Use of Ultrasonics in the Inspection and Characterization of Nonmetals

This chapter discusses some typical examples of the use of ultrasonics in the inspection of nonmetallic materials and products, that is, products made of concrete, ceramics, wood and wood composites, selected polymers, plastics, and polymer-composite materials. Ceramic materials such as porcelain, glass, and dense aluminum oxide have good ultrasonic transmission characteristics. The velocity of ultrasonic waves in porcelain is a function of the density/porosity. Evaluation of ceramic coatings on metallic substrates by ultrasonic methods has been investigated. Ceramic coatings may vary widely in their acoustic properties. Imperfect bonds between coatings and substrate have been detected through the use of the nonlinear interaction between high- and low-frequency ultrasonic waves. The imaging of the structure of wood, on various scales, has been investigated using several imaging methodologies, including ultrasound. The application of ultrasound to wood and wood products was in part facilitated by improvements in transducers, which have increased system dynamic range and transmission efficiency since about 1990.