Accession Number : ADA260119


Title :   Damage Evaluation of Structures Using Frequencies and Mode Shapes Extracted from Laser Interferometry


Descriptive Note : Final rept. Sep 1989-Aug 1992


Corporate Author : TEXAS UNIV AT EL PASO


Personal Author(s) : Osegueda, Roberto A


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a260119.pdf


Report Date : Nov 1992


Pagination or Media Count : 12


Abstract : Non destructive damage evaluation theories to detect, locate and quantify damage in structures from vibrational characteristic measurements are summarized. Modal analysis experiments were conducted on cantilever beams and suspended plates using a laser interferometer vibration pattern imager. Resonant frequencies and mode shapes measured before and after damage were used to assess the inflicted damage. Three theories of damage detection were tested with the experimental measurements. It was found that the exact eigenvalue sensitivity method, which relates changes in eigenvalues and mode shapes to damage parameters, worked well in detecting the damage after an analytical model of the undamaged system was identified. However, the method was very sensitive to errors in the mode shape measurements. A method based on sensitivity of damage to eigenvectors required measurements of small changes of eigenvectors and was not proven. A modal strain energy approach, which culminated in an expression relating changes in thickness to changes in modal curvatures, Is also summarized. Modal curvatures were obtained through curve-fitting and smoothing techniques. This method worked very well for cantilever beams but fail to conclusively detect damage in plates.... Damage evaluation, Laser interferometry, Model analysis.


Descriptors :   *DAMAGE ASSESSMENT , *PLATES , *CANTILEVER BEAMS , THICKNESS , VIBRATION , DETECTION , ENERGY , STRUCTURES , EIGENVALUES , SENSITIVITY , INTERFEROMETRY , CURVE FITTING , INTERFEROMETERS , ERRORS , RESONANT FREQUENCY , STRAIN(MECHANICS) , EIGENVECTORS , SHAPE , DAMAGE , NONDESTRUCTIVE TESTING , MODELS


Subject Categories : Structural Engineering and Building Technology
      Test Facilities, Equipment and Methods


Distribution Statement : APPROVED FOR PUBLIC RELEASE