The number of highway, railway, and mass transit steel bridges with welded details in the United States has been estimated at 123,000. It has been estimated that between 2,500 and 5,000 bridges have low fatigue resistance details. This study evaluated the ultrasonic time of flight diffraction (TOFD) method to locate and size flaws in steel members. This was done by measuring the location and depth of flaws implanted in steel plate specimens and of a fatigue crack in the flange of a full-scale steel plate girder. The data showed that the TOFD procedure was very accurate to locate flaws (within 5% of the actual location). The accuracy of the procedure to measure flaw depth depends, however, on the proximity of the flaw tip to the scanning surface. Flaw tips at depths 6 mm below the scanning surface were measured to an accuracy of 20% of the actual value. When the flaw tip was at a depth 3 mm below the scanning surface, flaw depth was overestimated. Additional scans on the opposite surface of the material may be used, however, to overcome this limitation and to obtain an accurate measurement of such flaws. The method offered good repeatability and can be used to accurately locate and size flaws with an appropriate scanning scheme.


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  • Accession Number: 00794091
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jun 25 2000 12:00AM