Accurate Simulations of EMAT Signal Amplitude and Shape Based on FEM Using a Coupled ECT-UT Formulation

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Simulations of the EMAT signal, both in amplitude and shape, in metallic materials to detect defects located far from the EMAT area are performed using a FEM model based on a coupled eddy-current (ECT) and ultrasonic (UT) formulation. The paper presents the progress and achievements in performing very accurate numerical FEM simulations of the EMAT signal when using different numerical integration techniques such as Crank-Nicolson, Backward Euler and Newmark-beta method to avoid the large discrepancies in the EMAT signal shapes when using various models. The approach to obtain convergence in the simulated EMAT signal, not only of the burst amplitude of the defect but also of the time-transient shape of the signal, is based on the combination of high-order finite elements using triangular/rectangular meshes and advanced numerical time integration to obtain the converged EMAT signal in the shortest time while maintaining the same shape of the EMAT signal simulation.