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Signal Processing for Ultrasonic Testing of Material with Coarse Structure

T. Stepinski and L. Ericsson, Uppsala University, Signals and Systems, Uppsala, Sweden

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Introduction

Consecutive polarity coincidence

Noncoherent Detector (NCD)

Fig 3: Example of estimated autocorrelation and power spectrum of grain noise.

Fig 4: Example of signal prototype, and its spectrum, flower=0.5 MHz, fupper=1.4 MHz.

Fig 5: Filter calculated from the noise correlation matrix and the signal prototype from above.

Temporal resolution of SSP vs NCD

Experimental results

Fig 12a: B-scan from Fig. 11 after processing with NDC Fig 12b: B-scan from fig. 11 after processing with SSP/CPC

Conclusions

Acknowledgement.

References

  1. V.L. Newhouse, N.M. Bilgutay, J. Saniie and E.S. Furgason, Flaw-to-Grain Echo Enhancement by Split-Spectrum Processing, Ultrasonics, March, 59-68 (1982).
  2. L. Ericsson and T. Stepinski, Verification of Split Spectrum Technique for Ultrasonic Inspection of Welded Structures in Nuclear Reactors. The European Journal of Non-Destructive Testing, 2, 2, 56-64 (1992).
  3. P. Karpur, P.M. Shankar, J.L. Rose and V.L. Newhouse, Split Spectrum Processing: Determination of the Available Bandwidth for Spectral Splitting. Ultrasonics, 26, July, 204-209 (1988).
  4. L. Ericsson, T. Stepinski and S. Dahlgren, Ultrasonic Pulse Detection with Split Spectrum Processing and Consecutive Polarity Coincidence, Proc. 13 th International Conf. on NDE in the Nuclear and Pressure Vessel Industries, Kyoto, 1995, pp 201-207.
  5. M. G. Gustafsson, Statistical Aspects of the Split Spectrum Technique, PhD dissertation, Uppsala University, 1995.
  6. L. Ericsson, M.G. Gustafsson, Perception and Entropy Inspired Ultrasonic Grain Noise Suppression using Noncoherent Detector Statistics, Proc. 7 th ECNDT, Copenhagen, 1998.
  7. L. Ericsson, T. Stepinski and M.G. Gustafsson, Suppressing Ultrasonic Grain Noise Using Noncoherent Detection, Proc. First International Conf. on NDE in Relation to Structural Integrity for Nuclear and Pressurised Components, Amsterdam, 1998.
  8. Q. Tian, X. Li and N.M. Bilgutay, Multiple Target Detection Using Split Spectrum Processing and Group Delay Moving Entropy, IEEE Trans. On UFFC, 42, pp.1076-1085, (1995).

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