Development of innovative ultrasonic nondestructive evaluation considering properties of phononic cristal

本研究的目标是发展创新的声子晶体中超声波传播的数值分析方法，并将声波传播分析的数值结果应用于下一代超声波无损评估技术的研究。得到了以下结果：1. 在边界元法的基础上，结合快速多极子法和自适应交叉逼近，提出了声子晶体中超声波传播的快速模拟方法。2. 编写了声子晶体带结构分析的程序代码，使澄清特殊波传播的频带成为可能。3. 应用所开发的程序模拟了弹性波的传播和散射，包括在特定频率产生的停止带等异常现象。

The objectives of this research project is to develop innovative numerical methods for analyses of ultrasonic wave propagation in phononic cristal and to apply numerical results of the wave propagation analysis to investigate a next-generation ultrasonic nondestructive evaluation technique. The following results were obtained. 1. The fast simulation method for ultrasonic wave propagation in phononic cristal was developed on the basis of a boundary element method in conjunction with fast multipole method and adaptive cross approximation. 2. The program code for the analysis of band structures of phononic cristal was created to make it possible to clarify the frequency band of peculiar wave propagation. 3. The developed code was applied to simulate wave propagation and scattering of elastic waves including unusual phenomena like stop band generated at specific frequencies.