Design and Numerical Simulation of Biasing System for Electromagnetic-Acoustic Transducer of Bulk Longitudinal Waves

A finite element model has been developed that allows one to study the distribution of the magnetic field generated by the biasing system of an electromagnetic-acoustic transducer of bulk longitudinal waves. Geometrical and electrical parameters of the biasing system for rolled sheet with a thickness of 20 mm were optimized. The selected parameters make it possible to provide the tangential component of the magnetic field strength of 35 kA/m, which is necessary for the magnetostrictive mechanism of electromagnetic-acoustic transformation. The dependences of the tangential component of the magnetic field strength on the surface of the investigated testing object and field distribution in various cross-sections of the biasing system are obtained. Based on the simulation results, a prototype biasing system was developed that implements the design of an electromagnetic-acoustic transducer of longitudinal waves and provides the required magnetic fields on the surface of the testing object. The experimental data, distribution of the magnetic flux density in the gap of the magnetic circuit and its current dependences in the coil of the biasing system, are in satisfactory agreement with the results of numerical simulation.