Influence of loading on the electromechanical admittance of piezoceramic transducers

Abstract

Damage detection using electromechanical (EM) impedance in structural health monitoring(SHM) of engineering structures is rapidly emerging as a useful technique. In the EMimpedance method, piezoceramic (PZT) transducers are either surface bonded to orembedded inside the host structure and are subjected to electric actuation. The EMadmittance signatures of the PZT transducers, which consist of real and imaginary parts,serve as indicators to predict the health/integrity of the host structure. However, in reallife, structural components such as slabs, beams and columns are constantly subjectedto some form of external loading. The EM admittance signature obtained forsuch a constantly loaded structure is different from that obtained when damagesare present in the structure. This paper presents an experimental and statisticalinvestigation to show the influence of loading on EM admittance signatures. It is alsoobserved that the susceptance signature is a better indicator than the conductancesignature for detecting in situ stress in the host structure. This observation isfurther supported by a statistical analysis. This paper is expected to be useful forthe non-destructive evaluation of engineering structures with external loading.