OS1309 Detection and Identification of Defects and the Structural Health Monitoring Method by Ultrasonic Pulse Echo Method Using the Piezoelectric Film

The passive and active electric potential CT method was proposed by using piezoelectric film for identification of cracks and defects. This method is based on the principle of mutual conversion between mechanical strains and electric potential of piezoelectric material. A smart-layer was constructed using the piezoelectric film, and attached on a structure with a defect In the passive method, the piezoelectric film is used as a sensor of strain distribution. When the structure was subjected to a mechanical load, the electric potential distribution appeared passively on the piezoelectric film due to the direct piezoelectric effect The defect can be identified from the distribution with the help of inverse analysis. It was found that the crack could be identified reasonably, although the defect depth was not well estimated for the defects located far from the layer. In the active method, the piezoelectric film is used as an ultrasonic wave transducer. When the electric signal was input to the smart-layer, acoustic wave was actively emitted from the layer due to the inverse piezoelectric effect, and a reflected wave was received on the layer. This method is useful for the identification of defects far from the layer. In this study, the applicability of the active method was examined. It was found that vertical crack, parallel crack, slant crack and multiple cracks could be estimated well.