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Infrared thermography is a valuable tool adapted for veterinary diagnostics with an increasing number of uses. However, proper image acquisition is hard, not only due to various factors affecting the image but also because informative image processing is a struggle. Thus, this study aims to quantify the area of maximum temperature (Area of Tmax) on the lateral surface of horses and foals to compare the Areas of Tmax between horses and foals and to compare two new approaches to the Area of Tmax quantification in horses. Infrared images were acquired with a thermographic camera from 12 horses and 12 foals in the same ambient condition. The backgrounds of the images were removed, and the images were then processed in Rainbow HC and a grayscale palette. Then, 10 images were created, showing the Areas of Tmax in gradually decreasing ranges. The evaluation of the Area of Tmax with two image processing methods showed higher maximum temperatures in foals, although the high-temperature values covered less of their total body area than in adult horses. The results indicate the struggles of foals with thermal homeostasis. The proposed methods—multi-colored annotated pixels on Rainbow HC and red-annotated pixels on grayscale—provide a common quality in the thermogram evaluation of foals and adult horses. Further research is essential to determine their diagnostic application. [ABSTRACT FROM AUTHOR]

Infrared thermography is a valuable tool adapted for veterinary diagnostics with an increasing number of uses. However, proper image acquisition is hard, not only due to various factors affecting the image but also because informative image processing is a struggle. Thus, this study aims to quantify the area of maximum temperature (Area of Tmax) on the lateral surface of horses and foals to compare the Areas of Tmax between horses and foals and to compare two new approaches to the Area of Tmax quantification in horses. Infrared images were acquired with a thermographic camera from 12 horses and 12 foals in the same ambient condition. The backgrounds of the images were removed, and the images were then processed in Rainbow HC and a grayscale palette. Then, 10 images were created, showing the Areas of Tmax in gradually decreasing ranges. The evaluation of the Area of Tmax with two image processing methods showed higher maximum temperatures in foals, although the high-temperature values covered less of their total body area than in adult horses. The results indicate the struggles of foals with thermal homeostasis. The proposed methods—multi-colored annotated pixels on Rainbow HC and red-annotated pixels on grayscale—provide a common quality in the thermogram evaluation of foals and adult horses. Further research is essential to determine their diagnostic application.

This article elucidates the need to consider the inherent spatial transfer function (blur), of any thermographic instrument used to measure thermal fields. Infrared thermographic data were acquired from a modified, commercial, laser-based powder bed fusion printer. A validated methodology was used to correct for spatial transfer function errors in the measured thermal fields. The methodology was found to make a difference of 40% to the measured signal levels and a 174 °C difference to the calculated effective temperature. The spatial gradients in the processed thermal fields were found to increase significantly. These corrections make a significant difference to the accuracy of validation data for process and microstructure modeling. We demonstrate the need for consideration of image blur when quantifying the thermal fields in laser-based powder bed fusion in this work.

Thermal imaging cameras are expensive, particularly those designed for measuring high temperature objects with low measurement uncertainty. A wide range of research and industrial applications would benefit from lower cost temperature imaging sensors with improved metrology. To address this problem, we present the first ever quantification methodology for the temperature measurement performance of an ultra-low cost thermal imaging system based on a smartphone sensor. The camera was formed from a back illuminated silicon Complementary Metal Oxide Semiconductor (CMOS) sensor, developed for the smartphone camera market. It was packaged for use with a Raspberry Pi computer. We designed and fitted a custom-made triplet lens assembly. The system performance was characterised with a range of state-of-the-art techniques and metrics: establishing a temperature resolution of below 10 °C in the range 600–1000 °C. Furthermore, the scene dependent aspects of combined uncertainty were considered. The minimum angular subtense for which an accurate thermal measurement could be made was determined to be 1.35°, which corresponds to a 23 mm bar at a distance of 1 m, or 45:1 field-of-view in radiation thermometer nomenclature. [ABSTRACT FROM AUTHOR]

A major contribution to the global trend in reducing energy consumption can be made by improving the thermal performance of buildings. Minimization of heat loss via the building envelope is key to maximizing building energy efficiency. The building envelope contains different types of thermal bridging that must be accounted for while assessing the overall building envelope thermal performance. Multiple thermal bridges commonly occur and the distance between them determines the degree to which they interact thermally. To avoid overestimation of the linear thermal transmittance, it is important to account for interaction effects. Complex multiple thermal bridging occurs in window systems. The thermal performance of windows depends not only on the window performance itself but also on its installation into the wall. This study demonstrates an application of the quantitative infrared thermography technique to evaluate the heat lost via multiple thermal bridging. It is shown that using this methodology, the heat loss via multiple thermal bridges can be easily estimated in an existing building envelope, without any knowledge of its internal structure or material properties. For windows, it is demonstrated that jointly assessing the additional heat loss through the window and due to the installation of the window into the wall is a practical way to determine the actual heat loss caused by the presence of a window. A window thermal transmittance or M -value is introduced to quantify the total additional heat loss through the building element due to the presence of the window. The methodology was validated against experimental measurements taken on different specimens in a hot box device. Results from the thermographic analysis also co-related well with results from finite element heat transfer and computational fluid dynamics simulations. [ABSTRACT FROM AUTHOR]

Improving the thermal performance of the existing building stock is essential to significantly reduce the overall energy consumption in the building sector. A key objective is the retrofitting of the existing building envelope. A necessary first step in the building envelope optimization process is the assessment of its actual thermal performance. This assessment should be repeated after retrofitting to clearly define the improvements that were made and the heat loss reduction that was achieved. In this study, an efficient, non-destructive, in-situ measurement method, based on an outdoor infrared thermographic survey, is developed to determine the thermal bridging performance. As wind velocity significantly influences the heat losses through the building envelope, this study includes quantification of the wind velocity impact on the Ψ -value. This was assessed by undertaking ITT of the same thermal bridge at various wind velocities, in a controlled environment, in a hot box device. The results showed that the Ψ -value is highly dependent on wind velocity so that measurement of the Ψ -value taken at different wind conditions cannot be directly compared. An adjustment procedure is proposed that can be used to convert the Ψ -value measured at any wind velocity to a standard value corresponding to a velocity of 4 m/s. From a practical point of view, this adjustment procedure makes the methodology widely applicable. [ABSTRACT FROM AUTHOR]

Thermal imaging cameras are expensive, particularly those designed for measuring high temperature objects with low measurement uncertainty. A wide range of research and industrial applications would benefit from lower cost temperature imaging sensors with improved metrology. To address this problem, we present the first ever quantification methodology for the temperature measurement performance of an ultra-low cost thermal imaging system based on a smartphone sensor. The camera was formed from a back illuminated silicon Complementary Metal Oxide Semiconductor (CMOS) sensor, developed for the smartphone camera market. It was packaged for use with a Raspberry Pi computer. We designed and fitted a custom-made triplet lens assembly. The system performance was characterised with a range of state-of-the-art techniques and metrics: establishing a temperature resolution of below 10 °C in the range 600–1000 °C. Furthermore, the scene dependent aspects of combined uncertainty were considered. The minimum angular subtense for which an accurate thermal measurement could be made was determined to be 1.35°, which corresponds to a 23 mm bar at a distance of 1 m, or 45:1 field-of-view in radiation thermometer nomenclature.

A key aspect in assessing the thermal standard of building envelopes is the quantification of the heat loss though thermal bridging, which can be expressed in terms of the linear thermal transmittance Ψ . Values of Ψ may be obtained from tabulated values for standard building details, from numerical modelling or from measurement. Where the internal structure of the building envelope is unknown, which is very often the case, measurement is the only option. This study shows how the infrared thermography technique (ITT) can be used as a non-invasive and easy-to-use method to provide quantitative measures of the actual thermal bridging performance. The novelty of this approach includes evaluation of the actual heat flow rate caused by thermal bridge q TB and Ψ -value by means of the ITT solely, without any supporting methods. Another important aspect of the methodology is that it accounts for the correlation between the surface temperature and the convective and radiative heat transfer coefficients. Values for these coefficients are assessed for the whole range of the surface temperatures recorded on the thermogram resulting in improve accuracy. The q TB and Ψ -value calculated using the presented methodology fully mirrors the real thermal performance of the thermal bridge. The methodology has been tested under laboratory conditions in a steady state in a hot box with excellent agreement. [ABSTRACT FROM AUTHOR]

Normal LWIR apparent emissivity is connected to the spectral emissivity of an aluminum nitride ceramic plate. The connection uses the general formula of emissivity suggested by Chrzanowski and the spectral response R ( λ ) of the IR system. This result allowed us to study the relevance of the apparent emissivity and to elaborate an indirect method for its quantification using only its spectral emissivity. The aim of this paper is to compare the performances of the classical single-heating method to the indirect one for apparent emissivity quantification. The comparison is done for five different targets: polycarbonate, soda lime glass (respectively 2 mm, 4 mm and 6 mm thick) and stainless steel. The total hemispherical emissivity of these materials varies in the range [0.2–0.95]. The single-heating method is firstly employed using a homemade experimental device in standard conditions. A complete study of all the error sources which affect the accuracy of the two methods is done (uncertainties of types A and B). The single-heating method quantifies the apparent emissivity with type B measurement uncertainty ranging within [0.7–4.2%]. Reproducibility is found to range within [0.5–16%] whereas the repeatability is comprised between 0.2% and 10%. The indirect method quantifies the apparent emissivity with type B measurement uncertainty ranging within [0.1–1.2%] and reproduces the measurements with deviation ranging within [0.1–4%] which is comparable to uncertainty of apparent emissivity measurements. Thus the indirect method offers a real and efficient alternative to the direct method and can therefore be implemented to quantify apparent emissivity prior to quantitative thermography. On the other hand, single-heating method could be an interesting approach to non-intrusive and non-destructive testing of materials by exploiting the potentiality of an in-situ mapping of their apparent emissivities. [ABSTRACT FROM AUTHOR]

In a previous work, we succeeded in connecting normal LWIR apparent emissivity to the spectral one of an aluminum nitride ceramic plate. The key problem was the knowledge of the effective spectral bandwidth in use in the system. Hence we have developed an analyzer which permits to identify the spectral bandwidth of IR system using only its raw data. It proceeds by minimizing the dispersion from linearity of the characteristic thermosignals/integrated radiance over a temperature range of the IR system. The capacities of the analyzer are tested for five commercial cameras. Each of these systems exhibits a similar formatting process implemented during the thermogram recording. The effective spectral bandwidth shows plausible values. It varies significantly from one model to the other and the residual non-linearity is connected to the NETD of the IR system. The robustness of the apparent emissivity measurements is also tested with the aid of emissivity reference of 0.5. The overall accuracy of the method is less than 1%, depending on the specular or diffuse part of the reflected irradiation. Applied in field situation, the method is suitable to detect absolute variation of emissivity of less than 6 ⋅ 10 −3 . We use the analyzer to determine the spectral bandwidth of a commercial 320 × 240 microbolometer uncooled IRFPA camera which had already served to characterize the normal LWIR apparent emissivity of the aluminum nitride ceramic plate. By using the spectral response of the two major microbolometer sensor technologies, the general formulation of apparent emissivity matches our apparent emissivity measurements. An agreement better than 0.6% in absolute value and a less than 6 ⋅ 10 −3 %/°C dispersion are found over the entire temperature range [40–130 °C]. [ABSTRACT FROM AUTHOR]

Highlights: [•] Methodology for generating as-built BIMs with descriptive data of building elements. [•] Non-destructive techniques applied to thermal and geometric inspection of buildings. [•] Automatic point cloud processing for the generation of the geometry of BIM. [•] Quantitative thermography approach for the calculation of U-values of the enclosure. [Copyright &y& Elsevier]

Highlights: [•] Characterization of normal LWIR apparent emissivity. [•] Implementation of the classical model of apparent emissivity. [•] Connection between spectral and apparent emissivity. [•] Agreement between the model and the measurements over a large temperature range. [•] Application for quantitative thermography using a commercial camera. [ABSTRACT FROM AUTHOR]

This paper aims at presenting the complete metrological problem associated to the thermomechanical characterization of materials. With this purpose in view, we first present a model based on irreversible thermodynamics that allows straightforward formulation of the set of the required state laws. Then, the state law, which links both entropy and temperature variables, is used within an entropy balance. It leads to the heat equation allowing for the identification of the different contributions involved in the apparent Thermomechanical Heat Source (THS). This THS is measured during the tensile experiment of a semicrystalline polymer, thanks to the monitoring of in-situ infrared temperature fields and the subsequent application of numerical reconstruction algorithms. Both stress-strain and THS-strain curves obtained experimentally over the same representative elementary volume are used simultaneously to identify the parameters of the behavioral model. The results first show that the model is able to describe the measured THS. Secondly, they allow for a clear analysis of various thermomechanical contributions (thermoelastic effect, total pure intrinsic dissipation, entropic couplings contribution reflecting microstructure transformations), which can be very helpful in understanding microscopic deformation phenomena. [ABSTRACT FROM AUTHOR]

Abstract: The inverse problem of 2D time-dependent heat source reconstruction is solved. The scientific objectives are the quantification of thermal effects associated to the mechanical deformation of materials during tensile tests. The experiment provides infrared measurements of the specimen’s surface temperature and the inverse algorithm aims at providing a volumic heat source that is free of errors due to heat diffusion. This algorithm is based on an analytical solution of the direct problem in the Laplace-Fourier domain. The solution proposed here is compared to a previously used method based on an adjoint formulation and a regularization of Tikhonov type. This allows to check the validity of the results. [Copyright &y& Elsevier]

Abstract: An inverse problem is considered here that consists in the reconstruction of heat source maps from the measurement of 2D temperature fields. The endorsed application concerns the thermomechanical characterization of materials submitted to mechanical loads. An infrared camera is used to record the temperature evolutions resulting from reversible or more usually irreversible heat dissipation. An algorithm is presented and checked theoretically on simulated data. It relies on a formulation in terms of a constrained optimization problem. One constraint imposes the observance of the heat governing equation. The second constraint is a penalty term of Tikhonov type. A discretization of the equations resulting from the minimization conditions yield a linear matrix form. The main problem concerns the conditioning of the sparse matrix so obtained, which is seriously damaged if one tries to get a very fine spatial resolution for the source. The strategy used for optimal regularization is obtained in two steps. First, prior information is obtained from experiments in a light inversion procedure. Second, this information is used for efficient regularization. This algorithm has the advantage of being easy to implement and independent from hypothesis on boundary conditions. The L-curve criterion is shown to produce good results and a robust processing for noisy data. [Copyright &y& Elsevier]

The effect of a surface coating on the response of a metallic substrate to pulsed thermal excitation is examined with the view to assessing its impact on the efficacy of quantitative thermographic evaluation as applied to the problem of material loss evaluation. An analytical model describing the response of a layered structure to a surface thermal excitation has been developed and its predictions are shown to be in excellent qualitative agreement with experimental observations. The results indicate that for materials with high thermal diffusivity, a surface paint layer bears important influence on the development of the surface thermal response and should be taken into account when undertaking quantitative assessments of thermographic data. [ABSTRACT FROM AUTHOR]

The objective of this paper is to use quantitative thermography for fatigue damage assessment and life prediction of welded components. The energy dissipation during fatigue process is taken as an effective index of fatigue damage to develop a nonlinear damage accumulation model, and the model is extended to evaluate the fatigue damage and residual life of the specimen subjected to variable loading. Experiments are performed to validate its applicability, and the relationships between the fatigue damage variable to the cycle number and the accumulated energy dissipation are presented and discussed. The results show that the energy dissipation has the same trend as the temperature increment evolution, and a power law relationship between the stress range and the energy dissipation is experimentally determined. The linear relationship between the accumulated energy dissipation and the cycle number is confirmed at different constant stress levels, and the total energy dissipation to failure is shown to be a constant value. The developed nonlinear damage accumulation model is used to predict the residual fatigue life, and a good agreement is achieved. It is concluded that the developed approach is applicable for fatigue damage accumulation and residual life evaluation of materials. • A nonlinear damage model is developed to evaluate fatigue damage accumulation. • The model is extended to predict fatigue damage evolution under variable loading. • The residual fatigue life is well evaluated based on the damage evolution curve. • The capability is demonstrated by theoretical and experimental validations. [ABSTRACT FROM AUTHOR]

This article elucidates the need to consider the inherent spatial transfer function (blur), of any thermographic instrument used to measure thermal fields. Infrared thermographic data were acquired from a modified, commercial, laser-based powder bed fusion printer. A validated methodology was used to correct for spatial transfer function errors in the measured thermal fields. The methodology was found to make a difference of 40% to the measured signal levels and a 174 °C difference to the calculated effective temperature. The spatial gradients in the processed thermal fields were found to increase significantly. These corrections make a significant difference to the accuracy of validation data for process and microstructure modeling. We demonstrate the need for consideration of image blur when quantifying the thermal fields in laser-based powder bed fusion in this work. [ABSTRACT FROM AUTHOR]