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Application of Self Nulling Eddy Current Probe Technique to the Detection of Fatigue Crack Initiation and Control of Test Procedures

  • S. Nath
  • M. Namkung
  • B. Wincheski
  • J. P. Fulton
Chapter

Abstract

A major part of fracture mechanics is concerned with studying the initiation and propagation of fatigue cracks. This typically requires constant monitoring of crack growth during fatigue cycles and the knowledge of the precise location of the crack tip at any given time. One technique currently available for measuring fatigue crack length is the Potential Drop method [1]. The method, however, may be inaccurate if the direction of crack growth deviates considerably from what was assumed initially or the curvature of the crack becomes significant. Another popular approach is to optically view the crack using a high magnification microscope, but this entails a person constantly monitoring it. The present proposed technique uses an automated scheme, in order to eliminate the need for a person to constantly monitor the experiment. Another technique under development elsewhere is to digitize an optical image of the test specimen surface and then apply a pattern recognition algorithm to locate the crack tip.

Keywords

Fatigue Crack Crack Length Fatigue Crack Growth Fatigue Cycle Peak Voltage 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. 1.
    R.H. Vanstone and T.L. Richardson, “Potential Drop Monitoring of Cracks in Surface Flawed Specimens”, Automated Test Methods for Fracture and Fatigue Crack Growth, ASTM Special Technical Publication 877, 1985, pp. 148–166.CrossRefGoogle Scholar
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    M. Namkung, J.P. Fulton, B. Wincheski and C.G. Clendenin, “An Application of a New Electromagnetic Sensor to Real-Time Monitoring of Fatigue Crack Growth in Thin Metal Plates”, Review of Progress in Quantitative NDE, Vol. 13B, edited by D.O. Thompson and D.E. Chimenti, (Plenum Press, New York, 1993), pp. 1633–1640.Google Scholar
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    B. Wincheski, J.P. Fulton, S. Nath, M. Namkung and J.W. Simpson, “Self Nulling Eddy Current Probe for Surface and Subsurface Flaw Detection”, Materials Evaluation, Vol. 52/No. 1, Jan. 1994, pp. 22–26.Google Scholar
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    B. Wincheski, M. Namkung, J.P. Fulton, J. Simpson and S. Nath, “Characteristics of Ferromagnetic Flux Focusing Lens in The Development of Surface/Subsurface Raw Detector”, Review of Progress in Quantitative NDE, Vol. 13B, edited by D.O. Thompson and D.E. Chimenti (Plenum Press, New York, 1993), pp. 1785 1792.Google Scholar
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Copyright information

© Plenum Press, New York 1995

Authors and Affiliations

  • S. Nath
    • 1
    • 2
  • M. Namkung
    • 1
  • B. Wincheski
    • 1
    • 2
  • J. P. Fulton
    • 1
    • 2
  1. 1.NASA Langley Research Center, MS 231HamptonUSA
  2. 2.Analytical Services and Materials, Inc.HamptonUSA

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