Data Processing of Corrosion Noise Polluted ECT Signals for Heat Exchanging Tubes of Cu-Ni Alloy
Tian Shuxia1, 2, Chen Zhenmao1
1. State Key Laboratory for Strength and Vibration of Mechanical Structures Xi’an Jiaotong University Xi’an 710049 China; 2. Zhengzhou University of Light Industry Zhengzhou 450002 China
Abstract：Based on numerical analyses and experiments, a scheme for automatic processing of eddy current testing (ECT) signals of a Cu-Ni alloy heat exchanging tube including large Ni corrosion noises is proposed and verified in this paper. Through numerical simulation, the features of the Ni corrosion noise are evaluated, and it is found that its major difference with that of crack signal is on the phases and the waveforms characteristics, and it is difficult to identify crack information from the polluted testing signals with conventional signal processing method. Based on this knowledge, a piecewise phase transformation algorithm and a pattern matching technique are proposed to extract the crack information from the noise polluted ECT signals. As validation experiments, test-pieces of tube segments taken from an aged practical heat exchanger are fabricated, and the proposed signal processing method is adopted for the measured ECT signals. The experimental results shown that the proposed signal processing method can identify and extract the crack information effectively from the testing signals with large Ni corrosion noises, and the proposed method is suitable for practical application to inspection of aged Cu-Ni alloy tubes.
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2015, Vol. 30 
