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Journal ArticleDOI

Detection of dis-bond between honeycomb and composite facesheet of an Inner Fixed Structure bond panel of a jet engine nacelle using infrared thermographic techniques

TL;DR: The Inner Fixed Structure (IFS) bond panel is a honeycomb sandwich panel with CFRP facesheet and a heat shield on one side, and a perforated CFRP faceheet on the other side, of a jet engine nacell as mentioned in this paper.
Abstract: The Inner Fixed Structure (IFS) bond panel is a honeycomb sandwich panel with CFRP facesheet and a heat shield on one side, and a perforated CFRP facesheet on the other side, of a jet engine nacell...
Citations
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Journal ArticleDOI
TL;DR: In this article, a new scheme deploying induction thermography to detect fiber breakage and identify its orientation is proposed, which is experimentally demonstrated on samples with realistic fiber breakages produced in a controlled manner.
Abstract: Carbon fiber reinforced polymer (CFRP) composites are preferred for their specific strength and toughness. As fibers are the main load-bearing constituent of composites, fiber breakage has a significant effect on their strength and stiffness. The complex nature of damage involving oriented fiber breakages across multiple layers has posed a challenge to manufacturers and end-users alike. While detailed investigations of the damage have been carried out using micro-CT scans, assessment of oriented fiber breakages with field-deployable non-destructive techniques would facilitate our understanding significantly. A new scheme deploying induction thermography to detect fiber breakage and identify its orientation is proposed. It is experimentally demonstrated on samples with realistic fiber breakage produced in a controlled manner. Further, a numerical model capturing the proposed inspection mechanism is described.

6 citations

Journal ArticleDOI
TL;DR: In this article , an ultrasonic guided wave propagation in an elastic-viscoelastic (steel-rubber) bilayer structure was investigated and several wave features, such as amplitude, phase velocity and phase delay, were measured and compared to determine the characteristic changes of the A0 wave mode in the steel layer alone as well as in the bilayer structures.
Abstract: This study investigates the ultrasonic guided wave propagation in an elastic–viscoelastic (steel–rubber) bilayer structure. 2D finite element models are developed in the frequency domain to simulate the wave propagation in the steel–rubber bilayer structure. The guided wave A0 mode is generated in the bilayer with a contact L-wave probe and detected with an out-of-plane laser vibrometer. Several wave features, such as amplitude, phase velocity and phase delay, are measured and compared to determine the characteristic changes of the A0 wave mode in the steel layer alone as well as in the bilayer structure. Studies are also performed for the bilayer structure when excited from the steel and rubber surfaces. The amplitude and phase velocity of the A0 mode are reduced in the bilayer compared to the steel layer alone. The phase velocity of the A0 wave mode in the bilayer does not depend on the viscoelastic properties of the rubber layer, rather depends only on the elastic properties of the rubber layer. The viscoelastic rubber layer in the bilayer structure does not sustain any independent wave mode; instead, it carries the A0 mode of the steel layer alone as a modified A0 wave mode in the bilayer structure. A parametric numerical study of the viscoelasticity of the rubber layer in the bilayer structure shows that the attenuation of the modified A0 mode in the bilayer is more affected by the bulk S-wave attenuation than the bulk L-wave attenuation. The rate of attenuation of the modified A0 mode in the bilayer is faster on the rubber surface than on the steel surface. A study on the A0 wave mode interaction with the interfacial disbond between steel and rubber layers is also carried out.

2 citations

Book ChapterDOI
01 Jan 2022

2 citations

Journal ArticleDOI
01 Aug 2022-Sensors
TL;DR: Wang et al. as mentioned in this paper proposed a threshold denoising model based on wavelet transformation with bilateral filtering (WTBF) and a salient components enhancement method based on a multi-scale retinex algorithm combined with frequency-tuned salient region extraction (MSRFT).
Abstract: Thermal imaging is an important technology in low-visibility environments, and due to the blurred edges and low contrast of infrared images, enhancement processing is of vital importance. However, to some extent, the existing enhancement algorithms based on pixel-level information ignore the salient feature of targets, the temperature which effectively separates the targets by their color. Therefore, based on the temperature and pixel features of infrared images, first, a threshold denoising model based on wavelet transformation with bilateral filtering (WTBF) was proposed. Second, our group proposed a salient components enhancement method based on a multi-scale retinex algorithm combined with frequency-tuned salient region extraction (MSRFT). Third, the image contrast and noise distribution were improved by using salient features of orientation, color, and illuminance of night or snow targets. Finally, the accuracy of the bounding box of enhanced images was tested by the pre-trained and improved object detector. The results show that the improved method can reach an accuracy of 90% of snow targets, and the average precision of car and people categories improved in four low-visibility scenes, which demonstrates the high accuracy and adaptability of the proposed methods of great significance for target detection, trajectory tracking, and danger warning of automobile driving.

1 citations

References
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01 Jul 2004
TL;DR: The results of the experiments in Task 4 did not entirely support our initial optimism as mentioned in this paper, however, some important limitations of the SIT system are fundamental, and some aspects of the performance could perhaps be attributed to shortcomings in the design or construction of this first demonstration unit.
Abstract: : The ultimate assessment of feasibility was determined in the final task; however, the tasks preceding it were required in order to construct an optimized test system. Our expectation at the outset of the projects was that the combination of induction heating and thermography would outperform systems based exclusively on either electromagnetic induction or thermography. The rationale was that the combined system would offer better capabilities for wide area inspection of large structures than induction systems, and better sensitivity to deep, low aspect ratio indications than pulsed thermography. Ultimately, the results of the experiments in Task 4 did not entirely support our initial optimism. Although the proof-of-principal system did offer the anticipated advantages for side area inspection, the sensitivity of the system did not exceed that of current pulsed thermography capabilities, and in fact, did not perform as well in some key respects. Although some aspects of the performance of the SIT system could perhaps be attributed to shortcomings in the design or construction of this first demonstration unit, analysis of the data indicates that some important limitations of the approach are fundamental.

2 citations