NDTnet 1998 Aug, Vol.3 No.8

Full-Text - Abstract

SQUID magnetic flux sensors are well established in biomedicin, registrating the brain and heart activity of human beings in a non invasive way. In this field the excellent field resolution of SQUID sensors better than 100 fT/Hz even at lowest frequencies is used. SQUID sensors can also be used in non destructive testing by applying an eddycurrent technique. So far however this technique is not widely used, because for practical reasons the methode is still on a scientific level. For instance the man made noise level in an industrial ambient is several orders of magnitude higher than the field resolution of the SQUID sensor. So external noise discrimination techniques have to be applied to really use the unique properties of the SQUID sensor in practice.

We designed, fabricated and tested a laboratory system for non destructive evaluation with a high temperature superconductor DC-SQUID applying an eddycurrent technique. The sensor was immersed in a liquid nitrogen bath. The system was designed for the evaluation of surface defects. The signal was generated by a conformable room temperature eddycurrent probe and transmitted to the SQUID with a so called flux transformer.

Experimental results obtained on surface cracks in gas turbine blades will be presented. More over special attention will be payed on the preparation and layout of the conformable eddycurrent probes.

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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