Advanced electromechanical impedence method for damage detection of concrete/composite structures

Abstract

Each year, structural health monitoring (SHM) techniques has been gaining significant amount of attention due to its possibility of increasing structural reliability. Although various nondestructive evaluation techniques exist for SHM, such as acustic emission, ultrasonic impedance, and impact echo testing, these techniques often require expensive and sophisticated hardware with expert operators, limiting their applications to a certain aspect. On the other hand, a nondestructive evaluation (NDE) technique widely known as electromechanical impedance (EMI) method has shown promising results as a local NDE method. In this study, advanced techniques related to EMI method is discussed to overcome some of the current existing problems. Firstly, eliminating the manual selection process of frequency ranges for EMI method is discussed and a solution using reusable EMI technique is introduced to overcome this problem. Commercialized neodymium magnet is used to create reusable PZT sensors which allows for a single sensor to monitor multiple areas simply by attaching or removing it onto steel structures. Since the reusable sensor is attached by magnetic force, the resonance frequency ranges of the sensor remains vaguely changed. Thus by knowing the resonance frequency ranges of the reusable sensor, the need for searching suitable frequency ranges for EMI method is eliminated. Secondly, the previous work is continued by expanding the introduced idea onto structures where EMI method is very difficult to perform. For structures with large surface areas, conducting EMI method can result in unsuccessful damage detection due to vague changes in the impedance signature. However, using a metallic object in between the PZT and the host structure can enhance the damage identification performance of the EMI method. The idea is furthered by applying this principle for conducting EMI method on structures with complex surface or elevated temperature. Since the piezoelectric cera...