Combining the spectral information of Dual-Band images to enhance contrast and reveal details

Quirin, Steven; Herrmann, Hans–Georg

doi:10.21611/qirt.2018.095

Cited by 5 publications

(5 citation statements)

References 6 publications

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“…These images represent a 2D temperature field that is assumed to accurately depict the surface temperature of the captured structure. Thermal imaging cameras can be calibrated and adjusted to radiation to measure more accurate results [7]. A two-point calibration with a calibration radiator is performed within the approximate temperature range to get temperature estimates as close to the real temperature as possible.…”

Section: Theoretical Frameworkmentioning

confidence: 99%

Estimating Thermal Material Properties Using Solar Loading Lock-in Thermography

2021

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This work investigates the application of lock-in thermography approach for solar loading thermography applications. In conventional lock-in thermography, a specimen is subjected to a periodically changing heat flux. This heat flux usually enters the specimen in one of three ways: by a point source, a line source or an extended source (area source). Calculations based on area sources are particularly well suited to adapt to solar loading thermography, because most natural heat sources and heat sinks can be approximated to be homogenously extended over a certain region of interest. This is of particular interest because natural heat phenomena cover a large area, which makes this method suitable for measuring large-scale samples. This work investigates how the extended source approximation formulas for determining thermally thick and thermally thin material properties can be used in a naturally excited setup, shows possible error sources, and gives quantitative results for estimating thermal effusivity of a retaining wall structure. It shows that this method can be used on large-scale structures that are subject to natural outside heating phenomena.

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Section: Theoretical Frameworkmentioning

confidence: 99%

Estimating Thermal Material Properties Using Solar Loading Lock-in Thermography

2021

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“…The effort to acquire the calibration points is further reduced by the method based on Planck's law proposed in [10][11][12]. This particular method needs only a couple of calibration images.…”

Section: Radiometric Calibrationmentioning

confidence: 99%

Numerical and Non-Destructive Analysis of an Aluminum-CFRP Hybrid 3D Structure

Silva

Fernandes

Schwarz

et al. 2021

Metals

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Advanced materials are widely used in many industries. They play an important role especially in the aeronautic and automotive sectors where weight reduction is required in order to reduce fuel consumption. Composite materials have a high strength to weight ratio and are applied in airplane construction. Nevertheless, sometimes it is not viable to replace all metal parts by composite ones due to the cost factor. In this sense, hybrid structures are highly welcome. In order to ensure the safety of these hybrid components during their entire life cycle, non-destructive testing evaluation (NDT&E) methods are used and sometimes they are the only option. In this study, we use infrared thermography (IRT) to inspect an aluminum-composite hybrid structure with a 3D shape. The sample has a composite part with a small metal inlay (EN AW-6082) overmolded with a thermoplastic layer. The inlay is bended to reach the desired 3D geometry. This sample was design to be used for the connection between an A- or B-pillar and a car roof made of carbon fiber reinforced polymer (CFRP). A dual-band infrared camera is used in order to capture images in two different spectral ranges. In addition, two data processing techniques for infrared images are applied to enhance the images: principal component thermography (PCT) and partial least squares thermography (PLST). Then, a signal-to-noise ratio analysis is performed with three randomly chosen previous known defects to assess the quality of the images and detected defects. Results showed that principal component thermography has a slight advantage over partial least squares thermography in our specific experiments. Specifically, for the long-wave infrared band, PCT presented, among the defects analyzed, PCT presented a mean value 12.5% higher while the standard deviation was almost three times lower than PLST. In parallel to the non-detructive analysis, a numerical finite element model was formulated in ANSYS® to analyze the total deformations to which the metal-composite-hybrid structure is subjected during a possible use. Results obtained with the numerical model indicate that the interface region between composite and metal parts is where the highest degree of deformation occur, which indicates possible regions where defects and failures may occur in real use cases.

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“…The advantage of using the raw data is, that you can include the calibration procedure wherever you like in your experiment and transfer it to all measurements taken before and after that. The effort to acquire the calibration points is further reduced by the method based on Planck's law proposed in [4], which only needs two calibration images whereas one was taken close to room temperature. The characteristic of a quantum detector is represented better by radiance than temperature values.…”

Section: Radiometric Calibrationmentioning

confidence: 99%