Study of the System Response Analysis for the Eddy Current Test Crack Assessment on SS 316 Metal Arc Welding Joints

Abstract

In modern industry, accurately assessing metal coupling by welding is critical. Given its reliability and other advantages, the eddy current test (ECT) is essential and commonly used in metal processing, especially welding. The classical ECT assesses the presence of discontinuities in the structure by monitoring the change in the probe's impedance. According to the wireless power transfer (WPT) theory, ECT members will exchange power wirelessly through mutual induction determined by inductance, capacitance, and resistance (LCR). The cracks will affect the mutual induction in the ECT's power exchange. Since LCRs are impedance components, the crack in the target will affect the system’s mutual induction, as it did to the impedance in the classical ECT. This study applies the WPT model of ECT, implements system response analysis to assess cracks, and compares the results with classical ECT. The test piece is a metal arc-welded joint on SS 316 with an implanted notch on the welded joint to simulate the crack. A series of initial tests were performed to ensure the test piece was defects-free. Simulation and a frequency scan were performed to acquire a safe measurement. The result was that both the classical ECT and the system’s response analysis successfully assessed the presence of cracks with excellent agreement. The system’s response analysis yields a more rapid result than classical ECT.