High spatial resolution imaging for structural health monitoring based on virtual time reversal
High spatial resolution imaging for structural health monitoring based on virtual time reversal
复制标题
基于虚拟时间反转的高空间分辨率成像结构健康监测
DOI：
10.1088/0964-1726/20/5/055018
复制
发表时间：
2011-05-01
影响因子：
4.1
通讯作者：
Shao, Zhixue
中科院分区：
文献类型：
--
作者：
Cai, Jian;Shi, Lihua;Shao, Zhixue
兰姆波在板状结构健康监测中有着广泛的应用。由于频散效应，兰姆波包将被拉长，损伤识别的分辨率将受到严重影响。这种影响可以通过时间反转过程（TRP）自动补偿。然而，补偿波的时间信息也同时被去除。为了提高兰姆波探测的空间分辨率，提出了虚拟时间反转（VTR）技术。在录像机中，为了保持时间信息，采用了一种可变元件的激励和接收机制（CERM），而不是传统的固定激励和接收机制（FERM）。此外，复杂的TRP过程被简单的信号操作所取代，这可以节省用于记录和产生时间反演兰姆波的硬件成本。在理论分析了VTR对色散损伤散射信号的影响后，讨论了阶跃脉冲激励下VTR的实现，包括损伤检测路径传递函数的获取。在此基础上，提出了一种基于VTR的稀疏压电阵列延迟求和成像方法，以提高其空间分辨率。实验验证表明，VTR对铝板中A0模损伤散射波包进行了部分再压缩和聚焦，并保留了其时间信息。基于VTR的成像方法可以清晰地显示板中的单个损伤和双相邻损伤，具有较高的空间分辨率。
Lamb waves are widely used in structural health monitoring (SHM) of plate-like structures. Due to the dispersion effect, Lamb wavepackets will be elongated and the resolution for damage identification will be strongly affected. This effect can be automatically compensated by the time reversal process (TRP). However, the time information of the compensated waves is also removed at the same time. To improve the spatial resolution of Lamb wave detection, virtual time reversal (VTR) is presented in this paper. In VTR, a changing-element excitation and reception mechanism (CERM) rather than the traditional fixed excitation and reception mechanism (FERM) is adopted for time information conservation. Furthermore, the complicated TRP procedure is replaced by simple signal operations which can make savings in the hardware cost for recording and generating the time-reversed Lamb waves. After the effects of VTR for dispersive damage scattered signals are theoretically analyzed, the realization of VTR involving the acquisition of the transfer functions of damage detecting paths under step pulse excitation is discussed. Then, a VTR-based imaging method is developed to improve the spatial resolution of the delay-and-sum imaging with a sparse piezoelectric (PZT) wafer array. Experimental validation indicates that the damage scattered wavepackets of A0 mode in an aluminum plate are partly recompressed and focalized with their time information preserved by VTR. Both the single damage and the dual adjacent damages in the plate can be clearly displayed with high spatial resolution by the proposed VTR-based imaging method.