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DEFECTS DIAGNOSIS OF NUCLEAR POWER PLANT STEAM GENERATOR TUBES USING THE HILBERTHUANG TRANSFORM IN EDDY CURRENT TESTING SIGNALS André Luiz Formigoni The nuclear power plant steam generator tubes are subjected to different levels of stress and loading at high temperatures, reducing its lifetime due to the development of defects and corrosion. The Eddy Current Testing (ECT) is a nondestructive testing used to diagnose defects of corrosion and discontinuities in the inner and outer surface of heat exchanger tubes. These tubes are subject to failure by different mechanisms of chemical and mechanical degradation such as fatigue and stress corrosion crack. The ECT signals are affected by different noises making the analysis a difficult task to the inspector. This dissertation presents the results of the main characteristics from the ECT signals using the Hilbert-Huang Transform (HHT) as an alternative method for the processing and signal analysis. The Hilbert-Huang Transform has its name given by the American National Aeronautics and Space Administration, NASA, as the result of Empirical Mode Decomposition (EMD) and the Hilbert Spectral Analysis (HSA) methods. The Eddy Current signals are transient, nonstationary and nonlinear. The HilbertHuang Transform applied in this work provided two alternative proceedings in signal processing, one in signal pre-processing acting as noise filter (De-noising) and another as signal analysis, which identifies the characteristics of signal timefrequency-energy.

Análise de defeitos em tubos de geradores de vapor de usinas nucleares utilizando a transformada de Hilbert-Huang em sinais de inspeção por correntes parasitas