Modified Dual Piezo Configuration for Improved Structural Health Monitoring Using Electro-Mechanical Impedance (EMI) Technique

This paper presents a new variant of the electro-mechanical impedance (EMI) technique encompassing sensor-actuator dual configuration for improved damage assessment. In this arrangement, called as dual piezo configuration (DPC), an outer piezoelectric ring acts as the actuator and an inner piezoelectric disc as the sensor. The configuration yields better results than the conventional EMI configuration employing the same piezo patch as the sensor as well as the actuator. This paper presents a more practical and modified version of DPC entailing a group of normal commercially available PZT patches. The piezo sensor configurations evaluated in the paper are: (a) single piezo configuration (SPC), which is conventionally employed in the EMI technique; (b) dual piezo configuration (DPC), which consists two different patches in ring type configuration; and (c) modified dual piezo configuration (MDPC), which uses four outer piezo patches for the actuation and a centrally located piezo patch for the sensing purpose. The paper first covers the comparison of the three configurations through finite element method (FEM), using an aluminum block of dimensions 48x48x10mm as the host structure and lead zirconate titanate (PZT) patches of size 10x10x0.3mm, analyzed through coupled field analysis. The simulation study is followed by an experiment on the aluminum block of the same size and finally on a prototype steel plate of dimensions 1200x970x8mm. Simulation results and experimental data prove that the proposed MDPC is much more sensitive to the occurrence than the conventional SPC. Also, MDPC ensures much larger zone of influence as compared to the conventional SPC as well as the DPC and it commands higher sensitivity. Hence, it can be employed on the large structures to detect damage, which is not possible by using the SPC which may warrant very large number of sensors. Thus, the proposed MDPC approach can be practically employed to detect the damage in large civil, mechanical and aerospace structures.