ULTRASONIC LAMB WAVE TOMOGRAPHY OF NON-UNIFORM INTERFACIAL STIFFNESS BETWEEN CONTACTING SOLID BODIES

In this work, the interfacial condition between two contacting solid bodies is determined using an ultrasonic Lamb wave tomography. An ultrasonic measurement setup based on parallel projection tomography that uses broadband transducers is presented. Time-frequency representation (TFR) is employed to improve identification of the arrival time and frequency contents of the transmitted wave modes. Experiments are carried out on an aluminum plate where the flat end of a solid aluminum bar is pressed perpendicular to the surface; then, the level and distribution of the interfacial stiffness is controlled by applied force on the bar. The tomographic reconstructions are performed during repeated loading cycles. Finally, reconstructed tomographic images of the contact area versus applied pressure are obtained. The method presented has potential applications in determining the loss of contact in mechanically joined structural components.