On the Potential of Instantaneous Frequency as a Damage Detection Tool

Using empirical mode decomposition (EMD) technology, the response signal of structure vibration is decomposed into several mono-component signals which become analytic signal by means of Hilbert transform. The phase differentiation of the analytic signals is defined as instantaneous frequency (IF). Through two numerical examples, the potential of IF as adamage detection tool is examined. The results indicate that in the case of a sudden severe damage in which the structure remains elastic after the damage, the technique can identify the time and extent of the damage; that in the case of hysteretic response, the instantaneous frequency is found inadequate as a robust indicator of modest nonlinearity; and in the case of severe nonlinear behavior, the IF shows some clear nonliear trends. Without measuring noise of the examples, there is a lot of work to be done before the technology is used practically.