Model experiments of damaged structural identification based on electro-mechanical impedance technique

Based on the electro-mechanical impedance (EMI) technology for structural health monitoring, model experiments were carried out to study the damage identification in a steel beam which is widely used in structural engineering. A precise impedance analyzer HP4294A was used to extract and analyze the electricity admittance signals in different frequency domain from the original undamaged and damaged model steel beam. The damaged model is made by presetting artificial cracks with appointed location and depth in the steel beam, and the damaged severity is imitated with the different quantities of cracks. The experiment results showed that, the conductance signals shifted to the left with the propagation of damages in the beam. The conductance signals in different frequency domain respond differently to the same damaged model, and a suitable frequency domain signals can detect more effectively if damages occurred in the model. In order to characterize the damage severity of structure quantitatively, three different damage indexes were employed in analyzing. The result showed that the only index MAPD (mean absolute percentage deviation) could quantify the damage degree precisely and effectively. It is also noted that the location of the damages in the structures could be identified through reasonable distribution of piezoelectric-ceramic patches and by analyzing the peak offset of conductance signals. The experimental studies lay the foundation for damaged structural detection based on the EMI technology.