Robust Signal Processing for Material Noise Suppression in Ultrasonic Nondestructive Testing
Ultrasonic nondestructive inspection of materials is often limited by the presence of backscattered echoes from the material structure, known as material or grain noise. The material noise can be difficult to distinguish from flaw echoes because their spectra overlap to a large extent. Due to the overlapping, application of conventional linear filters is generally not adequate for attenuating this type of noise. However, a suitable choice of the inspection frequency will cause the grain response to be considerable more noncoherent than the flaw response. This property arise from the fact that the material noise can be considered as an interference pattern made up of unresolved scatterers, while the flaw echoes will bear more resemblance to specular reflections. The implication of this difference is that the material noise can be suppressed by means of frequency diversity techniques which take advantage of its noncoherent nature.
Unable to display preview. Download preview PDF.
- 1.V.L. Newhouse, N.M. Bilgutay, J.Saniie and E.S. Furgason, Flaw-to-Grain Echo Enhancement by Split-Spectrum Processing. Ultrasonics, March 1982, pp 59–68.Google Scholar
- 2.J.L. Rose, P. Karpur and V.L. Newhouse, Utility of Split-Spectrum Processing in Ultrasonic Nondestructive Evaluation. Materials Evaluation, vol. 46, pp 114–122, 1988.Google Scholar
- 4.L. Ericsson, T. Stepinski, Verification of Split Spectrum Technique for Ultrasonic Inspection of Welded Structures in Nuclear Reactors. Accepted for publication in European Journal of NDT.Google Scholar
- 5.L. Ericsson, T. Stepinski, Signal Processing for Ultrasonic Testing of Anisotropic Materials. Swedish Nuclear Power Inspectorate, Report SKI TR 92: 1, 1992.Google Scholar