NDTnet 1998 Aug, Vol.3 No.8

Full-Text - Abstract

Introduction
Weld inspection is often accompanied with the separation between geometrical indications and indications from defects like cracks, especially if the cracks are starting in the root area. On the other hand a high probability of detection (POD) of small cracks is required. This requirement needs sensitive techniques like the 45° shear wave technique using the mirror effect approach. The question after defect detection is to find a suitable method for defect sizing. Since more than twenty years the Time Of Flight Diffraction technique (TOFD) is still under discussion for this purpose and there is an agreement in the world of NDT experts about the ability and the limitations for this application.

Experiments using the TOFD-Technique
In national standards and regulations and even in a new European draft standard the potential of the TOFD technique for detection is described and sometimes required inguide lines and technical papers of manufacturers. This was the reason for the experiments with the TOFD arrangement in the ultrasonic laboratory of BAM. The main task of the examinations was the comparison of the detectability of surface breaking cracks measured with common methods and the TOFD approach at carbon steel weldsand on stainless steel welds. An example received at a test specimen is shown below. The tip diffraction echo of a 5 mm deep spark eroded notch is clear visible, as well as the lateral wave and the back wall echo. In the contribution the results obtained at different deep notches and defects are presented and critical discussed with special emphasis to the defect detection.

Fig.

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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