A NOVEL SIGNAL-PROCESSING TECHNIQUE FOR EDDY-CURRENT TESTING OF STEAM-GENERATOR TUBES

In eddy-current testing of steam generator tubes of nuclear power plan ts, the signals of defects may be corrupted by noise and other nondefe ct signals arising from the probe lift-off and the structures attached to the tubes, resulting in unreliable detection and inaccurate charac terization of defects. In this paper, a novel signal processing techni que is presented to reduce the noise and nondefect signals by the use of a wavelet transform. The noise and nondefect signals are reduced by first decomposing testing signals irate wavelet components and then m odifying the wavelet coefficients, The defect signals embedded in nois e and nondefect signals are reconstructed through the inverse wavelet transform of the modified wavelet coefficients, The results of process ing the one-dimensional and two-dimensional signals horn eddy-current testing of tube test pieces show that. this signal processing techniqu e Is effective for extracting defect signals embedded in noise and non defect signals.