Structural vibration behavior is an essential signature of the integrity of structures and hence has been used for damagedetection. Structural vibration impedance by way of piezoceramic patch excitation and sensoring offers a local damagedetection technique. The commonly used damage index in this method is the rate of change of the real part of themeasured electromechanical impedance. This paper studies several damage indices constructed by the real and imaginaryparts or magnitude and phase of the measured impedance and attempts to answer the question of which part of thecomplex valued electromechanical impedance is better for damage assessment. It theoretically deducts and concludes thatthe damage index in terms of the change in real part is in fact not a properly defined index; on the other hand, the indicesin terms of the change in magnitude and phase are shown as clear and properly defined in physical concept. It is furtherdemonstrated by experiment that the damage index in the change of real part is not robust and is prone to measurementnoise, whereas the whole complex valued impedance offers optimized and robust damage index.
|Publication status||Published - 2009|