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Pulsed wavefield diffraction by circular cylindrical voids and cracklike defects - elastodynamic numerical modelling and experiments

: Langenberg, K.-J.; Schmitz, V.

4th European Conference on Non-Destructive Testing '87. Proceedings. Vol.4
Oxford: Pergamon Press, 1988
European Conference on Non-Destructive Testing <4, 1987, London>
Fraunhofer IZFP ()
GTD; modelling; physical optic; probe; stationary method; synthetic aperture

Ultrasonic non-destructive testing requires the physical understanding and mathematical modelling of elastic wave radiation and scattering, and the formulation of appropriate defect imaging and identification algorithms based on that understanding. Typical representatives of defect models comprise voluminous and cracklike scatters. Canonical geometries like twodimensional cylinders and strips with stressfree boundary conditions are investigated with respect to their pulsed time-domain longitudinal- and shear-mode diffraction, both theoretically and experimentally. The mathematical methods used are eigenfunction expansions and numerical solutions of integral equations. The experimental results obtained with 2 MHz probes on 10 mm cylindrical boreholes and diffusion bondes strips agree very closely with theory. An angle beam probe is modelled by its plane wave spectrum and included in a system model of pulsed wavefield diffraction. The effects of limited bandwidth raised-cosine pulses ver sus broadband Gaussian pulses is investigated theoretically and experimentally. (IZFP)