Damage severity assessment in composite structures using multi-frequency lamb waves

Abstract

When a narrowband tone burst excitation signal is used to generate Lamb waves in the thin composite plates, a suitable frequency of the excitation signal is typically chosen to excite a solitary mode of Lamb wave in the structure. However, if and as the damage severity changes in the structure, it may be possible that the frequency of the excitation signal may influence the response metric. In the present work, the use of a chirp signal as an excitation signal for damage severity assessment is proposed. The use of a chirp signal as an excitation signal may prove suitable for damage severity assessment because the chirp response contains a large frequency bandwidth, and the cumulative effect of all the frequencies with the delamination is reflected in the damage index. The sensitivity of the chirp response to varying delamination sizes is investigated through numerical simulations and experiments. The damage index calculated using the chirp response showed a monotonic trend with an increase in damage severity, in contrast to a bidirectional trend of the damage index when conventional narrow excitation signals are used.

Spacecraft Segment Damage Identification Method Based on Fiber Optic Strain Difference Field Reconstruction and Norm Calculation

“…The structural health-monitoring method based on piezoelectric sensing array excites and receives guided wave signals online through piezoelectric devices integrated inside or on the surface of the structure, and identifies the structural damage state based on the change in the guided wave signal characteristics [6,7], but it requires a large number of signal transmission cables, which is inclined to cause complexity of the monitoring system, and there are certain limitations in monitoring structural damage at large scales. In contrast, distributed fiber optic sensors have unique advantages such as resistance to electromagnetic and radio frequency interference, integration of transmission and sensing, and good applicability for real time monitoring of spacecraft structural damage [8,9].…”

Bolt tightness monitoring using multiple reconstructed narrowband Lamb waves combined with piezoelectric ultrasonic transducer

“…Even though the appropriate excitation frequency was determined, the reflection coefficients of narrowband ultrasonic waves in a notch still exhibit a cosinusoidal periodic shape [28], which means that the damage index based on narrowband excitation may be non-monotonic with the increase of damage. To tackle this problem, Nandyala et al [29] utilized broadband chirp signal as excitation and defined the decorrelation coefficient as the damage index based on chirp response in time domain. The results demonstrated that the damage index could reflect the cumulative effect of multiple frequencies and exhibit monotonic trends with the development of damage.…”

“…The chirp excitation-based narrowband signal reconstruction method has been used to select the optimal excitation frequency [25], achieve steady damage monitoring [29] and improve the damage localization accuracy [32,33], demonstrating the superiority of chirp excitation in ultrasonic wavebased structural health monitoring. The multiple-frequency components contained in the broadband chirp response possess different sensitivities to different bolt tightness conditions.…”

Structural damage quantification in shear buildings using mode shape slope ratio

“…Dafydd and Khodaei 27 used laser Doppler vibrometer to capture wavefield interaction via ultrasonic guided Lamb waves to characterize the through thickness severity in carbon-fibre-reinforced polymer structures. Later, Nandyala et al 28 extended the usage of multi-frequency lamb waves to quantify delamination in composite plates. Cheng et al 29 used output-only signals to establish relationships of damage severity with low-frequency components and showed its applicability on simple multi-degree-of-freedom (DoF) spring-mass system.…”