Research on nondestructive evaluation of inhomogeneous and anisotropic materials using highly accurate ultrasonic measurement

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In the present research, for the purpose of improving accuracy and reliability of ultrasonic nondestructive testing, fundamental characteristics of ultrasonic waves in inhomogeneous and/or anisotropic elastic solids are numerically analyzed, and material properties and defects in inhomogeneous and anisotropic solids are nondestructively evaluated by means of ultrasonic measurement with high accuracy.In numerical research of ultrasonic waves in solids, the following analyses were carried out ; 1. Boundary element analysis of scattering problems in anisotropic elastic solids, 2. Analysis of 3D scattering field by side-drilled hole and slit with uniform cross-section, 3. Multiple scattering analysis of elastic waves using fast multipole boundary element method, 4. Ultrasonic noise analysis by using multiple scattering approximation, and 5. Dispersion analysis of surface waves in a layered elastic solid.In the items 1 and 2, the boundary element methods with relevant fundamental solutions … More to concerned problems were developed and the items 3 and 4 are related to the multiple scattering analysis of a lot of inclusions in materials, which are numerical models for filaments of composite materials and grain boundaries in metals. In the item 5, the effect of an imperfect interface, on dispersive properties of time-harmonic extensional surface wave propagation in a pre-stressed symmetric layered composite was considered. These numerical analyses provided fundamental and valuable data for quantitative ultrasonic testing.In the researches of material evaluation, material damping of concrete was obtained, taking account of the energy loss in ultrasonic transducers and wave profiles, and a new optimal waveform, called matched pulse, in ultrasonic testing for concrete was proposed. Also inhomogeneity and anisotropy in steel plate were nondestructively evaluated by measuring leaky surface waves. In ultrasonic evaluation of defects, defect echoes were numerically simulated by means of multi-Gaussian beam method and 2.5D boundary element method, and some defect imaging methods like time reversal focusing and TDTG were applied to the ultrasonic array data. Less