Theoretical And Experimental Studies Of PZT Impedance Method In Structural Damage Detection

The characteristics of stiffness and strength in components change a lot compared with those at the design state. When the structure suffer the natural catastrophe or sustain for a long time, the damage will occur in the structure, evenly result in safe emergency because of the accumulation of damage, thereby, studying the method which can succeed in detecting the change of structural parameters efficiently and conveniently, furthermore evaluate the health condition of structures in time would be very important. Supported by the National Natural Science Foundation of China (No.50378041) the thesis has studied theoretically and experimentally the piezo-electricity (PZT) impedance method in structural damage detection. Firstly, in this thesis the traditional methods to detect structure damage are discussed, the merits and the defect are pointed out. The new method using the PZT impedance method to detect the structural damage is also introduced, emphasis has been paid on the comparison of the PZT impedance method and the other main traditional methods. Then, the basic theory of the application of the PZT impedance method in structural damage identification is analyzed which includes the notion and feature of the intelligent material, the application of PZT in the intelligent structure, the basic theory of piezo-electricity vibration and the deduction the relation between PZT and the structure coupling electrical impedance. Finally, the effectiveness of the proposed PZT impedance method used in the structural damage detection has been verified by two kinds of experiments, i.e., the damage detection of steel beams with four various support conditions in three damage states and the age strength tracing of a concrete cubic block. The experimental results reveal that analyzing the varying rules of piezo-electricity admittance spectrum curves can judge whether the steel beam damages or not, and the damage magnitudes of the steel beam in three damage states are quantitatively identified by using a damage condition factor. It can be also found from the experiment that the various strength regulation (Young's modulus) of the concrete cubic block in age can traced by the spectrum curve of the PZT piezo-electricity admittance, which is coincidence with the conclusion by traditional method. As a new damage detection method, the PZT impedance method is developing, and much endeavor needs to be done for its application in practice. Thus, further research is required concerning the utilization of the PZT impedance method in the type, dimension, position localization of the complicated structure, meanwhile the further research regarding the strict relation between PZT piezo-electricity admittance and the age strength of concrete is needed.