Abstract
An eddy-current-based SQUID NDE system was constructed for in situ inspectionof copper heat exchanger tubes using an HTS SQUID gradiometer and aHelmholtz-type-coil inducer. Thin copper tubes of 6.35 mm in diameter and0.8 mm in thickness were selected from products as specimens. Artificial flaws of100 µm in width, 15–25 mmin length and 10–50 µm in depth were made on the surfaces of the tubes. The tubes were moved at a velocity of1.6–32 m min−1 by a motor through the Helmholtz-type coil, which generated an excitation field of10 µT at 3 kHz. The SQUID NDE system could detect an anomalous magnetic response due to a flaw of10 µm in depth on thetube moving at 32 m min−1.
Published Version
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