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A wide range of behaviors, including non-monotonic rejuvenation and relaxation, and the ability to qualitatively change the effect by varying the structural state of the glass was observed during thermal cycling of bulk metallic glasses. For this, we considered various bulk metallic glasses, Zr44Ti11Cu10Ni10Be25, Pd43Cu27Ni10P20, Pt57.5Cu14.7Ni5.3P22.5, and La55Al25Ni20, at various fictive temperatures to study the effect of thermal cycling on structure, thermal signature, and fracture toughness. For some BMGs and conditions considered here, thermal cycling results in a looser structure and an increase in fracture toughness. We found that for certain other BMGs and conditions, thermal cycling results in relaxation, reflected in a denser structure, and a decrease in fracture toughness. All these responses are non-monotonic and reveal a pronounced extremum with fracture toughness values of ± 50% of the original value, before approaching a value similar to the original value prior to thermal cycling. Such richness in response to thermal cycling suggests incompleteness of the previous picture where monotonically decreasing local stresses resulting in a homogenization of the structure with increasing cycle number. Our finding suggests that relative comparisons of various contributions including activation barriers for α-relaxation have to be considered which are also constantly changing, to decide if further cycling results in an increase or a decrease in fracture toughness. The fracture toughness’ response to thermal cycling can be correlated with the average atomic structures’ response to thermal cycling, while the thermal response does not exhibit an obvious correlation.

Digital thermal imaging is considered as a non-invasive diagnostic tool and a real-time monitoring technique for indicating the physiological changes of the underlying tissue from the superficial thermal signature. A thermal camera can detect temperature variations in the body, as low as 0.1°C. The observed colour pattern depends on the prevailing temperature of the target in a controlled environment. This colour-based thermal pattern is further processed for identifying abnormalities. This process of identification is done by applying various methods such as histogram equalisation, Otsu thresholding and morphologic function. These steps are applied to thermal images of a foot acquired from volunteers and abnormalities were identified. The identification process was based on a threshold obtained from the histogram and it was found to be in the range of 76–80.

Thermal safety hazards are a bottleneck problem that constrains the development of lithium-ion batteries with high energy density. Although the internal short circuit (ISC) caused by separator rupture has been identified as a primary driver of catastrophic failure, the effects of separator architecture and high-temperature robustness on thermal runaway behaviors still need fundamental understanding. This study investigates custom-built pouch cells assembled with a wide range of separators to understand the impact of separators on cell-level thermal stability and resistance to catastrophic ISC. Carefully designed thermal abuse tests reveal how the separator shrinkage, melting, and collapse correlate with micro and massive ISC to drive the unstoppable thermal runaway. Cells are subjected to extreme operating conditions to facilitate quantification of the role of separator characteristics on the thermal runaway signature. The implications of separator distinctions on modulating chemical crosstalk between anode and cathode are explored to determine the dominant mechanism that triggers the onset of thermal runaway, with mitigation strategies being proposed from a new perspective.

A physics-based analytical model to assess residual stresses in additive manufacturing made of metallic materials is presented and validated experimentally. The model takes into consideration the typical multi-pass aspect of additive manufacturing. First, the thermal signature of the process is assessed by predicting the temperature for the problem of a moving heat source, then, the thermally induced stresses in a homogenous semi-infinite medium are determined. Taking the thermal stresses as input, the residual stresses are calculated analytically to obtain the distribution across the depth. Good agreement is obtained between the analytical prediction and X-ray measurements made on Selective Laser Melted 316L Stainless Steel. In addition, the analytical approach enables in-depth interpretations of results with basis in the true mechanisms of the process. Thus, the present model appears as a promising tool for optimization of process parameters in additive manufacturing, which in turn will improve the understanding of process parameters and their effect on properties of the final product.

In this work, the IR thermography has been used to study the steel specimens (DIN 50125 Standard) undergoing the tensile tests. The tensile tests were performed using GUNT® Hamburg Universal Material Tester. The tensile specimens were clamped, and the test force was applied using a hand-operated hydraulic system. A dial gauge measured the elongation of the specimens. The steel specimens were coated with high emissivity paint. Using the WP 300.20 system for data acquisition, the measured values for force and displacement were recorded in a PC. The IR thermographic imaging was performed using the FLIR® T1030sc IR camera and ResearchIR Max software. The tests have revealed that the steel specimens show noticeable thermal signature when undergoing tensile loading.

The infrared detection technology has been widely explored in military domain for signature acquisition and search and tracking of targets. Thermal signatures of any targetare fingerprints for detection by Thermal Imaging System (TIS). Armoured vehicles and equipments are very prone for detection by adversary’s TIS. Multi-layered Textile Structures (MTS) have been designed and developed by efficient insulating materials for thermal signature suppression of ground based targets in 8–12 µm. These structures were evaluated by FLIR TIS in 7.7–11.5 µm at temperatures 50, 100, 150 °C and stand-off distances 8, 16, 24 mm from hot plate. The maximum thermal suppression efficiency of MTS04 and MTS06 are 91.25% and 96.25% respectively. The MTS04 is suitable for thermal suppression of targets upto100°C and MTS06 is more effectiveupto150°C. Spatial configuration of MTS04 and MTS06 as per thermal zones of the target can be arranged for design and development of effective thermal camouflage system for static and dynamic objects.

Blood perfusion quantification is important vital parameters in different diagnostic procedure, using infrared thermography imaging; it is reliable to use this technique as non-contact, non-invasive blood flow measurement method. Therefore, we developed a measurement protocol for blood flow over the arm's anterior surface. By using the superficial brachial and radial veins to be monitored under the impact of cold-excitation of (2 °C to 5 °C), the blood perfusion signal was detected using thermal imager of long-wave infrared spectral range (LWIR, 7μm - 14 μm). The simulation of Penne's bioheat transfer equation was performed to be compared with results obtained from the infrared thermography. Furthermore, the proposed blood flow monitoring using external adjusting of the excitation temperature, by using (cold-compress, or cold air-stream) applied to the region under testing. The signal detected resembles to the hemodynamic pulse of the superficial veins, in the definition of systolic and diastolic phases of the cardiac cycle. Moreover, statistical analysis applied to the BFIRT signals from 24 subjects to estimate the skin's mean temperature after recovery from the thermal excitation.

Additive Manufacturing provides the opportunity to fabricate components of nearly limitless complexity compared to that of traditional manufacturing techniques. However, thermal gyrations imparted into the material from the passing of the heat source cause challenges in fabricating complex structures with the proper process parameters. While the thermal history of the material can be simulated, validating the simulations requires access to thermal data generated through in-situ process monitoring. While generation of in-situ thermal data seems trivial, acquiring and developing reliable calibrations for metallic materials is difficult due to the physical state of the material transitioning from powder to liquid to a solid. To be discussed is the methodology taken to integrate IR in-situ process monitoring within the electron beam melting process and the approach developed to accurately correlate a materials emissivity to temperature during the build process. Further the wealth of information contained within the thermal data will be discussed in the context of understanding of microstructural evolutions within the material during the build process, identification of material defects, and ability to determining the similarity/repeatability of builds fabricated with identical processing parameters as based only on the thermal signature of the build.

The most effective way to reduce the thermal signature is to reduce the emissivity. The goal of our research is to create the material, which can reduce the thermal signature, and make it interflow with environment. The materials and material compositions concealing the thermal signature of the object were developed using aluminium coatings and conductive metalized fibres, i. e. yarns with stainless steel staples or coated with silver. The analysis of the prepared samples was carried out with equipment consisting of a stand with integrated heating controller imitating the human body. The concealing properties of the samples in the far infrared (FIR) spectral range were evaluated using ThermaCAM Reporter 7.0. The thermal signature analysis of prepared samples demonstrates that respectable results could be obtained using yarns coated with silver and materials coated with aluminium, but the first one is more flexible and preferable for clothing.DOI: http://dx.doi.org/10.5755/j01.ms.19.4.1730

The non-contact acousto-thermal signature (NCATS) is a nondestructive evaluation technique with potential to detect fatigue in materials such as noisy titanium and polymer matrix composites. The underlying physical mechanisms and properties may be determined by parameter estimation via nonlinear regression. The nonlinear regression analysis formulation, including the underlying models, is discussed. Several models and associated data analyses are given along with the assumptions implicit in the underlying model. The results are anomalous. These anomalous results are evaluated with respect to the accuracy of the implicit assumptions.

WOS; International audience; Since the pioneer works of Gough and Joule, the thermal characterisation of elastomers under mechanical loading has been investigated by numerous research teams. This is not surprising as the thermal signature of rubber is very useful data to investigate the dissipation mechanisms as well as the thermodynamical variables and couplings. In former recent studies dealing with fatigue investigations, an experimental protocol was developed. This protocol imposes cyclic loading to hourglass shaped samples, takes into account the large displacements and permits dissociation between the intrinsic dissipation, responsible for the mean temperature variation (called heat build-up in the literature) and thermomechanical couplings responsible for the temperature variation around this mean value during one cycle. Up to now, the mean temperature has been investigated in order to feed an energetic fatigue criterion. The aim of the present study is to investigate the thermomechanical couplings and the ability of thermal measurements to exhibit some specific thermomechanical properties observed for rubberlike materials. The materials studied are natural rubber and styrene butabiène rubber compounds filled with several amounts of carbons blacks. The experimental data clearly exhibit interesting features such as the thermoelastic inversion point and difference in the temperature signal between mechanical loading and unloading. This rich database is analysed and correlated to other results from the literature. The main results obtained are dealing with the ability of accurate measurements to characterise the thermodynamic couplings and to detect the stress induced crystallisation.

The attention of the present paper was devoted to nondestructive evaluation of masonry structures with a Focal Plane Array infrared camera. Tests were carried out in laboratory on specimens, which simulated one- and two-layer structures, with defects of different geometry and nature and located at different depths. The defects detection was analysed through a cause/effect relationship between the characteristics of defects and hosting material and the observed defect thermal signature, or contrast, on the hosting material.

The effect of the underlying blood vessel on the transient thermal response of the skin surface with and without a melanoma lesion is studied. A 3D computational model of the layers of the skin tissue with cancerous lesion was developed in COMSOL software package. Heat transfer in the skin layers and the lesion is governed by the Pennes bio-heat equation, while the blood vessel is modeled as fully developed pipe flow with constant heat transfer coefficient. The effect of various pertinent parameters, such as diameter of the blood vessel, lateral location of the blood vessel relative to the lesion, flow velocity of the blood, on the skin surface temperature distribution, have been studied in the paper. The results show significant influence of the underlying blood vessel on the temperature of the skin surface and lesion as well as on the surrounding healthy tissue. Thus, a need for development of evaluation criteria for detection of malignant lesions in the presence of blood vessels is is discussed.

Thermal camouflage and cloaking can transform an actual heat signature into a pre-controlled one. A viable recipe for controlling and manipulating heat signatures using thermal metamaterials to empower cloaking and camouflage in heat conduction is demonstrated. The thermal signature of the object is thus metamorphosed and perceived as multiple targets with different geometries and compositions, with the original object cloaked.

The role of detecting non-metallic and weakly conducting inclusions in hot melts during the manufacturing process is of major importance. However, the key impediment to assessing melt cleanliness is the quantification of the level of inclusions. In this paper, we present the theory and practice in using a magnetic force-based detection system capable of monitoring small inclusions of micron-size dimensions. The idea is to force the non-conducting inclusions to a detection location (the free melt surface) by electromagnetic Archimedes forces. Further, an infrared (IR) imaging system can then be applied to detect their thermal signature. Finally, a novel image-processing algorithm is used to analyze the inclusion level on the measurement surface.

A new hybrid remote-sensing method, using active high-power microwave (HPM) illumination and passive infrared (IR) detection, is being developed at the Defence Research Establishment Ottawa (DREO) for the detection of shallowly buried landmines.

Thermal evolution of ion implantation-induced defects and the influence of concurrent titanium silicidation in pre-amorphized p-type Si (implanted with 25 KeV, 1016 cm2Si+) under rapid thermal processing (RTP) have been investigated. Presence of implantation-induced electrically active defects has been confirmed by current-voltage (IV) and deep level transient spectroscopy (DLTS) measurements. DLTS characterization results show that the evolution of electrically active defects in the Si implanted samples under RTP depend critically on the RTP temperature: Hole traps HI (0.33 eV) and H4 (0.47 eV) appear after the highest temperature (950 °C) anneal, while a single trap H3 (0.26 eV) shows up at lower anneal temperatures (≤ 900 °C). The thermal signature of H4 defect is very similar to that of the iron interstitial while those of HI and H3 levels appear to originate from some interstitial-related defects, possibly complexes. A most interesting finding is that the above interstitial related defects can be eliminated completely with Ti silicidation, apparently a result of vacancy injection. However the silicidation process itself introduces a new H2 (0.30 eV) level, albeit at much lower concentration. This same H2 level is also seen in unimplanted samples under RTP. The paper will present details of defect evolution under various conditions of RTP for samples with and without the self-implantation and silicidation.

Keywords: Camouflage, statistical effectiveness, thermal infrared, low emissive coatings, low emissive paints, thermal signature, emissive signature component, reflective component, target signature, background signature, signature models, camouflage criterion, detection.

Electron diffraction has been conducted in thin free-standing films of $N$-(4-n-butoxybenzylidene)-4-n-octylaniline (4O.8). The surface smectic-A layers first exhibit a transition to the hexatic-B phase at a temperature where a strong heat-capacity anomaly has been observed, and then undergo a second transition to the crystal-B phase. The surface hexatic-B--crystal-B transition is not accompanied by any detectable thermal signature, but coincides with the onset of shear response. This smectic-A--hexatic-B--crystal-B transition sequence is then repeated in the interior of the films in a novel layer-by-layer manner.

The principles governing infrared imaging for aerodynamic surface-flow visualization in cryogenic wind tunnels are reviewed, with emphasis on boundary-layer transition detection. The applicability of the technique to low temperatures is illustrated through examples of transition, shock and vortical burst detection.

emission from a photographic flash cube. The graph displays spectral irradiancefor the 96 channels over the spectral range (additional blocking filters areintroduced at short wavelengths). The spectral emission data is collected at 1msec intervals and stored and displayed to produce an isometric representationof the emission.

Detailed considerations for the design of a low-gravity thermocapillary flow experiment are presented. The basic configuration is one in which a fluid contained in a circular dish is subjected to an imposed surface heat flux. Specific consideration is given to the imposed thermal signature, thermal boundary conditions, free-surface deformations, and g-jitter effects. Numerical analysis and ground-based and drop-tower tests are utilized to ensure that reasonable flows are obtained in which measurements can be made relatively easily. The configuration chosen is of further importance because it differs from others in which oscillations were observed.