Development of simulator of ultrasonic waves in inhomogeneous and anisotropic body

本课题旨在开发一种超声数值模拟工具，用于对非均匀各向异性弹性固体进行准确、高效的超声无损评价。在超声波模拟中，数值方法的设计必须考虑以下优点：高精度和高效的计算成本，能够实现任意形状的缺陷和外边界，并对超声波检测中从传输到接收的所有波过程进行数学建模。利用数值模拟数据，还需要开发一种缺陷形状可视化的逆分析方法。为此，对以下课题进行了深入的研究。非均质各向异性弹性固体边界元分析程序的改进。改进了各向异性弹性固体中弹性波散射分析的边界元程序，提高了积分格式的效率，并采用了远场表达式。并提出了一种快速的多边界元法。超声检测的建模及边界元法与射线理论相结合方法的发展基于时不变线性系统的单个波过程对超声检测进行了建模。针对超声检测中的波过程之一散射过程，提出了一种结合边界元法和高斯波束理论的方法。各向异性固体的逆散射分析。提出了超声在各向异性弹性固体中的线性化逆散射分析方法，并讨论了其适用性。各向异性弹性固体的超声检测。对高性能钢进行了超声检测，研究了声各向异性对超声波在钢中的影响。

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.