A migration technique used in geophysical exploration to interpret the backscattering wave field and to image the flaws in the structure is proved to be an effective method detecting and imaging multiple damages in a plate structure. A structural health monitoring system (SHMS) with integrated actuators/sensors can be used to activate and receive lowest-order antisymmetric Lamb waves. The proposed approach is executed by a two-dimensional finite difference method both in simulating the reflection waves and in implementing the prestack migration. An analytical solution based on Mindlin plate theory is utilized to verify the accuracy of the numerical algorithm. An excitation-time imaging condition is presented based on the ray tracing concept, and prestack reverse-time migration is executed to propagate the reflection energy back to the damages. The plate is imaged in terms of the transverse deformation velocity after migration is executed. Thus the dimensions, locations and seriousness of the damages can be displayed visually. Numerical examples show that multiple damages can be detected effectively and the image of the damages correlates with the characters of target damages.%通过地球物理勘探中的偏移技术解释波场后向散射和损伤成像,被证明是一种探测板式结构中多重损伤成像与探测的有效方法.集驱动、传感一体化方法可以用来激发和接受低阶反对称Lamb波.这种方法利用二维有限差分法模拟反射波和进行叠前偏移操作,并由Mindlin板理论的解析解验证数值计算的精确度.对于基于射线追踪概念的时间激励成像条件也被运用到损伤探测中.用叠前逆时偏移技术将损伤反射能量传播回来,同时对偏移后承受横向变形的板进行照相.这样损伤的位置、尺寸以及严重程度可以直观地展示出来.数值算例显示多重损伤可以被有效地探测到,并且损伤成像与目标损伤的特征密切相关.
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