Infrared Thermography Technique Research Articles

Pulse-heating infrared thermography inspection of bonding defects on carbon fiber reinforced polymer composites.

Non-destructive analysis of fiber reinforced polymer (FRP) composites is important for confirming the long-term safety and durability of concrete structures. In this study, a pulse-heating infrared thermography technique was used to detect and characterize bonding defects of externally bonded carbon fiber reinforced polymers (CFRP) on concrete surface structures. The CFRP composite contains various bonding defects of three different sizes located at five different depths. Sequential thermal images were obtained to describe the temperature contrast and shapes of the bonding defects. Through analysis of the maximum temperature response, we investigated the effects of defect size and depth on the defect temperature response. The relationship between the defect depth and maximum temperature response was used to quantitatively estimate the defect depth. In addition, finite element simulations were performed on the CFRP composites with bonding defects to investigate the temperature response of various defects, which showed good agreement with the experimental results. This confirms the effectiveness of the infrared thermography method to detect and characterize bonding defects of FRP composites bonded on concrete structures.

Characterization of indentation damage resistance and thermal diffusivity of needle‐punched Musa sapientum cellulosic fiber/unsaturated polyester composite laminates using IR thermography

AbstractThis work focuses on the evolution of a novel technique, employed to fabricate a plant fiber‐reinforced composites without any hazardous chemical treatment for alternative carcinogenic synthetic fiber‐reinforced polymer composites. The fibers were extracted from the agro‐waste pseudostem of banana plant. Anatomical studies were carried out on fibers to ratify their reinforcement potentiality. The cellulosic fibers were needle‐punched and commingled with unsaturated polyester for fabricating nonwoven needle‐punched banana fiber composites (NPBFC). Quasistatic indentation tests were conducted for inducing damage on NPBFC, random banana fiber composites (RBFC), and random glass fiber composites (RGFC). Mechanical parameters, such as, peak force, linear stiffness, dent depth, and absorbed energy were used for evaluating indentation damage resistance. However, the optimal properties were achieved at 40 wt% fiber content. The load‐bearing capacity of NPBFC having 2420 N is supercilious than RBFC and comparable with RGFC. Moreover, the extent of damage area and thermal diffusivity for optimized NPBFC are 178 mm2 and 0.11 mm2/s, respectively, computed using infrared thermography technique. This result reveals that the optimized NPBFC has better indentation damage resistance and thermal insulating property than RBFC and RGFC. This study concludes that the synthesized NPBFC can be used for the application of industrial safety helmet and automotive parts.

Pitting Hole Evaluation by Active Infrared Thermography in Stainless Steel 304

Nowadays, infrared thermography technique is widely use in an engineering study to inspect various types of problem. In this experiment, active infrared thermography method is applied to overcome the constraint locating pitted inside pipe. The main purpose of this experiment is to examine the location of pitted occur in the stainless steel 304 and at the same time to identify the transient effect on the pipe against the duration of time radiation exposed. This experiment uses two unit of spotlight as sources of heat to emit radiation energy to the surface of the pipe. A FLIR T640 thermography camera was used to record the thermal contrast of the pipe in real time using FLIR Tools+ software installs in the laptop. This experiment was tested at normal surrounding temperature. All of the temperature data is then interpreted into contour graph by using Microsoft Excel to see the defect area based on temperature distribution. Based on the result, the most significant temperature drops within highest gradient observed at cooling phase are within 7s, 2s and 1s interval for 10s, 20s and 30s of radiation exposure respectively. The time of the pitted to appear is related to the exposure time of the radiation. The finding of this experiment shows that short duration time of radiation exposure will give the longer time interval of significant gradient to appear. Therefore, this experiment proves that infrared thermography is one of the non- destructive testing methods that can be used in inspecting the pipeline.

Role of coatings in the formation of defects in advanced high strength steel welds

Infrared thermography technique (IRT) uses longer wavelength electromagnetic radiations emitted by a hot body to compute its temperature. The radiant energy absorbed by the thermographic system is transformed into electronic signals by sensors and into visible signals known as a thermogram. Besides highly sophisticated military applications, the non-contact infrared thermography is extensively used in medical, electrical, mechanical and many other domains. This paper exploits the infrared thermography technique for precise measurement of temperature across the weld interfaces obtained with two different welding processes, viz. nut projection welding and cold metal transfer gas metal arc welding (CMT-GMAW). The recorded temperature was processed to obtain peak temperature, heat generated, heat affected zones, and to understand the effect of coating on the heat generation and defect formation. IRT results reveal that the weld quality and strength is significantly influenced by the weld pool temperature and region of heat generation in CMT and nut projection welding, respectively.

Non-Destructive Investigation of Dispersion, Bonding, and Thermal Properties of Emerging Polymer Nanocomposites Using Close-Up Lens Assisted Infrared Thermography

AbstractPolymer nanocomposites possess unique sets of properties that make them suitable for different applications, including structural and flame-retardant material, electromagnetic wave reflector, sensors, thin film transistor, flexible display, and many more. The properties of these nanocomposite are dependent on nanofiller dispersion and bonding with polymer matrix (i.e. particle-matrix interaction). Thermography is a non-destructive method that may be used to gain insight into dispersion and particle-matrix interaction. Infrared (IR) radiation emitted from these nanomaterial polymer composite depends on the emissivity of the individual components. In addition, during flash heating and cooling, different thermal conductivity of components in the nanocomposite can influence pixel intensity differently in the IR image or video being captured. We have used an economical mid wavelength IR camera Fluke RSE600 equipped with a close-up macro lens and algorithm based on MATLAB image processing toolbox to analyse dispersion, voids and thermal diffusivity of patented graphene polymer nanocomposite materials (G-PMC) in micro-scale. These G-PMCs can act as a standard material to determine the potential of our IR thermography technique due to their homogeneity and lack of impurity due to unique fabrication process. Thermal diffusivity and dispersion of nanoparticles in our G-PMCs was estimated after irradiation with a xenon flash lamp by spatially mapping transient IR radiations from different G-PMCs using the Fluke RSE600 thermal imager. Results from thermography experiments were compared with scanning electron microscope (SEM) and Raman spectroscopy results. Micro-scale thermography was able to detect millimetre scale thermal diffusivity variation in the injection molded G-PMC samples and relate it to change in dispersion of nanofillers, unlike SEM and Raman, where micro-scale measurements could not determine the reason behind millimetre scale property variation. We believe this low cost, fast, micro-scale, non-destructive technique will provide valuable insight into functional polymer nanocomposite fabrication and corresponding electrical and thermal properties.

Cryopreservation of primary cultures of mammalian somatic cells in 96-well plates benefits from control of ice nucleation

Cryopreservation of mammalian cells has to date typically been conducted in cryovials, but there are applications where cryopreservation of primary cells in multiwell plates would be advantageous. However excessive supercooling in the small volumes of liquid in each well of the multiwell plates is inevitable without intervention and tends to result in high and variable cell mortality. Here, we describe a technique for cryopreservation of adhered primary bovine granulosa cells in 96-well plates by controlled rate freezing using controlled ice nucleation. Inducing ice nucleation at warm supercooled temperatures (less than 5 °C below the melting point) during cryopreservation using a manual seeding technique significantly improved post-thaw recovery from 29.6% (SD = 8.3%) where nucleation was left uncontrolled to 57.7% (9.3%) when averaged over 8 replicate cultures (p < 0.001). Detachment of thawed cells was qualitatively observed to be more prevalent in wells which did not have ice nucleation control which suggests cryopreserved cell monolayer detachment may be a consequence of deep supercooling. Using an infra-red thermography technique we showed that many aliquots of cryoprotectant solution in 96-well plates can supercool to temperatures below −20 °C when nucleation is not controlled, and also that the freezing temperatures observed are highly variable despite stringent attempts to remove contaminants acting as nucleation sites. We conclude that successful cryopreservation of cells in 96-well plates, or any small volume format, requires control of ice nucleation.

Correlation between Tensile Deformation Behavior and Microstructural Morphology of Nuclear Grade Austenitic Stainless Steel Weld Joints using Infrared Thermography Technique

Tensile deformation behavior of nuclear grade Austenitic Stainless Steel (SS) and its weld joints fabricated by Gas Tungsten Arc Welding (GTAW) and Activated flux Gas Tungsten Arc Welding (AGTAW) processes were studied and correlated with relevant microstructural morphologies using Infrared Thermography (IRT) technique. The microstructure of base metal showed a complete austenite phase. GTAW Fusion Zone (FZ) exhibited both primary ferrite and primary austenite mode of solidification. Meantime, AGTAW FZ exhibited only primary austenite mode of solidification A strain rate of 4.4x10-4 s-1 was used during the tensile test of the base metal and weld samples. The failure locations of the base metal, GTAW and AGTAW samples were noticed at the center of the gauge portion, the base metal side away from Fusion Line (FL) and Heat Affected Zone (HAZ) respectively. Temperature variations of the base metal and weld zones were recorded in the form of thermograms using the IR camera at the different stages of the tensile deformation. During deformation study, peak temperatures of 39.2 oC, 38.8 oC and 34 oC were observed at the base metal, GTAW and AGTAW samples respectively. The lesser peak temperature of the AGTAW sample compared to the base metal and GTAW samples indicated that the AGTAW sample undergone lesser deformation. Moreover, tensile deformation behaviors of the base metal and weld samples were correlated with their microstructural morphologies using corresponding temperature curves.

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.

Detection of Delamination with Various Width-to-depth Ratios in Concrete Bridge Deck Using Passive IRT: Limits and Applicability.

In bridge structures, concrete decks have a higher risk of damage than other components owing to the direct impact of traffic. This study aims to develop a comprehensive system for bridge inspection using passive infrared thermography (IRT). Experiments were conducted on a concrete specimen (assumed as the surface of the bridge deck) embedded artificial delaminations with different width-to-depth ratios (WTDRs). Both professional handheld IR camera (H-IRC) and a UAV mounted with an IR camera (UAV-IRC) were employed simultaneously to capture the surface temperature of the structure. The present work indicates that the passive IRT technique with an H-IRC can be used to detect delaminations located at depths of 4 cm or less from the structure surface if the WTDRs are not lesser than 1.9 for daytime and 2.5 for nighttime when testing on a sunny day. In addition, the larger the WTDR, the higher the temperature difference can be produced, thus delaminations could be observed more clearly. Furthermore, our study suggests that the concrete bridge deck inspection using passive IRT can produce appropriate results if the inspection is performed from 10:00 to 15:00 or from 19:30 to approximately 2:00 on a sunny day. Good agreement between the results obtained from tests using H-IRC and UAV-IRC was observed, which validates the application of UAV-IRC in real structure inspection.

Hand-Arm Vibration Assessment and Changes in the Thermal Map of the Skin in Tennis Athletes during the Service.

During recent years the number of tennis athletes has increased significantly. When playing tennis, the human body is exposed to many situations which can lead to human injuries, such as the so-called tennis elbow (lateral epicondylitis). In this work a biomechanical analysis of tennis athletes, particularly during the service, was performed, considering three different types of over-grip and the presence of one anti-vibrator device. One part of the study evaluates the exposure to hand-arm vibration of the athlete, based on the European Directive 2002/44/EC concerning the minimum health and safety requirements, regarding the exposure of workers to risks from physical agents. The second part of the study considers an infrared thermography analysis in order to identify signs of risk of injury, particularly tennis elbow, one of the most common injuries in this sport. The results show that the presence of the anti-vibrator influences the vibration values greatly in the case of athletes with more experience and also for athletes with less performance. The presence of the Cork and/or Tourna on the racket grip does not have any significant effect on the hand-arm vibration (HAV), similarly in the case of athletes with the best performance and athletes with less technique. The results indicated that the infrared thermography technique may be used to identify the risk of injuries in tennis players.

Defect Detection using Active Contour Method

This paper reports on the non-destructive (NDT) method to inspect industrial equipment's quality and anomalies by using infrared thermography techniques to identify defects in an artifact such as water, oil or other fluid materials and any disruption or sub-surface fractures by using different types of procedure to recognize defects. Here we discuss various types of thermography techniques, quadratic frequency modulated thermal wave post-processing and region-based active contour image segmentation technique.

Debonding defects detection of FMLs based on long pulsed infrared thermography technique

Fiber metal laminates (FMLs) are the popular materials in the fields of aerospace, automobile and rail transportation. In the process of preparation and service, the defects of matrix, fiber fracture and fiber matrix debonding are easily produced, which poses a threat to the safety of FMLs’ quality, performance and the operational safety of the aircraft and other equipment using the material. Aiming at developing a method for defects detection in FMLs by long pulsed infrared thermography, test was applied to FMLs with debonding defects. Halogen lamps were used as active heat source into the sample, and the infrared image sequence was collected with an infrared camera A325sc. Thermal wave signal reconstruction, pulsed phase thermography and principal component analysis methods were used to process the original image sequences. Experimental results show that the signal-to-noise of processed images by these three methods are all increased, while that of principal component analysis method increases significantly under the same given test parameters, and it can be used to detect the defects in FMLs.

Three approaches to evaluate of the heat dissipated during fatigue crack propagation experiments

This work is devoted to the comparative analysis of three techniques for measurement of energy dissipation in metals under fatigue crack propagation: original contact heat flux sensor, post-processing of the infrared thermography data and lock-in thermography. The contact heat flux sensor allows real-time recording of the heat source value. Non-contact temperature measurements by infrared thermography techniques allows one to calculate the heat source field on the specimen surface using the solution of heat conductivity equation. Lock-in thermography is a well-established technique for measuring of the dissipated energy under cyclic loading based on the analysis of the second harmonic amplitude of the thermal signal. This paper deals with the V-notched flat specimens made of stainless steel AISE 304 subjected to cyclic loading. It was shown that the dissipated energy values estimated by different techniques have a good qualitative agreement. Contact and non-contact measurements can be used for investigation on energy dissipation either in combination or separately. The measured values allows one to propose a relation between the fatigue crack growth rate and dissipated heat near the crack tip.

Infrared emissivity characterization of carbon nanotubes dispersed poly(ethylene terephthalate) fibers

The infrared (IR) emissivity of a set of polymeric fibers composed of randomly oriented carbon nanotubes dispersed into a poly(ethylene terephthalate) matrix host was investigated. Samples containing different amounts of carbon nanotubes in the range between 1 and 10 wt% were analyzed. The effects of the included carbon nanotubes on electrical and morphological properties were studied by means of electric conductance, scanning electron micrography and white light interferometry investigations, respectively. The emissivity was characterized in the 3.5–5.1 μm spectral range by using the infrared thermography technique under heating regime. To analyze the obtained results, a theoretical model based on the Maxwell Garnett theory has been proposed. A percolation effect in the electrical conductance and a gradual increase of the emissivity has been observed, respectively with increasing carbon nanotubes content. In particular, morphological investigations showed the emerging surface roughness when carbon nanotubes are added to the polymeric matrix which may further contribute to the increase of the emissivity value. On the basis of the obtained results, it can be concluded that the investigated composite fibers have the potential to develop new materials enabling both high IR emission and large electrical conduction.

Numerical model and experimental validation for online monitoring of cold metal transfer joining of aluminium to galvanized steel

The effect of zinc coating on the weld brazability of dissimilar Al–steel joint made by the cold metal transfer (CMT) process using the passive infrared (IR) thermography sensing technique was investigated using a numerical model. The numerical model was developed to understand the heat transfer phenomena during the CMT process. In the developed model, a thin thermally resistive layer (TTRL) was introduced at the interface of the two joining metals in order to manipulate the absence of zinc deposition on the steel sheet. The model could clearly identify the lack of weld deposition. The results were compared with experimental observations. Two cases are considered in this paper. The first study identifies the sensitivity of the IR thermography technique and the second one reveals the resolution in defect detection. The developed 3D model can be used as a tool to identify the defects caused during welding and can provide insights into the online monitoring of cold metal transfer joining process.

Measurements of detailed heat transfer characteristics on a high-pressure turbine vane endwall with coolant injection

Detailed heat transfer characteristics over high-pressure turbine endwall surfaces with coolant injection were experimentally studied in this paper. Heat transfer experiments were conducted in a properly scaled-up endwall model for an engine-representative oncoming flow profile with a high freestream turbulence intensity of 9.8% at an exit Reynolds number of 0.76 × 106 and an exit Mach number of 0.37. Cooling for the endwall was accomplished by upstream purge flow from a slot and film coolant from three axial rows of discrete film-cooling holes within the vane passage on the endwall. An engine-like coolant-to-mainstream density ratio of 1.70 was achieved by using cooled foreign gas. High-resolution measurements of the endwall heat transfer coefficients were conducted by using a steady, high-resolution infrared thermography technique based on the superposition principle for purge flow blowing ratios of 0.1–0.45 and film coolant injection blowing ratios of 1.4–3.6, respectively. In particular, the effects of the cooling geometries without blowing were considered to simulate hole blockage due to deposition. Results showed that local heat transfer coefficients near the film-cooling hole exits were significantly enhanced due to strong interactions between film coolant injection and mainstream flows, but those downstream of the slot were inhibited, somewhat, by purge flow, resulting from the suppression of purge flow on horseshoe vortex at the vane leading edge. The inhibiting effects of purge flow on the endwall heat transfer are more prominent when purge flow and the film coolant are injected simultaneously. For the discrete holes, higher coolant injection rates generate increased heat transfer levels. Because ingestion and re-injection of mainstream flows through the slot or the film-cooling holes without blowing, the presence of both cooling geometries causes heat transfer enhancement, and the enhancement by the film-cooling holes is higher than that by the slot. The detailed heat transfer measurements in this paper can provide useful thermal boundaries for an optimized endwall film-cooling design that will be investigated in a follow-up study.

The heat conduction model and leakage characterization of the sealing interface

In this paper, a new leakage characterization method for the sealing interface is proposed to detect the leakage location and measure the leakage rate based on the temperature field and the temperature gradient field. First, the formulas of the leakage rate are theoretically established based on the two-dimensional and the three-dimensional heat conduction model, respectively. Second, the finite element models of the general leakage area and the concentrated leakage area are built, in which the leakage rate calculated by means of heat conduction model fits the simulated leakage rate well. Finally, the interface leakage experiment is conducted using a sealed box with a rubber-aluminum alloy sealing interface, which validates the effectiveness of this new characterization principle for determining the leakage rate and the leakage location. The results indicate that the feasibility of the leakage characterization method for the sealing interface based on the temperature field and the temperature gradient field obtained from the infrared thermography technique.

Differences in methane production, yield and intensity and its effects on metabolism of dairy heifers

The effects of divergent phenotypic classification in crossbreed Holstein × Gyr dairy heifers for methane emissions in relation to performance, digestibility, energy and nitrogen partition, blood metabolites and temperature of body surface were evaluated. Thirty-five heifers were classified as high and low emission for CH4 production (g/day), yield (g/kg dry matter intake) and intensity (g/kg average daily gain). Digestibility was evaluated by total collection of feces and urine. Gas exchanges were obtained in open-circuit respiratory chambers. A completely randomized design was used and divergent groups were compared by Fisher's test. No differences were found in intake traits between groups of CH4 production and intensity. The low yield group had higher intake. For digestibility and temperature at different body sites were no differences between variables. High production group had higher energy losses as methane and heat production. Low intensity group had higher digestible energy, energy balance and ratio between metabolizable and digestible energy. Urinary nitrogen was 14.3% lower for low production group. There was a difference between methane yield divergent groups for nitrogen intake, digestible and retained. Energy and nitrogen partitioning traits are correlated to the animals divergent for methane production and yield. The low production group presented lower blood insulin concentration. It was not possible to identify divergent animals for CH4 emission using the infrared thermography technique.

Investigation of heating characteristics of domestic gas cookers via a methodology of infrared thermography

The heat flux measurement method based on the infrared thermography technique is first applied to study the heating characteristics of domestic gas cookers. Unlike the traditional means of heat flux measurement, the infrared thermography technique is non-intrusive and can help measure the heating flux distribution within two-dimensional space, which is very interesting to design and optimization aspects. The evolution of the temperature field of a heated pan is recorded to calculate the heating flux using the two-dimensional unsteady heat balance equations and inverse method. The heat radiation and natural convection can either be estimated or neglected in the calculation of the heating flux. Resistance foils with known electro-heating power are applied as the heating source to validate the feasibility and accuracy of this method. The uncertainty analyses show a maximum error of 15% in the local distribution and the error of 6% for the power. The heating flux distributions are measured for six gas cookers with different power modes. The results clearly reflect the mechanisms of the heat flux distributions linking to the designed structures of the burners. A dimensionless unevenness factor derived from the uniformity of heating flux distribution is defined for a better understanding of the locally overheating problems.

The Use of Infrared Thermography (IRT) as Stress Indicator in Horses Trained for Endurance: A Pilot Study.

Simple SummaryThe aim of this study was to evaluate the possibility of using infrared thermography technique (IRT) to detect physiological stress in endurance horses. Infrared thermography technique, serum cortisol, blood count, and hearth rate (HR) were used as stress-indicators before and after training of different intensities (low, moderate, and high). As expected, all the studied parameters increased after the training, but HR remained below 64 bpm as requested by Fédération Equestre Internationale (FEI) endurance rules. Heart rate and white blood cells were the only parameters which significantly rose with the training intensity. Max temperature in the left and right eye (ET) was positively and significantly correlated with HR. These preliminary findings suggest that the tested horses were sufficiently fit and IRT may be a useful non-invasive tool to assess physiological stress in endurance horses.The aim of this pilot study was to document the effects of endurance training at different intensities on heart rate (HR), blood count, serum cortisol, and maximal temperatures of different body locations, namely eye, crown, pastern pasterns, gluteus and longissimus dorsi muscle (mm), measured by infrared thermography technique (IRT) in horses trained for endurance. Possible associations among the studied parameters were also investigated. Our hypothesis was that temperature, measured by IRT after endurance training of different intensities would vary depending on the intensity and would be positively correlated with HR and serum cortisol. Eight horses were tested before and after training of different intensities (low, moderate, and high). The results partially supported our hypothesis; all the studied parameters increased after training (p < 0.05), eye temperature (ET) correlated positively with HR (p < 0.01), and crown temperature (CT) correlated positively with cortisol (p < 0.01). However, only HR and white blood cells increased with the intensity of the exercise (p = 0.0016 and p = 0.0142, respectively). Our findings suggest the evaluation of ET and CT may become a useful non-invasive tool to detect physiological stress during training and to evaluate how the horses cope with the training. Infrared thermography technique may also become a useful tool for the early identification of horses that are not fit to compete or to continue the competition. However, further studies should be conducted on a larger number of horses and during competitions to ascertain our preliminary findings.