Laser Experimental Study of the Surface Vibrations of EMUS Sensor

AbstractIn order to ensure a comprehensive monitoring of the material structuration in liquid phase, the traditional ultrasonic techniques require excitation in contact which is often inadequate for online tracking. To monitor the material evolution remotely, a new electromagnetic ultrasonic sensor (EMUS) was successfully developed in our laboratory. The EMUS transducer is based on a resonant thickness shear mode sensor (TSM) magnetically coupled to a high frequency antenna. The TSM resonator consists in a piezoelectric AT-cut quartz plate with metal electrodes on opposite sides. The application of a radio frequency electrical signal gives rise to the excitation of a shear mechanical resonance. The work presented here allows characterizing the acoustic behavior of the EMUS. A laser vibrometer is used to scan the surface of the TSM resonator and visualize the propagation of the generated surface waves. This study shows a good agreement between experimental and theoretical results which encourages the study of acoustic interaction between the TSM resonator and a material in contact with the quartz surface. They therefore suggest that this non-destructive technique can be used to extract the viscoelastic properties of materials