Wave Energy Evaluation for Ultrasonic Air-Coupled Material Characterization

摘要

Ultrasonic non-destructive evaluation and material characterization involve the processing of the acquired data on the basis of efficient computer models both for transducer generated beams and scattered wave fields. The simulation of wave processes in coupled source-structure environments is also beneficial for the design and optimization of such non-destructive inspection systems. The present work deals with the development of analytically based, and so cost-effective, simulation tools for ultrasonic probing of fluid-immersed elastic plates, using contactless (air-coupled) transducers. Explicit integral representations for the generated and scattered wave fields have been obtained, using the Fourier transform technique. In the far field, the bulk acoustic waves and guided elastic waves are described by asymptotic representations, derived from those path integrals as the contribution of phase saddle points and residues from the integrand's poles. The present study is focused on the source energy partition among the generated waves of different types and among different directions of wave propagation. The dependence of the total source energy and its parts on the frequency and source distance to the plate is illustrated by numerical examples.