Multiple Electrodes Active Pulse Echo Method Using a Piezoelectric Film for Crack Identification

Abstract

The present authors proposed the smart layer composed of piezoelectric film and flexible printed circuit for the crack identification. The smart layer was used in the passive electric potential CT method, which identifies cracks from the electric potential distribution incurred due to the direct piezoelectric effect on a piezoelectric film pasted on a structure. On the contrary by applying an electric pulse actively on an electrode on the smart layer, a pulse echo can be emitted due to the inverse piezoelectric effect. Reflected waves received at several electrodes can be used for crack identification. In the present study a large number of electrodes on the smart layer were used for emitting the pulse echo and also for receiving the reflected echo. The mono probe method and the dual probe method were proposed. The multiple electrodes active pulse echo method using the smart layer was applied to the identification of through-thickness cracks. It was found that the cracks can be easily detected and a rough estimation of the crack location can be made by receiving flaw echo and bottom echo in the mono probe method. The dual probe method was found useful for detailed identification of the cracks from the time-of-flight of reflected signals for various combinations of the pulsing and receiving electrodes.