Piezoelectric wafer active sensors may be applied on aging aircraft structures to monitor the onset and progress of structural damage such as fatigue cracks and corrosion. The state of the art in piezoelectric-wafer active sensors structural health monitoring and damage detection is reviewed. Methods based on (a) elastic wave propagation and (b) the Electro–Mechanical (E/M) impedance technique ...

Due to the high frequency range employed, the impedance-based technique is very sensitive to minor changes in the near field of piezoelectric sensors. The sensitivity of this technique to local changes is very useful in most cases. However, due to the difficulties in developing an analytical model at such high frequency ranges, this technique can not correlate a change in electrical impedance w...

A digital signal processor based evaluation board has been utilized in the development of hardware for the impedance-based structural health monitoring technique. This hardware employs digital output to generate a rectangular excitation pulse train for structural excitation, and receives a digital input to sense the structural response. The DC power supply to this hardware is now replaced with ...

Electromechanical (E/M) impedance method is emerging as an effective and powerful technique for structural health monitoring. The E/M impedance method utilizes as its main apparatus an impedance analyzer that reads the in-situ E/M impedance of piezoelectric wafer active sensors (PWAS) attached to the monitored structure. Laboratory-type impedance analyzers (e.g. HP4194) are bulky, heavy, and ex...

This paper presents an overview of research performed at the AGH University of Science and Technology in the field of the electromechanical impedance method for damage detection in mechanical structures. A theoretical background on the described method is made in the first part of the paper. Next, results of numerical analyses of the electromechanical impedance for simple mechanical structures ...

This paper describes the use of the electro-mechanical (E/M) impedance method for health monitoring of aging aerospace structures. As a nondestructive evaluation technology, the E/M impedance method allows us to identify the structural dynamics directly by obtaining the E/M impedance signatures of attached piezoelectric wafer active sensors (PWAS). The theoretical model for 2-D structures, whic...

In this work, three machine learning approaches were evaluated for detecting anomalies in impedance-based structural health monitoring (ISHM – Impedance-based Structural Health Monitoring) of a specimen controlled environment. Supervised, unsupervised, and semi-supervised algorithms chosen to compare them regarding an aluminum beam with failure induced by surface machining on one the faces. Aft...

Electro-mechanical impedance method is emerging as an important and powerful technique for structural health monitoring. The E/M impedance method utilizes as its main apparatus an impedance analyzer that reads the in-situ E/M impedance of the piezoelectric wafer active sensors (PWAS) attached to the monitored structure. Present-day impedance analyzer equipments (e.g. HP4194) are bulky, heavy an...