NDTnet 1998 Aug, Vol.3 No.8

Full-Text - Abstract

Utilization of digital automatic ultrasonic systems to map internal discontinuities in materials increases everyday as a consequence of better productivity and facility of results interpretation provided by this technique. The influence of the experimental and signal processing setup in the discontinuity imaging is frequently imprecise and difficult to be theoretically evaluated. Some parameters that have an influence in the final discontinuity mapping are the type of transducer (frequency, diameter, bandwidth, focus, etc.), equipment configurations (gain, filtering, frequency and bandwidth of the excitation pulse, etc.), positioning system parameters (step, gap between transducer and the surface, stability, coupling, etc.), evaluation criteria and signal processing.

The statistical planning of experiments is proposed in this paper as a way of evaluate some of these parameters (separately or in combination) with a minimum of experimental work but with a reasonable level of reliability. As an example of application, three experimental factors (transducer, pulse attenuation and filtering, evaluation criteria) were evaluated to map planar discontinuities in a C-Scan images by immersion technique. Among the statistical planning of experiments methods, the complete factorial at two levels was chosen due to the simplicity and powerfulness that it can treat problems with few variables. The transducers used have frequencies of 5 and 10MHz and are broadband (100%). The pulse attenuation and filtering parameters were the default of the equipment for the first configuration, and for the second a improved by visual observation. The evaluation criteria used are represented by two reference curves. The influence of the parameters were analyzed as the percent of area error related to the real discontinuity image. The results indicated the main parameters and their combinations, that are more influent in the results.

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:

Publication Contact:
7th ECNDT, Park Alle 345, DK-2605 Broendby, Denmark, Fax: +45 46 26 70 11, Email: 101373.3414@compuserve.com