Multiphysics Modeling of a Lorentz Force-Based Meander Coil Electromagnetic Acoustic Transducer via Steady-State and Transient Analyses

Electromagnetic acoustic transducer (EMAT) is a kind of non-contact ultrasonic transducer, and during its operation, no liquid coupling is required. Despite this advantage, EMAT has low transduction efficiency and its performance depends on the tested object, thus further research of its complex multiphysics transduction mechanism involving both electromagnetic and elastodynamic phenomena is paramount. In this paper, an approach to solve directly the underlying integro-differential equations involved in the eddy current model was proposed, for both steady-state and transient analyses. Skin effect and proximity effect were observed in a generalized multi-conductor electromagnetic model, both for the complete and incomplete equations. Time-varying distributions of the Lorentz force vector were solved from the static bias magnetic field and sinusoidal current density waveforms converted from the corresponding complex phasors of the frequency-domain solution for a meander coil EMAT. For a plate model without any defect and a plate model with a slot defect, the waveforms of displacement component at two points from transient analyses were recorded. The simulated traveling velocities of the wave packets were calculated to compare with the theoretical group velocities of S0 and mode-converted A0 modes of Lamb waves.