title: Review of air-coupled ultrasonic materials characterization.
abstract: This article presents a review of air-coupled ultrasonics employed in the characterization or nondestructive inspection of industrial materials. Developments in air-coupled transduction and electronics are briefly treated, although the emphasis here is on methods of characterization and inspection, and in overcoming limitations inherent in the use of such a tenuous sound coupling medium as air. The role of Lamb waves in plate characterization is covered, including the use of air-coupled acoustic beams to measure the elastic and/or viscoelastic properties of a material. Air-coupled acoustic detection, when other methods are employed to generate high-amplitude sound beams is also reviewed. Applications to civil engineering, acoustic tomography, and the characterization of both paper and wood are dealt with here. A brief summary of developments in air-coupled acoustic arrays and the application of air-coupled methods in nonlinear ultrasonics complete the review. In particular, the work of Professor Bernard Hosten and his collaborators at Bordeaux is carefully examined.
authors.affiliation: Department of Aerospace Engineering, Center for Nondestructive Evaluation, Iowa State University, Ames, IA 50011-2271, USA. Electronic address: chimenti@iastate.edu.
authors.forename: D E
authors.initials: DE
authors.lastname: Chimenti
keywords: Air-coupled transducers; Air-coupled ultrasonics; Materials characterization; Nondestructive evaluation