GUIDED ACOUSTIC-WAVE PROPAGATION FOR PORCELAIN COATING CHARACTERIZATION

In this paper a measurement technique to obtain dispersion curves for guided acoustic modes in porcelain-coated steel is described. The meas urement is performed with two angled ultrasonic longitudinal transduce rs in a pitch catch configuration by employing an immersion technique. Phase velocities for the guided modes are selected through the variat ion of the angle formed by the transmitter beam with the surface norma l vector. The excitation signal of the transmitting transducer is a na rrow band pulse. For each phase velocity, the guided mode frequencies are recovered by evaluating the frequency minima of the reflection coe fficient.