NDTnet 1998 Aug, Vol.3 No.8

Full-Text - Abstract

In 1994 a Germany-wide usergroup, was established to attain comparisons and common improvements on pulse-echo-testing-methods for concrete-building-structures. This cooperation turned out to be very aspiring for the participating teams. While pulse-echo-testing was rarely applied to realistic specimen before, the improvements and experiences gained since then led to a significantly better estimation of the facilities and limitations of the different applied techniques [1].

The equipment submitted by the University Of Dortmund is the pulse-echo-testing- system NFUS2300, which enables a fast data-entry and -computation to B-Scans. Up to 10 "shots" per second are directly encoded to indicated-color or grayscale-lines into a computergenerated B-Scan. While the information of the signal-amplitude and -phase together with the deviations produced by moving the ultrasonic transducer on the concrete-surface is preserved within the B-Scan, a whole 2-D sketch of the specimen along the transducer's path comes to the tester's eyes [2]. Especially very slight deviations produced by voids or ducts in deeper locations often stay recognisable. To increase the contrast and simultaneously suppress to much scattering by the gravel a concrete-specific low-pass-filtering of the signal is indispensable. Additionally the excitation-pulse for the transducer must be most perfect adapted to the transducer and concrete that is actually in use. All these adjustments are at the testers disposal and require some experience with the testing system. According to this a number of mesurements made at the specimen of the usergroup as well as newer testings at laboratory- specimen with some typical results will be shown and discussed. An estimation of the specific facilities of the equipment in use and of potential improvements in the future will be presented.

References:
[1] Wollbold, F. and Neisecke, J.: Ultrasonic-Impulse-Echo- Technique - Advantages of an Online-Imaging technique for the Inspection of Concrete, In: Proceedings of the International Symposium NDT in Civil Engineering, Berlin, 26.-28. 09. 95: Deutsche GeselIschaft für Zerstörungsfreie Prüfung, Vol.2, pp. 1135-1143
[2] Hillger, W.: Inspection of Concrete by Ultrasonic-Pulse-Echo- Technique, In: Proceedings of the 6th European Conference on Non Destructive Testing, Nice 1994, pp. 1159-1163

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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