Thermal Imaging Technique Research Articles

A comparative evaluation of thermal camera and visual counting methods for primate census in a riparian forest at the Lower Kinabatangan Wildlife Sanctuary (LKWS), Malaysian Borneo.

A number of primate census techniques have been developed over the past half-century, each of which have advantages and disadvantages in terms of resources required by researchers (e.g., time and costs), availability of technologies, and effectiveness in different habitat types. This study aims to explore the effectiveness of a thermal imaging technique to estimate the group size of different primate species populations in a degraded riparian forest in the Lower Kinabatangan Wildlife Sanctuary (LKWS), Sabah. We compared this survey technique to the conventional visual counting method along the riverbank. For 38days, a total of 138 primate groups were observed by thermal camera and visually throughout the study. Optimal conditions for the thermal camera were clear weather, not more than 100m distance from the observer to the targeted area, boat speed ranging between 5 and 12km/h, and early morning between 04:30 and 05:30am. The limitations of the thermal cameras include the inability to identify individual species, sexes, age classes, and also to discern between animals closely aggregated (i.e., mothers with attached infants). Despite these limitations with the thermal camera technique, 1.78 times more primates were detected than counting by eye (p < 0.001), showing the potential benefit of using thermal cameras as an important tool in primate surveys. Nevertheless, ground truthing must be conducted immediately after, or simultaneously during, the thermal survey to verify the species of animals observed on the thermal imagery.

USE OF THERMAL IMAGING TESTS IN THE STEEL INDUSTRY

The paper presents the possibilities and selected examples of practical use of the thermal imaging technique in the metallurgical industry as a non-invasive testing method for measuring temperature distribution on the surface of the examined object. This method can be used in all stages of steel production, from charge preparation to finished product, as well as diagnostics of technical devices. The paper emphasises the non-invasive nature of the examination, which does not disturb the production cycle.

Novel Analytical Approach for Estimation of Thermal Diffusivity and Effusivity for Detection of Osteoporosis

Infrared thermography is a full field, non-contact inexpensive, patient friendly and safe imaging modality for estimation of thermo-physical properties of various bio-materials. Among the widely used thermal wave imaging modalities, recently proposed frequency modulated thermal wave imaging technique gained importance due to its quantitative characterization capabilities along with its deeper subsurface visualization abilities. This work highlights a novel analytical analysis for three dimensional Fourier heat diffusion equation by considering internal heat generation. An aperiodic pulse compression favorable thermal wave imaging method is proposed for estimation of thermo-physical properties of bone for identification of severity of osteoporosis. Effect of osteoporosis on thermo-physical properties such as thermal effusivity and diffusivity has been studied. Further proposed analytical approach has been validated by results obtained from the commercially available finite element based COMSOL software.

Time Resolved Hyperspectral Quantum Rod Thermography of Microelectronic Devices: Temperature Transients in a GaN HEMT

The trend of miniaturization and rapid progress in the cost-competitive microelectronic industry require high resolution, fast, accurate and cost-effective thermal characterization techniques. These techniques aid the assessment of reliability and performance bench-marking of new device designs for the realistic operation conditions. We present a time resolved, surface sensitive, sub-micron resolution wide field thermal imaging technique, exploiting fast radiative recombination rates of quantum rod photoluminescence to probe temperature transients in semiconductor devices. We demonstrate a time resolution of $20~\mu \text{s}$ on a single finger AlGaN/GaN HEMT. This technique provides an image of the surface temperature transients regardless of the device design/material system under test. The results were verified with transient thermo-reflectance measurements.

Monitoring of the soil moisture regime of an earth-filled dam by means of electrical resistance tomography, close range photogrammetry, and thermal imaging

Small earthen dams usually lack a detailed monitoring system that would provide high-resolution data concerning changes in seepage flow. Geophysical methods and remote sensing are useful techniques for non-destructive and non-invasive investigation of subsurface processes. We have utilized a combination of electrical resistivity tomography (ERT), close range photogrammetry, and unmanned aerial vehicle (UAV) thermal imaging techniques to detect specific superficial and internal structures of a historical earth-filled dam. Longitudinal and transversal profiles of a typical fishpond dam in the Czech Republic were measured. The dam was constructed during the fifteenth century, but has since gone through some minor reconstruction. The aims of the applied geophysical methods are to detect and localize the boundary of the dam foundation, new earth material from reconstruction, the cone of water depression, the reservoir’s outlet location, potential internal erosion, cavities, and heterogeneity in water content pattern and any other anomalies. The primary results show that ERT is suitable to detect dam stratification and large anomalies. The UAV monitoring system provided reliable data for a surface temperature distribution map which corresponded well to topsoil water content and electrical resistivity.

A Preliminary Study on Leakage Detection of Deteriorated Underground Sewer Pipes Using Aerial Thermal Imaging

Due to less visibility, underground facilities such as sewer pipelines are subjected to degradation until a major failure occurs. So, leakage detection of deteriorated underground sewer pipes is necessary to prevent expensive rehabilitation costs. The major causes of the frequent occurrence of ground subsidence and sewer leakage are excessive use of groundwater, reckless exploitation of natural resources, etc. In this study, the aerial thermal imaging (ATI) technique has been used to identify the leakage points in sewer pipelines by analyzing surface thermal diffusion behavior of the ground surface. Leakage is suspected at points of anomalous temperature variation. Then, ground-penetrating radar and closed-circuit television surveys have been carried out to strengthen the suspicion of sewer leakage. Irregular, erratic parabolic-shaped lines are observed at the points where the leakage is suspected through ATI. Finally, the test-pit excavation and simple cone penetration tests have been carried out which confirms the sewer leakage points. The leakage points are confirmed by a greater depth of penetration. The results of the cone penetration test carried out in E-21 and 23-24 sewer pipelines show that the depth of penetration at the leakage points is about 35 cm, which is greater than the depth of penetration at other points. So, it can be concluded that the aerial thermal imaging technique is an effective method to predict leakage in deteriorated underground sewer pipelines.

Research on Modulated Thermal Wave Radar Imaging Technique for Photothermal Properties of Semi-transparent Materials

The photothermal characteristics of semi-transparent medium are the basis for describing the transmission process of photothermal radiation. Therefore, the related measurement researches have important application value for the non-destructive testing of high-tech module. In the present work, an infrared thermal wave radar imaging (TWRI) technique combined with sequential quadratic programming (SQP) algorithm was proposed for simultaneous reconstruction of the photothermal property distributions in 2D semi-transparent materials containing defects. The Fourier transform, Hilbert transform, and the Chirp lock-in correlation algorithm were applied and the results of the amplitude and phase information of the temperature signals were compared, so as to identify the position of internal defects, which reduced the number of parameters needed to reconstruct. Then, the SQP algorithm was introduced to simultaneously reconstruct the absorption coefficient and thermal conductivity coefficient distributions in the medium. The TWRI-SQP technique absorbs the advantages of fast identification of defects by TWRI technique and the accurate reconstruction of the photothermal properties of the semi-transparent materials by SQP algorithm. The number of internal defects, geometric dimensioning, shape, and photothermal properties can be reconstructed accurately. The results show that this method is practical and robust to detect the photothermal properties of 2D semi-transparent materials with defects.

Time-resolved temperature-jump measurements and steady-state thermal imaging of nanoscale heat transfer of gold nanostructures on AlGaN:Er3+ thin films.

For a nanostructure sitting on top of an AlGaN:Er3+ thin film, a new thermal imaging technique is presented where dual cameras collect bandpass filtered videos from the H and S bands of Er3+ emission. We combine this thermal imaging technique with our newly developed time-resolved temperature measurement technique which relies on luminescence thermometry using Er3+ emission. This technique collects time-resolved traces from the H and S bands of Er3+ emission. The H and S signal traces are then used to reconstruct the time-resolved temperature transient when a nanostructure is illuminated with a pulsed 532 nm light. Two different types of samples are interrogated with these techniques (drop-casted gold nanosphere cluster and lithographically prepared gold nanodot) on the AlGaN:Er3+ film. Steady-state and time-resolved temperature data are collected when the samples are immersed in air and water. The results of time-resolved temperature-jump measurements from a cluster of gold nanospheres show extremely slow heat transfer when the cluster is immersed in water and nearly 200-fold increase when immersed in air. The low thermal diffusivity for the cluster in water suggests poor thermal contact between the cluster and the thermal bath. The lithographically prepared nanodot has much better adhesion to the AlGaN film, resulting in much higher thermal diffusivity in both air and water. This proof-of-concept demonstration opens a new way to measure the dynamics of the local heat generation and dissipation at the nanoparticle-media interface.

Mechanisms of failure in coal samples from underground water reservoir

Using goaf as water storage space plays an important role in the ecological environment and economic development of arid mining areas, while water content affects the rock strength and the stability of coal pillars in underground water reservoirs by changing crack propagation. In this work, variable-angle shear tests (compression-shear tests) were conducted for coal samples with moisture contents of 0%, 7.10%, 15.68%, 22.90%, and 23.09% to develop new insights into the mechanisms of crack propagation and strength weakening, combined with acoustic emission (AE) technique and infrared thermal imaging technique. The results show that the main cracks in dry coal samples exist along the shear surface, while the fracture surface in the saturated samples deviates from the shear surface and many irregular shear cracks form. The shear strength, cohesion, and internal friction angle of coal samples decrease linearly or exponentially with water content. Given this result, we discuss the Mohr-Coulomb criterion for coal samples based on water content. Increasing the water content weakens the effect of increased heating at the center of the coal samples, and especially the saturated coal samples emitted less infrared radiation than the loading device in the destructive phase. The average infrared radiation temperature (AIRT), AE energy rate and shear stress distribution are all correlated, which reflect the characteristics of the destructive process within water-containing samples. After the formation of macro-fractures, the increased contact area of fracture surfaces with the air causes heat to suddenly reduce. These results indicate the failure mechanism involving the destabilized deformation of coal samples under compression shear, which gives a useful reference for designing waterproof coal pillars and underground reservoir dams.

Investigation into the effect of fabric structure on surface temperature distribution in weft-knitted fabrics using thermal imaging technique

The aim of this paper was to evaluate the surface temperature distribution in several single and double jersey weft-knitted fabrics. Plain knitted fabrics as well as those with, double cross-tuck, cross-tuck, double cross-miss, and cross-miss pattern together with plain rib and interlock structures were under consideration in term of their structural differences. In order to investigate the temperature distribution in produced samples, all the fabrics were placed on a 35?C adjusted hot plate instrument and thermal images were captured by an infrared thermal camera. The results revealed that the presence of tuck stitches in single jersey weft-knitted fabrics increase the air permeability due to the increasing the fabrics? porosity, which in turn leads to decrease their thermal resistance as compared with plain knitted structure. On the other hand, addition of miss stitches in single jersey knitted structures would decrease the thickness of fabrics and improves their heat transfer ability. The obtained results, from rib and interlock knitted structures, suggested their lower heat conductivity in comparison to the single jersey knitted samples.

Evaluating Concrete Damage in Bridge Decks with and without Overlays Using Nondestructive Testing Procedures

Abstract The state of Wyoming alone has 13.1 million square feet of bridge deck, and evaluation of those decks has become an important part of the Wyoming Department of Transportation’s (WYDOT) management of bridge repairs. The authors believe that development and advancement of nondestructive evaluation methods over the past 25 years may provide a more efficient, standardized, and accurate method for evaluating bridge deck conditions compared with current practices. A study was performed on three bridge decks in Wyoming: the First Street Bridge in Casper, the Douglas I-25 Bridge, and the Remount I-80 Bridge. For each bridge, an investigation was done using standard WYDOT practices for chain dragging. In addition, the bridges were evaluated using impact echo, thermal imaging, and ground-penetrating radar (GPR) techniques. All three methods considered were successful, and the damage locations between the impact echo, thermal imaging, and GPR generally correlated well. Based on this study, a complete bridge deck evaluation should combine impact echo with GPR testing to provide the most accurate predictions of delamination and debonding in support of optimal maintenance decisions.

Theoretical study on infrared thermal wave imaging detection of semiconductor silicon wafers with micro-crack defects

The semiconductor silicon wafer with micro-crack defects was detected using infrared thermal wave imaging technique. The 3-D thermal conduction model in semiconductor silicon wafer excited by linear frequency modulated continuous laser was established, and it was solved by finite element method. The results show the effectiveness of the proposed method for detecting micro-crack defects in semi?conductor silicon wafers.

Non-Destructive Characterization of Railway Materials and Components with Infrared Thermography Technique.

Infrared (IR) thermography technology is one of the leading non-destructive evaluation (NDE) techniques based on infrared detection. Infrared thermography, in particular, has the advantage of not only being used in non-contact mode but also provides full images, real-time inspection, and relatively fast results. These advantages make it possible to perform thermal imaging analysis of railway materials and/or components, such as brake disc simulation, monitoring of abnormal heat generation, and monitoring of temperature changes, during mechanical tests. This study introduces the current state of research on railway materials and/or components using IR thermography technology. An attempt was made to characterize the deterioration of electrical equipment of diesel electric locomotives using infrared thermal imaging techniques. In addition, surface temperature monitoring was performed during tensile testing of railway steels using a high-speed infrared camera. Damage evolution due to the hot spot generation of railway brake discs was successfully monitored using high-speed IR cameras. In this paper, IR thermal imaging technology, used as a non-destructive evaluation analysis in the railway field, was introduced, and the results of recent research are presented.

Infrared imaging of a non-stationary thermal conductive process and observation of its Green’s kernel

A simple experiment is devised to visualize, through the infrared thermal imaging technique, the time dependence of the transient temperature distribution in a solid, metallic rod. The Laplace transform method is adopted to obtain a theoretical model which is numerically solved. The particular case of a thermal shock imposed to one end of a single rod is then considered and a simplified form of the Laplace transform solution is analytically developed. The resulting expression is shown to constitute the Green’s heat kernel for the rod problem. This propagator has a simple analytical expression which allows for its explicit study and comparison with the experimental temperatures. The onset of a ‘heat wave’ and its temperature peak is observed and described within the Green fundamental solution. Further comparisons are also made in terms of numerical simulations based on a free app devoted to thermal partial differential equations. The experiment and the mathematical treatment here presented have been developed especially for undergraduate physics students in an educational framework.

A study on anomalous yield drop behaviour in modified beta titanium alloys

ABSTRACTThe yield drop phenomenon observed in the Ti–15V-3Al–3Sn-3Cr (Ti–15–3) beta-titanium alloy and its anomalous behaviour in the boron and carbon added Ti–15–3 alloys have been studied. While the base and the carbon containing alloys exhibit yield drop, the boron containing alloy with smaller grain size than base alloy does not appear to show this phenomenon. Tensile tests were interrupted at different stress levels followed by analyses of slip lines and sub-structural characteristics using scanning and transmission electron microscopes to understand this anomalous yield point phenomenon. Infrared thermal imaging technique was used to map the strain localisation and the spatiotemporal evolution of deformation along the gauge length of the specimens during the tensile tests. Deformation in these alloys initiates only in a few grains. Pile-up of dislocations in these grains subsequently triggers the formation of dislocations in other grains and their rapid multiplications. The spreading of deformation by the generation of dislocations from pile up dislocations in one grain to neighbouring un-deformed grains and their rapid multiplication to new regions influence the yield drop phenomenon and its characteristics. It is shown in this study that microscopic instability in the grain level is a necessary, but not the sufficient condition for the manifestation of macroscopic instability during tensile deformation in polycrystalline materials. The presence of boride particles at grain boundaries restricts the slip transfer across the grains as well as the spreading of deformation to new regions, which causes the suppression of yield drop in the boron containing alloy.

Defect detection capabilities of independent component analysis for Barker coded thermal wave imaging

Active pulse compression favourable infrared imaging techniques are promising evaluation techniques among other thermal non-destructive testing and evaluation modalities for identification of subsurface defects in the test samples. This is due to their merits such as high defect detection sensitivity and resolution by using relatively low peak power heat sources and in a moderate experimentation time in comparison with widely used pulse and modulated conventional thermal wave imaging modalities. Various data processing methods have been developed to extract the thermal features of defects from the captured thermographic data. The cross-correlation based pulse compression method is recommended for Barker coded thermal wave imaging technique as it enhances the concentration of applied thermal energy into mainlobe and distributes the significantly less energy into the sidelobes of cross correlation data. In this paper, the stated property of Barker coded thermal wave imaging along with the independent component analysis approach has been utilised. The study in this paper is focused on the application of independent component analysis approach on captured thermal response data, entire cross correlation data and only the mainlobe of CC data. The results obtained clearly indicate that the application of independent component analysis on cross correlation data has improved the detectability, visibility, and contrast (interms of signal-to-noise values) of the defects. Further, the results obtained with the different methods have been compared by taking Signal to noise ratio as the figure of merit.

Thermal Imaging Techniques in Agricultural Applications

Thermal imaging innovation has transformed into an important technique in all fields as a result of its non-ruinous, non-contact method to choose thermal properties and highlights of any object/zone of interest. It is a procedure of improving the permeability of objects in a dark environment by detecting the objects infrared radiation and shaping an image based on that obtained data. This method will be useful in all fields where temperature difference helps in analyzing the area/object. The potential use of this technique in the agricultural field includes irrigation scheduling, soil properties mapping, plant disease detection, crop yield estimation, evaluating the maturity of the crop, etc. This paper briefly reviews some of the works on thermal imaging for agricultural applications.

Experimental investigation on thermal characteristics of hot surface by synthetic jet impingement

This paper analyses the thermal behavior of impinging synthetic jet by employing various orifice shapes such as circular, square, and rectangular for a given hydraulic diameter. The effect of thickness of orifice plate on heat transfer behaviour is studied in this investigation. An electromagnetic actuator is used as an oscillating diaphragm for the generation of synthetic jet. A stainless steel (SS) foil (AISI-304) with 0.05 mm thickness is used as the test specimen. It is heated by DC power source (APLAB, L-3260). The surface temperature of the test specimen is measured by using a thermal imaging technique during synthetic jet impingement. Tests are carried out for wide range of Reynolds number (Re = 1183–5448), different values of jet-to-plate distance (z/d = 0–30), various orifice plate thicknesses (t = 1.6–5 mm), for a given hydraulic diameter of the orifice. The peak value of the heat transfer coefficient is found to be 16.1 times more than the heat transfer coefficient for natural convection. A correlation is proposed for Nusselt number.

Predicting the Presence of Natural Gas Hydrates Potential in the Maritime Regions of Pakistan by Correlating Experimental Study and Pre Available Seismic Surveys

ABSTRACT This paper provides a feasibility model of using satellite imaging technology to indicate hydrate presence and evaluate gas hydrate saturation trapped in the premises of Pakistan. The study compiles an effort to justify the potential of gas hydrates in Pakistan and their effective extraction. Satellite images of the Arabian Sea are correlated with previously available Bottom Simulating Reflectors (BSRs) to predict the presence of hydrates and potential energy trapped in them. Additionally, the innovative and optimistic hydrate-detection technique of thermal imaging is merged to add the methodological value. The thermal gradient helps to understand the thermodynamic behavior of subsea natural gas hydrates in particular area. Unfortunately, gas production from hydrates is still commercially unaccepted because very limited ventures have been launched in this domain. But no doubt, all those limited projects have shown very promising results. In case of Pakistan, the prolific expedition to hunt for hydrates was made in 1998 with Pak-Germany collaboration. The expedition revealed that the gas hydrates buried under Makran Coast in the Arabian Sea are around 29% saturated with methane gas; 7.5% free gas also exists with hydrates. Further, the BSRs in the Arabian Sea are traced at the depth of 500 to 800 m below the seafloor. On the other hand, demand for natural gas rises by 60 to 75 MMCFD every year in Pakistan; therefore, the development of natural gas hydrates can be a prudent solution to meet the future energy demand of whole country. The novelty of this paper is the incorporation of satellite imaging technology to prove natural gas hydrate potential in the maritime vicinity of Pakistan.

In Situ Observation of Adiabatic Shear Band Formation in Aluminum Alloys

We used high-speed X-ray phase contrast imaging and infrared thermal imaging techniques to study the formation processes of adiabatic shear bands in aluminum 7075-T6 and 6061-T6 alloys. A modified compression Kolsky bar setup was used to apply the dynamic loading. A flat hat-shaped specimen design was adopted for generating the shear bands at the designated locations. Experimental results show that 7075-T6 exhibits less ductility and a narrower shear band than 6061-T6. Maximum temperatures of 720 K and 770 K were locally determined within the shear band zones for 7075-T6 and 6061-T6 respectively. This local high temperature zone and the resulting thermal instability were found to relate to the shear band formation in these aluminum alloys.