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...
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10 citations
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
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
01 Jan 2022
2 citations
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.
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References
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01 Jan 2008
TL;DR: In this article, the effect of the crack parameters length, depth and inclination angle on defect detection was discussed, and a series investigation on forged components showed a good probability of detection and a low false alarm rate compared to magnetic particle testing.
Abstract: Dynamic thermography with inductive excitation is analysed as an alternative to magnetic particle inspection or to eddy current testing. Given by the relation of the electromagnetic skin depth, the thermal penetration depth and the crack dimensions to be detected, different regimes for defect detection are identified. The effect of the crack parameters length, depth and inclination angle are discussed. In ferritic steel, at induction frequencies of 100-200 kHz, perpendicular open cracks with a length of 7.5 mm were detectable when their depth was minimum 0.15 mm. For inclined cracks, the sensitivity is even higher. Experiments were performed on cold and warm forged steel components. The signal-to noise ratio obtained from defects was usually high, the critical limitation on technical surfaces is the background due to surface roughness and due to surface contamination. A series investigation on forged components showed a good probability of detection and a low false alarm rate compared to magnetic particle testing. The short testing times of a few 100 ms per object view will allow short cycle times for mass products.
51 citations
Journal Article•
48 citations
TL;DR: In this article, the authors defined the total area of jet impingement in terms of the number of holes and the amount of heat transferred from a hole to a lipskin.
Abstract: Nomenclature Aimp = total area of jet impingement a;b;c = constants C = constant Cp = specie c heat capacity of air Cx = distance between the holes d = hole diameter G = mass e ow per unit area of impingement h = heat transfer coefe cient N = average heat transfer coefe cient, q=Aimp.Tpiccolo i N Tlipskin) L = length of nozzle N = number of holes Nu = local Nusselt number Nu = average Nusselt number Pr = Prandtl number q = heat transfer from impinging air, w £Cp £.Tpiccolo i N Texhaust/£3600 Re = Reynolds number based on hole diameter, .w=Nholes/£.d=Aholeπ/ ReG = Reynolds number based on impingement area, 4Gd=oπ T = temperature N T = average temperature w = mass e ow rate Zn = perpendicular distance from hole to lipskin µ = jet impingement angle π = dynamic Viscosity
47 citations
"Detection of dis-bond between honey..." refers background in this paper
...It provides an aerodynamic shell for minimum drag [1], incorporates de-icing capability [2], noise attenuation [3], and mechanisms to reverse engine thrust for braking [4]....
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TL;DR: In this paper, an investigation has been made of the potential of pulsed-transient thermography for identifying the location of fixtures beneath aircraft skins to facilitate accurate automated assembly operations.
Abstract: In this work, an investigation has been made of the potential of pulsed-transient thermography for identifying the location of fixtures beneath aircraft skins to facilitate accurate automated assembly operations. Representative test structures, comprising of aircraft skin (i.e. aluminium (Al) or carbon fibre reinforced plastic (CFRP)) positioned over a thick strut fixture of Al or CFRP, were investigated experimentally and analysed using finite difference thermal modelling software, taking into account the size and depth of the features, as well as the thermal properties of the investigated materials. The ability of the technique to detect a subsurface fixing and to provide information about its location was analysed. Results from the modelling and the experimental analysis are presented and discussed.
44 citations
"Detection of dis-bond between honey..." refers background in this paper
...beneath aircraft skins [7], notches under multi-ply composite patching, porosities [8], delamination [9], impact damages on carbon fibre reinforced plastic panels [10] and...
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TL;DR: An overview on the current state-of-the-art regarding the use of flash thermography to evaluate the porosity percentage in fiber reinforced composite materials and to present the latest results, which are gathered by the authors, on porous carbon fiber reinforced polymer laminates.
Abstract: It is a fact that the presence of porosity in composites has detrimental effects on their mechanical properties. Then, due to the high probability of void formation during manufacturing processes, it is necessary to have the availability of non-destructive evaluation techniques, which may be able to discover the presence and the distribution of porosity in the final parts. In recent years, flash thermography has emerged as the most valuable method, but it is still not adequately enclosed in the industrial enterprise. The main reason of this is the lack of sufficient quantitative data for a full validation of such a technique. The intention of the present work is to supply an overview on the current state-of-the-art regarding the use of flash thermography to evaluate the porosity percentage in fiber reinforced composite materials and to present the latest results, which are gathered by the authors, on porous carbon fiber reinforced polymer laminates. To this end, several coupons of two different stacking sequences and including a different amount of porosity are fabricated and inspected with both non-destructive and destructive testing techniques. Data coming from non-destructive testing with either flash thermography or ultrasonics are plotted against the porosity percentage, which was previously estimated with the volumetric method. The new obtained results are a witness to the efficacy of flash thermography. Some key points that need further consideration are also highlighted.
35 citations
"Detection of dis-bond between honey..." refers background in this paper
...beneath aircraft skins [7], notches under multi-ply composite patching, porosities [8], delamination [9], impact damages on carbon fibre reinforced plastic panels [10] and...
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