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18 pages, 12791 KiB

Open AccessArticle

Quantification of the Effective Detectable Period for Concrete Voids of CLP by Lock-In Thermography

by Chunyoung Kim, Seongmin Kang, Yoonjae Chung, Okhwan Kim and Wontae Kim

Appl. Sci. 2023, 13(14), 8247; https://doi.org/10.3390/app13148247 - 16 Jul 2023

Cited by 3 | Viewed by 1063

Abstract

This study is to inspect the voids between the concrete containment building and the containment liner plate (CLP) in the light-water reactor type nuclear power plant with lock-in thermography (LIT) inspection technology. For that, a finite element method (FEM) model containing concrete voids [...] Read more.

This study is to inspect the voids between the concrete containment building and the containment liner plate (CLP) in the light-water reactor type nuclear power plant with lock-in thermography (LIT) inspection technology. For that, a finite element method (FEM) model containing concrete voids was created, and the thermal distribution change of the CLP surface was simulated through numerical analysis simulation of various LIT inspection conditions and converted with real-time thermography data. For the simulated temperature distribution image and the amplitude and phase images calculated by the four-point method, the signal-to-noise ratio (SNR) is analyzed based on the sound area and void areas. As a result, the difference in SNR according to the size of voids was remarkable, and the effective detectable period (EDP), which was common to each inspection condition, was derived. Furthermore, a CLP concrete mockup identical to the model shape is produced, and the thermal image of the EDP is analyzed through the experiment with the same analysis technique, and the results are compared. Although there are some differences between the numerical analysis conditions and the experimental environments, the deduction and utilization of EDP through FEM simulation are considered useful approaches to applying LIT to inspect concrete voids on the back of the CLP. Full article

(This article belongs to the Special Issue Latest Advances and Applications of Infrared Thermography Non-Destructive Testing (NDT))

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22 pages, 10602 KiB

Open AccessArticle

Detection and Characterization of Artificial Porosity and Impact Damage in Aerospace Carbon Fiber Composites by Pulsed and Line Scan Thermography

by Clemente Ibarra-Castanedo, Pierre Servais, Matthieu Klein, Thibault Boulanger, Alain Kinard, Sébastien Hoffait and Xavier P. V. Maldague

Appl. Sci. 2023, 13(10), 6135; https://doi.org/10.3390/app13106135 - 17 May 2023

Cited by 8 | Viewed by 1653

Abstract

Nondestructive testing (NDT) of composite materials is of paramount importance to the aerospace industry. Several NDT methods have been adopted for the inspection of components during production and all through the aircraft service life, with infrared thermography (IRT) techniques, such as line scan [...] Read more.

Nondestructive testing (NDT) of composite materials is of paramount importance to the aerospace industry. Several NDT methods have been adopted for the inspection of components during production and all through the aircraft service life, with infrared thermography (IRT) techniques, such as line scan thermography (LST) and pulsed thermography (PT), gaining popularity thanks to their rapidity and versatility. On one hand, LST is an attractive solution for the fast inspection of large and complex geometry composite parts during production. On the other hand, PT can be employed for the characterization of composite materials, e.g., the determination of thermal diffusivity and defect depth estimation. In this study, the use of LST with an uncooled microbolometer camera is explored for the identification of artificially produced porosity and barely visible impact damage (BVID) on academic samples. The performance of LST is quantitatively assessed with respect to PT (considered the gold standard in this case) using a high-definition cooled camera through the contrast-to-noise ratio (CNR) criterium. It is concluded that, although in most cases the measured CNR values were higher for PT than for LST (as expected since a high-definition camera and longer acquisition times were used), the majority of the defects were clearly detected (CNR ≥ 2.5) by LST without the need of advanced signal processing, proving the suitability of LST for the inspection of aerospace composite components. Furthermore, the deepest defect investigated herein (z ≈ 3 mm) was detected solely by LST combined with signal processing and spatial filtering (CNR = 3.6) and not by PT (since pulse heating was not long enough for this depth). In addition, PT was used for the determination of the thermal diffusivity of all samples and the subsequent depth estimation of porosity and damaged areas by pulsed phase thermography (PPT). Full article

(This article belongs to the Special Issue Latest Advances and Applications of Infrared Thermography Non-Destructive Testing (NDT))

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10 pages, 1354 KiB

Open AccessArticle

Machine Learning-Based Pain Severity Classification of Lumbosacral Radiculopathy Using Infrared Thermal Imaging

by Jinu Rim, Seungjun Ryu, Hyunjun Jang, Hoyeol Zhang and Yongeun Cho

Appl. Sci. 2023, 13(6), 3541; https://doi.org/10.3390/app13063541 - 10 Mar 2023

Cited by 1 | Viewed by 1620

Abstract

Pain is subjective and varies among individuals. Doctors determine pain severity based on a patient’s self-reported symptoms. In such situations, a language barrier may prevent patients from expressing their pain accurately, which may cause doctors to underestimate their pain degree. Moreover, patients’ subjective [...] Read more.

Pain is subjective and varies among individuals. Doctors determine pain severity based on a patient’s self-reported symptoms. In such situations, a language barrier may prevent patients from expressing their pain accurately, which may cause doctors to underestimate their pain degree. Moreover, patients’ subjective descriptions of pain can determine their eligibility for secondary benefits, as in the case of compensation for traffic or industrial accidents. Therefore, to perform a multiclass prediction of the severity of lumbar radiculopathy, the authors applied digital infrared thermographic imaging (DITI) to a machine-learning (ML) algorithm. The DITI dataset included data from a healthy population and patients with radiculopathy with herniated lumbar discs at the L3/4, L4/5, and L5/S1 levels. The dataset of 1000 patients was split into training and test datasets in a 7:3 ratio to evaluate the model’s performance. For the training dataset, the average accuracy, precision, recall, and F1 score were 0.82, 0.76, 0.72, and 0.74, respectively. For the test dataset, these values were 0.77, 0.71, 0.75, and 0.73, respectively. Applying the ML algorithm to a pain-severity classification using thermographic images will aid in the treatment of lumbosacral radiculopathy and allow providers to monitor the therapeutic effect of interventions through an assessment of physiological evidence. Full article

(This article belongs to the Special Issue Latest Advances and Applications of Infrared Thermography Non-Destructive Testing (NDT))

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14 pages, 2193 KiB

Open AccessArticle

Skin Temperature: The Impact of Perfusion, Epidermis Thickness, and Skin Wetness

by Gennadi Saiko

Appl. Sci. 2022, 12(14), 7106; https://doi.org/10.3390/app12147106 - 14 Jul 2022

Cited by 8 | Viewed by 4085

Abstract

This work aimed to elucidate the primary factors which affect skin temperature. A simple thermophysical model of the skin, which accounts for radiative, convective, and evaporative heat losses, has been developed to address it. The model is based on the skin’s morphology and [...] Read more.

This work aimed to elucidate the primary factors which affect skin temperature. A simple thermophysical model of the skin, which accounts for radiative, convective, and evaporative heat losses, has been developed to address it. The model is based on the skin’s morphology and consists of passive (nonviable tissue) and active (viable tissue) layers. The bioheat equation was solved for these layers using realistic assumptions. It was found that other than the ambient temperature, blood perfusion and epidermis thickness are the primary factors responsible for the skin temperature variations. The main temperature drop in the skin is attributed to the cooling of the blood in the venous plexus. The temperature drop in the epidermis is on the scale of 0.1 °C for the normal epidermis but can be 1.5–2 °C or higher in calluses. Thus, local skin temperature variations can indicate the epidermis thickness variations, particularly in callus-prone areas. The effects of relative air humidity and skin wetness on skin temperature were also quantified. The presence of free moisture on the skin (e.g., wet wound) significantly increases the heat transfer, resulting in a skin temperature drop, which can be on the scale of several degrees Celsius. The relative air humidity significantly contributes (by slowing heat dissipation) only in the case of evaporative heat loss from wet skin. Therefore, wet skin is undesirable and should be avoided during a thermographic assessment. Full article

(This article belongs to the Special Issue Latest Advances and Applications of Infrared Thermography Non-Destructive Testing (NDT))

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13 pages, 14499 KiB

Open AccessArticle

Design and Construction of an LED-Based Excitation Source for Lock-In Thermography

by Patrick Dahlberg, Nils J. Ziegeler, Peter W. Nolte and Stefan Schweizer

Appl. Sci. 2022, 12(6), 2940; https://doi.org/10.3390/app12062940 - 13 Mar 2022

Cited by 5 | Viewed by 2893

Abstract

Active thermography is an established technique for non-destructive testing and defect localisation. For external excitation, powerful light sources are commonly used. In addition to a high optical output, a good signal shape and response characteristic as well as control ports, which allow for [...] Read more.

Active thermography is an established technique for non-destructive testing and defect localisation. For external excitation, powerful light sources are commonly used. In addition to a high optical output, a good signal shape and response characteristic as well as control ports, which allow for multiple operation modes, are important for active thermography applications. In this work, the schematics for an excitation source based on infrared LEDs is presented. It features multiple control modes for easy integration into existing measurement setups as well as sophisticated control electronics to realize a wide range of excitation patterns. The phase and amplitude stability of this prototype is investigated and compared to the performance of a modulated halogen lamp as well as a halogen lamp and mechanical chopper combination. Full article

(This article belongs to the Special Issue Latest Advances and Applications of Infrared Thermography Non-Destructive Testing (NDT))

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16 pages, 4996 KiB

Open AccessArticle

Defect Recognition of Roll-to-Roll Printed Conductors Using Dark Lock-in Thermography and Localized Segmentation

by Haitao Zheng, Linghao Zhou, Ryan Marks, Tuomas Happonen and Thomas M. Kraft

Appl. Sci. 2022, 12(4), 2005; https://doi.org/10.3390/app12042005 - 15 Feb 2022

Cited by 4 | Viewed by 2281

Abstract

The demand for flexible large area optoelectronic devices such as organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs) is growing. Roll-to-roll (R2R) printing enables cost-efficient industrial production of optoelectronic devices. The performance of electronic devices may significantly suffer from local electrical defects. The [...] Read more.

The demand for flexible large area optoelectronic devices such as organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs) is growing. Roll-to-roll (R2R) printing enables cost-efficient industrial production of optoelectronic devices. The performance of electronic devices may significantly suffer from local electrical defects. The dark lock-in infrared thermography (DLIT) method is an effective non-destructive testing (NDT) tool to identify such defects as hot spots. In this study, a DLIT inspection system was applied to visualize the defects of R2R printed silver conductors on flexible plastic substrates. A two-stage automated defect recognition (ADR) methodology was proposed to detect and localize two types of typical electrical defects, which are caused by complete or partial breaks on the printed conductive wires, based on localized segmentation and thresholding methods. Full article

(This article belongs to the Special Issue Latest Advances and Applications of Infrared Thermography Non-Destructive Testing (NDT))

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17 pages, 5439 KiB

Open AccessArticle

Mini-Crack Detection of Conveyor Belt Based on Laser Excited Thermography

by Fei Zeng, Sheng Zhang, Tao Wang and Qing Wu

Appl. Sci. 2021, 11(22), 10766; https://doi.org/10.3390/app112210766 - 15 Nov 2021

Cited by 11 | Viewed by 7258

Abstract

For a belt conveyor, a belt with mini-cracks influences the safety of the operation of the belt conveyor devices significantly. The lumpy material rubbing against a belt with mini-cracks will lead to detrimental tears on the belt while the conveyor works at high [...] Read more.

For a belt conveyor, a belt with mini-cracks influences the safety of the operation of the belt conveyor devices significantly. The lumpy material rubbing against a belt with mini-cracks will lead to detrimental tears on the belt while the conveyor works at high speeds. In order to detect mini-cracks in a timely manner, before the occurrence of large tears, a new mini-crack detection method for conveyor belts based on laser excited thermography is proposed. A laser beam is applied to generate a heat wave on the belt surface, so the corresponding thermal images can be recorded by an infrared camera. Then, an algorithm for extracting and fusing the features of mini-crack belt’s thermal images is firstly proposed by using time sequence analysis. It could transform multiple sequential thermal images into a single thermal image according to the frame difference method, so that the infrared thermal response of the mini-crack over time could be recorded quickly. To reveal the features of mini-crack, the power function image enhancement algorithm is proposed. After that, the threshold segmentation and Hough transform algorithm are used to determine the size of the mini-crack. The experimental results show that the mini-cracks with length of 50–140 mm, width of 1–10 mm, and depth of 5 mm can be successfully detected, and the detection accuracy could reach 96%. The detection results of different sizes of mini-crack show that the laser excited thermography has high damage sensitivity (1 mm diameter mini-crack detection), high accuracy (96%), lower power consumption (15 W laser excitation), and high SNR (signal-to-noise ratio). Full article

(This article belongs to the Special Issue Latest Advances and Applications of Infrared Thermography Non-Destructive Testing (NDT))

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12 pages, 51071 KiB

Open AccessFeature PaperArticle

Automated Defect Detection Using Threshold Value Classification Based on Thermographic Inspection

by Seungju Lee, Yoonjae Chung, Ranjit Shrestha and Wontae Kim

Appl. Sci. 2021, 11(17), 7870; https://doi.org/10.3390/app11177870 - 26 Aug 2021

Cited by 14 | Viewed by 3095

Abstract

Active infrared thermography is an attractive and reliable technique used for the non-destructive evaluation of various materials and structures, because it enables non-contact, large area, high-speed, quantitative, and qualitative inspection. However, the defect detectability is significantly deteriorated due to the excitation of a [...] Read more.

Active infrared thermography is an attractive and reliable technique used for the non-destructive evaluation of various materials and structures, because it enables non-contact, large area, high-speed, quantitative, and qualitative inspection. However, the defect detectability is significantly deteriorated due to the excitation of a non-uniform heat source and surrounding environmental noise, requiring additional signal processing and image characterization. The lock-in infrared thermography technique has been proven to be an effective method for quantitative evaluation by extracting amplitude and phase images from a 2D thermal sequence, but it still involves a lot of noise, providing difficulties in detection. Therefore, this study explored the possibility of improving the signal-to-noise ratio by applying filtering to a stainless-steel plate with circular defects. Thereafter, automated defect detection was performed based on the threshold value through the binary images. In addition, a comparative analysis was performed to evaluate the detectability according to the presence or absence of a filtering application. Full article

(This article belongs to the Special Issue Latest Advances and Applications of Infrared Thermography Non-Destructive Testing (NDT))

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8 pages, 804 KiB

Open AccessArticle

Validation of Eye Temperature Assessed Using Infrared Thermography as an Indicator of Welfare in Horses

by Su-Min Kim and Gil-Jae Cho

Appl. Sci. 2021, 11(16), 7186; https://doi.org/10.3390/app11167186 - 4 Aug 2021

Cited by 19 | Viewed by 3270

Abstract

This study aimed to validate eye temperature (ET) assessed using infrared thermography (IRT) as an indicator of welfare in horses. Moreover, this study aimed to determine the most accurate position for ET measured using IRT and to validate this approach as a gold-standard [...] Read more.

This study aimed to validate eye temperature (ET) assessed using infrared thermography (IRT) as an indicator of welfare in horses. Moreover, this study aimed to determine the most accurate position for ET measured using IRT and to validate this approach as a gold-standard measurement method. As the quantitative data obtained by IRT have strongly influenced the ET results depending on the specific location of the measurement area, an accurate definition of the regions of interest (ROI) was established. A total of 176 horses (Thoroughbred, Warmblood, and Halla horses) were used at the racing course of the Korea Racing Authority and public horse-riding clubs in South Korea. The present study also compared temperatures among three ROIs of the eye—lacrimal sac, medial canthus, and lateral canthus—at rest. Correlations between ET, rectal temperature (RT), heart rate (HR), and respiratory rate (RR) were assessed. There were no significant correlations between HR, RR or RT; however, among the three ROIs, the temperature of the medial canthus was positively correlated with RT (p < 0.05). Furthermore, the size of ROI was negatively correlated with accuracy of temperature measurement. These results indicate that the most suitable area for ET measurement using IRT in horses is the medial canthus, and it is recommended to use the average temperature of the smallest ROIs (2 × 2 pixels) for temperature analysis. Therefore, this study offers a validated protocol in which ET measured using IRT in the horses is useful as an indicator of welfare. Full article

(This article belongs to the Special Issue Latest Advances and Applications of Infrared Thermography Non-Destructive Testing (NDT))

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20 pages, 7800 KiB

Open AccessArticle

Patient/Breast-Specific Detection of Breast Tumor Based on Patients’ Thermograms, 3D Breast Scans, and Reverse Thermal Modelling

by Olzhas Mukhmetov, Aigerim Mashekova, Yong Zhao, Anna Midlenko, Eddie Yin Kwee Ng and Sai Cheong Fok

Appl. Sci. 2021, 11(14), 6565; https://doi.org/10.3390/app11146565 - 16 Jul 2021

Cited by 2 | Viewed by 2444

Abstract

Background: Mammography is the preferred method for the diagnosis of breast cancer. However, this diagnostic technique fails to detect tumors of small sizes, and it does not work well for younger patients with high breast tissue density. Methods: This paper proposes a novel [...] Read more.

Background: Mammography is the preferred method for the diagnosis of breast cancer. However, this diagnostic technique fails to detect tumors of small sizes, and it does not work well for younger patients with high breast tissue density. Methods: This paper proposes a novel tool for the early detection of breast cancer, which is patient-specific, non-invasive, inexpensive, and has potential in terms of accuracy compared with existing techniques. The main principle of this method is based on the use of temperature contours from breast skin surfaces through thermography, and inverse thermal modeling based on Finite Element Analysis (FEA) and a Genetic Algorithm (GA)-based optimization tool to estimate the depths and sizes of tumors as well as patient/breast-specific tissue properties. Results: The study was conducted by using a 3D geometry of patients’ breasts and their temperature contours, which were clinically collected using a 3D scanner and a thermal imaging infrared (IR) camera. Conclusion: The results showed that the combination of 3D breast geometries, thermal images, and inverse thermal modeling is capable of estimating patient/breast-specific breast tissue and physiological properties such as gland and fat contents, tissue density, thermal conductivity, specific heat, and blood perfusion rate, based on a multilayer model consisting of gland and fat. Moreover, this tool was able to calculate the depth and size of the tumor, which was validated by the doctor’s diagnosis. Full article

(This article belongs to the Special Issue Latest Advances and Applications of Infrared Thermography Non-Destructive Testing (NDT))

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Review

Jump to: Research

21 pages, 6127 KiB

Open AccessReview

Latest Advances in Common Signal Processing of Pulsed Thermography for Enhanced Detectability: A Review

by Yoonjae Chung, Seungju Lee and Wontae Kim

Appl. Sci. 2021, 11(24), 12168; https://doi.org/10.3390/app112412168 - 20 Dec 2021

Cited by 24 | Viewed by 5191

Abstract

Non-destructive testing (NDT) is a broad group of testing and analysis techniques used in science and industry to evaluate the properties of a material, structure, or system for characteristic defects and discontinuities without causing damage. Recently, infrared thermography is one of the most [...] Read more.

Non-destructive testing (NDT) is a broad group of testing and analysis techniques used in science and industry to evaluate the properties of a material, structure, or system for characteristic defects and discontinuities without causing damage. Recently, infrared thermography is one of the most promising technologies as it can inspect a large area quickly using a non-contact and non-destructive method. Moreover, thermography testing has proved to be a valuable approach for non-destructive testing and evaluation of structural stability of materials. Pulsed thermography is one of the active thermography technologies that utilizes external energy heating. However, due to the non-uniform heating, lateral heat diffusion, environmental noise, and limited parameters of the thermal imaging system, there are some difficulties in detecting and characterizing defects. In order to improve this limitation, various signal processing techniques have been developed through many previous studies. This review presents the latest advances and exhaustive summary of representative signal processing techniques used in pulsed thermography according to physical principles and thermal excitation sources. First, the basic concept of infrared thermography non-destructive testing is introduced. Next, the principle of conventional pulsed thermography and signal processing technologies for non-destructive testing are reviewed. Then, we review advances and recent advances in each signal processing. Finally, the latest research trends are reviewed. Full article

(This article belongs to the Special Issue Latest Advances and Applications of Infrared Thermography Non-Destructive Testing (NDT))

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14 pages, 39238 KiB

Open AccessReview

How Infrared Radiation Was Discovered—Range of This Discovery and Detailed, Unknown Information

by Waldemar Minkina

Appl. Sci. 2021, 11(21), 9824; https://doi.org/10.3390/app11219824 - 21 Oct 2021

Cited by 3 | Viewed by 5538

Abstract

The reason for writing this article is that the details and mainly the scope of the fundamental discovery of infrared radiation are not widely known, and different accounts of this story are found in the literature. For example, not everyone knows that the [...] Read more.

The reason for writing this article is that the details and mainly the scope of the fundamental discovery of infrared radiation are not widely known, and different accounts of this story are found in the literature. For example, not everyone knows that the discoverer of infrared radiation, F. W. Herschel, simultaneously studied its properties, which he, then, described in detail in his publications. It can be concluded that the history of the discovery of infrared radiation is treated marginally in the literature. This is not fair, considering the fact that infrared radiation is of fundamental importance to modern man. On the other hand, the history of the discovery of, for example, X-rays or Maxwell’s electromagnetic radiation is well known—this information is passed on to students of electrical faculties during lectures on “Fundamentals of Physics” or “Fundamentals of Electrical Engineering”. Although it is currently believed that the significance of infrared radiation for modern man is comparable to that of X-rays, when I ask the students during lectures who discovered infrared radiation and how, there is usually a deafening silence. Full article

(This article belongs to the Special Issue Latest Advances and Applications of Infrared Thermography Non-Destructive Testing (NDT))

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