Application of active structural health monitoring technique to aircraft fuselage structures
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Damage identification of complex structures can be performed using an Active Structural Health Monitoring System (ASHMS) utilizing an array of piezoceramic (PZT) sensor- actuators and an electromechanical impedance analyzer. Based on the theory of electromechanical impedance for surface-bonded collocated sensor-actuators, the system provides the means of implementing effective Non-Destructive-Evaluation health monitoring to a structure at any point in its life cycle. When integrated into a structure, the ASHMS can identify the location and extent of damage through a statistical analysis algorithm which compares the electromechanical admittance of the structure's current condition with the structure's `baseline' condition over a defined frequency range. This paper presents a model independent method of structure damage identification based on statistical analysis of the changes in the electromechanical impedance of the structural response. Using a small section of an airplane fuselage with free-free boundary conditions as the test structure, a prototype system has been successfully developed which automatically measures and collects the electromechanical admittance data from an array of transducers. The measurement system developed can apply large voltages to the PZT transducers, while accurately determining the spectral and harmonic information of the frequency range of interest resulting in an increase in the measurement sensitivity and the area monitored by a single transducer. The system can accurately measure and collect large amounts of structural information with a limited number of transducers in a very short period of time. The post-analysis of the measured structural variation can be performed with the advanced signal processing algorithm presented herein within seconds of data collection. The results show a remarkable accuracy of damage location identification for a complex structure. The basic research conducted so far indicates that the ASHMS and associated processing techniques have a promising potential for health monitoring of real complex structures.