Performance of Electro-Mechanical Impedance Technique for Detection of Moderate and Severe Damages

As buildings and structures get older, they start to wear down, which is a significant concern worldwide. Detecting damage early and measuring its extent are crucial for safety, preventing substantial failures, and extending the life of structures through repairs or upgrades. One efficient method for this purpose is the electro-mechanical impedance technique, which makes use of piezoelectric sensors. This technique operates in a high frequency range and can detect minor damage. This study examines how well the EMI method using PZT patches as actuators and sensors can detect moderate and severe damage in structures. The main focus of this study is to assess damage based on the EMI technique’s impedance signature using a PZT patch and an LCR meter. PZT transducers create stress waves that move through the structure, and any changes in these waves indicate damage. To find the level of damage, the Root Mean Squared Deviation method was employed to calculate the differences in the electrical properties of a structure and its healthy state. Experiments were carried out to simulate various levels of damage on a 500 x 100 x 100 mm beam under controlled conditions. Artificial damage that ranged from incipient to severe was introduced, and responses were recorded in terms of admittance (conductance and susceptance). The percent change of equivalent stiffness and equivalent mass was calculated. Based on the change in these parameters, classification of moderate and severe damage was done. Moderate damage involved significant changes in stiffness and mass, reflecting a large effect on the structural properties of the system. Severe damage, on the other hand, resulted in a small drop in stiffness and only minor changes in mass, reflecting that the structural response had reached a threshold where further deterioration did not significantly affect these parameters. In addition, the RMSD rose in an increasing manner with the severity of damage, indicating a greater degree of deviation in dynamics as the level of structural deterioration increased. The impedance signature correlation with these structural changes validated the reliability of this technique. In general, this method not only detects the initial development of structural damage but also differentiates its severity, and thus it is a sound tool for real-time structural health inspection.