Guided Waves for Aircraft Panel Monitoring

Abstract

The reported research concerns experimental investigation toward the monitoring of an aircraft panel. Guided wave propagation phenomena were used to obtain information about the state of the monitored structure. A curved aluminium panel with rivets was investigated. Piezoelectric transducer was used to excite guided waves in chosen structural element. The generated signal was amplified before applying it to the transducer in order to ensure measurable amplitude of excited guided waves. Measurement of the wave field was realized using laser scanning vibrometer that registered the velocity responses at a points belonging to a defined mesh. This contactless measurement technique allowed to investigate phenomena related to wave propagation in the aircraft panel. In the first stage, due to high complexity of the element, baseline measurements were taken. Next, a discontinuity (additional mass) was introduced on the panel surface and the measurements were repeated. Signal processing methods for features extraction from signals were proposed. These features were applied in order to detect and localize the presence anomalies in the investigated panel. The signal processing was conducted in MATLAB with the procedures developed by the authors. The used measurement technology (vibrometer) allowed to register whole wavefield of the propagating guided waves. This allowed to visualize the interaction of the waves with rivets. After introducing the discontinuity on the panel surface wave interaction with it was investigated. Two positions of the additional mass were considered. One just before the riveted stiffener and second after the stiffener. Because of this the influence of the stiffener on the damage detection abilities could be investigated. It can be concluded that the guided wave can be used for monitoring of such complex structures. The vibrometer measurements allowed learn about the guided wave propagation phenomena and perform successful damage localization.