中文摘要：

采用有限元方法对超声衍射时差（TOFD）检测技术进行分析。首先使用COMSOL有限元分析软件对超声TOFD检测技术建模;而后基于该模型分析超声波的产生、传播和接收过程;最后通过改变模型参数,研究缺陷几何尺寸对超声TOFD检测信号的影响。研究结果表明：超声TOFD信号中直通波、上端衍射波、下端衍射波、底面反射波信号的相位依次变化180°;当缺陷位于工件上表面或下表面时,探头只能接收到四种基本超声信号中的一部分。

英文摘要：

In order to describe the principle of ultrasonic TOFD, finite element method is used for analysis on ultrasonic time of flight diffraction（TOFI）） detecting technology. Firstly, use COMSOL for modeling;then process of generation,transmission and reception of ultrasonic are analyzed with the help of finite element model of TOFD; finally,effects of defect sizes on ultrasonic TOFD detecting signals is studied by changing model parameters. Research results show that the phase of direct wave, upper diffraction wave, lower diffraction wave, and bottom reflection wave in TOFD signals change in turn 180°; probe can only receive part of the four basic ultrasonic signals if the defect lies on the sample surface.