. The relation between the magnetostrictive coefficient d33 and magnetic field is determined. The effect of the stress and the magnetic field on the Young's modulus of the materials can be predicted.2. The static characteristics of MPLC are analyzed by the finite element method, based on the minimum potential energy principal. According to the calculating and experimental data, the linear working range of magnetostrictive material was defined. In this working range the main relevant factors which affect the magnetoelectric effect of MPLC were discussed, including the number of layer, magnetization direction of magnetostrictive layer, polarization of piezoelectric layer and magnet direction etc. The results can be used for the optimization of the structure of MPLC.3. A finite element model is founded to solve the dynamic characteristics of the magnetoelectric composites, via Hamilton principles according to the standard square equations of magnetostriction and linear constitutive equations of piezoelectricity. The dynamic Young's modulus is gotten through the nonlinear theoretical model. The dynamic characteristics of Terfenol-D/PZT/Terfenol-D three-layered magnetoelectric composite are analyzed using MATLAB software. The calculating results show that the model can predict the change of output voltage with the time in different direct and alterative current magnetic fields.4. The finite element mode analysis of L-T typed Terfenol-D/PZT/Terfenol-D three layered magnetoelectric composites is carried out. The magnetoelectric voltage coefficient is 3280 mV.Oe-1 under the first order resonance state. The calculating results show that the magnetoelectric voltage coefficient under the first order resonance state is 1-2 order higher than it at low frequency state. The former 3 step model patterns are plotted using eigenfunction. Theoretic analysis and simulations show that the three layered magnetoelectric composites should work at 1st vibration mode; the delaminating phenomenon of the composites should be happened at 2nd and 3rd vibration mode leading to destroy the properties of magnetoelectric composites.5. The converse magnetoelectric coefficient of L-T magnetostrictive/piezoelectric multilayer magnetoelectric composite is calculated by means of equivalent circuit method. The relation between the performance parameters, the volume ratio of magnetostriction and piezoelectric layer and the converse magnetoelectric coefficient were studied. The results for the multilayer magnetoelectric composite provide a theoretical basis in the electric-elastic-magneto application, and it is helpful to optimize the structure of the magnetic field sensor.
|
PDF Full Text Request