The Analysis of the Possible Use of Low-Temperature Alloys as an Auxiliary Layer between the Piezoelectric Transducer and a Test Piece with Complex Geometry

The possibility of using low-temperature Wood’s and Rose’s alloys as an auxiliary layer between the piezoelectric transducer and a test piece with continuously changing surface curvature radius and thickness is considered. The main purpose of the auxiliary layer is to provide a close acoustic contact between the piezoelectric transducer and the test piece with complex geometry. The materials of the auxiliary layer are selected so that the acoustic impedance values are close to those of carbon and alloy steels. This provides minimum reflection of the longitudinal wave from the boundary of the ‘steel — auxiliary layer’ system.  This makes it possible to control the system as a whole and therefore test thin-walled pieces (less than 1 mm thickness). The experiments and analysis of the calculations of the acoustic duct for similar systems have shown that the application of the auxiliary layer reduces test sensitivity (the minimum defect that can be detected equals the square of a disk reflector with the 1.4 mm radius), and thus is unacceptable for testing critical pieces.

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