Forward and Inverse Processing in Electromagnetic NDE Using Squids

McKirdy, D.M., Cochran, A. , Donaldson, G.B. and McNab, A. (1996) Forward and Inverse Processing in Electromagnetic NDE Using Squids. In: Review of Progress in Quantitative Nondestructive Evaluation 15, Seattle, WA, USA, 30 Jul - 04 Aug 1995, pp. 347-354. ISBN 9781461380276 (doi: 10.1007/978-1-4613-0383-1_44)

Abstract

Electromagnetic NDE has been successfully applied to the detection of surface cracks and is routinely used to locate flaws in airframes, pipelines and in steel offshore oil platforms. However, there are still many problems to be solved, particularly in the aviation industry, which require the detection of deeper flaws such as corrosion in multi-layered structures and cracks around rivet holes which are obscured by the head of the rivet. Most systems use coils as detectors (though Hall probes are occasionally used), which have low sensitivity at low frequencies due to the fact that the induced voltage is proportional to the rate of change of magnetic flux through the coil. Unfortunately it is necessary to use low frequencies to detect deep subsurface flaws on account of the skin-depth effect, otherwise the electromagnetic field cannot propagate down to the depth of the flaw. SQUID (Superconducting Quantum Interference Device) sensors are ideally suited to overcome the deficiencies of coils, because they are primarily detectors of magnetic flux which, together with their high sensitivity, makes the detection of deep flaws more likely. SQUIDs have been successfully used for measuring very low magnetic fields, particularly in the field of biomagnetism, and it is hoped to exploit this sensitivity to detect flaws at large stand-off distances for example in pipelines which are surrounded by thick layers of cladding.

• Item Type: Conference Proceedings
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Cochran, Professor Sandy
• Authors: McKirdy, D.M., Cochran, A., Donaldson, G.B., and McNab, A.
• College/School: College of Science and Engineering > School of Engineering > Systems Power and Energy
• ISBN: 9781461380276