Research On Performances And Applications Of PZT Smart Module

With the rapid development of new material technology, the information technology and the computer technology, the civil engineering has an unprecedented improvement. At the same time, with the development of economy and technology, the health monitoring of large-scale structure especially concrete structure is highly demanded. Because of the double grading in concurrently traditional compound materials structure and the function compound materials structure, the intelligent material structure more and more shows its importance and draw much interesting of engineers. Effort has been made by scientific research institutions, experts and even governments on the research and the applications of intelligence material structure and health monitory system.Based on the previous research, this thesis details the research on the temperature characteristics of piezoelectric ceramic embedded in concrete which constructs the piezoelectric embedded concrete smart module, and the experimental researches on the concrete ultrasonic detecting by piezoelectric-embedded ceramic module. The contributions of this paper are listed as follows.(1) The components of concrete are analyzed. The mechanical, distortional and durability performance of concrete structure is researched, which provides the essential theory explain for the coupling between piezoelectric ceramic and concrete. Such theory also provides the explanation for the experimental results in both the stress and temperature experiment of piezoelectric-embedded ceramic module.(2)The piezoelectric characteristics of the smart module are studied. Starting from the electric and mechanic feature of piezoelectric material, the mechanisms and the equivalent circuit model of the piezoelectric ceramics embedded in concrete are established. The principle of structure health monitory by using the equivalent circuit parameters of piezoelectric ceramic are studied. It is found that the changes of the equivalent circuit parameters take on near linearity with the environmental quantities such as stress and temperature.(3)Considering the situation of being embedded in concrete, this thesis studies the influence of geometry size and the casting process of concrete modules on the performance of the embedded piezoelectric ceramic. The choice of the ceramics and the structure design for the certain thickness of the rubber on the piezoelectric ceramic before buried in the concrete is analyzed. For the piezoelectric ceramic embedded in concrete, the use of rubber not only reduces the stress concentration caused by concretion, but also prevents two electrode of piezoelectric ceramic from short circuit as well as corrosion destruction, etc. The experimental results show that thickness of rubber does not make much influence on the stress response of the equivalent circuit parameters of the embedded ceramic. The technique of stress monitory by piezoelectric-embedded concrete element is represented.(4)The temperature response of the piezoelectric ceramic in two different situations——a) the ceramic is covered with different thickness rubber layers, and b) the ceramic is embedded in different depth——are compared. The changes of the characteristic frequencies and the equivalent circuit parameters of the piezoelectric ceramics are researched. It is found that the characteristic frequencies and the equivalent circuit parameters are sensitive to temperature. However, the temperature response of the equivalent circuit parameters will also be affected by stress (cross sensitivity).(5)Ultrasonic wave and its acoustic impedance of the medium in the path of propagation are studied. The characteristic of the ultrasonic wave transmitting in the concrete is summarized. The experimental setup of the ultrasonic wave experiment with piezoelectric-embedded ceramic module is described. The experimental results show that by using the piezoelectric ceramic embedded in concrete as the ultrasonic wave transducer, the ultrasonic wave can be emitted with relative low energy loss. The characteristics of the received wave such as speed, time, wave amplitude and shape, etc, are analyzed in detail.