Acoustical signals are a useful means for detection of flaws in physical structures. Small structures are checked this way by monitoring the samples for acoustical signal count or count rate. Any flaws in the structure are located by observing the relatively high acoustical activity within a given area of the sample. Based on the technique used in small structures, acoustical monitoring has been extended to large structures by dividing the large samples into small areas and then by monitoring each individual area separately. The sample used in this development is a 105-in. (263-cm) diameter tank which consists of 3480 areas each approximately 10 in. (63 cm). The tank surface is proportioned to allow the layout of 20 equilateral triangles in the form of a slightly distorted icosahedron. Twelve transducers are equally positioned on the tank surface at the vertex of each of these triangles. Although noise rejection is used throughout the system, i.e., dual element transducers and bandpass filters, a constant background or random noises uniformly raise the totals of a large number of signal counts from all the storage areas. In this technique, a growing flaw area is localized and easily identified using the statistical capabilities of the on-line computer. For example, mean averages can be obtained of desired specific sub-areas of the entire trank at any time. The rate of emission signals for any given time can also be obtained. Statistical calculations are obtained from all input data in less than one second.

  • Supplemental Notes:
    • This article appeared in a publication Analytical Techniques. A Compilation.
  • Corporate Authors:

    National Aeronautics and Space Administration

    400 Maryland Avenue, SW
    Washington, DC  United States  20546
  • Authors:
    • Sugg, F E
    • Moskal, F J
  • Publication Date: 1975-1

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Filing Info

  • Accession Number: 00128506
  • Record Type: Publication
  • Report/Paper Numbers: NASA CR-2028
  • Contract Numbers: MFS-24402, NPO-11612, MFS-16968
  • Files: TRIS
  • Created Date: Apr 21 1976 12:00AM