Modern Ultrasonic Instruments for the Nondestructive Inspection of Metal Products

• Published in: Metallurgist (New York) 2003-07, Vol.47 (7-8), p.324-329
• Main Author: Samokrutov, A A
• Format: Article
• Language: English
• ISSN: 0026-0894; 1573-8892
• DOI: 10.1023/A:1027428918742

Ultrasonic methods of inspection have come a long way in the last 75 years, since our compatriot S.Ya. Sokolov claimed the world's first patent for an ultrasonic method of nondestructive testing. A large number of ultrasonic NT devices have been developed in the interim, due to the wide range of problems that must be solved in manufacturing. Thus, serious attention has also been given to the matter of optimizing their nomenclature. For the ultrasonic NT of metal products, manufacturers use general-purpose flaw detectors, specialized detectors, thickness gages, and instruments that measure the physicomechanical properties and stress state of products. Although there is a large variety of manual testers, most of them operate on the principle of the echo-pulse method of ultrasonic NT. Here, a pulse of ultrasonic vibrations is sent into the metal product from the surface that is in contact with the transducer. The transducer then receives echo signals reflected from the opposite wall of the product and from any defects that are present. When piezoelectric transducers (PZT) are used, transmission of the ultrasonic vibrations into the product and reception of the echo signals are done through a layer of a liquid couplant (water, oil, or special gels). Direct-coupled, discrete-coupled, or oblique transducers are used, depending on the goal of the test. In modern ultrasonic testers, the data signals are processed using digital technologies.