Thermographic Observations Research Articles

Effects of Transversal Temperature Distribution and Phase State on Strip Profile During Hot Rolling Process

Transversal temperature distribution and phase transformation of the strip steel in hot rolling process are analyzed by thermographic observations and thermal simulation tests. The effects of transversal temperature distribution and phase state on strip profile are investigated by finite element (FE) simulations, in which the material model of the strip steel is generated from the thermal simulation tests and a constitutive model. FE calculation shows that the decreased temperature at the edge causes smaller strip crown with the dual‐phase state, while it leads to edge bulges in strip profile under single‐phase state. With the convex temperature distribution, large strip crown is witnessed under dual‐phase state; small crowns or even edge bulges appear under the single‐phase state. For the concave temperature distribution, opposite conclusions are drawn compared with the convex temperature distribution. Measures to prevent edge bulges and control the strip crown are proposed and applied to industrial production. Reheating the edge area and assigning large target crown to the former stand of the finishing mill can avoid the edge bulges. Strip crown of the steel is more significantly affected by the bending force under dual‐phase state than that under single‐phase state.

Thermographic Observation and Hydrodynamic Patterns of Inclined Ethanol Droplet Train Impingement on a Non-Uniformly Heated Glass Surface

Droplet train impingement is a fundamental approach to mimic the complicated interactions between the fluid and the substrate in advanced thermal engineering applications in industry. Differently from previous studies, the main original contribution of this study is to perform an inclined droplet train impingement on a non-uniformly heated surface. Ethanol was used as the liquid for droplet train impingement applications, while glass substrate was selected as the target surface. The inclined flow angle was 63 degrees. Both optical and thermographic observations were performed on the target surface by focusing on the droplet impact area. Three experimental sets were created with the Weber numbers 667.57, 841.90, and 998.01. A surface temperature range was selected between 85.00 °C and 200.00 °C, which was above the boiling point of the ethanol. The maximum spreading length was measured at 0.97 mm at the surface temperature of 82.00 °C for the experiment with the Weber number of 998.01, whilst the minimum spreading length was found at 0.18 mm at the highest surface temperature for the experiment with the Weber number of 667.57. A uniform splashing direction was observed above 170.00 °C for all experiments, which meant that the sign of the transition regime appeared.

The Ancient Varieties of Mountain Maize: The Inheritance of the Pointed Character and Its Effect on the Natural Drying Process

The introduction of mechanized agricultural practices after the Second World War and the use of productive hybrids led to a gradual disappearance of local maize varieties. However, 13 landraces are still cultivated in North-Western Italy, in the Lombardy region; those that are cultivated in mountainous areas (roughly up to 1200 m in altitude) are often characterized by the pointed shape of their seeds (i.e., “Nero Spinoso”, “Rostrato Rosso di Rovetta”, “Spinato di Gandino” and “Scagliolo di Carenno”) and the presence of pigments (i.e., “Nero Spinoso”, “Rostrato Rosso di Rovetta”). The pointed shape of the seeds is an ancient characteristic of maize-ancestors, which negatively affects the yield by not allowing optimal “filling” of the ear. This study reports work on four different Italian varieties of pointed maize in order to assess the genetic bases of the “pointed character” and to try to explain the reasons for this adaptation to the mountain environment. The data obtained by genetic analysis, seed air-drying modeling and thermographic camera observations demonstrated that the “pointed trait” is controlled by the same genes across the different varieties studied and suggested that this peculiar shape has been selected in mountainous areas because it promotes faster drying of the seed, with the presence of pigments implementing this effect.

Geometric correction for thermographic images of asteroid 162173 Ryugu by TIR (thermal infrared imager) onboard Hayabusa2

The thermal infrared imager (TIR) onboard the Hayabusa2 spacecraft performed thermographic observations of the asteroid 162173 Ryugu (1999 JU_3) from June 2018 to November 2019. Our previous reports revealed that the surface of Ryugu was globally filled with porous materials and had high surface roughness. These results were derived from making the observed temperature maps of TIR using a projection method onto the shape model of Ryugu as geometric corrections. The pointing directions of TIR were calculated using an interpolation of data from the SPICE kernels (NASA/NAIF) during the periods when the optical navigation camera (ONC) and the light detection and ranging (LIDAR) observations were performed. However, the mapping accuracy of the observed TIR images was degraded when the ONC and LIDAR were not performed with TIR. Also, the orbital and attitudinal fluctuations of Hayabusa2 increased the error of the temperature maps. In this paper, to solve the temperature image mapping problems, we improved the correction method by fitting all of the observed TIR images with the surface coordinate addressed on the high-definition shape model of Ryugu (SFM 800k v20180804). This correction adjusted the pointing direction of TIR by rotating the TIR frame relative to the Hayabusa2 frame using a least squares fit. As a result, the temperature maps spatially spreading areas were converged within high-resolved 0.5^circ by 0.5^circ maps. The estimated thermal inertia, for instance, was approximately 300sim350 Jm^{-2}s^{-0.5}K^{-1} at the hot area of the Ejima Saxum. This estimation was succeeded in case that the surface topographic features were larger than the pixel scale of TIR. However, the thermal inertia estimation of smooth terrains, such as the Urashima crater, was difficult because of surface roughness effects, where roughness was probably much smaller than the pixel scale of TIR.

Characterization of 2017A Anodized Aluminum Alloy by Infrared Thermographic Techniques and SEM Observations During Tensile Testing

The aim of this research is to determine the effect of an electrochemical treatment (anodizing) on the mechanical behavior of 2017A aluminum alloys to improve corrosion. Two surface treatments state, namely, anodized and unanodized were considered. Meanwhile, the tensile and fracture tests for laboratory specimens to failure, yield strength, tensile strength and fracture surface of anodic films at different conditions were investigated. The damage initiation and progression during tensile testing was tracked through the use of complementary non-destructive evaluation by means of technique called infrared thermography. The results showed that the fracture life of anodized specimens was reduced a lot compared to aluminum alloy, which can be attributed to the surface crack sites initiated at the oxide layer. The fracture surface analyses also revealed that the number of crack initiation sites enlarged on the anodizing specimens.

Heat distribution in material during fused deposition modelling

PurposeThe paper aims to investigate the problem of heat distribution in FDM 3D printing. The temperature distribution of the material is important because of the occurrence of shrinkage and crystallization phenomena that affect the dimensional accuracy and strength of the material.Design/methodology/approachThe study uses a thermoplastic material (polylactide) and a test stand equipped with a 3D printer adapted to perform thermographic observations. The main source of heat in the study was a molten laminate material and a hot-end head.FindingsWhen the material is molten at the temperature of 190°C, the temperature of a previous layer increases above the glass transition point (Tg = 64.8°C) and reaches to about 80°C. In addition, at the boundary of the layers, there occurs a permanent bonding of the consecutive layers because of their partial melting. The paper also reports the results of porosity of PLA samples printed at the temperature ranging between 205 and 255°C. The degree of porosity depends on the temperature of the extruded material.Practical implicationsThe results may be helpful for designers of various printed parts and construction engineers of printing heads and 3D printer chambers.Originality/valueThermograms of material layers with a height of 0.3 mm are obtained using a thermal imaging camera with a lens for macro magnification (43 pixels/mm).

Fatigue damage in GFRP

PurposeComposite materials are increasingly used in the structural and mechanical fields, thanks to their high strength‐to‐weight ratios and the possibility of tailoring them to meet specific requirements. This study is focused on the damage to a glass fiber reinforced composite under different loading conditions. The aim is to find, by coupling mechanical tests with thermal analyses, a damage parameter, able to define the damage initiation in the studied material.Design/methodology/approachThe object of this work is a glass‐fiber reinforced plastic (GFRP) laminate. To study the damage of this material under different loading conditions, static, dynamic and fatigue tests were carried out. During these tests, the surface temperature of the specimens was monitored by means of an IR‐camera. In the dynamic tests, a D‐mode (dissipation mode) analysis was also performed allowing the dissipated energy to be determined.FindingsIn the literature, thermography is an experimental technique which has always been applied to the study of homogeneous materials. Results obtained from the proposed experimental tests on this GFRP composite show how this practice can be applied also to this kinds of materials, to identify their damage initiation. From these observations, the results can be used to definite a stress corresponding to the damage initiation, which can be related to the fatigue behavior, and useful in design stage with these materials.Originality/valueThis paper provides for a useful tool to understand and predict fatigue behavior of a GFRP composite, from thermographic observations. Applications of thermography to the study of composite materials is an innovative research field, and the presented results seems satisfactory and promising for further experimental investigations.

Experimental Results in DBD Plasma Actuators for Air Flow Control

In this paper, several planar dielectric barrier discharge fluid-dynamics actuators have been experimentally investigated. The actuator is made by an electrode pair separated by a dielectric. It is characterized by a planar geometry, and it induces a volume force on the gas above it which modifies the fluid dynamics within the aerodynamic boundary layer. Several actuator geometries, dielectric materials, ac supply voltages, and supply frequencies have been used. Rotational and vibrational temperatures have been determined by means of spectroscopic measurements. Vibrational temperatures have been found to be one order of magnitude higher than the rotational ones, confirming the nonthermal behavior of the discharge. The translational temperature has been evaluated by thermographic observations of the dielectric surface heated by the plasma. The values of the translational temperature are in a very good agreement with those of the rotational temperature. Electric measurements have been carried out to determine the average power delivered to the discharge and to estimate the average electron number density. In the plasma induced by the discharge above the actuator, an average electron density of has been determined. The gas speed of the induced wall jet has been measured with a Pitot tube. The average power delivered to the electrodes increases with a power law of the applied voltage and linearly with the supply frequency. The induced speed increases with the increase of the average power until a plateau is reached. The efficiencies of the different actuators have been compared by evaluating the relation between average power and induced gas speed.

In situ thermographic observations on the compression behavior of a relaxed Zr-based bulk-metallic glass

Using an infrared camera, the plastic deformation of a relaxed Zr52.5Cu17.9Ni14.6Al10.0Ti5.0 bulk-metallic glass in a moderately high strain rate compression was observed in situ. The specimen exhibits an inhomogeneous deformation, which is manifested by serrated plastic flow, shear banding, and obvious work softening. Shear-banding operations were observed throughout the plastic deformation. Shear-banding operations started before the nominal yielding; shear bands could not block each other, but their interaction seems to accelerate the plastic deformation. A significant increase in the specimen’s temperature was observed due to shear banding.

Assessment of the performance of organic and mineral-based insulation products used in exterior walls and attics in dwellings

The assessment of the performance of organic and mineral-based insulation products used in exterior walls and attics in traditional Danish housing estate was evaluated. The assessment covered the ability of the materials to be handled on site as well as measurements of the performance of the materials once installed and exposed to normal use of the dwellings and Danish weather conditions over a 2-year period. Evaluations were based on, on-site observations, thermographic observations and measurements of temperature and moisture conditions within the different materials used. Eight different products were used for thermal insulation including six organic and two mineral fibre materials. Loose-fill material and predefined fixed-shape products were used. The eight different products were installed in 16 dwellings, two neighbouring dwellings were insulated with each product. Exterior walls were constructed without PE vapour barriers while ceilings were constructed with PE vapour barriers.

Infrared thermographic observations of rock failure : Minh Phong Luong, in: Comprehensive rock engineering. Vol. 4, ed J.A. Hudson, (Pergamon), 1993, pp 715–730

Infrared thermographic observations of rock failure : Minh Phong Luong, in: Comprehensive rock engineering. Vol. 4, ed J.A. Hudson, (Pergamon), 1993, pp 715–730

Thermographic observations in unilateral carpal tunnel syndrome: Report of 61 cases

This study was undertaken to assess the sensitivity and specificity of thermographic diagnosis of unilateral carpal tunnel syndrome in a patient population large enough to permit meaningful statistical analysis. Sixty-one persons with clinical diagnoses of unilateral carpal tunnel syndrome confirmed by electrodiagnostic examination and 40 symptom-free volunteers underwent standard thermographic examinations. The thermographic images were then randomly sorted and interpreted by an experienced physician thermographer. Fifty-seven of the 61 patients with carpal tunnel syndrome were found to have thermographic abnormalities, while only one of the control group was found to have such an abnormality. Individual area sensitivity was highest in the dorsal area, but addition of other regions increased this measure; specificity ranged between 98% and 100%. These findings would appear to confirm the value of thermography in the diagnosis of unilateral carpal tunnel syndrome.

Thermographic observations on rats with experimental neuropathic pain

Infrared thermographic images were obtained from the plantar hind paws of rats with an experimental nerve injury that produces signs of neuropathic pain. Thermograms confirmed that the experimental neuropathy produces signs resembling those of patients with neuropathic pain. The hind paws on the nerve-damaged side were abnormally hot, abnormally cold, or apparently normal 8–16 days post injury, a variability that is seen clinically in neuropathic pain patients. Abnormally cold hind paws became warm as soon as the injured sciatic nerve was transected, indicating that the underlying vasoconstriction was mediated by neural impulse activity. Xylazine (Rompun), a sympatho-inhibitory α 2-adrenoceptor agonist that normally increases cutaneous temperature, caused the hind paw on the control side to warm, as anticipated, while causing paradoxical cooling of abnormally hot hind paws, and even of ‘normal temperature’ paws on the nerve-injured side. These findings shed light on possible mechanisms underlying abnormal deviations of skin temperature as a symptom of nerve injury. The findings also attest to the usefulness of the experimental animal model of neuropathic pain and of the thermographic method.

Neonatal skin temperature distribution using infra-red colour thermography.

1. Infra-red Colour Thermography was used to visualize skin temperatures over seven neonates nursed in a modified temperature controlled incubator. 2. Temperature distributions were recorded on cine film which was analysed to evaluate mean skin temperatures; these were subsequently compared with values obtained from multiple, weighted measurements from a thermocouple thermometer. In all cases, there was agreement to within +/- 0 . 6 degrees C. 3. Thermograms in thermo-neutral conditions (approximately 32 degrees C) showed a temperature distribution with the warmest skin overlying the central hot 'core' and temperatures falling towards the extremities. Temperature patterns in a cooler environment (approximately 28 degrees C) showed features due to the conductive or thermogenic nature of the structures underlying the skin. 4. Multiple skin temperature recordings made at two environmental temperatures were obtained from a further twelve infants. 5. Linear regression of skin temperature against rectal--environmental difference, performed for each of the measured sites, showed that the upper arm and, to a lesser extent, the upper thigh temperatures represented the mean value most closely. The upper abdomen and head were both warmer and less responsive to environmental change than the mean skin temperature. These findings were supported by the thermographic observations.

On the Feasibility of Obtaining Three-Dimensional Information From Thermographic Measurements

Despite its many advantages, thermography as a medical diagnostic tool has two basic limitations: 1 its images are indirect manifestations of interior thermal structure and hence do not yield explicit spatial information; 2 it is fundamentally two-dimensional. It is shown in the present paper that the three-dimensional variations of the temperature-dependent volume heat source, often called the blood perfusion term in the bio-heat equation, can be extracted from time dependent thermographic observations. On the other hand, spatial variations of the metabolic healing term cannot be determined from a similar procedure. Numerical experiments are performed to explore the sensitivity of the technique in determining the magnitude and location of a hypothetical lesion. Limitations of the technique in terms of the thermal penetration depth and signal-to-noise ratio are also examined.