Image Reconstruction Of Flaws Using Ramp Response Signatures

Varadan, Vasundara V.; Tsao, S. J.; Varadan, Vijay K.; Tittmann, B. R.

doi:10.1117/12.940280

Cited by 2 publications

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“…It can be used to discriminate between the echoes back scattered by a crack and by an interface by performing spectral analysis: the transfer function between the two echoes must be a ramp function [8][9].…”

Section: Introductionmentioning

confidence: 99%

Ultrasonic discrimination and modelling for crack-tip echoes

Lasaygues¹

2011

Nondestructive Testing and Evaluation

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International audienceThe problem of discriminating between the acoustical signatures of an open crack tip and an interface is approached by modelling the various ultrasonic signatures and by a signal processing method. In the modelling study, the Kirchhoff approximation (the physical optics approximation) is used to describe the far field scattered by an arbitrary object with non-negligible dimensions in comparison with the wavelength, and to express this field depending on the incident field. It is established that, under this condition, the impulse response of an open crack tip is proportional to the first-order derivative of the impulse response of the transmitter. In the signal processing study, spectral and wavelet analyses were applied to the discrimination problem. The basic idea was to discriminate signatures simultaneously in time and in frequency (scale) domain. This method was found to be an effective means of testing models for the interactions between waves and flaws. Both aspects (modelling and signal processing) were studied numerically and experimentally, and the validity of the results was tested on an industrial sample

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Section: Introductionmentioning

confidence: 99%

Ultrasonic discrimination and modelling for crack-tip echoes

Lasaygues¹

2011

Nondestructive Testing and Evaluation

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“…The ramp response technique has been widely utilized in electromagnetic inverse scattering for profile reconstruction [4][5][6][7][8]. Similar to the electromagnetic wave field, the ramp response technique also has been successfully applied in the acoustic wave field [9][10][11][12] and the elastic wave field [17] for solving inverse scattering problems, such as underwater acoustical imaging and nondestructive evaluation. In general, most researchers made use of the backscattering signals to calculate the ramp response of an object, except for Foo and his colleagues [4].…”

Section: Introductionmentioning

confidence: 99%

Acoustical imaging of underwater objects using the bistatic ramp response signals

Liu

Varadan

2003

Smart Mater. Struct.

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Underwater acoustical imaging techniques and the inverse analysis of acoustic scattering problems have now found many important engineering applications. Most of the inverse techniques use the backscattering signals in the acoustical far field to retrieve the shape and size information of an underwater object, such as the ramp response technique. This paper addresses a modified ramp response technique, which could be used to reconstruct the 3D image of an object for the bistatic case. This technique shows that the bistatic ramp response is proportional to the profile function of an underwater object based on the small bistatic angle assumption. The numerical examples demonstrate that the bistatic ramp response technique is still valid to obtain an excellent profile function even for the bistatic case with a fairly large bistatic angle. The numerical results also suggest that, if the object is of a more slender shape, then its bistatic ramp response will be closer to the exact profile function for a larger bistatic angle. Finally, a 3D image of a spheroid with a/b = 5 has been reconstructed using the bistatic ramp response signals in three incident directions. This bistatic ramp response technique allows us to reconstruct the 3D image of an underwater object with only one receiver.

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Image Reconstruction Of Flaws Using Ramp Response Signatures

Cited by 2 publications

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Ultrasonic discrimination and modelling for crack-tip echoes

Ultrasonic discrimination and modelling for crack-tip echoes

Acoustical imaging of underwater objects using the bistatic ramp response signals

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