Development of a Passive/Active Defect Monitoring System Using Piezoelectric Material

本文介绍了一种基于压电材料的有源和无源缺陷监测系统的研制：在不加电流的情况下，被动地获得压电薄膜上的电势分布，并从压电薄膜中主动发射超声波，并利用响应进行逆分析来识别缺陷。所获得的主要结果概括如下：1.为了构建被动电位CT(Computer Tomography)方法，提出了一种从压电薄膜上观察到的电位分布来识别裂纹的逆分析方案。结果表明，该方法适用于三维裂纹的识别，即使在电势相互作用较大的情况下，也可以估计裂纹的位置、大小和穿透厚度多个裂纹的个数。将被动电位CT方法应用于复合材料缺陷的识别。用有限元方法分析了分层对粘贴在复合材料上的压电膜的电势的影响。结果表明，该方法适用于分层位置和大小的合理估计。为了构建被动/主动电位CT方法，研制了一种既可用于被动缺陷识别又可用于主动缺陷识别的智能传感器和装置。使用传感器可以发射超音波。考察了传感器位置和裂纹位置对检测结果的影响。结果表明，利用传感器获得的超声波响应可以对裂纹进行识别。

The present study deals with the development of the active and passive defect monitoring system using the piezoelectric material: the electric potential distribution is passively obtained on the piezoelectric film without application of an electric current and also supersonic wave is actively emitted from the piezoelectric film, and the responses are used for defect identification using the inverse analysis. The major results obtained are summarized as follows.1. For the construction of the passive electric potential CT (computed tomography) method, an inverse analysis scheme was proposed for identification of cracks from the electric potential distribution observed on the piezoelectric film. It was found that the method is applicable to identification of a three-dimensional crack, and estimation of crack location, size and numbers of through-thickness plural cracks, even when the interaction between electric potentials was significant.2. The passive electric potential CT method was applied to the identification of defect in composite materials. The effect of the delamination on the electric potential on piezoelectric film pasted on the composite materials was examined using the finite element method. It was found that the method is applicable to the reasonable estimation of the location and size of the delaminations.3. For the construction of the passive/active electric potential CT method, a smart sensor and devices were developed which can be used for both for the passive and the active identification of defects. Using the sensor the supersonic waves were emitted. The effect of the location of sensor and the crack was examined. It was found that the crack can be identified from the supersonic wave response obtained by the sensor.