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

本研究以提高超声无损检测的精度和可靠性为目的，对非均匀和各向异性弹性固体中超声波的基本特性进行了数值分析，并通过高精度的超声测量对非均匀和各向异性固体中的材料性质和缺陷进行了无损评价。1.各向异性弹性固体散射问题的边界元分析；2.等截面边孔和缝隙的三维散射场分析；3.用快速多极边界元方法分析弹性波的多次散射；4.用多重散射近似进行超声噪声分析；5.层状弹性固体中表面波的频散分析。在第1和2项中，采用了具有相关基本解的边界元方法…第三项和第四项涉及材料中大量夹杂物的多重散射分析，它们是复合材料细丝和金属晶界的数值模型。在第五项中，考虑了非理想界面对预应力对称层状复合材料中时谐拉伸表面波传播的频散特性的影响。在材料评价研究中，考虑了超声换能器的能量损失和波形的能量损失，得到了混凝土材料的阻尼值，并提出了一种新的混凝土超声检测的最佳波形--匹配脉冲。通过对泄漏表面波的测量，对钢板内部的不均匀和各向异性进行了无损评价。在缺陷超声检测中，采用多高斯束方法和2.5维边界元方法对缺陷回波进行了数值模拟，并对超声阵列数据进行了时间反转聚焦和TDTG等缺陷成像处理。较少

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