Thermography Method Research Articles

Thermography and rasterstereography as a combined infrared method to assess the posture of healthy individuals

The demand for noninvasive methods to assess postural defections is increasing because back alterations are more common among the healthy population. We propose a combined infrared method of rasterstereography and thermography to assess the back without harmful effects. This study aims to provide reference data on rasterstereography and thermography to evaluate the back of a healthy population and to further study the correlation between these two methods. This cross-sectional research involved 175 healthy individuals (85 males and 90 females) aged 22 to 35 years. There is a large Cohen’s d effect size in the cervical depth (males = 43.77 ± 10.96 mm vs. females = 34.29 ± 7.04 mm, d = 1.03), and in the lumbar lordosis angle (males = 37.69 ± 8.89° vs. females = 46.49 ± 8.25°, d = − 1.03). The back temperature was different for gender in the cervical area (males = 33.83 ± 0.63 °C vs. females = 34.26 ± 0.84 °C, d = − 0.58) and dorsal area (males = 33.13 ± 0.71 °C vs. females = 33.59 ± 0.97 °C, d = − 0.55). Furthermore, in the female group there was a moderate correlation of lumbar temperature with lumbar lordosis angle (r = − 0.50) and dorsal temperature with shoulders torsion (r = 0.43). Males showed a moderate correlation for vertebral surface rotation RMS with cervical (r = − 0.46), dorsal (r = − 0.60), and lumbar (r = − 0.50) areas and cervical temperature with shoulders obliquity (r = 0.58). These results highlight a possible correlation between rasterstereography and thermography, which may elucidate the underlying mechanics of spinal alterations and thermal muscle response. Our findings may represent reference data for other studies using noninvasive methods to assess postural alterations.

Review of the Experimental Methods for Evaluation of Windows’ Thermal Transmittance: From Standardized Tests to New Possibilities

One of the most important parameters that indicate the energy performance of a window system is the thermal transmittance (U-value). Many research studies that deal with numerical methods of determining a window’s U-value have been carried out. However, the possible assumptions and simplifications associated with numerical methods and simulation tools could increase the risk of under- or over-estimation of the U-value. For this reason, several experimental methods for investigating the U-value of windows have been developed to be used either alone or as a supplementary method for validation purposes. This review aims to analyze the main experimental methods for assessing the U-value of windows that have been published by national and international standards or as scientific papers. The analysis criteria include the type of the test in terms of boundary conditions (laboratory or in situ), the part of the window that was tested (only the center of glazing or the entire window), and the data analysis method (steady-state or dynamic). The experimental methods include the heat flow meter (HFM) method, guarded hot plate (GHP) method, hot box (HB) method, infrared thermography (IRT) method, and the so-called rapid U-value metering method. This review has been set out to give insights into the procedure, the necessary equipment units, the required length of time, the accuracy, the advantages and disadvantages, new possibilities, and the gaps associated with each method. In the end, it describes a set of challenges that are designed to provide more comprehensive, realistic, and reliable tests.

Infrared Thermography for Early Detection of Pepper yellow leaf curl virus on Chili Plants

Infrared Thermography for Early Detection of Pepper yellow leaf curl virus on Chili Plants Observations of plant pests and diseases are generally carried out by looking for visual symptoms for each disease target. Agricultural technology 4.0 began to be used for the development of plant disease detection methods. It was reported that there were differences in color and temperature between diseased and healthy plants which could be recorded by a thermal camera. This study aimed to determine the potential of the FLIR One Pro-IOS thermal camera to record differences in color and temperature between viral-infected and healthy chili plants. Chili plants in the greenhouse that were inoculated with Pepper yellow leaf curl virus (PYLCV) experienced an increase in temperature 3 days after inoculation (28.62 ℃) compared to plants that were not inoculated with PYLCV (27.32 ℃). Digital image recording of chili leaf samples from the field showed that plants infected by multiple viruses (Chilli veinal mottle virus, Pepper mottle virus and PYLCV) has higher temperature than those infected with a single virus. The lowest and highest mean temperatures were recorded in plant samples infected with PepMV (17.74 ℃) and mixed infected by PYLCV and ChiVMV (25.68 ℃). Digital images of virus-infected plants tend to show a predominance of bright yellow, while virus-free plants showed a predominance of dark purple. Further analysis confirmed higher digital numbers for diseased plant images than healthy plants. The thermography method has the potential to be an early detection method because it can detect viral infection before visual symptoms appear.

Experimental Assessment of Thermohydraulic Performance of a Rectangular Solar Air Heater Duct Using Twisted V-Shaped Staggered Ribs

AbstractThe present experimental effort aims to determine the thermohydraulic performance of a rectangular solar air heater duct with V-shaped ribs staggered over the absorber plate. The performance test is conducted with variable roughness constraints, including relative roughness pitch (P/e) values between 7 and 11, relative staggered distance (d/e) values between 2 and 6, and relative arm length of twisted V-rib (S/e) values between 4.39 and 10.26, and flow Reynolds number values between 3000 and 21,000. The method of liquid crystal thermography is used to observe the dispersion of the Nusselt number over the roughened absorber surface. The maximum Nusselt number and friction factor enhancement ratio for roughened surfaces is determined to be 3.43 and 2.57 times that of a smooth plate, respectively. The parameters of rib configurations are adjusted based on the achieving greatest thermohydraulic performance (THP) index, which corresponds to P/e of 9, d/e of 4, and S/e of 6.15, yielding an optimum thermohydraulic performance measure of 2.69.

Evaluation of temperature on different wheelchair cushions using infrared thermography method

Evaluation of temperature on different wheelchair cushions using infrared thermography method

Towards deep computer vision for in-line defect detection in polymer electrolyte membrane fuel cell materials

Polymer Electrolyte Membrane (PEM) fuel cells are a promising source of alternative energy. However, their production is limited by a lack of well-established methods for quality control of their constituent materials like the membrane-electrode assembly during roll-to-roll manufacturing. One potential solution is the implementation of deep learning methods to detect unwanted defects through their detection in scanned images. We explore the detection of defects like scratches, pinholes, and scuffs in a sample dataset of PEM optical images using two deep learning algorithms: Patch Distribution Modeling (PaDiM) for unsupervised anomaly detection and Faster-RCNN for supervised object detection. Both methods achieve scores on performance metrics (ROC-AUC and PRO-AUC for PaDiM and AP for Faster-RCNN) that are comparable to their scores on benchmark datasets. These methods also have the potential to detect a wider range of defects compared to IR thermography and previous optical inspection methods. Overall, deep learning shows promise at detecting relevant defects of interest and has the potential to achieve real-time defect detection.

A Crack Detection Method for Aero-engine Blade Based on Air-Flow Thermography

Aero-engine blade is one of the core components of aero-engine and its safe service is crucial to the normal operation of aero-engine. Thus, it is very important to localize and quantify cracks of aero-engine blades to prevent safety accidents. To guarantee the structural health of aero-engine blades, the air-flow thermography (AFT) method which has advantages of non-contact, high performance, and sensitivity, was proposed for detection of the blade cracks. Firstly, the theoretical thermal response model was established and the crack simulation models with different depths were constructed. Then a detection system was established to detect the artificial cracks with different depths and orientations. Results showed that the proposed method can effectively quantify the cracks with different depths from 0.2 mm to 1.0 mm and characterize the crack orientations. In addition, the natural crack on the blade was detected and the principal component analysis (PCA) method was used to enhance the crack contrast with the background.

Measurement of Microscopic Thermal Diffusivity Distribution for Ryugu Sample by Infrared Lock-in Periodic Heating Method

The thermophysical properties of small Solar System bodies are essential to be determined, on which the thermal evolution of small bodies largely depends. The carbonaceous asteroid Ryugu is one of the small undifferentiated bodies formed in the early Solar System. Hayabusa2 explored the asteroid Ryugu and returned the surface samples in 2020 for detailed on-ground investigation, including measurements of thermal properties. Because the available sample amount was limited, this study developed a novel method to measure the thermal diffusivity of small and irregularly shaped samples of about 1 mm in diameter by combining lock-in thermography and periodic heating methods on the microscale. This method enables us to measure the thermal diffusivity of both flat-plate and granular shape samples by selecting the suitable detecting direction of the temperature response. Especially, when the sample has a flat-plate shape, the anisotropic distribution of the in-plane thermal diffusivity can be evaluated. This method was applied to six Ryugu samples, and the detailed anisotropic distribution of the thermal diffusivity was obtained. The measurement results showed that the samples show local thermal anisotropy caused by cracks and voids. The average thermal diffusivity among all samples was (2.8 to 5.8) × 10−7 m2·s. Based on the density and specific heat of the samples obtained independently, the thermal effusivity was estimated to be 791 J·(s1/2·m2·K) to 1253 J·(s1/2·m2·K), which is defined as the resistance of surface temperature to the change of thermal input. The determined thermal effusivity, often called thermal inertia in planetary science, is larger than the observed value of 225 ± 45 J· (s1/2·m2·K) of the asteroid Ryugu's surface, obtained from the diurnal temperature change of the rotating asteroid by a thermal infrared camera onboard Hayabuas2. This difference is likely to be attributed to the difference in the analytical scale between the sample and the surface boulders compared with the thermal diffusion length. Consequently, it was found that the present result is more representative of the thermal diffusivity and thermal inertia of local part of individual Ryugu particles.

Infrared thermography method to detect cracking of nuclear fuels in real-time

The efficiency and performance of nuclear fuels are essential to the safety, reliability, and economics of nuclear energy. Crack formation occurs relatively early in the fuel operation cycle and lowers its life and efficiency; accordingly, understanding crack formation and propagation in fuels is key to evaluating and improving fuel performance. The harsh environment inside a nuclear reactor is the primary challenge for real-time fuel monitoring. A coherent fiber optic bundle (CFOB) based infrared thermography (IRT) method may be a viable method for real-time fuel monitoring. A radiation hardened, temperature resistant CFOB can be used to transmit a real-time image from inside the harsh reactor environment to the near infrared (NIR) camera outside the reactor. In this paper, the feasibility of the method was tested and confirmed on oxide nuclear fuel surrogates in a laboratory setting. Two different fuel surrogate materials are showcased with and without the CFOB using furnace heating, laser heating, and reflected illumination from an incandescent bulb. The behavior of common features, such as cracks, mounds and pits, were all compared in detail for the different heating/illumination techniques and samples for temperatures ranging from 23–500°C. The effects of five different image processing techniques were also studied. Cracks down to ≈300nm wide with a field of view of ≈6.4×5.12mm were easily detected with the IRT system with and without the CFOB.

An innovative experimental energy-based approach for the life prediction of notched details

Fatigue assessment of mechanical components can be very challenging due to the presence of macroscopic defects and notches. However, local approaches as the Stain Energy Density, have shown how the fatigue resistance is strictly related to the local stress field near the notch tip and not on the overall dimensions of the component. It is necessary to know some peculiar material’s parameters to apply those local approaches. A short way to obtain such parameters can be to apply Thermographic Methods, such as the Risitano’s Thermographic Method and the Static Thermographic Method, monitoring the energy release during stepwise fatigue and static tensile tests. In this work, experimental tests were performed on plain and double edge steel notched specimens. The SED method has been applied through finite element models, with the easy application of the volume-free procedure, to evaluate its trend at several stress levels. The analysis of the energy release and of the local averaged strain energy density during a static tensile test may be adopted as a novel approach to relate the local stress state with a macroscopic stress value that introduce in the material the first micro plasticization leading to the failure of the component.

Fatigue assessment of 3D-printed porous PLA-based scaffold structures by Thermographic Methods

Additive manufacturing with Fused Deposition Modelling (FDM) provides new opportunities for biomedical applications by manufacturing more complex structure for tissue scaffolds. In contrast to traditionally manufacturing methods such as injection moulding, FDM-made structures are produced with layer-by-layer adhesion mechanism. Moreover, setting different parameters is critically important to obtain reliable components, consequently fatigue analysis of these structures gets complicated. Therefore, a scaffold must be designed to replace human bone and withstand to static and fatigue loads. Although PLA scaffolds fabricated by FDM have been widely investigated, the fatigue behaviors research on them have been narrowly published; therefore, it is necessary to analyze the fatigue behaviour of PLA scaffolds because of their wide application in medical science. In this study, fatigue analysis of scaffolds-like specimens made by PLA is carried out by monitoring the energy release of such structures. Thermographic Methods are applied to obtain, in a short time and with few materials’ consumption, fatigue life information of scaffold-like structures produced with different printing parameters.

Thermal analysis under static and fatigue conditions on HDPE

High Density Polyethylene (HDPE) represents one of the best choices for water and gas distribution pipeline thanks to its light weight and good mechanical performance. One of the strengths of this plastic material is the possibility to join it via welding adopting a procedure according to the standard. However, the welding procedure can severally alter the mechanical performance of the material under service loads. In the present work comparison between virgin and welded HDPE specimens is carried out adopting rapid approaches, such as the Risitano’s Thermographic Method and the Static Thermographic Method, monitoring the evolution of the specimen’s superficial temperature under static tensile and fatigue tests. Mechanical performance has been compared, as well as the fatigue limit obtained with traditional fatigue tests, showing good agreement. Reliable fatigue data have been obtained in a very short amount of time and with few specimens by adopting Energy Methods.

Detection and quantification of artificial delaminations in CFRP composites using ultrasonic thermography

Delamination is inevitable during either fabrication or service of a carbon fiber reinforced polymer (CFRP) component. These flaws are major degradation phenomena that are difficult to be detected by nondestructive testing techniques, especially for closed delamination. This study performed an experimental investigation on delamination detection in CFRP plates using ultrasonic thermography with an ultrasonic transducer. In this work, a CFRP composite plate with delaminations was manufactured by a compression molding process. The ultrasonic was excited in the specimen and the heat was activated at the delaminations. Temperature distribution on the specimen surface was recorded by an infrared camera. The effects of wave propagation distance, delamination size, and depth were analyzed. Furthermore, the three most established signal processing techniques of thermography, namely thermal signal reconstruction (TSR), principal component analysis (PCA), and fast Fourier transform (FFT) were employed to deal with the subtracted-background thermal data. The performance of each algorithm was evaluated by temperature contrast, and global signal-to-noise ratio (SNR). Finally, the delamination area was quantitatively measured by Otsu’s thresholding method. The results indicate that the first and second principal components (PC1 and PC2) of PCA provide the highest SNR and the largest number of delaminations detected, respectively. The delamination of ϕ5 and a depth of 1.5 mm can be detected with excellent image quality. Hence, ultrasonic thermography can provide an efficient and cost-effective thermographic method for delamination detection in CFRP structures.

Analysis of step-heating thermography methods for defect depth prediction

In this study, five theoretical equations of specific characteristic peak times are proposed to predict the defect depth for step-heating thermography. These equations were derived for test samples with surfaces under adiabatic and convective heat transfer conditions, where, as demonstrated from experiments, the effect of convection on depth prediction can be significant for materials with low thermal conductivities. Two glass fiber reinforced plastic (GFRP) samples with flat-bottom holes at various depths were inspected by step-heating thermography, and the defect depths were predicted by these five methods. Based on the experimental results, the prediction accuracy and the performance of these depth prediction methods are discussed.

Field Inspection of High-Density Polyethylene (HDPE) Storage Tanks Using Infrared Thermography and Ultrasonic Methods

High-density polyethylene (HDPE) is widely used for above-ground storage tanks (ASTs). However, there are currently no guidelines for the non-destructive testing (NDT) and evaluation (NDE) of HDPE ASTs. Moreover, the feasibility, limitations, and challenges of using NDT techniques for the field inspection of HDPE ASTs have not been well established. This study used both infrared thermography (IRT) and ultrasonic testing (UT) for the field inspection of HDPE ASTs. Highlighting the implementation challenges in the field, this study determined that: (1) ambient environmental parameters can affect IRT accuracy; (2) there is an ideal time during the day to perform IRT; (3) the heating source and infrared camera orientation can affect IRT accuracy; and (4) with proper measures taken, IRT is a promising method for flaw detection in HDPE ASTs. Additionally, UT can be used following IRT for detailed investigation to quantify the size and depth of defects. The manuscript concludes with a discussion of the limitations and best practices for the implementing of IRT and UT for HDPE AST inspections in the field.

Internal Defect Detection of Structures Based on Infrared Thermography and Deep Learning

Rapid and accurate detection of internal defects in bridges has always been a major concern of the management and maintenance departments. In the present study, an intelligent method for the detection of structural internal defects is proposed based on infrared thermography and deep learning. Through theoretical analysis, numerical simulations and laboratory experiments, the classification, localization and quantification of internal defects of concrete structures were achieved with the infrared thermography and deep learning method. The mean average precision for classification and localization of internal defects is 96.59%, the mIoU for pixel-level segmentation is 95.19%, and the average relative error for damage quantification is 0.70%. The feasibility of the trained model is verified with new images, and the results show that the trained model can capture infrared thermal features of internal defects with different sizes and depths. This method has the advantages of low cost, high accuracy, easy operation, and large area scanning of concrete structures, which can provide a good reference for the detection of internal defects of concrete structures.

Phytase influence on soymilk protein colloid stability studied with thermographic method

Coagulation of soymilk is well studied from a technological point of view. However, physicochemical features of the process of soymilk protein colloidal stability destruction may be of interest both from a purely scientific point of view and for improving production processes. In this study, an attempt was made to analyze the role of phytinates in formation of the colloidal stability of soymilk proteins. A possible role of the dissociation of phosphate groups of phytic acid in the rise of an electric charge stabilizing soy protein micelles in water solution has been suggested. The ability of phytase to cut off the phosphate groups of phytic acid was used to substantiate our assumption. To study the kinetics of coagulation of soymilk proteins, a thermographic method was used. The results of the experiments show that the addition of phytase to soymilk can significantly accelerate its acid coagulation, which is an indirect confirmation of the above assumption.

Thermogravimetry of bentonite "navbahor" in nanocatalytic extraction technology and investigation of the convective ehfef drying process

This study presents the results of a study of the process of thermography and convective drying of the retention substance bentonite used in the production of nanocatalysts based on Zol-gel technology. The study of the drying process using the energy of the convex-EHFEF EMF (extremely high-frequency electromagnetic field) in the preparation of a nanocatalystsfrom the retaining substance of bentonite is illuminated by the derivatogram of bentonite from the Navbahor deposit determined by the thermographic method. The determination of the porous structure and the comparable surface surface of the catalysts was carried out in an automatic gas adsorption analyzer using the Brunauer, Emmet, and Wyres (bet) method.The size and pore size of the catalysts were determined from data on desorption and adsorption isotherms, respectively, at a relative pressure R/R0=0.99 in accordance with the BJH (Barette-Joyner-Halend) model. Based on the purpose of the work, the study of the drying process in the technology of obtaining a nan catalyst and the acceleration of its process and technology with its introduction into EHFEF (extremely high frequency electromagnetic field) EMC, was achieved to improve the quality of the porosity of catalysts. In particular, the analysis of the results obtained on the experimental scheme of the grooved-convex drying device, textural descriptions of bentonite of the Navbahor deposit, determined on the basis of standard techniques, porosity of the sample by the method of temperature nitrogen adsorption is presented.

Measurement of the thermal diffusivity of optical materials and products by a new thermographic express method that does not require cutting samples from bulk

Thermal diffusivity a and thermal conductivity λ are important for many building, structural and functional material applications. They determine the intensity of heat transfer, the quality of thermal insulation, the rate of heating / cooling, reaching a stationary mode, and the efficiency of power equipment. In laser technology, the radiation strength of the optical components of the system depends upon them, and in laser technologies with material removal they determine the speed and quality of processing. Most methods for measuring a and λ in solid materials require cutting out samples of a certain geometry, which makes them unsuitable for testing finished products. The paper proposes and describes an express method for determining a and λ in translucent materials, which does not require cutting a sample from a controlled object. It consists in the analysis of a non-stationary temperature field on the surface of the test object using a high-speed thermal imaging camera. The unsteady heating spot was created by a focused laser beam. It was switched on abruptly and operated in the mode of continuous irradiation with a constant intensity during the entire time of measurements. Heat propagated from this spot to the periphery, creating a non-stationary temperature field containing information about a and λ. The a value was extracted from the primary data using original algorithms and software. A thermal imager, as a recorder of a dynamic temperature field, provides a number of advantages – non-contact, high speed and a large amount of information (each of the many hundreds of thousands of pixels of a professional thermal imager matrix is a temperature sensor in a small surface area). Measurements of a and λ in semitransparent materials of laser optics have their own specifics. The low radiation absorption coefficient and the possible curvature of the surface (for example, in lenses) require special measures, which are described in the article. Due to the large amount of information contained in the dynamic patterns of the thermal field and the possibility of averaging over a large data array, the RMS of the thermal diffusivity measurement does not exceed 2 %.

The Effect of Laser Shock Peening on the Thermophysical Parameters of Metals

Using Ti64 titanium alloy as an example, the article discusses the change in the thermophysical parameters of metals under the influence of a hardening method such as laser shock peening the essence of which is the formation of residual compressive stresses in the material under the influence of high-intensity laser radiation. The experiments are carried out with plates made of Ti64 titanium alloy, which is one of the most common construction materials in modern industry. One of the plates is a control specimen, and the surface of the second one is subjected to laser processing. The thermophysical parameters of specimens are determined using the infrared thermography method, the advantage of which is the ability to simultaneously measure two coefficients, thermal diffusivity and thermal conductivity of an explored material. The specimen is heated by the laser for some time, which can be perceived as a point heat source on the surface of the plate. Simultaneously with the laser action, the surface temperature of the specimen is recorded by an infrared camera. The thermophysical coefficients are determined as optimization parameters when matching experimental data with the analytical solution of the heat equation for a geometry similar to the experimental setup.