Is TOFD Blind for ID and OD Surfaces?

TOFD (Time of Flight Diffraction) is a new post modern technology in nondestructive testing, NDT. It is based on the diffraction phenomena of sound rather than reflection which is used in classical ultrasonic testing. One of the major applications of TOFD in industry is the ultrasonic examination of welds. While doing so, one should choose the most convenient ultrasonic configuration (i.e.different probe angles, probe center spacing, frequencies and diameters) in conjunction with the material being tested. The goal of this article is to emphasize the effectiveness of this method on top surface (ID) and bottom surface (OD) of welds.

References
  • M.G. Silk, B.H. Lidington, June 1975, "The potential of scattered or diffracted ultrasound in the determination of crack depth". Non-Destructive Testing,
    Volume 8, Issue 3.
  • ASME, Boiler and Pressure Vessel Construction Code, 2013 Edition, Section V Nondestructive Examination, Section VIII, Rules for Construction of Pressure Vessels, Division 1&2, Section I, Rules for Construction of Power Boilers.
  • Introduction to Phased Array Ultrasonic Technology Applications: R/D Tech Guideline, Olympus NDT, 3rd Printing 2007.
  • “Back to Basics: Time of Flight Diffraction and Acceptance Criteria: A Perfect Team,” J.A. Dijkstra, J.E. Deraad and T. Bouma, M.E., Vol. 56, No. 3, March 1998, p. 396.
  • “Ultrasonic Testing of Welds by Time of Flight Diffraction: Codes, Guidelines and Standards,” Anmol S. Birring and
    Bharat K. Nidathavolu, M.E., Vol. 63, No. 9, September 2005, pp. 910-914.
  • “An Ultrasonic Time of Flight Diffraction Technique for Characterization of Surface-Breaking Inclined Cracks,” C. V. Krishnamurthy and B. H. Narayana, M.E., Vol. 67, No. 2, February 2009, pp. 141-148.
  • ASTM E2373 / E2373M - 14 Standard Practice for Use of the Ultrasonic Time of Flight Diffraction (TOFD) Technique.
  • ISO 10863, 2011 Edition, Non-destructive testing of welds - Ultrasonic testing - Use of time-of-flight diffraction technique (TOFD.)
  • ENV 583-6, 2008 Edition, The European TOFD standard draft. Non-destructive testing – Ultrasonic examination part 6: Time of Flight diffraction technique as a method for defect detection and sizing.
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