COMPARATIVE ULTRASONIC RESPONSE OF MACHINED SLOTS AND FATIGUE CRACKS IN 7075 ALUMINUM

To assess the suitability of machined flaws as standards for ultrasonic inspection for fatigue cracks, reference blocks were developed for quantitative comparison of pulse echo amplitudes produced by machined flaws and true fatigue cracks of corresponding size and configuration. Flaw shapes investigated were rectnagular, triangular, and half penny, representing the most commonly encountered fatigue crack configurations. For each shape, electric discharge machined (EDM) and saw slits were produced; actual fatigue cracks were grown in low cycle (less than 10 to the 4th power) and in high cycle (greater than 10 to the 5th power) conditions. Ultrasonic parameters investigated were frequency, bandwidth and wave mode. The ultrasonic signals produced by low cycle fatigue cracks averaged 5 dB stronger than those from high cycle cracks of corresponding size and configuration. Depending on flaw and transducer characteristics, a receiver referenced to machined flaws required added gain of 10 to 34 dB for reliable detection of the corresponding true fatigue cracks. Narrow band pulser/receivers and transducers produced the stronger signals, but the broad band equipment produced the larger flaw signal-to-background noise ratio.

  • Availability:
  • Supplemental Notes:
    • This article was presented at the National Conference of the American Society for Nondestructive Testing, March 10-12, 1975, in Los Angeles, California. The work was performed at Southwest Research Institute under a contract for the USAF NDI Program, Kelly AFB, Texas.
  • Corporate Authors:

    American Society for Nondestructive Testing

    914 Chicago Avenue
    Evanston, IL  USA  60202
  • Authors:
    • Birchak, J R
    • Gardner, C G
  • Publication Date: 1976-12

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 275-280
  • Serial:
    • Materials Evaluation
    • Volume: 34
    • Issue Number: 12
    • Publisher: American Society for Nondestructive Testing
    • ISSN: 0025-5327

Subject/Index Terms

Filing Info

  • Accession Number: 00148430
  • Record Type: Publication
  • Contract Numbers: F41608-73-D-6739
  • Files: TRIS
  • Created Date: Mar 15 1977 12:00AM