Research On Piezoelectric Impedance Technology For Structural Health Monitoring

Piezoelectric impedance technology for structural health monitoring is a brand-new method for structural damage detection appearing in recent years. In this thesis, the application of piezoelectric impedance technology in detecting two different types of structural damages has been studied, including bolted joint looseness and beam crack. Experimental results have shown that, not only these damages can be detected successfully, but also the damage growth rate can be judged qualitatively.Theoretical analysis on coupling impedance between piezoelectric porcelain (PZT) and the structure is presented in detail. The relations between electrical impedance of PZT and mechanical impedance of structure are induced. Based on these theories, an experiment applying the impedance-based structural health monitoring technique for detecting damage in structures is designed. By structural finite elements analysis, a range of frequency is attained to which the damage in structures is sensitive. A new method of impedance measure is also developed, which can reduce the equipment cost and size greatly and expand the range of detection. After investigating the qualitative damage identification method based on PZT's impedance graph, a quantitative identification method based on health index is proposed, which can express the health status scientifically and exactly. Experimental results show that the bolted looseness at different places and beam crack of different sizes can be detected successfully with good repetitivity.