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High Efficiency Photoacoustic Cell Utilizing PZT for Flaw Detection

IP.com Disclosure Number: IPCOM000052831D
Original Publication Date: 1981-Jul-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Vigliotti, DR: AUTHOR [+2]

Abstract

A photoacoustic cell is described for determining the location and size of flaws in thin solid materials by measuring the photoacoustic response resulting from absorption by a solid in contact with the liquid.

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High Efficiency Photoacoustic Cell Utilizing PZT for Flaw Detection

A photoacoustic cell is described for determining the location and size of flaws in thin solid materials by measuring the photoacoustic response resulting from absorption by a solid in contact with the liquid.

The photoacoustic cell shown in the drawing utilizes a hollow cylindrical PZT (lead-zirconium-titanate) element 1 to form the main part of the cell. The advantages of this cell are (1) a large surface detection area which enhances the total force on the piezoelectric material to obtain maximum piezoelectric voltage,
(2) a means for coupling thermal waves from the solid under investigation which results in a large enhancement in the oscillating pressure in the photoacoustic cell. This enhancement factor can be derived from the theory described in [1] and is similar to experimental results described in [5]. Although cylindrical PZT has been used extensively (e.g., [6]), this system is used in conjunction with optically high abosorbing solids for flaw detection.

The PZT cylinder 1, polarized in its thickness direction, forms the major portion of the cell. A phase-sensitive detection scheme includes a lock-in amplifier for detecting a frequency synchronized signal and a pre-amplifier FET for matching impedances between internal parts of the cell and the amplifier. The cell is filled with water 2 with the sample 5 under test affixed by a flange 3 and a 0-ring 4 at one end. The thermal wave produced by the absorption of a modulated light beam at the water-solid interface produces a pressure wave that is greatly enhanced by the water-solid interface compared to a solid-air interface. This has been shown theoretically, utilizing the...