The Dynamic Performance Of The Piezoelectric Actuators In Structural Health Monitoring Study

In recent years, piezoelectric materials have been used in many fields, such as industry, transportation, healthcare, aviation, aerospace etc. As the study hot point, nondestructive evaluation has attracted the attention of many researchers. In the new subject research (based on smart piezoelectric sensors/actuators integration technology), high-frequency elastic wave in an elastic structure induced by surface-bonded piezoelectric actuator under high-frequency electric loads, can properly capture the changes in local dynamics due to incipient structural damage. In this thesis, based on electromechanical coupling analysis, theoretical analyses on the excitation and detection of acoustic waves in an elastic structure to detect the creation and evolution of structural defects with piezoelectric actuators are established. The valuable results obtained have instructional significance on nondestructive evaluation (NDE) and enhancing the integral performance of these models during practical application.In this thesis, theoretical analyses on the excitation and detection of acoustic waves in an elastic structure to detect the creation and evolution of structural defects with piezoelectric actuators under three more realistic different structural modes were established.(1) Based on the basic theory of elasticity, the analytical solution to elastic wave in an elastic structure induced by piezoelectric actuator can be obtained by integration of the normal strain, and the displacement and traction shall be continuous according to the continuity conditions between the piezoelectric actuator and the elastic structure, then, the elastic wave propagation problem can be dealed with in further degree. Propagation property of high-frequency elastic wave in an elastic structure induced by surface-bonded piezoelectric actuator are analyzed, and the interaction between geometric parameters, material combination, loading frequency and the wastage of wave propagation is also discussed, which can provide criterion for damage identification in local structure.(2) For the two dimensional (2-D) in-plane (P-SV) problem, the analytical solution to piezoelectric strip is presented. Theoretical model for the excitation and detection of acoustic waves in an elastic plate to detect the creation and evolution of structural defects with piezoelectric actuators is established. Basic electric and acoustic properties including impedance, resonant frequencies and mode shapes are calculated. Energy trapping, an important phenomenon which happens in the place confined to be under and close to the actuators, is observed and examined. The results obtained are helpful for the structural damage detection, especially the detection of incipient minimal structural damage.