Experimental Study of Detectable Sizes of Surface Flaws on Copper Tubes by Nondestructive Inspection Using High-$T_{\text{c}}$ Superconducting Quantum Interference Device

概要

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Detectable sizes of shallow flaws on thin copper tubes were experimentally investigated using an eddy-current-based nondestructive inspection system with a high-$T_{\text{c}}$ superconducting quantum interference device (SQUID) gradiometer. At an excitation field of 5.6 μT at 3 kHz, a magnetic anomaly due to the shallowest flaw of 10 μm depth, 100 μm width, and 15 mm length on the surface of a tube specimen of 6.35 mm outer diameter and 0.8 mm thickness was successfully measured. Signal amplitude due to a flaw was proportional to effective flaw volume that made an induced eddy current detour. The experimental results indicate that the detectable volume of a surface flaw on a copper tube should be $1\times 10^{6}$ μm3 with some increase in signal-to-noise ratio.
2006-09-25