Abstract: The longitudinal and transverse transducers having plane and curved surfaces with 20～100MHz frequency were planed
and prepared. The acoustic parameters and defect size within ceramic parts of engine were determined by means of directly coupling mode. the creditability of measurement was improved by
alternately using longitudinal (susceptible to pore) and transverse (satisfying with measurement of crack) transducers. As a result of numerous measurements the relational curves of “distance-
amplitude-normal” of defects were established for searching the size of defects within materials measured. On the basis of determination,
according to the theory of fracture mechanics, the quality evaluation and classification of ceramic parts can be made for judgment of pass/abandonment.

Key words: ultrasonic technique, ceramic parts of engine, nondestructive evaluation