NDTnet 1998 Aug, Vol.3 No.8

Abstract

The paper discusses the results of studying the applicability of the ultrasonic NDT methods for detection of explosion welding defects. Investigations were performed in the planar welded joints of 3 and 4 mm thick aluminium alloys.It is shown that the conventional techniques of ultrasonic testing do not provide enough information on the quality of welded joints of aluminium alloys, as the defects in the form of oxide films often found in these joints are almost transparent acoustically.In order to detect defects of the type of oxide films and assess the local strength of explosion welded joints from aluminium alloys, it is intended to use an acoustic microscope which operates in the frequency range of 15 to 50 MHz, provides the A-, B- and C-scanning, as well as storage and processing of the control results in an IBM PC computer.

Investigations were performed at the frequency of 25 MHz, by B- and C-scanning of the specimens of welded joints with the focusing transducer.Testing detected the typical for explosion welding wavy areas which are located in the zone of fusion of one metal with the other, as well as defects caused by the presence of oxide films, which was confirmed by metallographic investigations.The Figure gives a typical sample of a C-scan with a clear wavy pattern in thefusion zone. The dimensions of thescanning zone were 32 x 16 mm², scanning pitch being 0.lmm. The wave length of the wavelike process in- the fusion zone is between 0.1 and 0.8 mm, which was confirmed by metallographic investigations.
The feasibility of measurement of these waves amplitude was demonstrated with a B-scan performed normal to the direction of the wavelike process propagation.

C-scan of the explosion welding fusion zone

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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