[4C5] Study on the beam directivity of a steered meander-line coil EMAT
S Hurrell, P Charlton, S Mosey, O Rees-Lloyd and R Lewis
University of Wales, UK
Electromagnetic acoustic transducers (EMATs) generate and receive ultrasonic waves via a combination of bias magnetic fields and an alternating eddy current induction. Meander-line coil (MLC) EMATs generate these waves into a material at an angle normal to the surface. With a fixed coil spacing, the angle of these waves is controlled by the frequency of the current through the coil. This paper presents the methodology used to measure the beam directivity of the shear waves, through simulations and experimental validations on aluminium. Results show that the maximum shear wave occurred at a steering angle of 32º, the steering limit was reached at a steering angle of 40º and the beam directivity became unfocused beyond steering angles of 60º.
