Damage detection using the impedance-based SHM approach under dynamic and static loads

Abstract

The Structural Health Monitoring (SHM) methods are used to inspect and detect structural damage. And one of the methods that is showing promising results is the Structural Health Monitoring based on Electromechanical Impedance (Impedance-based Structural Health Monitoring - ISHM). This tool stands out as a versatile technique, which can be easily applied in complex structures due to the portability of instruments, ease and agility in data processing, generating real-time information about the structure. This method is based on the principle of Electromechanical Impedance (EMI), which uses the interaction between the mechanical and electrical properties of a piezoelectric transducer, coupled or incorporated in a structure, to measure impedance signatures. With these signatures, it is possible to qualitatively evaluate the presence of the damage. And to quantify changes in impedance signatures, it is used mathematical functions called damage metrics. Despite the advantages of the impedance method, this technique still has some disadvantages, such as influence on temperature variation, static and dynamic loads, causing false positives in the damage detection. This article focuses on the application of the Impedance based SHM method, performing two experiments on structures under external vibrations, static loads and temperature variations to analyze their influence on impedance signatures. For this, an aluminum beam was made with a piezoelectric transducer bonded on its surface. In addition, to evaluate the damage detection of the technique under various boundary conditions, a damage was simulated in the structure, which nut and bolt were removed from the beam.