Development of simulator of ultrasonic waves in inhomogeneous and anisotropic body

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This research project aims at developing a numerical simulation tool of ultrasonic waves for accurate and efficient ultrasonic nondestructive evaluation of an inhomogeneous and anisotropic elastic solid. In simulation of ultrasonic waves, the numerical method has to be designed taking account of the following advantages; high accuracy and efficient computational cost, being capable of arbitrary shaped defects and outer boundaries, and mathematical modeling of all wave processes from transmission to receipt in ultrasonic testing. Using numerical data in simulation, an inverse analysis method also needs to be developed for visualization of defect shapes. For these purposes, intensive research has been done for the following subjects.1.Improvement of programming code of boundary element analysis for inhomogeneous and anisotropic elastic solid.A BEM code for scattering analysis of elastic waves in anisotropic elastic solid has been improved by carrying out the integration scheme more efficiently and using far-field expressions. Also a fast multiple boundary element nethod has been developed.2.Modeling of ultrasonic testing and development of combined method of BEM and ray theoryUltrasonic testing has been modeled by individual wave processes based on the time invariant linear system. For scattering process which is one of wave processes in ultrasonic testing, a combined method of BEM and Gaussian beam theory has been developed.3.Inverse scattering analysis in anisotropic solid.Linearized inverse scattering analysis has been developed for ultrasonic waves in anisotropic elastic solid and its applicability has been discussed.4.Ultrasonic testing for anisotropic elastic solid.Ultrasonic testing for high performance steel has been done to investigate the effect of acoustically anisotropic property on ultrasonic waves in steel.