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Measurement of Thin Case Depth in Hardened Steel by Ultrasonic Pulse-Echo Angulation Techniques

  • Morris S. Good
  • Joseph L. Rose
Chapter

Abstract

This study evaluated ultrasonic pulse-echo angulation as a nondestructive technique for measuring thin case depths (less than 2 mm) in hardened steel. In concept, this method has been used to measure case depths greater than 2 mm and has also been suggested as a technique for determining nominal grain size. It has not been applied to case depths less than 2 mm because impediments, such as the obscuring effect of the front interface echo, the extremely low signal-to-noise ratio of grain backscatter, and the small area localization usually required by industrial inspection procedures prevent accurate measurement.

Study results indicate that improved signal processing techniques (i.e., RF signal averaging, and smoothing) can overcome these obstacles. The final algorithm predicted effective case depth at 0.91, 1.40, and 1.98 mm at ultrasonically calculated values of 0.94, 1.40, and 2.11 mm, with respective standard deviations of 0.25, 0.23, and 0.81 mm. The extremely localized fluctuations in the case depth specimen contributed significantly to the measured standard deviation.

Key Words

shear wave backscatter case depth ultrasonic pulse-echo RF signal averaging spatial averaging Hilbert transform moving average window martensite pearlite 

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References

  1. 1.
    Emerson, P. J., 1976, Alternative Methods for Measuring Case Depth in Ferrous Components, British J. of NDT 18, 2.Google Scholar
  2. 2.
    Perennes, C., Chretien, N., Jussiaume, A., and Gaillot, D., Nondestructive Testing of Hardening Depth in Steel Cylinders by Two Ultrasonic Methods, “Proceedings of Ninth World Conference on Nondestructive Testing,” Session 1B-2, November 1979.Google Scholar
  3. 3.
    Taylor, J. L., 1978, An Introduction to Case Hardening Processes, British J. of NDT 18, 2.Google Scholar
  4. 4.
    Goebbels, K., 1980, Structure Analysis by Scattered Ultrasonic Radiation, “Research Techniques in Nondestructive Testing, Vol. IV,” Academic Press, New York.Google Scholar
  5. 5.
    Krautkramer, J., and Krautkramer, H., 1977, “Ultrasonic Testing of Materials,” trans. Springer-Verlag, New York.Google Scholar

Copyright information

© Plenum Press, New York 1984

Authors and Affiliations

  • Morris S. Good
    • 1
    • 2
  • Joseph L. Rose
    • 1
    • 2
  1. 1.Sigma Research IncorporatedRichlandUSA
  2. 2.Drexel UniversityPhiladelphiaUSA

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