Detection and Evaluation of Dissimilar Metal Weld Defects Based on the Tx-Rx Pulsed Eddy Current Testing Probe

Abstract

Dissimilar metal welds (DMWs), widely used in many components of nuclear power plants, may cause catastrophic failures because of damages (such as corrosion). Pulsed eddy current testing (PECT) could be used for DMW detection for its advantages of broadband property and high lift-off immunity. However, the research on PECT for DMW detection has seldom been studied because its structure and material are complicated. In this paper, the detection and evaluation of flaws in DMWs are studied based on the transmitter-receiver (Tx-Rx) PECT probe. Simulation and experiment studies show that, for better detection accuracy, the Tx coil of the probe should be located above the pressure vessel, the Rx coil should be located above the weld, and the minimum distance between the Tx and Rx coils is suggested. Moreover, the peak value of the differential signal and the coefficient a₁ of the fitted differential signals with a second-order Gaussian function can be used for defect evaluation. The research in this paper is beneficial for DMW detection by using PECT Tx-Rx probes.