PVF2 Transducers for Nondestructive Evaluation of Ceramics and Brittle Materials.
Final rept. 1 Jul 77-31 Dec 80,
STANFORD UNIV CA EDWARD L GINZTON LAB OF PHYSICS
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An experimental system using PVP2 piezoelectric film as the active element has been demonstrated . It provides electronically-controlled, high-speed two-dimensional ultrasonic imaging on the surface of a ceramic sample. Scanning bulk waves are converted to surface waves at the ceramic surface. The system produces an electronically focused, highly convergent surface wave beam with an fl aperture, with variable focal length and is capable of arbitrary scanning patterns by changing the phase distribution of rf signals applied to a linear array of electrodes via a microcomputer. Simulated flaws on the surface were used in an initial investigation of the beam shape and imaging characteristics, which are found to be consistent with theoretical predictions. Using a frequency of 5 MHz, a resolution in the range of 1.5 to 2 mm is observed. The field of view of 10 cm in the present system could be increased to larger values by straight-forward extensions of the present design. The PVF2 transducer array is easily, quickly and inexpensively fabricated using standard photolithographic techniques. The system uses a scanning transmitter array and nonscanning receiving transducer. Substitution of a second, identical array as receiver would also be straightforward, to produce a unique double-scanning surface wave system with higher resolving power, dynamic range, and discrimination against artifacts. The PVF2 film is capable of operation at much higher frequencies, for higher resolving power, which could be exploited using a higher-frequency electronics section.
- Ceramics, Refractories and Glass