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Computed imaging with elastic waves

: Mayer, K.; Kreutter, T.; Langenberg, K.-J.; Schmitz, V.

WCNDT '89. 12th World Conference on Non-Destructive Testing. Proceedings
Amsterdam, 1989
ISBN: 0-444-87450-X
World Conference on Non-Destructive Testing <12, 1989, Amsterdam>
Conference Paper
Fraunhofer IZFP ()
Abbildung; Beugungstomographie; Elastodynamik; Holographie; inverse Beugung; synthetische Apertur; Turbinenwelle

Elastic wave scattering by defects in solids can be interpreted in terms of timely separated pressure and shear wavefronts, each of which is approximately characterized by a scalar potential. Formulation of the inverse scattering problem for scalar wavefields then yields a general solution via the backpropagation ansatz, if the defect can either be considered as a weakly scattering inclusion or a strongly scattering crack or void. Holography, ALOK, SAFT, Echo Tomography and other algorithms for computed imaging turn out to be special solutions within this generalized diffraction tomography framework and therefore relate to each other in a quantitative way. In addition, fast and powerful data processing alternative like Fourier-Transform-SAFT are proposed and have recently been implemented for threedimensional computed imaging, either for planar or cylindrical measurement surfaces, the latter one relating to turbine shaft testing.