Nondestructive evaluation of advanced materials by use of electromechanical interactions

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We have formulated electromagneto-mechanical properties for actuator materials like piezoelectric, magnetostrictive and photostrictive materials, and magnetic or conductive structural materials under stress and electromagnetic fields, which have been applied to integrity evaluation of advanced materials. The obtained results are as follows.1. For optic material PLZT, we have shown that the response of the photovoltage can be regarded as a first-order delay system for optic radiation, and a power law follows between light strength and the saturated electromotive force. Our accurate measurement implies that the photovoltage takes maximum around 370-380nm wavelength higher than the conventional result. In conclusion, the basic model is completed for application to integrity evaluation of optic materials.2. As monitoring method by piezoelectric highpolymer film. we examined laminated films and detection of inner wall flaws. According to the laminated directions of two films, we have two ki … More nds of films suitable for evaluation of the nominal stress from isotropic sensitivity and evaluation of shear strain. It is shown that the location and the shape of an inner wall flaw can be detected from the electric potential distribution of the film attached on the outer wall of a circular pipe.3. As for the formulation of magnetomechanical behavior of magnetic materials, we have paid attention to variation of the elastic coefficients. We have proposed determination method of the elastic coefficients of uniaxial materials under uniaxial stress and the magnetic field. That is, the independent five coefficients are determined by measuring the speeds of a longitudinal and two transverse waves and the longitudinal and transverse magnetostrictions. Appling the method to Ni and low carbon steel, we have obtained the elastic coefficients with hysteresis and stress dependence. From the studied, we have established magnetic and mechanical constitutive equations of ferromagnetic materials applicable to mechanical and electromagnetic design. Less