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 measurement is performed with two angled ultrasonic longitudinal transducers in a pitch catch configuration by employing an immersion technique. Phase velocities for the guided modes are selected through the variation of the angle formed by the transmitter beam with the surface normal vector. The excitation signal of the transmitting transducer is a narrow band pulse. For each phase velocity, the guided mode frequencies are recovered by evaluating the frequency minima of the reflection coefficient.