Efficient Modeling of Finite Acoustic Beam Excitation and Detection of Interface and Bulk Waves on Planar and Cylindrical Fluid-Solid Structures

Abstract

Ultrasonic (UT) nondestructive evaluation (NDE) of fluid-immersed bulk or layered elastic materials is commonly carried out with a single or a pair of acoustic transducers used in pulse-echo or pitch-catch modes. Applications range from determining material properties to identifying interior and/or surface defects. Some of the configurations often encountered in UT-NDE, and that are considered in this paper, are depicted in Figure 1. These sketches show a transmitting transducer radiating a continuous or pulsed finite beam that excites interface or bulk waves within the elastic part. Acoustic energy radiated back by the elastic part into the fluid is collected by a receiving transducer which converts it into a voltage. Quantitative modeling of this class of experiments, even under assumptions of ideal conditions (e.g. homogeneous and isotropic layers and defect-free structures), is important for design optimization purposes and for understanding and interpreting the data acquired. It also provides a first step towards tackling non-ideal configurations. There is a large body of work that address this objective through various approaches (analytical, numerical, hybrid, etc); the reader is referred to References in this issue and in past issues of the Proceedings of this conference. This paper presents recent developments in the application of analytic methods to comprehensive and efficient modeling of the type of configurations depicted in Fig. 1. Comprehensive in the sense that the methodology used can account for 1) arbitrary three-dimensional (3D) diffraction and orientation of transmitting and receiving transducers; 2) interface and layering wave effects such as the excitation of surface and modal waves in the structures inspected.