Abstract
An overview of a SQUID application for non-destructive testing (NDT) is given by focusing to recent highlights in the field of aeronautics. Research on NDT and non-destructive evaluation using a high-Tc SQUID is progressing at a remarkable pace. A testing procedure for extremely thick-walled structures is needed to construct megaliner aircraft. Artificial defects at a depth of up to 40 mm were measured in a bolted three-layer aluminum sample. Ferrous inclusions in aircraft turbine discs may originate cracks and eventually lead to engine failure. Detection techniques for the inclusion were developed using a high-Tc SQUID, and were then used for testing aircraft turbine discs at the aircraft engine manufacturer BMW Rolls-Royce GmbH. Aircraft wheels are subjected to enormous stress and braking-generated heat during take-off and landing. To safely detect small hidden flaws generated by the stress and heat an automated eddy-current testing system was developed using a high-Tc SQUID in combination with Joule-Thomson machine cooling mounted on a robot. The wheel testing, conducted at the Lufthansa hub at Frankfurt/M. Airport, proved the reliability and stability of the operation. Carbon-fiber composites are advanced composite materials and are used in aircraft and rockets because they are light, strong and heat-resistant. SQUID-NDT techniques applied to C/C increase the possibility of detecting defects and classifying carbon-fiber composites. Improvements in high-Tc SQUID performance and the development of a cryocooler with less magnetic noise have contributed to the progress of SQUID-NDT. Techniques to use the cryocooler without injuring the sensitivity of the high-Tc SQUID are discussed.
