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The method of strain energy mode shapes allows the determination of changes in structural integrity from changes in the vibrational response of a structure. The modified method presented does not require knowledge of the undamaged state of the structure. Genetic algorithms (GA) are applied to produce a sufficiently optimized amplitude characteristic of a filter used to extract damage information from strain energy mode shapes. Finite element modeling has been used to produce a training data set with the known location of damages. The amplitude characteristic of the filter has been encoded as a genetic string where the pass coefficient for each harmonic of its discrete Fourier transform representation is a number between zero and one in 8-bit Gray code. The genetic optimization has been performed based on the minimization of the signal-to-distortion ratio. The amplitude characteristic of the filter was not limited to any specific configuration, i.e. either low-or high-pass or specific cut-off frequencies. The results obtained from the GA confirmed the theoretical predictions and allowed improvement in the method's sensitivity to damages of lower magnitude.
Date of Conference: 2002