【摘要】 在存在界面(或)底面时,用现有的时间反转法进行超声自适应聚焦的目标探测时,虽然可以获得处理增益,但却不能区分目标和界面(或底面)。这是因为界面反射波和目标反射波将完全相干叠加在一起形成相干峰。普通超声脉冲反射法在检测接近于界面的目标时也有同样的缺点。本文提出了一个改进的时间反转法即换元接收的时间反转法,这时界面反射波的相干峰将消失,因此它可以实现在有界面时目标是否存在的鉴别。更多还原

【Abstract】 In the presence of an interface (or bottom), the processing gain can be obtained in the ultrasonic self-adaptive focusing and the target detection of time reversal, but it can’t distinguish the target from the interface due tothe coherent superposition of the interface reflection wave and the target reflection wave. There exists same shortcomingin general pulse reflection method in ultrasonic flaw detection. A modified time reversal method (i.e. exchanging-elementtime reversal method) is proposed in this paper. With this method, the reflection waves on the interface from differentelement arrive on the receiver at different times and the coherent peak will disappear. Therefore, the target (flaw) canbe distinguished from the interface.更多还原