Influence investigation of electromagnetic-acoustic transducer parameters on thickness measurement accuracy by numerical modeling methods

The electromagnetic-acoustic method is applied in the control of the electrically conductive products thickness. This method is based on the electrodynamic interaction of eddy currents induced in an electrically conductive material with an external magnetic field. Acoustic waves are generated with multiple reflections from the media interface. The recorded signal reflected allows determining the product thickness. Electromagnetic-acoustic transducer includes a magnetic system, generating and receiving coils. Thickness measurement accuracy of the control object is determined by the geometry of the generating and receiving coils, as well as the size of the gap between them. To assess this effect by the experimental data is rather difficult task. The acoustic wave propagation numerical model in a plate with electromagnetic-acoustic thickness measurement is proposed and developed for the problem solution. The numerical model is implemented in the COMSOL Multiphysics software environment using a discontinuous high-order Galerkin method with time explicit integration scheme. Model adequacy was confirmed using the results of a full-scale experiment, for which a specialized electromagnetic-acoustic thickness gauge with a transducer and a thickness gauge were used. To estimate the uncertainty of thickness measurements, an array of values of the received signal was processed in the MathCad software environment. The adequacy of the model has been confirmed by comparing the simulation results with a full-scale experiment. The influence of the transducer design on the thickness measurement accuracy was estimated. Conclusions are drawn, as well as general recommendations for the development of an electromagneticacoustic transducer, and methods for object thickness measuring are given based on the investigation results. The results can be used in the design of an electromagnetic-acoustic transducer and in the development of thickness measurement techniques.