Food 3D Printing is a novel technology which allows manufacturing three dimensional edible objects with customized shape and structure, by extruding and depositing progressively several layers. The ...overall process is complex since many phenomena occurs simultaneously: non-Newtonian flows, heat transfer, sintering between different layers and solidification of the printed material after deposition. This study focuses on the interplay between the rheological and thermal properties of chocolate products, and printing conditions, in order to predict the stability of 3D printed structures. The effect of printing velocity (Vp) and environmental temperature (Te) on chocolate printed structure was investigated using IR thermography to characterize the local cooling dynamics.3D edible structures can be manufactured successfully only below a critical print velocity which depends on the environmental temperature. At Te=18°C, Vp should be lower than 16 mm/s while at 20 °C lower than 8 mm/s. This conditions ensure a sufficient cooling and solidification of the cocoa butter, which is needed for print stability. A stability criterion based on the local yield stress is proposed to explain the stability or collapse of the 3D printed structures. The understanding provided by this work can help optimising food 3D printing conditions and product formulation.
•IR Thermography is used to characterize quantitatively the temperature of 3D printed food..•A strong change in rheology, due to cooling, after deposition ensures stability.•Room temperature strongly affects heat transfer dynamics and print stability.•Lower printing velocity allows printing structures at higher room temperature.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Developed thermo-mechanical model produces results consistent with exp. measurements.•Model enables the consideration of any type of spur gear tooth profile.•High-speed thermography offers detailed ...insight into thermal response of polymer gears.•Tooth flash temperature gradient quickly dissipates after meshing cycle completion.•Geometric tolerance deviations influence the temperature rise on a given tooth pair.
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The presented work is focused on the development of a comprehensive thermo-mechanical model for predicting the temperature rise in thermoplastic polymer spur gears with any desired profile geometry while running. The specific constitutional behavior of thermoplastics influences the gear-meshing pattern, which can deviate substantially from ideal gear meshing, as typically exhibited by metal gears in moderate-loading conditions. Taking this aspect into account is of paramount importance if realistic temperature-rise predictions are to be made. The thermal response of the considered gear pair is studied thoroughly from both the analytical and experimental standpoints. Good agreement was found between the results of the model and the experimental measurements performed using a high-speed thermal imaging infrared camera, although it was also observed that the real-life temperature rise can increase noticeably if large geometric tolerance deviations from the ideal profile geometry are present. The presented experimental approach also offers the possibility to observe the temperature rise inside and outside the meshing cycle.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Infrared (IR) thermography (IRT) is a non-destructive testing inspection technique widely used in numerous applications for void and defect detection in various materials such as fiber-reinforced ...composites. The IRT implementation requires solving the inverse heat transfer problem, i.e., calculating the defect attributes (e.g., shape, size, location) from a measured temporal and spatial surface temperature variation. This inverse problem, unlike its equivalent forward problem, is ill-posed and the uniqueness of the solution is not proven. To tackle this challenge, the k-nearest neighbors (k-NN) machine learning (ML) algorithm is employed to provide a model for predicting a penny-shaped defect size, thickness, and location in composite laminates. The study is based on simulations and synthetic data produced by ABAQUS finite element analysis (FEA) of the heat transfer model in defective composites to train the ML algorithm. The surface temperature vs. time and vs. distance diagrams are extracted from the FEA. The data diagrams are then used to extract the training features of the ML by considering the physics of the problem. This ML is trained by 502 FEA run data sets where firstly 10 features, and then 4 features, are selected from the mentioned FEA diagrams to predict the defect traits.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Performance evaluation of bubble base evaporation mechanisms on surfaces of varying wettability.•Experiments under nucleate pool boiling regime.•Transition from microlayer to pure contact line ...evaporation-driven growth phenomena.•Integration of IR thermography with rainbow schlieren-based videography.•Coupled vapor bubble dynamics and bubble base heat transfer mechanisms.
Absolute surface wettability effects on the characteristics of nucleate pool boiling heat transfer under saturated conditions are investigated with water as working fluid. Wettability of the base surface (ITO-coated sapphire) is modified by coating 60 nm thick SiO2 film using different thin film deposition techniques. In this way, two surfaces with modified wettability (30 o and 65 o static contact angles) have the same surface chemistry with negligible variation in surface roughness, while the base surface itself acts as the third surface with 90 o static contact angle. Experiments are conducted for various constant heat flux conditions. Bubble dynamics and temperature distributions of the substrate surface are mapped in-situ using high speed videography and IR thermography, respectively. Pool boiling curves and overall heat transfer coefficient curves, obtained from the recorded IR images, showed that the overall boiling performance increases with enhanced surface wettability. The observed enhancement has been explained on the basis of the modified bubble dynamics and the associated bubble base evaporation mechanism. The bubble dynamics parameters such as bubble departure diameter and departure frequency, and nucleation site density (NSD) were found to get altered so as to augment the total evaporative heat flux with increasing surface wettability. The heat transfer coefficients and heat transfer rates corresponding to bubble base evaporation for isolated vapor bubble revealed that higher wettability surfaces outperform the surfaces with lower wettability in heat transport through bubble base evaporation. The corresponding underlying mechanisms have been identified. In addition, it was found that the microlayer evaporation mechanism is more efficient as compared to that based on pure contact line evaporation in transporting the heat away from the surface.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This work demonstrates the sustainable machining of unidirectional carbon fiber reinforced plastics (UD-CFRP) laminates. Surface integrity, machining induced damages, cutting temperature and forces ...were considered as main output responses to analyze the machining quality at various machining parameters under dry and cryogenic conditions. UD-CFRP laminates with fiber orientations 0°, 45°, 90°, and 135° were chosen as workpiece material. Infrared thermography (IRT) technique was adopted to capture the in-situ cutting temperature for both dry and cryogenic conditions. Results indicate a significant decrease in damage factor, surface roughness and cutting temperature when milling was conducted under cryogenic conditions despite an increase in resultant forces for all fiber orientations. Scanning electron microscopy (SEM) was carried out to capture the micrograph of machined surface, which signifies the change in fiber fracture mode when machining was done under cryogenic conditions. 3D-topography were also performed to assess the surface integrity of machined surface showing improvement in the machined surface quality under cryogenic condition.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In common thermoplastic additive manufacturing (AM) processes, a solid polymer filament is melted, extruded though a rastering nozzle, welded onto neighboring layers and solidified. The temperature ...of the polymer at each of these stages is the key parameter governing these non-equilibrium processes, but due to its strong spatial and temporal variations, it is difficult to measure accurately. Here we utilize infrared (IR) imaging – in conjunction with necessary reflection corrections and calibration procedures – to measure these temperature profiles of a model polymer during 3D printing. From the temperature profiles of the printed layer (road) and sublayers, the temporal profile of the crucially important weld temperatures can be obtained. Under typical printing conditions, the weld temperature decreases at a rate of approximately 100°C/s and remains above the glass transition temperature for approximately 1s. These measurement methods are a first step in the development of strategies to control and model the printing processes and in the ability to develop models that correlate critical part strength with material and processing parameters.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The impact behaviour of woven kevlar fibre/flax fibre/epoxy (WK-F-E) hybrid composites that is made of 12 layers of flax fibres (F) sandwitched in 4 layers of plain-woven Kevlar 49 fibres (WK) is ...investigated via the use of two configurations: woven Kevlar/unidirectional flax/epoxy 0-902K/06FS (WK-UDF-E) and woven Kevlar/cross-ply flax/epoxy 0-902K/(0/90)3FS (WK-CPF-E) laminates. The specimens were subjected to low velocity impact using a pendulum impactor. IR thermography images of the damaged area, in addition to high-speed imaging, and optical microscopy were used to investigate the impact performance in terms of the energy absorbed during impact, damage size, and indentation depth. The results showed that both the WK-UDF-E and WK-CPF-E composites exhibited similar characteristics under low velocity impact with an impact energy penetration threshold of 27 J and impact toughness of 187 kJ/m2, which is slightly better than those of aluminum alloys and carbon/epoxy composites. An approximate tripling of the penetration energy threshold of UD pure flax composites was observed with hybridization.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•A new non-invasive methodology using infrared thermography on activated carbon.•An accurate analytical alternative for characterization and monitoring is discussed.•Infrared ...thermography data correlate with exhaustion level of activated carbons.•Infrared thermography results correlate with outcome of dedicated analytical methods.•Infrared thermographic parameters correlate with surface area and pore volumes.
A new non-invasive methodology based on infrared thermography (IRT) to evaluate the exhaustion level of granular activated carbon (GAC) at different depths of a target industrial water treatment filter is studied. IRT results are discussed in terms of adsorption capacity and correlated with dedicated analytical methods: N2 gas adsorption, TGA, TD-GC/MS and NMR. Findings revealed that the surface temperature and surface thermal density parameters are contingent with the exhaustion level as well as the surface area and pore volumes of the GAC samples. Surface temperature decreased with 80% and the surface thermal density with 35% comparing exhausted Top-GAC and virgin GAC. Linear correlation was found between IRT parameters and the exhaustion profile of 98%. During GAC exploitation the surface area was reduced to 85% and the total volume of pore to 80%. The IRT method demonstrated to be simple and accurate and suitable for GAC management of water treatment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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