Non-linear Lamb Waves for Locating Defects in Single-Lap Joints

Abstract

A novel method based on Non-linear Lamb waves behavior and Local Defect Resonance (LDR) is proposed for locating and evaluating disbonds in Single-Lap Joints (SLJ) typically used in aerospace industry. The presence of damages/defects such as disbonds leads to the presence of sub-and super-harmonics components in the frequency response. The maximum acoustic wave-damage interaction is reached by particular excitation frequencies that enhance the Non-linear response causing LDR. The LDR frequency is experimentally evaluated through the appearance of a single subharmonic component in the frequency spectrum of signals received by piezoelectric transducer (PZT) bonded on the structure. The Non-linear properties of Lamb waves are exploited to make defects generate subharmonic waves at LDR frequency. An algorithm is implemented for damage/defect localization that is accurately obtained by knowing PZTs positions, Time of Flight (ToF) and propagation properties of subharmonics packet. Several disbonds with different dimensions are artificially reproduced on an aluminum SLJ: experimental and FE results show good accordance both in usual (single damage) and critical (multi-damage) scenario. The paper proposes a baseline-free method for the disbonds detection, characterization and localization in SLJs that uses the PZT signals without affecting adhesive interface, thus allowing for an active health monitoring.

Ultrasonic Guided-Waves Sensors and Integrated Structural Health Monitoring Systems for Impact Detection and Localization: A Review

“…For example, the separation of the two modes S 0 and A 0 by CWT o STFT is relevant for the evaluation of the DToAs for low and high velocity impacts, as we will describe in Section 2.2 . However, simple analysis with CWT or STFT may still be too restrictive in the presence of structures with inserts, reinforcement elements, and therefore several methods have recently been proposed to overcome this problem, such as those reported in [ 30 , 31 , 32 , 35 , 36 , 37 ]. The well-known time-reversal approachis another important method introduced in [ 38 ] to compensate for the dispersion and alleviate the complexity of Lamb wave signal interpretation; this approach was adopted by Zeng et al [ 39 ].…”

Ultrasonic Guided-Waves Sensors and Integrated Structural Health Monitoring Systems for Impact Detection and Localization: A Review

“…For example, the separation of the two modes S 0 and A 0 by CWT o STFT is relevant for the evaluation of the DToAs for low and high velocity impacts, as we will describe in Section 2.2. However, simple analysis with CWT or STFT may still be too restrictive in the presence of structures with inserts, reinforcement elements, and therefore several methods have recently been proposed to overcome this problem, such as those reported in [30][31][32][35][36][37]. The well-known time-reversal approachis another important method introduced in [38] to compensate for the dispersion and alleviate the complexity of Lamb wave signal interpretation; this approach was adopted by Zeng et al [39].…”

Structural health monitoring of adhesive joints using Lamb waves: A review

“…Due to the complex nature of LW, several data processing methods have been adopted, namely for adhesive joints. However, those techniques have been implemented just in small and simple structures that have only one type of damage 9‐14 . To allow for large‐scale and complex geometry parts inspection, there have been two main research lines.…”

“…However, those techniques have been implemented just in small and simple structures that have only one type of damage. [9][10][11][12][13][14] To allow for large-scale and complex geometry parts inspection, there have been two main research lines. One involves utilizing data driven procedures, where the algorithm decides the best location for the sensors and actuators, according to the accuracy and resolution necessary.…”