Application of piezoelectric impedance technology in structural damage detection

Recently, the impedance-based damage detection technique has been developed as a promising tool for real-time structural damage assessments. The basic concept of this method is using the electromechanical coupling property, in which the electrical impedance of piezoelectric materials is directly related to the mechanical impedance of the host structure. Through detection the measured electrical impedance and comparing it with a reference measurement, we can qualitatively determine structural damage is starting or has already been occurred. However, it usually needs high quality impedance analyzer for detecting very small damage. Moreover, laboratory-type impedance analyzers are bulky, heavy, and relatively expensive. They can not easily carried into the field for on-site structural damage detection. In this paper, we develop a field-portable small-size impedance measurement system for structural damage detection. The system consists of a rectangle wave generator, computer, AD converter and piezoelectric element. We present some experimental results for testing the torque loose in the bolt for a truss structure. The results indicate that an accuracy of the impedance measurement system proposed in this paper is almost as accurate as the commercial multipurpose impedance analyzer. It could be used on the structures for damage detection, and for very small damage.