Damage detection in aircraft structures using dynamically measured static flexibility matrices

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Two methods for detecting the location of structural damage in an aircraft fuselage using modal test data are presented. Both methods use the dynamically measured static flexibility matrix, which is assembled from a combination of measured modal vectors, frequencies, and driving point residual flexibilities. As a consequence, neither method requires a mode-to-mode correlation, and both avoid tedious modal discrimination and selection. The first method detects damage as a softening in the point flexibility components, which are the diagonal entries in the flexibility matrix. The second method detects damage from the disassembled elemental stiffnesses as determined using a presumed connectivity. Vibration ... continued below

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10 p.

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Robinson, N.A.; Peterson, L.D.; James, G.H. & Doebling, S.W. February 1, 1996.

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Description

Two methods for detecting the location of structural damage in an aircraft fuselage using modal test data are presented. Both methods use the dynamically measured static flexibility matrix, which is assembled from a combination of measured modal vectors, frequencies, and driving point residual flexibilities. As a consequence, neither method requires a mode-to-mode correlation, and both avoid tedious modal discrimination and selection. The first method detects damage as a softening in the point flexibility components, which are the diagonal entries in the flexibility matrix. The second method detects damage from the disassembled elemental stiffnesses as determined using a presumed connectivity. Vibration data from a laser vibrometer is used to measure the modal mechanics of a DC9 aircraft fuselage before and after induced weakening in a longitudinal stringer. Both methods are shown to detect the location of the damage, primarily because the normal stiffness of the reinforced shell of the fuselage is localized to a few square centimeters.

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10 p.

Notes

OSTI as DE96006321

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  • 14. international modal analysis conference, Dearborn, MI (United States), 12-15 Feb 1996

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  • Other: DE96006321
  • Report No.: LA-UR--95-4382
  • Report No.: CONF-960238--9
  • Grant Number: AC04-94AL85000
  • Office of Scientific & Technical Information Report Number: 205155
  • Archival Resource Key: ark:/67531/metadc667698

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  • February 1, 1996

Added to The UNT Digital Library

  • June 29, 2015, 9:42 p.m.

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  • Feb. 29, 2016, 1:49 p.m.

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Robinson, N.A.; Peterson, L.D.; James, G.H. & Doebling, S.W. Damage detection in aircraft structures using dynamically measured static flexibility matrices, article, February 1, 1996; New Mexico. (digital.library.unt.edu/ark:/67531/metadc667698/: accessed August 20, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.