Applications of Ultrasonic Microscopy to the Evaluation of Ceramic Materials

Modern ceramic materials offer many attractive physical and mechanical properties for a wide and rapidly growing range of industrial applications. But the criticality of many of those applications sets technical challenges to the materials and inspection industries. NDE needs may be classified into three groups: controls on manufacturing processes, characterization of material properties, and detection of defects. Good process control techniques, important to all industries, assume even more importance for many ceramics, especially structural ceramics, because of specific characteristics such as a relatively low fracture-toughness. Apart from detection of discrete defects, techniques will also be needed to monitor uniformity of properties, and to inspect for bond strength, for example. Characterization of physical, chemical, and thermo-mechanical properties will use many of the orthodox techniques of the materials scientist, modified as necessary to accomodate generic differences from other materials. Flaw population studies, and the detection of defects — cracks, voids, inclusions, delaminations, etc. — to ensure material and product integrity, will require both unusually high sensitivity and high reliability, due to the unusually small size of defects (of the order of 25 urn diameter) which may be fracture-critical