Application of the FRF curvature energy damage detection method to plate like structures

The objective of current work is to show the effectiveness of using frequency response function (FRF) curvature energy damage index and to establish its capability to detect and localize damage. The dimension of aluminium plate under consideration is 0.25m×0.25m×0.003m with fixed-fixed support condition Damage is simulated by reducing the thickness of one element for different damage cases. The mode shape and FRF energy data of the square plate with damage of different sizes are obtained by free vibration analysis using MATLAB 7.0. Testing the frequency intervals, it is found that the FRF curvature energy damage index method defined in the range of frequencies include the eigen frequencies. The damage index is found to be a function of the frequency bandwidth and variation of FRF curvature energy damage index versus frequency range (band width) seems to provide further information in choice of optimum frequency range response analysis. This typical analysis presented wider frequency ranges, including several higher modes, the difference of curvature energies of the damaged and undamaged model becomes less significant. The influence of noise in the FRF data seems to be quite small. It also found that influence of excitation location is not important for the damage detection. It is observed that by using FRF curvature energy damage index data, damage location can be identified provided the reduction in elemental thickness is more than 10%.