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

本研究涉及使用压电材料的主动和被动缺陷监测系统的发展：电势分布被动地获得在压电膜上，而不施加电流，也超声波主动地从压电膜发射，并且响应用于使用逆分析的缺陷识别。主要研究结果如下：1.针对被动电位CT（computed tomography）方法的构造，提出了一种从压电薄膜上观察到的电位分布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，以及裂纹位置、尺寸和贯穿厚度的多个裂纹的数量的估计，即使当电势之间的相互作用是显着的.将被动电位CT法应用于复合材料缺陷的识别。采用有限元方法研究了分层对粘贴在复合材料上的压电薄膜电势的影响。结果表明，该方法适用于合理估计分层的位置和大小.为了构建被动/主动电位CT方法，开发了一种智能传感器和装置，可用于被动和主动识别缺陷。使用传感器发射超声波。分析了传感器位置和裂纹位置的影响。结果发现，裂纹可以识别由传感器获得的超声波响应。

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.