| dc.description | This dissertation presents the strategies used for developing four damage indices, based on various signal analysis methods, used for locating and quantifying structural damage. The proposed damage indices demonstrate the effectiveness of a series of coupled mathematical/engineering approaches that enable us to detect damage in structures, reliably and accurately. The proposed health monitoring methodology is based on monitoring the vibration response of structures using piezoelectric sensors. The Fast Fourier transformation (FFT), FFT integration, wavelet transformation (WT), wavelet packet transformation (WPT) and the Empirical Mode Decomposition (EMD) methods are used to examine the structure's dynamic response signals caused by an impacting force. Novel "damage indices" expressions are developed based on the evaluation of the vibration induced energies. The proposed methodologies were verified both numerically and experimentally. Finite element analysis was used to simulate the response, of healthy structures, as well as structures with various size damages with piezoelectric patches mounted on them. Various damage cases were studied to verify the proposed damage indices. The proposed formula was also used to assess the integrity of bonded joints. Experimental results demonstrated that the proposed methodologies could detect the integrity of adhesive bonded joints with the use of only a single sensor. A system identification technique was developed based on EMD and the Hilbert-Huang transform (HHT) and was verified numerically for a six degree freedom mass-spring system. Experimental investigation was also carried out for evaluation of damping of PVC pipes with equipped piezoelectric sensors with the various available techniques and the results were compared to that obtained through the proposed EMD/HHT system identification method. | en_US |
