Ultrasonic wave propagation characteristics of green ceramics

Propagation of ultrasonic waves in green (unfired) ceramics is studied, and the effectiveness of ultrasonic methods for nondestructive evaluation is assessed. The objective is to obtain useful information on defects, cracking, delaminations, agglomerates, inclusions, regions of high porosity, and anisotropy. Conventional ultrasonic techniques are difficult to apply to flaw detection in green ceramics because of the high attenuation, fragility, and couplant-absorbing properties of these materials. However, velocity, attenuation, and spectral data were obtained with pressure-coupled transducers and provided useful information related to density variations and the presence of agglomerates and elastic anisotropy.