Location

La Jolla, CA

Start Date

1-1-1998 12:00 AM

Description

Ultrasonic inspection plays an important role in numerous industrial fields. One of the prominent tasks is the determination of location, shape, size and orientation of defects. In isotropic materials, the location of reflectors can be inferred from time-of-flight measurements, angle of insonification and transducer position. In anisotropic media, however, such a procedure is aggrevated by several phenomena, which are the direction dependence of the ultrasonic velocities, the beam skewing effect and the modified radiation characteristics of flaws with respect to wave scattering. In this contribution, analytical relationships are presented for the scattering of ultrasound at defects in such media. Based on the mathematical formulation of Huygens’ principle, these relationships are obtained for traction-free scatterers using Kirchhoff’s approximation. Asymptotic evaluation yields explicit expressions, which are further incorporated in the Generalized Point Source Synthesis method. Numerical results are obtained for rectangular and circular reflectors, selected to compare with notches and flat-bottomed holes, respectively. Evaluation is performed in view of the radiation characteristics of these defects, considering (quasi-) longitudinal wave scattering in orthotropic composite material. Also, the elaborated relationships have been applied to calculate echo dynamic curves in dependence of transducer position for pulse-echo technique. Good comparison with experimental results has been obtained for transversely isotropic weld material.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

17A

Chapter

Chapter 1: Standard Techniques

Section

Elastic Wave Scattering/Backscattering

Pages

57-64

DOI

10.1007/978-1-4615-5339-7_7

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Theoretical Evaluation of Ultrasonic Scattering by Flaws in Anisotropic Media

La Jolla, CA

Ultrasonic inspection plays an important role in numerous industrial fields. One of the prominent tasks is the determination of location, shape, size and orientation of defects. In isotropic materials, the location of reflectors can be inferred from time-of-flight measurements, angle of insonification and transducer position. In anisotropic media, however, such a procedure is aggrevated by several phenomena, which are the direction dependence of the ultrasonic velocities, the beam skewing effect and the modified radiation characteristics of flaws with respect to wave scattering. In this contribution, analytical relationships are presented for the scattering of ultrasound at defects in such media. Based on the mathematical formulation of Huygens’ principle, these relationships are obtained for traction-free scatterers using Kirchhoff’s approximation. Asymptotic evaluation yields explicit expressions, which are further incorporated in the Generalized Point Source Synthesis method. Numerical results are obtained for rectangular and circular reflectors, selected to compare with notches and flat-bottomed holes, respectively. Evaluation is performed in view of the radiation characteristics of these defects, considering (quasi-) longitudinal wave scattering in orthotropic composite material. Also, the elaborated relationships have been applied to calculate echo dynamic curves in dependence of transducer position for pulse-echo technique. Good comparison with experimental results has been obtained for transversely isotropic weld material.