The Experts below are selected from a list of 612 Experts worldwide ranked by ideXlab platform
Kersemans Mathias - One of the best experts on this subject based on the ideXlab platform.
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Multi-scale gapped smoothing algorithm for robust baseline-free damage detection in optical infrared Thermography
'Elsevier BV', 2021Co-Authors: Poelma Gaéta, Hedayatrasa Saeid, Segers Joos, Van Paepegem Wim, Kersemans MathiasAbstract:Flash Thermography is a promising technique to perform rapid non-destructive testing of composite materials. However, it is well known that several difficulties are inherently paired with this approach, such as non-uniform heating, measurement noise and lateral heat diffusion effects. Hence, advanced signal-processing techniques are indispensable in order to analyze the recorded dataset. One such processing technique is Gapped Smoothing Algorithm, which predicts a gapped pixel’s value in its sound state from a measurement in the defected state by evaluating only its neighboring pixels. However, the standard Gapped Smoothing Algorithm uses a fixed spatial gap size, which induces issues to detect variable defect sizes in a noisy dataset. In this paper, a Multi-Scale Gapped Smoothing Algorithm (MSGSA) is introduced as a baseline-free image processing technique and an extension to the standard Gapped Smoothing Algorithm. The MSGSA makes use of the evaluation of a wide range of spatial gap sizes so that defects of highly different dimensions are identified. Moreover, it is shown that a weighted combination of all assessed spatial gap sizes significantly improves the detectability of defects and results in an (almost) zero-reference background. The technique thus effectively suppresses the measurement noise and excitation non-uniformity. The efficiency of the MSGSA technique is evaluated and confirmed through numerical simulation and an experimental procedure of Flash Thermography on carbon fiber reinforced polymers with various defect sizes
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Adaptive spectral band integration in Flash Thermography : enhanced defect detectability and quantification in composites
'Elsevier BV', 2021Co-Authors: Poelma Gaéta, Hedayatrasa Saeid, Segers Joos, Van Paepegem Wim, Kersemans MathiasAbstract:In Flash Thermography, the maximum inspectable defect depth is limited when only the raw thermographic sequence is analyzed. The introduction of pulsed phase Thermography (PPT), in which phase (contrast) images at different thermal wave frequencies are obtained, significantly improved the maximum inspectable depth while reducing the effects of non-uniform heating and non-uniform surface properties. However, in a practical environment, the evaluation of many phase images per inspection is a cumbersome procedure. In this paper, a novel Adaptive Spectral Band Integration (ASBI) procedure is introduced for the post-processing of Flash thermographic datasets, which yields a unique damage index map. ASBI integrates the most useful spectral information for each pixel individually, obtaining a maximized defect detectability and an almost zero-reference level. The performance of ASBI with respect to defect detectability as well as defect sizing and depth inversion is evaluated thoroughly with both experimentally and numerically generated datasets. The ASBI procedure is successfully applied on various composite coupons with flat bottom holes and barely visible impact damage, as well as on a stiffened aircraft composite panel with a complex cluster of production defects. The ASBI procedure is compared with existing data-processing techniques in literature, illustrating an enhanced performance
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A robust multi-scale gapped smoothing algorithm for baseline-free damage mapping from raw thermal images in Flash Thermography
2020Co-Authors: Poelman Gaétan, Hedayatrasa Saeid, Van Paepegem Wim, Segers Joost, Kersemans MathiasAbstract:Flash Thermography is a promising non-destructive testing technique for the inspection of composite components. However, non-uniform heating, measurement noise and lateral heat diffusion complicate the interpretation of thermographic measurements. In order to overcome these difficulties, a novel baseline-free processing technique called ‘Multi-Scale Gapped Smoothing Algorithm’ is presented. This algorithm constructs a damage map directly from the measured data, in which an (almost) zero-reference background is obtained, and where measurement noise and excitation non-uniformity are effectively suppressed. The efficiency of the proposed technique is evaluated and confirmed through synthetic data and experimental results of a carbon fiber reinforced polymer with various artificial defects
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An experimental study on the defect detectability of time- and frequency-domain analyses for Flash Thermography
'MDPI AG', 2020Co-Authors: Poelman Gaétan, Hedayatrasa Saeid, Van Paepegem Wim, Segers Joost, Kersemans MathiasAbstract:A defect's detectability in Flash Thermography is highly dependent on the applied post-processing methodology. The majority of the existing analysis techniques operate either on the time-temperature data or on the frequency-phase data. In this paper, we compare the efficiency of time- and frequency-domain analysis techniques in Flash Thermography for obtaining good defect detectability. Both single-bin and integrated-bin evaluation procedures are considered: dynamic thermal tomography and thermal signal area for the time-domain approach, and frequency domain tomography and adaptive spectral band integration for the frequency-domain approach. The techniques are applied on various carbon fiber reinforced polymer samples having a range of defect sizes and defect types. The advantages and drawbacks of the different post-processing techniques are evaluated and discussed. The best defect detectability is achieved using the integrated procedure in frequency domain
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Efficient detection of production defects in a CFRP aircraft component by means of Flash infrared Thermography
2020Co-Authors: Poelman Gaétan, Hedayatrasa Saeid, Van Paepegem Wim, Segers Joost, Kersemans MathiasAbstract:Flash Thermography is a promising technique to perform quick and non-contact non-destructive testing of composite materials. However, several limitations such as non-uniform heating and lateral heat diffusion complicate the accurateness of this technique. This paper presents an experimental case study of Flash Thermography for the non-destructive testing of a CFRP component of an aircraft with production defects. Three post-processing techniques, namely Differential Absolute Contrast (DAC), Pulsed Phase Thermography (PPT) and Principal Component Thermography (PCT), are applied to the recorded dataset. A qualitative comparison between these processing techniques is performed based on their defect enhancement capabilities in a component with industrial complexity
Van Paepegem Wim - One of the best experts on this subject based on the ideXlab platform.
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Multi-scale gapped smoothing algorithm for robust baseline-free damage detection in optical infrared Thermography
'Elsevier BV', 2021Co-Authors: Poelma Gaéta, Hedayatrasa Saeid, Segers Joos, Van Paepegem Wim, Kersemans MathiasAbstract:Flash Thermography is a promising technique to perform rapid non-destructive testing of composite materials. However, it is well known that several difficulties are inherently paired with this approach, such as non-uniform heating, measurement noise and lateral heat diffusion effects. Hence, advanced signal-processing techniques are indispensable in order to analyze the recorded dataset. One such processing technique is Gapped Smoothing Algorithm, which predicts a gapped pixel’s value in its sound state from a measurement in the defected state by evaluating only its neighboring pixels. However, the standard Gapped Smoothing Algorithm uses a fixed spatial gap size, which induces issues to detect variable defect sizes in a noisy dataset. In this paper, a Multi-Scale Gapped Smoothing Algorithm (MSGSA) is introduced as a baseline-free image processing technique and an extension to the standard Gapped Smoothing Algorithm. The MSGSA makes use of the evaluation of a wide range of spatial gap sizes so that defects of highly different dimensions are identified. Moreover, it is shown that a weighted combination of all assessed spatial gap sizes significantly improves the detectability of defects and results in an (almost) zero-reference background. The technique thus effectively suppresses the measurement noise and excitation non-uniformity. The efficiency of the MSGSA technique is evaluated and confirmed through numerical simulation and an experimental procedure of Flash Thermography on carbon fiber reinforced polymers with various defect sizes
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Adaptive spectral band integration in Flash Thermography : enhanced defect detectability and quantification in composites
'Elsevier BV', 2021Co-Authors: Poelma Gaéta, Hedayatrasa Saeid, Segers Joos, Van Paepegem Wim, Kersemans MathiasAbstract:In Flash Thermography, the maximum inspectable defect depth is limited when only the raw thermographic sequence is analyzed. The introduction of pulsed phase Thermography (PPT), in which phase (contrast) images at different thermal wave frequencies are obtained, significantly improved the maximum inspectable depth while reducing the effects of non-uniform heating and non-uniform surface properties. However, in a practical environment, the evaluation of many phase images per inspection is a cumbersome procedure. In this paper, a novel Adaptive Spectral Band Integration (ASBI) procedure is introduced for the post-processing of Flash thermographic datasets, which yields a unique damage index map. ASBI integrates the most useful spectral information for each pixel individually, obtaining a maximized defect detectability and an almost zero-reference level. The performance of ASBI with respect to defect detectability as well as defect sizing and depth inversion is evaluated thoroughly with both experimentally and numerically generated datasets. The ASBI procedure is successfully applied on various composite coupons with flat bottom holes and barely visible impact damage, as well as on a stiffened aircraft composite panel with a complex cluster of production defects. The ASBI procedure is compared with existing data-processing techniques in literature, illustrating an enhanced performance
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A robust multi-scale gapped smoothing algorithm for baseline-free damage mapping from raw thermal images in Flash Thermography
2020Co-Authors: Poelman Gaétan, Hedayatrasa Saeid, Van Paepegem Wim, Segers Joost, Kersemans MathiasAbstract:Flash Thermography is a promising non-destructive testing technique for the inspection of composite components. However, non-uniform heating, measurement noise and lateral heat diffusion complicate the interpretation of thermographic measurements. In order to overcome these difficulties, a novel baseline-free processing technique called ‘Multi-Scale Gapped Smoothing Algorithm’ is presented. This algorithm constructs a damage map directly from the measured data, in which an (almost) zero-reference background is obtained, and where measurement noise and excitation non-uniformity are effectively suppressed. The efficiency of the proposed technique is evaluated and confirmed through synthetic data and experimental results of a carbon fiber reinforced polymer with various artificial defects
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An experimental study on the defect detectability of time- and frequency-domain analyses for Flash Thermography
'MDPI AG', 2020Co-Authors: Poelman Gaétan, Hedayatrasa Saeid, Van Paepegem Wim, Segers Joost, Kersemans MathiasAbstract:A defect's detectability in Flash Thermography is highly dependent on the applied post-processing methodology. The majority of the existing analysis techniques operate either on the time-temperature data or on the frequency-phase data. In this paper, we compare the efficiency of time- and frequency-domain analysis techniques in Flash Thermography for obtaining good defect detectability. Both single-bin and integrated-bin evaluation procedures are considered: dynamic thermal tomography and thermal signal area for the time-domain approach, and frequency domain tomography and adaptive spectral band integration for the frequency-domain approach. The techniques are applied on various carbon fiber reinforced polymer samples having a range of defect sizes and defect types. The advantages and drawbacks of the different post-processing techniques are evaluated and discussed. The best defect detectability is achieved using the integrated procedure in frequency domain
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Efficient detection of production defects in a CFRP aircraft component by means of Flash infrared Thermography
2020Co-Authors: Poelman Gaétan, Hedayatrasa Saeid, Van Paepegem Wim, Segers Joost, Kersemans MathiasAbstract:Flash Thermography is a promising technique to perform quick and non-contact non-destructive testing of composite materials. However, several limitations such as non-uniform heating and lateral heat diffusion complicate the accurateness of this technique. This paper presents an experimental case study of Flash Thermography for the non-destructive testing of a CFRP component of an aircraft with production defects. Three post-processing techniques, namely Differential Absolute Contrast (DAC), Pulsed Phase Thermography (PPT) and Principal Component Thermography (PCT), are applied to the recorded dataset. A qualitative comparison between these processing techniques is performed based on their defect enhancement capabilities in a component with industrial complexity
Hedayatrasa Saeid - One of the best experts on this subject based on the ideXlab platform.
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Multi-scale gapped smoothing algorithm for robust baseline-free damage detection in optical infrared Thermography
'Elsevier BV', 2021Co-Authors: Poelma Gaéta, Hedayatrasa Saeid, Segers Joos, Van Paepegem Wim, Kersemans MathiasAbstract:Flash Thermography is a promising technique to perform rapid non-destructive testing of composite materials. However, it is well known that several difficulties are inherently paired with this approach, such as non-uniform heating, measurement noise and lateral heat diffusion effects. Hence, advanced signal-processing techniques are indispensable in order to analyze the recorded dataset. One such processing technique is Gapped Smoothing Algorithm, which predicts a gapped pixel’s value in its sound state from a measurement in the defected state by evaluating only its neighboring pixels. However, the standard Gapped Smoothing Algorithm uses a fixed spatial gap size, which induces issues to detect variable defect sizes in a noisy dataset. In this paper, a Multi-Scale Gapped Smoothing Algorithm (MSGSA) is introduced as a baseline-free image processing technique and an extension to the standard Gapped Smoothing Algorithm. The MSGSA makes use of the evaluation of a wide range of spatial gap sizes so that defects of highly different dimensions are identified. Moreover, it is shown that a weighted combination of all assessed spatial gap sizes significantly improves the detectability of defects and results in an (almost) zero-reference background. The technique thus effectively suppresses the measurement noise and excitation non-uniformity. The efficiency of the MSGSA technique is evaluated and confirmed through numerical simulation and an experimental procedure of Flash Thermography on carbon fiber reinforced polymers with various defect sizes
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Adaptive spectral band integration in Flash Thermography : enhanced defect detectability and quantification in composites
'Elsevier BV', 2021Co-Authors: Poelma Gaéta, Hedayatrasa Saeid, Segers Joos, Van Paepegem Wim, Kersemans MathiasAbstract:In Flash Thermography, the maximum inspectable defect depth is limited when only the raw thermographic sequence is analyzed. The introduction of pulsed phase Thermography (PPT), in which phase (contrast) images at different thermal wave frequencies are obtained, significantly improved the maximum inspectable depth while reducing the effects of non-uniform heating and non-uniform surface properties. However, in a practical environment, the evaluation of many phase images per inspection is a cumbersome procedure. In this paper, a novel Adaptive Spectral Band Integration (ASBI) procedure is introduced for the post-processing of Flash thermographic datasets, which yields a unique damage index map. ASBI integrates the most useful spectral information for each pixel individually, obtaining a maximized defect detectability and an almost zero-reference level. The performance of ASBI with respect to defect detectability as well as defect sizing and depth inversion is evaluated thoroughly with both experimentally and numerically generated datasets. The ASBI procedure is successfully applied on various composite coupons with flat bottom holes and barely visible impact damage, as well as on a stiffened aircraft composite panel with a complex cluster of production defects. The ASBI procedure is compared with existing data-processing techniques in literature, illustrating an enhanced performance
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A robust multi-scale gapped smoothing algorithm for baseline-free damage mapping from raw thermal images in Flash Thermography
2020Co-Authors: Poelman Gaétan, Hedayatrasa Saeid, Van Paepegem Wim, Segers Joost, Kersemans MathiasAbstract:Flash Thermography is a promising non-destructive testing technique for the inspection of composite components. However, non-uniform heating, measurement noise and lateral heat diffusion complicate the interpretation of thermographic measurements. In order to overcome these difficulties, a novel baseline-free processing technique called ‘Multi-Scale Gapped Smoothing Algorithm’ is presented. This algorithm constructs a damage map directly from the measured data, in which an (almost) zero-reference background is obtained, and where measurement noise and excitation non-uniformity are effectively suppressed. The efficiency of the proposed technique is evaluated and confirmed through synthetic data and experimental results of a carbon fiber reinforced polymer with various artificial defects
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An experimental study on the defect detectability of time- and frequency-domain analyses for Flash Thermography
'MDPI AG', 2020Co-Authors: Poelman Gaétan, Hedayatrasa Saeid, Van Paepegem Wim, Segers Joost, Kersemans MathiasAbstract:A defect's detectability in Flash Thermography is highly dependent on the applied post-processing methodology. The majority of the existing analysis techniques operate either on the time-temperature data or on the frequency-phase data. In this paper, we compare the efficiency of time- and frequency-domain analysis techniques in Flash Thermography for obtaining good defect detectability. Both single-bin and integrated-bin evaluation procedures are considered: dynamic thermal tomography and thermal signal area for the time-domain approach, and frequency domain tomography and adaptive spectral band integration for the frequency-domain approach. The techniques are applied on various carbon fiber reinforced polymer samples having a range of defect sizes and defect types. The advantages and drawbacks of the different post-processing techniques are evaluated and discussed. The best defect detectability is achieved using the integrated procedure in frequency domain
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Efficient detection of production defects in a CFRP aircraft component by means of Flash infrared Thermography
2020Co-Authors: Poelman Gaétan, Hedayatrasa Saeid, Van Paepegem Wim, Segers Joost, Kersemans MathiasAbstract:Flash Thermography is a promising technique to perform quick and non-contact non-destructive testing of composite materials. However, several limitations such as non-uniform heating and lateral heat diffusion complicate the accurateness of this technique. This paper presents an experimental case study of Flash Thermography for the non-destructive testing of a CFRP component of an aircraft with production defects. Three post-processing techniques, namely Differential Absolute Contrast (DAC), Pulsed Phase Thermography (PPT) and Principal Component Thermography (PCT), are applied to the recorded dataset. A qualitative comparison between these processing techniques is performed based on their defect enhancement capabilities in a component with industrial complexity
Poelman Gaétan - One of the best experts on this subject based on the ideXlab platform.
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A robust multi-scale gapped smoothing algorithm for baseline-free damage mapping from raw thermal images in Flash Thermography
2020Co-Authors: Poelman Gaétan, Hedayatrasa Saeid, Van Paepegem Wim, Segers Joost, Kersemans MathiasAbstract:Flash Thermography is a promising non-destructive testing technique for the inspection of composite components. However, non-uniform heating, measurement noise and lateral heat diffusion complicate the interpretation of thermographic measurements. In order to overcome these difficulties, a novel baseline-free processing technique called ‘Multi-Scale Gapped Smoothing Algorithm’ is presented. This algorithm constructs a damage map directly from the measured data, in which an (almost) zero-reference background is obtained, and where measurement noise and excitation non-uniformity are effectively suppressed. The efficiency of the proposed technique is evaluated and confirmed through synthetic data and experimental results of a carbon fiber reinforced polymer with various artificial defects
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An experimental study on the defect detectability of time- and frequency-domain analyses for Flash Thermography
'MDPI AG', 2020Co-Authors: Poelman Gaétan, Hedayatrasa Saeid, Van Paepegem Wim, Segers Joost, Kersemans MathiasAbstract:A defect's detectability in Flash Thermography is highly dependent on the applied post-processing methodology. The majority of the existing analysis techniques operate either on the time-temperature data or on the frequency-phase data. In this paper, we compare the efficiency of time- and frequency-domain analysis techniques in Flash Thermography for obtaining good defect detectability. Both single-bin and integrated-bin evaluation procedures are considered: dynamic thermal tomography and thermal signal area for the time-domain approach, and frequency domain tomography and adaptive spectral band integration for the frequency-domain approach. The techniques are applied on various carbon fiber reinforced polymer samples having a range of defect sizes and defect types. The advantages and drawbacks of the different post-processing techniques are evaluated and discussed. The best defect detectability is achieved using the integrated procedure in frequency domain
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Efficient detection of production defects in a CFRP aircraft component by means of Flash infrared Thermography
2020Co-Authors: Poelman Gaétan, Hedayatrasa Saeid, Van Paepegem Wim, Segers Joost, Kersemans MathiasAbstract:Flash Thermography is a promising technique to perform quick and non-contact non-destructive testing of composite materials. However, several limitations such as non-uniform heating and lateral heat diffusion complicate the accurateness of this technique. This paper presents an experimental case study of Flash Thermography for the non-destructive testing of a CFRP component of an aircraft with production defects. Three post-processing techniques, namely Differential Absolute Contrast (DAC), Pulsed Phase Thermography (PPT) and Principal Component Thermography (PCT), are applied to the recorded dataset. A qualitative comparison between these processing techniques is performed based on their defect enhancement capabilities in a component with industrial complexity
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Application of Flash Thermography and advanced post-processing techniques for rapid NDT of CFRP aircraft component : a case study
2019Co-Authors: Poelman Gaétan, Hedayatrasa Saeid, Van Paepegem Wim, Segers Joost, Kersemans MathiasAbstract:Flash Thermography is a promising technique to perform quick and non-contact non-destructive testing of composite materials. However, several limitations such as non-uniform heating and lateral heat diffusion complicate the accurateness of this technique. This paper presents an experimental case study of Flash Thermography for the non-destructive testing of a CFRP component of an aircraft with production defects. Three post-processing techniques, namely Differential Absolute Contrast (DAC), Pulsed Phase Thermography (PPT) and Principal Component Thermography (PCT), are applied to the recorded dataset. A qualitative comparison between these processing techniques is performed based on their defect enhancement capabilities in a component with industrial complexity
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Flash Thermography of composites : evaluation of advanced post-processing approaches
2019Co-Authors: Poelman Gaétan, Hedayatrasa Saeid, Van Paepegem Wim, Segers Joost, Kersemans MathiasAbstract:Carbon fiber reinforced polymers (CFRP) are composite materials that offer a high stiffness-to-weight ratio in comparison to traditional metals, which explains their increasing use in many high-end applications (e.g. aerospace). However, composites are prone to internal damage that may deteriorate the structural integrity, and thus require reliable and non-destructive testing (NDT) approaches. Infrared Thermography (IRT) is a promising NDT technique which provides fast, full-field measurements, and in which hidden defects are detectable based on their thermal signatures. In Flash Thermography (FT), which is the thermographic technique of interest for this contribution, the component’s surface temperature is rapidly elevated through the application of an intense optical Flash. Subsequent recording of the cooling down of the stimulated surface, by means of a high-end infrared camera, allows to detect defects by searching for anomalies in the surface temperature (due to heat build-up above the defect). Considering the anisotropic diffusivity and high damping of thermal waves in CFRP, advanced post-processing techniques are indispensable to detect deep defects (> 2 mm in CFRP). In this paper, FT is performed on several CFRPs with various defects (flat bottom holes, Teflon inserts and barely visible impact damage). This thermographic dataset is then analyzed using various post-processing techniques, including pulsed phase Thermography (PPT), principal component Thermography (PCT), thermographic signal reconstruction (TSR) and dynamic thermal tomography (DTT), in order to improve the defect detectability and assessment. The performance of the employed processing techniques is critically evaluated
Segers Joost - One of the best experts on this subject based on the ideXlab platform.
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A robust multi-scale gapped smoothing algorithm for baseline-free damage mapping from raw thermal images in Flash Thermography
2020Co-Authors: Poelman Gaétan, Hedayatrasa Saeid, Van Paepegem Wim, Segers Joost, Kersemans MathiasAbstract:Flash Thermography is a promising non-destructive testing technique for the inspection of composite components. However, non-uniform heating, measurement noise and lateral heat diffusion complicate the interpretation of thermographic measurements. In order to overcome these difficulties, a novel baseline-free processing technique called ‘Multi-Scale Gapped Smoothing Algorithm’ is presented. This algorithm constructs a damage map directly from the measured data, in which an (almost) zero-reference background is obtained, and where measurement noise and excitation non-uniformity are effectively suppressed. The efficiency of the proposed technique is evaluated and confirmed through synthetic data and experimental results of a carbon fiber reinforced polymer with various artificial defects
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An experimental study on the defect detectability of time- and frequency-domain analyses for Flash Thermography
'MDPI AG', 2020Co-Authors: Poelman Gaétan, Hedayatrasa Saeid, Van Paepegem Wim, Segers Joost, Kersemans MathiasAbstract:A defect's detectability in Flash Thermography is highly dependent on the applied post-processing methodology. The majority of the existing analysis techniques operate either on the time-temperature data or on the frequency-phase data. In this paper, we compare the efficiency of time- and frequency-domain analysis techniques in Flash Thermography for obtaining good defect detectability. Both single-bin and integrated-bin evaluation procedures are considered: dynamic thermal tomography and thermal signal area for the time-domain approach, and frequency domain tomography and adaptive spectral band integration for the frequency-domain approach. The techniques are applied on various carbon fiber reinforced polymer samples having a range of defect sizes and defect types. The advantages and drawbacks of the different post-processing techniques are evaluated and discussed. The best defect detectability is achieved using the integrated procedure in frequency domain
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Efficient detection of production defects in a CFRP aircraft component by means of Flash infrared Thermography
2020Co-Authors: Poelman Gaétan, Hedayatrasa Saeid, Van Paepegem Wim, Segers Joost, Kersemans MathiasAbstract:Flash Thermography is a promising technique to perform quick and non-contact non-destructive testing of composite materials. However, several limitations such as non-uniform heating and lateral heat diffusion complicate the accurateness of this technique. This paper presents an experimental case study of Flash Thermography for the non-destructive testing of a CFRP component of an aircraft with production defects. Three post-processing techniques, namely Differential Absolute Contrast (DAC), Pulsed Phase Thermography (PPT) and Principal Component Thermography (PCT), are applied to the recorded dataset. A qualitative comparison between these processing techniques is performed based on their defect enhancement capabilities in a component with industrial complexity
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Application of Flash Thermography and advanced post-processing techniques for rapid NDT of CFRP aircraft component : a case study
2019Co-Authors: Poelman Gaétan, Hedayatrasa Saeid, Van Paepegem Wim, Segers Joost, Kersemans MathiasAbstract:Flash Thermography is a promising technique to perform quick and non-contact non-destructive testing of composite materials. However, several limitations such as non-uniform heating and lateral heat diffusion complicate the accurateness of this technique. This paper presents an experimental case study of Flash Thermography for the non-destructive testing of a CFRP component of an aircraft with production defects. Three post-processing techniques, namely Differential Absolute Contrast (DAC), Pulsed Phase Thermography (PPT) and Principal Component Thermography (PCT), are applied to the recorded dataset. A qualitative comparison between these processing techniques is performed based on their defect enhancement capabilities in a component with industrial complexity
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Flash Thermography of composites : evaluation of advanced post-processing approaches
2019Co-Authors: Poelman Gaétan, Hedayatrasa Saeid, Van Paepegem Wim, Segers Joost, Kersemans MathiasAbstract:Carbon fiber reinforced polymers (CFRP) are composite materials that offer a high stiffness-to-weight ratio in comparison to traditional metals, which explains their increasing use in many high-end applications (e.g. aerospace). However, composites are prone to internal damage that may deteriorate the structural integrity, and thus require reliable and non-destructive testing (NDT) approaches. Infrared Thermography (IRT) is a promising NDT technique which provides fast, full-field measurements, and in which hidden defects are detectable based on their thermal signatures. In Flash Thermography (FT), which is the thermographic technique of interest for this contribution, the component’s surface temperature is rapidly elevated through the application of an intense optical Flash. Subsequent recording of the cooling down of the stimulated surface, by means of a high-end infrared camera, allows to detect defects by searching for anomalies in the surface temperature (due to heat build-up above the defect). Considering the anisotropic diffusivity and high damping of thermal waves in CFRP, advanced post-processing techniques are indispensable to detect deep defects (> 2 mm in CFRP). In this paper, FT is performed on several CFRPs with various defects (flat bottom holes, Teflon inserts and barely visible impact damage). This thermographic dataset is then analyzed using various post-processing techniques, including pulsed phase Thermography (PPT), principal component Thermography (PCT), thermographic signal reconstruction (TSR) and dynamic thermal tomography (DTT), in order to improve the defect detectability and assessment. The performance of the employed processing techniques is critically evaluated