Optimization of the laser-EMAT detection system based on FEM

To solve the complicated operation problems of the laser ultrasonic method and the low sensitivity of electromagnetic acoustic transducers, that both have noncontact characteristics in their respective detection processes. It is difficult to observe the effects of different parameters on the relevant physical fields. In this paper, the finite element simulation method was used to analyse the influence of the matching relationship between the pulsed laser and the electromagnetic ultrasonic transducer on the detection sensitivity, and the optimal design basis of the laser sound-magnetic detection system was studied. The simulation model of the laser acoustic-magnetic detection system was established by using finite element software. The characteristics of the temperature field and displacement field of ultrasonic excitation by a Gaussian laser pulse were analysed through orthogonal numerical simulation, and the influence of the parameter change of the electromagnetic ultrasonic transducer on the detection sensitivity was observed. The results indicate that the voltage signal received by the spiral coil can correctly respond to the ultrasonic displacement field generated by the thermal expansion effect of the incident laser in the solid. When the height to width ratio of the magnet was 1.5 times, the magnetic field intensity distribution at the driving layer was optimal, and the effect of the lifting distance on the energy conversion efficiency presented the law of negative exponential. The receiving performance of the electromagnetic ultrasonic transducer at different receiving spacings was evaluated.