基于Mindlin板理论的偏移损伤成像数值仿真研究

提出了一种应用散射Lamb波的偏移技术对板结构中多部位损伤进行实时识别.基于Mindlin板理论,推导了板结构中弥散性弯曲波频率-波数域的快速偏移方法.首先对由线性传感器阵列激励和接收到的入射和散射波场在波数-频率域分别进行延拓,然后根据Huygens原理,结合波场延拓的时间一致性原理施加成像条件,对损伤进行成像识别.数值仿真研究采用基于Mindlin板理论的有限差分法模拟结构中含不同形状及尺寸损伤时的散射波场.对模拟散射波场进行偏移成像的结果表明该方法不仅能够识别多部位损伤的位置,还具有识别损伤程度的能力,其快速计算的优点满足在线结构健康监测系统对实时性的要求.

A SIMULATION STUDY ON MIGRATION TECHNIQUE FOR DAMAGE IMAGING BASED ON MINDLIN PLATE THEORY

Currently, structural health monitoring (SHM) is one of the most promising directions in the research field of smart materials and structures. However, up to now, most of the developed methods can only detect and localize the damage, quantitatively identify the extent of the damage, especially for multiple damages, remain a challenge task. This paper proposed a migration approach for identification of multiple damages in plate-like structure in real time using scattered Lamb waves. Based on Mindlin plate theory, the fast frequency-wavenumber domain migration technique for dispersive flexural wave was deduced for the first time. According to the Huygens' Principle, damages were imaged by applying a time-coincidence imaging condition after extrapolating the excited and scattered wave fields. Numerical simulation study employed a Mindlin plate theory-based finite difference method to generate synthetic scattered wave fields with damages of different shapes and sizes in the structure. Imaging results for the synthetic wave fields have demonstrated that the proposed method has the capability of not only localizing multiple damages but also identifying their extent; its advantage of fast calculation meets the requirement of real-time damage identification for an on-line structural health monitoring system.