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1
Motygin, Vladimir, Natalja Iltchenko, Dmitry Polyshchuk e Anna Veremienko. "New method for thermo-optical modeling in liquid crystals". Applied Optics 41, n. 23 (10 agosto 2002): 4870. http://dx.doi.org/10.1364/ao.41.004870.
Testo completo
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Kim, Kyoung Joon, Avram Bar-Cohen e Bongtae Han. "Thermo-optical modeling of an intrinsically heated polymer fiber Bragg grating". Applied Optics 46, n. 20 (20 giugno 2007): 4357. http://dx.doi.org/10.1364/ao.46.004357.
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Askar, Sameh, Ahmed E. Abouelregal, Marin Marin e Abdelaziz Foul. "Photo-Thermoelasticity Heat Transfer Modeling with Fractional Differential Actuators for Stimulated Nano-Semiconductor Media". Symmetry 15, n. 3 (6 marzo 2023): 656. http://dx.doi.org/10.3390/sym15030656.
Testo completoAbstract (sommario):
The term “optical thermoelasticity” is used to describe how the optical properties of a material change when it is heated or deformed mechanically. The issues of effective elastic and heat transfer symmetry are given particular focus. This study gives a new nonlocal theoretical formulation for a thermo-optical elastic material that can be used to describe how thermomechanical waves and plasma waves relate to the symmetry of semiconductor materials such as silicon or germanium. The suggested model includes the idea of nonlocal elasticity and a modified Moore–Gibson–Thompson (MGT) heat conduction equation with nonsingular fractional derivative operators. The heat transfer equation has been converted and generalized into a nonsingular fractional form based on the concepts of Atangana and Baleanu (AB) using the Mittag–Leffler kernel. The developed model is used to examine the effect of thermal loading by ramp-type heating on a free plane of unbounded semiconductor material symmetries. Using the Laplace transform approach, we may analytically obtain linear solutions for the investigated thermo-photo-elastic fields, such as temperature. The Discussion section includes a set of graphs that were generated using Mathematica to evaluate the impact of the essential parameters.
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Kim, Kyoung Joon, Avram Bar-Cohen e Bongtae Han. "Thermo-optical modeling of polymer fiber Bragg grating illuminated by light emitting diode". International Journal of Heat and Mass Transfer 50, n. 25-26 (dicembre 2007): 5241–48. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2007.06.038.
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Boutelier, D., e O. Oncken. "3-D thermo-mechanical laboratory modeling of plate-tectonics: modeling scheme, technique and first experiments". Solid Earth 2, n. 1 (24 maggio 2011): 35–51. http://dx.doi.org/10.5194/se-2-35-2011.
Testo completoAbstract (sommario):
Abstract. We present an experimental apparatus for 3-D thermo-mechanical analogue modeling of plate tectonic processes such as oceanic and continental subductions, arc-continent or continental collisions. The model lithosphere, made of temperature-sensitive elasto-plastic analogue materials with strain softening, is submitted to a constant temperature gradient causing a strength reduction with depth in each layer. The surface temperature is imposed using infrared emitters, which allows maintaining an unobstructed view of the model surface and the use of a high resolution optical strain monitoring technique (Particle Imaging Velocimetry). Subduction experiments illustrate how the stress conditions on the interplate zone can be estimated using a force sensor attached to the back of the upper plate and adjusted via the density and strength of the subducting lithosphere or the lubrication of the plate boundary. The first experimental results reveal the potential of the experimental set-up to investigate the three-dimensional solid-mechanics interactions of lithospheric plates in multiple natural situations.
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Zanuto, Vitor S., Otávio A. Capeloto, Marcelo Sandrini, Luis C. Malacarne, Nelson G. C. Astrath e Stephen E. Bialkowski. "Analysis of the Thermo-Reflectivity Coefficient Influence Using Photothermal Pump–Probe Techniques". Applied Spectroscopy 71, n. 5 (18 novembre 2016): 970–76. http://dx.doi.org/10.1177/0003702816662888.
Testo completoAbstract (sommario):
Recent improvements in the modeling of photo-induced thermo–optical–mechanical effects have broadened the application of photothermal techniques to a large class of solids and fluids. During laser excitation, changes in optical reflectivity due to temperature variation may affect the photothermal signal. In this study, the influence of the reflectivity change due to heating is analyzed for two pump–probe photothermal techniques, thermal lens and thermal mirror. A linear equation for the temperature dependence of the reflectivity is derived, and the solution is tested using optical properties of semi-transparent and opaque materials. For semi-transparent materials, the influence of the reflectivity change in photothermal signals is less than 0.01%, while for opaque materials it is lower than 3%.
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Sobotka, Evelyn, Johannes Kreyca e Erwin Povoden-Karadeniz. "Intragranular ferrite nucleation on MX carbonitrides and dislocations". Journal of Physics: Conference Series 2635, n. 1 (1 novembre 2023): 012028. http://dx.doi.org/10.1088/1742-6596/2635/1/012028.
Testo completoAbstract (sommario):
Abstract The competing mechanisms of ferrite nucleation on (Ti,V)(C,N) MX carbonitrides and dislocations, as well as their dependence on deformation, are investigated experimentally by thermo-mechanical treatments and via simulation. The impact of recrystallization and the resulting austenite grain size on intragranular ferrite nucleation is evaluated. The austenite-to-ferrite transformation temperatures, affected by different microstructures, are examined by isothermal uniaxial single-hit compression tests on a dilatometer DIL 805 and compared to thermal treatments without deformation. Different resulting microstructures are analyzed by using optical light microscopy. The experimental data is used for the validation of thermo-kinetic simulations with the mean-field modeling software MatCalc using the implemented models for the austenite grain evolution, the on-particle nucleation of ferrite on the surface of MX particles, the dislocation density evolution, and recrystallization.
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Louchev, Oleg A., Yoshiharu Urata, Masaki Yumoto, Norihito Saito e Satoshi Wada. "Thermo-optical modeling of high power operation of 2 μm codoped Tm,Ho solid-state lasers". Journal of Applied Physics 104, n. 3 (agosto 2008): 033114. http://dx.doi.org/10.1063/1.2936967.
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Liu, Gang, Anh-Tuan Vu, Olaf Dambon e Fritz Klocke. "Glass Material Modeling and its Molding Behavior". MRS Advances 2, n. 16 (2017): 875–85. http://dx.doi.org/10.1557/adv.2017.64.
Testo completoAbstract (sommario):
ABSTRACTPrecision molding is a replicative production method for the mass production of complex glass optics in high precision. In contrast to the traditional material removal process, such as grinding and polishing, the surface as well as the entire shape of the optical component is created by deforming glass at elevated temperatures using precise molding tools with optical surfaces. The molded glass components present high shape accuracy and surface finish after the molding process, therefore no further processing is required. During the molding process, the glass is heated in the molding tool up to above the transition temperature Tg, then pressed into desired shape and cooled down to approximately 200 °C. The precision glass molding is therefore a complex thermo-mechanical process, in which the glass lens undergoes uneven cooling speed and stress distribution. These lead to several drawbacks on the molded glass optics, such as form deviation, index change and fracture. In this study, FEM simulation was employed in order to achieve preliminary understanding of the molding process. The FEM model included viscoelasticity behavior of glass material (stress-relaxation, structure-relaxation and thermos-rheological simplicity), as well as thermodynamics model of the molding machine. In the form of a case study of a real molding example, the form deviation, index change and fracture of the molded glass optic were predicted in advance of the molding experiment by means of the numerical calculation of thermal shrinkage, volume change and stress distribution respectively. The good agreement between simulation results and molding experiment results proves the accuracy of the developed FEM model.
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Zhang, Qinghua, Bohayra Mortazavi e Fadi Aldakheel. "Molecular Dynamics Modeling of Mechanical Properties of Polymer Nanocomposites Reinforced by C7N6 Nanosheet". Surfaces 4, n. 3 (24 agosto 2021): 240–54. http://dx.doi.org/10.3390/surfaces4030019.
Testo completoAbstract (sommario):
Carbon-nitride nanosheets have attracted remarkable attention in recent years due to their outstanding physical properties. C7N6 is one of the hotspot nanosheets which possesses excellent mechanical, electrical, and optical properties. In this study, the coupled thermo-mechanical properties of the single nanosheet C7N6 are systematically investigated. Although temperature effects have a strong influence on the mechanical properties of C7N6 monolayer, thermal effects were not fully analyzed for carbon-nitride nanosheet and still an open topic. To this end, the presented contribution aims to highlight this important aspect and investigate the temperature influence on the mechanical stress-strain response. By using molecular dynamics (MD) simulation, we have found out that the C7N6 monolayer’s maximum strength decreases as the temperature increase from 300 K to 1100 K. In the current contribution, 5% to 15% volume fractions of C7N6/P3HT composite were employed to investigate the C7N6 reinforcing ability. Significantly, the uniaxial tensile of C7N6/P3HT composite reveals that 10%C7N6 can enhance the maximum strength of the composite to 121.80 MPa which is 23.51% higher than the pure P3HT matrix. Moreover, to better understand the enhanced mechanism, we proposed a cohesive model to investigate the interface strength between the C7N6 nanosheet and P3HT matrix. This systematic study provides not only a sufficient method to understand the C7N6 thermo-mechanical properties, but also the reinforce mechanism of the C7N6 reinforced nanocomposite. Thus, this work provides a valuable method for the later investigation of the C7N6 nanosheet.
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Marzougui, Ons, Naoufel Ben Moussa e Farhat Ghanem. "Numerical modeling of phase transformations of Ti6Al4V during electrical discharge machining". Matériaux & Techniques 112, n. 3 (2024): 302. http://dx.doi.org/10.1051/mattech/2023047.
Testo completoAbstract (sommario):
Conventional machining of Ti6Al4V parts with complex shapes is often a tough task due to its low thermal conductivity and its high strength-to-density ratio. Thus, electrical discharge machining (EDM) comes as a better alternative that surpasses these manufacturing difficulties. In this work, a coupled thermo-mechanical model was built using the FEM software package Abaqus to estimate the sublayers final microstructure of a Ti6Al4V machined workpiece. The proposed numerical model aims to replicate a single-spark electrical discharge machining process. Phase transformations kinetic laws of the biphasic titanium alloy and heat flux distribution subroutines were implemented. XRD analysis, metallurgical sample preparation and optical microscope imaging were performed to investigate electrical discharge machining effects on Ti6Al4V part and to validate the numerical proposed model. Close agreement was found between experimental investigation results and numerical outcomes. The numerical model considers the remaining amount of 10% of β phase redeposited at the end of the discharge phase additionally to the martensitic phase α’.
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Yi, Duo. "Development of a flame spraying coating–based fiber composite structure: A thermo-mechanical finite element study". Journal of Intelligent Material Systems and Structures 31, n. 16 (21 luglio 2020): 1950–58. http://dx.doi.org/10.1177/1045389x20942324.
Testo completoAbstract (sommario):
The optical fiber smart composite structures have been widely applied for the structural health monitoring, and the packaging technique of integrating optical fiber sensor with host structure is one of the key issues. The flame spraying coating provides strong adhesive strength with good heat resistance, which is particularly suitable for the packaging applications in harsh environments. However, the elaboration process of flame spraying coating–based fiber composite structure faces great challenges due to the flame spraying mechanisms. This study evaluates numerically an overall effect of flame spraying coating formation process on the structural and the optical properties of the embedded fiber optic based on a three-dimensional finite element model. First, the lumped capacitance method is used; both the average heat flux density in the whole spraying process and the specific heat flux density of each torch sweep are estimated to initialize the thermo-mechanical modeling. Then, the stress distributions in both radial and axial directions of the embedded fiber are discussed separately. Next, the variation of refractive index of the embedded fiber optic due to the residual strain is also investigated. Finally, the elaboration parameters including torch displacement and velocity are evaluated and optimized. The simulation results show that the embedded fiber optic maintains good structural and optical properties with the presented elaboration conditions, and therefore its transmission and sensing performance can be ensured.
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Kiran, Abhilash, Ying Li, Josef Hodek, Michal Brázda, Miroslav Urbánek e Jan Džugan. "Heat Source Modeling and Residual Stress Analysis for Metal Directed Energy Deposition Additive Manufacturing". Materials 15, n. 7 (30 marzo 2022): 2545. http://dx.doi.org/10.3390/ma15072545.
Testo completoAbstract (sommario):
The advancement in additive manufacturing encourages the development of simplified tools for deep and swift research of the technology. Several approaches were developed to reduce the complexity of multi-track modeling for additive manufacturing. In the present work, a simple heat source model called concentrated heat source was evaluated for single- and multi-track deposition for directed energy deposition. The concentrated heat source model was compared with the widely accepted Goldak heat source model. The concentrated heat source does not require melt pool dimension measurement for thermal model simulation. Thus, it reduces the considerable time for preprocessing. The shape of the melt pool and temperature contour around the heat source was analyzed for single-track deposition. A good agreement was noticed for the concentrated heat source model melt pool, with an experimentally determined melt pool, using an optical microscope. Two heat source models were applied to multi-track 3D solid structure thermo-mechanical simulation. The results of the two models, for thermal history and residual stress, were compared with experimentally determined data. A good agreement was found for both models. The concentrated heat source model reported less than the half the computational time required for the Goldak model. The validated model, for 3D solid structure thermo-mechanical simulation, was used to analyze thermal stress evolution during the deposition process. The material deposition on the base plate at room temperature results in lower peak temperatures in the layers near the base plate. Consequently, the higher thermal stress in the layers near the base plate was found, compared to the upper layers during the deposition process.
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Razenkov, I. A. "Engineering and Technical Solutions When Designing a Turbulent Lidar". Atmospheric and Oceanic Optics 35, S1 (dicembre 2022): S148—S158. http://dx.doi.org/10.1134/s1024856023010141.
Testo completoAbstract (sommario):
Abstract Design characteristics of a turbulent lidar, which affect its thermo-mechanical stability, are determined. Two different designs are compared with different approaches to the selection of transceiving optics and detectors and arrangement of the temperature control system for stabilizing the lidar optical bench. A procedure is suggested for simulation of the lidar transceiver, including the calculation of the displacements of optical elements relative to the base points on the optical bench and the ray tracing from the laser into the atmosphere and back. The effect of the temperature gradient between the opposite sides of the optical bench on the operation of the receiving channels is analyzed. The results of the experimental study of lidar resistance to temperature changes are described. Recommendations for improving the design of a turbulent lidar are formulated.
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Berger, Evan, Michael Miles, Andrew Curtis, Paul Blackhurst e Yuri Hovanski. "2D Axisymmetric Modeling of Refill Friction Stir Spot Welding and Experimental Validation". Journal of Manufacturing and Materials Processing 6, n. 4 (18 agosto 2022): 89. http://dx.doi.org/10.3390/jmmp6040089.
Testo completoAbstract (sommario):
The development of the simulation of refill friction stir spot welding (RFSSW) is critical to be able to predict the behavior of aluminum in the process under specific parameters. A two-dimensional axisymmetric thermo-mechanical model of the RFSSW process for 7075-T6 aluminum alloy sheet was developed and validated with experimental data. Welding temperatures and material flow, including defect formation, were accurately predicted by the model. While these results are encouraging, further development of bonding criteria is needed for simulation models, in order to enable the prediction of properties such as joint strength. The simulation was validated by a comparison of temperatures measured in the weld, which were demonstrated to be accurate at all positions in and around the weld nugget, within 10% of measured values. Additional validation of material flow was performed with post-weld optical microscopy where the simulation is shown to be able to predict the presence or absence of internal volumetric defects based on the variation in process parameters. Finally, the prediction of the tool process forces during the welding cycle were evaluated; however, both probe and shoulder forces were overestimated using the standard flow stress data for AA 7075-T6.
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Gorajek, Lukasz, Przemyslaw Gontar, Jan Jabczynski, Jozef Firak, Marek Stefaniak, Miroslaw Dabrowski, Tomasz Orzanowski et al. "Characterization of Absorption Losses and Transient Thermo-Optic Effects in a High-Power Laser System". Photonics 7, n. 4 (22 ottobre 2020): 94. http://dx.doi.org/10.3390/photonics7040094.
Testo completoAbstract (sommario):
(1) Background: The modeling, characterization, and mitigation of transient lasers, thermal stress, and thermo-optic effects (TOEs) occurring inside high energy lasers have become hot research topics in laser physics over the past few decades. The physical sources of TOEs are the un-avoidable residual absorption and scattering in the volume and on the surface of passive and active laser elements. Therefore, it is necessary to characterize and mitigate these effects in real laser systems under high-power operations. (2) Methods: The laboratory setup comprised a 10-kW continuous wave laser source with a changeable beam diameter, and dynamic registration of the transient temperature profiles was applied using an infrared camera. Modeling using COMSOL Multiphysics enabled matching of the surface and volume absorption coefficients to the experimental data of the temperature profiles. The beam quality was estimated from the known optical path differences (OPDs) occurring within the examined sample. (3) Results: The absorption loss coefficients of dielectric coatings were determined for the evaluation of several coating technologies. Additionally, OPDs for typical transmissive and reflective elements were determined. (4) Conclusions: The idea of dynamic self-compensation of transient TOEs using a tailored design of the considered transmissive and reflecting elements is proposed.
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Paar, Armin, Leonel Elizondo, Michael Brandner, Thomas Trickl, Bernhard Sonderegger, Coline Beal e Christof Sommitsch. "Application of Thermo-Calc TCFE7 to High-Alloyed Mottled Cast Iron". Materials Science Forum 879 (novembre 2016): 1431–36. http://dx.doi.org/10.4028/www.scientific.net/msf.879.1431.
Testo completoAbstract (sommario):
The thermodynamic modeling of alloy systems consisting of stable and metastable phases e.g. high-alloyed mottled cast iron can be problematic. Thermodynamic databases are rather well-developed for low, medium and high alloyed steels (e.g. HSS) but the application of those databases is not yet very common for high-alloyed (mottled) cast irons. The Thermo-Calc software together with the TCFE7 database is used to calculate isopleth and property diagrams, using the CALPHAD method. Additionally Scheil-Gulliver calculations are performed to simulate the effects of microsegregation during solidification. The results from the thermodynamic calculations are compared with measurements on own samples and with literature values. Those measurements include quantitative light-optical analysis, SEM with BSE detector, EDX measurements for the distribution of the alloying elements as well as XRD and DSC measurements. The investigations show the possibilities which are offered by thermodynamic calculations for high-alloyed mottled cast iron as well as the limitations and the compromises which have to be taken into account when calculating stable and metastable phases existing next to each other.
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Costa, D. C. T., M. C. Cardoso, Gláucio S. da Fonseca, Luciano Pessanha Moreira, M. Martiny e S. Mercier. "Strain-Induced Martensite Formation of AISI 304L Steel Sheet: Experiments and Modeling". Materials Science Forum 869 (agosto 2016): 490–96. http://dx.doi.org/10.4028/www.scientific.net/msf.869.490.
Testo completoAbstract (sommario):
Metastable austenitic stainless steels are prone to strain-induced martensite transformation (SIMT) during deformation at room temperature, as in the case of sheet metal forming processes. The SIMT is influenced by the chemical composition, grain size, temperature, deformation mode or stress state and strain-rate. In this work, interrupted and continuous uniaxial tensile tests were performed in AISI 304L sheet to evaluate the SIMT as a function of strain and strain-rate effects. The SIMT was evaluated by feritscope and temperature in-situ measurements and both XRD and optical microscopy techniques. The SIMT kinetics was also investigated by means of thermo-mechanical finite element simulations using a phenomenological model. In the small strain range, the yield stress increases with the strain-rate whereas in the large strain domain a cross-effect in the stress-strain curve is observed given that the SIMT is inhibited due to the specimen heat generation. A very good correlation between XRD and feritscope measurements was found from the interrupted uniaxial tensile testing. The finite element numerical simulations allowed to identify the parameters of a phenomenological model which describes the SIMT kinetics of AISI 304L steel sheet as a function of plastic-strain, strain-rate and temperature effects.
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Sivan, Yonatan, e Shi-Wei Chu. "Nonlinear plasmonics at high temperatures". Nanophotonics 6, n. 1 (6 gennaio 2017): 317–28. http://dx.doi.org/10.1515/nanoph-2016-0113.
Testo completoAbstract (sommario):
AbstractWe solve the Maxwell and heat equations self-consistently for metal nanoparticles under intense continuous wave (CW) illumination. Unlike previous studies, we rely on experimentally-measured data for metal permittivity for increasing temperature and for the visible spectral range. We show that the thermal nonlinearity of the metal can lead to substantial deviations from the predictions of the linear model for the temperature and field distribution and, thus, can explain qualitatively the strong nonlinear scattering from such configurations observed experimentally. We also show that the incompleteness of existing data of the temperature dependence of the thermal properties of the system prevents reaching a quantitative agreement between the measured and calculated scattering data. This modeling approach is essential for the identification of the underlying physical mechanism responsible for the thermo-optical nonlinearity of the metal and should be adopted in all applications of high-temperature nonlinear plasmonics, especially for refractory metals, for both CW and pulsed illumination.
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Seo, Sang-Woo, Youngsik Song e Hojjat Rostami Azmand. "Photothermal liquid release from arrayed Au nanorod/hydrogel composites for chemical stimulation". Journal of Micromechanics and Microengineering 32, n. 1 (30 novembre 2021): 015003. http://dx.doi.org/10.1088/1361-6439/ac39fa.
Testo completoAbstract (sommario):
Abstract Controlled photothermal actuation of liquid release is presented using periodically arrayed hydrogel columns in a macroporous silicon membrane. Thermo-responsive hydrogel is mixed with Gold (Au) nanorods, and surface plasmon-induced local heating by near-infrared (NIR) light is utilized as an actuation method. We adopted theoretical modeling, which treats the hydrogel as a poro-viscoelastic medium to understand the mechanical and liquid transport properties of the hydrogel. To demonstrate the feasibility of the liquid release control using NIR light, we first characterized the temperature response of Au nanorod embedded hydrogel in the silicon membrane using its optical transmission behavior to confirm the successful device fabrication. Next, the liquid release characteristics from the structure were studied using fluorescent imaging of fluorescein dye solution while pulsed NIR light was illuminated on the structure. We successfully demonstrate that the liquid release can be controlled using remote NIR illumination from the presented structure. Considering the periodically arrayed configuration with high spatial resolution, this will have a potential prospect for optically-addressable chemical release systems, which benefit retina prosthesis interfaces.
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Trzepieciński, Tomasz, Marcin Szpunar, Robert Ostrowski, Waldemar Ziaja e Maciej Motyka. "Advanced FEM Insights into Pressure-Assisted Warm Single-Point Incremental Forming of Ti-6Al-4V Titanium Alloy Sheet Metal". Metals 14, n. 6 (24 maggio 2024): 619. http://dx.doi.org/10.3390/met14060619.
Testo completoAbstract (sommario):
This study employs the finite element (FE) method to analyze the Incremental Sheet Forming (ISF) process of Ti-6Al-4V titanium alloy. The numerical modeling of pressure-assisted warm forming of Ti-6Al-4V sheets with combined oil-heating and friction stir rotation-assisted heating of the workpiece is presented in this article. The thermo-mechanical FE-based numerical model took into account the characteristics of the mechanical properties of the sheet along with the temperature. The experimental conditions were replicated in FEM simulations conducted in Abaqus/Explicit, which incorporated boundary conditions and evaluated various mesh sizes for enhanced accuracy and efficiency. The simulation outcomes were compared with actual experimental results to validate the FE-based model’s predictive capacity. The maximum temperature of the tool measured using infrared camera was approximately 326 °C. Different mesh sizes were considered. The results of FEM modeling were experimentally validated based on axial forming force and thickness distribution measured using the ARGUS optical measuring system for non-contact acquisition of deformations. The greatest agreement between FEM results and the experimental result of the axial component of forming force was obtained for finite elements with a size of 1 mm. The maximum values of the axial component of forming force determined experimentally and numerically differ by approximately 8%. The variations of the forming force components and thickness distribution predicted by FEM are in good agreement with experimental measurements. The numerical model overestimated the wall thickness with an error of approximately 5%. By focusing on the heating techniques applied to Ti-6Al-4V titanium alloy sheet, this comparative analysis underlines the adaptability and precision of numerical analysis applied in modeling advanced manufacturing processes.
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Salomone, Rita, Vito Speranza, Sara Liparoti, Giuseppe Titomanlio e Roberto Pantani. "Modeling and Analysis of Morphology of Injection Molding Polypropylene Parts Induced by In-Mold Annealing". Polymers 14, n. 23 (1 dicembre 2022): 5245. http://dx.doi.org/10.3390/polym14235245.
Testo completoAbstract (sommario):
It is generally recognized that high-temperature treatments, namely annealing, influence the microstructure and the morphology, which, in turn, determine the mechanical properties of polymeric parts. Therefore, annealing can be adopted to control the mechanical performance of the molded parts. This work aims to assess the effect of annealing on the morphology developed in isotactic polypropylene (iPP) injection-molded parts. In particular, a two-step annealing is adopted: the polymer is injected in a mold at a high temperature (413 or 433 K), which is kept for 5 min (first annealing step); afterward, the mold temperature is cooled down at 403 K and held at that temperature for a time compatible with the crystallization half-time at that temperature (second annealing step). The characterization of morphology is carried out by optical and electronic scanning microscopy. The temperature of the first annealing step does not influence the thickness of the fibrillar skin layer; however, such a layer is thinner than that found in the molded parts obtained without any annealing steps. The second annealing step does not influence the thickness of the fibrillar skin layer. The dimension of spherulites found in the core is strongly influenced by both annealing steps: the spherulite dimensions enlarge by the effect of annealing steps. A model that considers spherulite and fibril evolutions is adopted to describe the effect of molding conditions on the final morphology distribution along the part thickness. The model, which adopts as input the thermo-mechanical histories calculated by commercial software for injection molding simulation, consistently predicts the main effects of the molding conditions on the morphology distributions.
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Kostyukhin, A. S., E. A. Pavlukhin e V. V. Malyy. "Development and experimental testing of the technique of ultrasonic control of brazed joints of heat exchangers". Journal of Physics: Conference Series 2127, n. 1 (1 novembre 2021): 012054. http://dx.doi.org/10.1088/1742-6596/2127/1/012054.
Testo completoAbstract (sommario):
Abstract High reliability requirements are imposed on the quality of the soldered joints. Typical defects in the soldered joints of heat exchangers are non-soldered. The minimum size of the non-penetration area that must be detected is about 1 square millimeter. The existing assessment of the quality of soldering is reduced to destructive tests. These tests include hydraulic and pneumatic tests. There are control technologies that use non-destructive methods. For example, the applicability of the ultrasonic echo method based on thermo-optical (laser) excitation of ultrasonic waves has been proven. However, continuous inspection of the liquid-propellant engine chamber using the traditional echo method is not rational, since the inspection speed is limited by the size of detected defects (1 square millimeter) and amounts to a few millimeters per minute. In order to increase the scanning speed without losing the ability to reliably detect defects such as “non-soldered”, it is proposed to use phased array antennas (PA) as a means of implementing the ultrasonic echo method. The paper considers the issues related to the interpretation of the information obtained when scanning the soldered joint, as well as issues related to modeling the acoustic field in the model of the soldered joint of the heat exchanger.
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Vattathurvalappil, Suhail Hyder, Mahmoodul Haq e Saratchandra Kundurthi. "Hybrid nanocomposites—An efficient representative volume element formulation with interface properties". Polymers and Polymer Composites 30 (gennaio 2022): 096739112210846. http://dx.doi.org/10.1177/09673911221084651.
Testo completoAbstract (sommario):
Reinforcement of polymers with multiple inclusions of varying length scales and morphologies enable enhancement and tailorability of thermo-mechanical properties in resulting polymers. Computational material models can eliminate the trial-and-error approach of developing these hybrid reinforced polymers, enable prediction of interphase properties, and allow virtual exploration of design space. In this work, computational models, specifically representative volume elements were developed for acrylonitrile butadiene styrene polymer reinforced with nanoscale iron oxide particles and micro-scale short carbon fibers. These representative volume elements were used to predict the tensile modulus of resulting polymer nanocomposite with varying particle concentrations, orientations, interphases, and clustering to realistically replicate the actual material as observed in optical and electron microscopy. The interphase elastic modulus was obtained through established analytical formulations and incorporated into the representative volume elements by defining an interphase region around the reinforcements. The tensile modulus estimated using representative volume elements agreed well with the experiments, evidently showing that the effective tensile modulus of the polymer nanocomposite increased with increase in interphase thickness, aspect ratio, and particle content. Clustering was only observed in Fe3O4 nanoparticles but its size did not have any effect on the effective tensile modulus. The developed computational modeling framework and the resultant prediction of tensile modulus offers a design path which can be extended to other polymer nanocomposites containing multiple inclusions.
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Nicolay, Pascal, Hugo Chambon, Gudrun Bruckner, Christian Gruber, Sylvain Ballandras, Emilie Courjon e Matthias Stadler. "A LN/Si-Based SAW Pressure Sensor". Sensors 18, n. 10 (16 ottobre 2018): 3482. http://dx.doi.org/10.3390/s18103482.
Testo completoAbstract (sommario):
Surface Acoustic Wave (SAW) sensors are small, passive and wireless devices. We present here the latest results obtained in a project aimed at developing a SAW-based implantable pressure sensor, equipped with a well-defined, 30 μm-thick, 4.7 mm-in-diameter, Lithium Niobate (LN) membrane. A novel fabrication process was used to solve the issue of accurate membrane etching in LN. LN/Si wafers were fabricated first, using wafer-bonding techniques. Grinding/polishing operations followed, to reduce the LN thickness to 30 μm. 2.45 GHz SAW Reflective Delay-Lines (R-DL) were then deposited on LN, using a combination of e-beam and optical lithography. The R-DL was designed in such a way as to allow for easy temperature compensation. Eventually, the membranes were etched in Si. A dedicated set-up was implemented, to characterize the sensors versus pressure and temperature. The achieved pressure accuracy is satisfactory (±0.56 mbar). However, discontinuities in the response curve and residual temperature sensitivity were observed. Further experiments, modeling and simulations were used to analyze the observed phenomena. They were shown to arise essentially from the presence of growing thermo-mechanical strain and stress fields, generated in the bimorph-like LN/Si structure, when the temperature changes. In particular, buckling effects explain the discontinuities, observed around 43 °C, in the response curves. Possible solutions are suggested and discussed.
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Buyak, N., V. Deshko, I. Bilous, M. Gureev e O. Holubenko. "EN Assessment of the window replacement influence on building energy consumption and human thermal comfort on the basis of dynamic modeling". Refrigeration Engineering and Technology 55, n. 5-6 (28 marzo 2020): 282–92. http://dx.doi.org/10.15673/ret.v55i5-6.1656.
Testo completoAbstract (sommario):
The dynamic modeling of the energy characteristics of building structures with the help of energy-saving double-glazed windows was carried out in the work. The influence of different variants of windows replacement on the heat energy state of a typical mass building for various glazing coefficients in dynamic grid models created on the basis of the Energy Plus software product was analyzed. It is found that argon-filled glass, selective-coated glass on the outer and inner glass can reduce the energy requirement for the building by 8-10% compared to the double-glazed glass without selectively coating and filling the chambers with air. The load on the heating system is significantly different for the orientations North and South. It is assumed that the coefficient of glassy glass in the orientation of the South during the off-season (autumn / spring), less heating (switched on / off later). For North and South orientations, energy-saving windows with selective coating and / or filled up with inert gas cells have a different effect, which is explained by the coefficients of solar heat transmission, which was obtained on the basis of the simulation model. In addition, current standards in Ukraine do not provide all variants of the coefficients of optical transmittance characteristics of solar heat gains. In this work, a dynamic hourly simulation of the building energy demand in heated space for representative rooms N and S oriented for different glazing coefficients and window types has been carried out. Range of PMV change, average radiating temperature and air temperature in the room for the heating period were estimated. It was established that changing windows glazing can affect the PMV to change almost two times, which indicates the need for an integrated approach to the assessment of thermal comfort. Namely, the importance of taking into account the dynamic changes in the environment parameters and possible thermo-modernization were detected
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Yaqoob, M. Z., Ahtisham Ali, Majeed A. S. Alkanhal, A. Ghaffar, Y. Khan e M. Umair. "Temperature-Dependent Electromagnetic Surface Wave Supported by Graphene-Loaded Indium Antimonide Planar Structure". International Journal of Optics 2024 (5 gennaio 2024): 1–10. http://dx.doi.org/10.1155/2024/9607121.
Testo completoAbstract (sommario):
In this study, the propagation characteristics of EM surface waves supported by the graphene-coated indium antimonide (InSb) planar waveguide have been investigated theoretically and numerically. The modeling of graphene has been performed by use of Kubo formalism whereas the relative permittivity of indium antimonide has been calculated using Drude’s model. The results for transverse electric (TE) and transverse magnetic (TM) polarized surface waves have been computed analytically and numerically. The major challenge is to model the atomically thick graphene sheet over the InSb grounded slab. To get the temperature-dependent characteristic equation for the electromagnetic surface waves, the surface current boundary conditions’ approach has been employed. The numerical results have been computed for both the TE and TM polarization states and reported that the TE does not support the propagation of surface waves. The dispersion relation, effective mode index, phase speed, propagation length, and field profile have been computed in Mathematica under TM polarization. The graphene and indium antimonide have been found active for low and high Terahertz regions, respectively. As temperature increases, the plasma frequency of the InSb increases due to this reason with the increase of temperature and the resonance frequency, leading to a shift in the dispersion curve. Moreover, with the increase of temperature, the effective wave number of transverse magnetic polarized surface waves also increases. Resultantly, the confinement of such surface waves supported by graphene-loaded InSb increases. It is shown that with the variation of temperature of indium antimonide, the surface waves propagating across the interface can be tuned in the Terahertz region and can be exploited for thermo-optical sensing, near-field communications waveguides, and graphene-based temperature sensor designing.
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Sala, Filip. "Beam splitting in chiral nematic liquid crystals". Photonics Letters of Poland 10, n. 4 (31 dicembre 2018): 109. http://dx.doi.org/10.4302/plp.v10i4.867.
Testo completoAbstract (sommario):
By lunching the beam into the chiral nematic liquid crystals it is possible to achieve a non-diffractive beam similar to a soliton. This effect is caused by the molecular reorientation i.e. nonlinear response of the material forming the areas of higher refractive index. Diffraction is suppressed by the focusing effect. For appropriate launching conditions it is also possible to achieve a beam which splits into two or more separate beams. Such phenomenon is discussed in this article and analyzed theoretical. To model this effect Fully Vectorial Beam Propagation Method coupled with the Frank-Oseen elastic theory is used. Simulations are performed for various input beam powers, widths, polarization angles and launching positions. Full Text: PDF ReferencesG. Assanto and M. A. Karpierz, "Nematicons: self-localised beams in nematic liquid crystals", Liq. Cryst. 36, 1161–1172 (2009) CrossRef G. Assanto, Nematicons: Spatial Optical Solitons in Nematic Liquid Crystals, John Wiley & Sons Inc. Hoboken, New Jersey (2013) DirectLink A. Piccardi, A. Alberucci, U. Bortolozzo, S. Residori, and G. Assanto, "Soliton gating and switching in liquid crystal light valve", Appl. Phys. Lett. 96, 071104 (2010). CrossRef D. Melo, I. Fernandes, F. Moraes, S. Fumeron, and E. Pereira, "Thermal diode made by nematic liquid crystal", Phys. Lett. A 380, 3121 – 3127 (2016). CrossRef U. Laudyn, M. Kwaśny, F. A. Sala, M. A. Karpierz, N. F. Smyth, G. Assanto, "Curved optical solitons subject to transverse acceleration in reorientational soft matter", Sci. Rep. 7, 12385 (2017) CrossRef M. Kwaśny, U. A. Laudyn, F. A. Sala, A. Alberucci, M. A. Karpierz, G. Assanto, "Self-guided beams in low-birefringence nematic liquid crystals", Phys. Rev. A 86, 013824 (2012) CrossRef F. A. Sala, M. M. Sala-Tefelska, "Optical steering of mutual capacitance in a nematic liquid crystal cell", J. Opt. Soc. Am. B. 35, 133-139 (2018) CrossRef U. A. Laudyn, A. Piccardi, M. Kwasny, M. A. Karpierz, G. Assanto, "Thermo-optic soliton routing in nematic liquid crystals", Opt. Lett. 43, 2296-2299 (2018) CrossRef F. A. Sala, M. M. Sala-Tefelska, M. J. Bujok, J. "Influence of temperature diffusion on molecular reorientation in nematic liquid crystals", Nonlinear Opt. Phys. Mater. 27, 1850011 (2018) CrossRef I-C Khoo Liquid crystals John Wiley & Sons, Inc (2007) DirectLink P. G. de Gennes, J. Prost, The Physics of Liquid Crystals, Clarendon Press (1995) DirectLink U. A. Laudyn, P. S. Jung, M. A. Karpierz, G. Assanto, "Quasi two-dimensional astigmatic solitons in soft chiral metastructures", Sci. Rep. 6, 22923 (2016) CrossRef J. Beeckman, A. Madani, P. J. M. Vanbrabant, P. Henneaux, S-P. Gorza, M. Haelterman, "Switching and intrinsic position bistability of soliton beams in chiral nematic liquid crystals", Phys. Rev. A 83, 033832 (2011) CrossRef A. Madani, J. Beeckman, K. Neyts, "An experimental observation of a spatial optical soliton beam and self splitting of beam into two soliton beams in chiral nematic liquid crystal", Opt. Commun. 298–299, 222-226, (2013) CrossRef G. D. Ziogos, E. E. Kriezis, "Modeling light propagation in liquid crystal devices with a 3-D full-vector finite-element beam propagation method", Opt. Quant. Electron 40, 10 (2008) CrossRef F. A. Sala, M. A. Karpierz, "Chiral and nonchiral nematic liquid-crystal reorientation induced by inhomogeneous electric fields", J. Opt. Soc. Am. B 29, 1465-1472 (2012) CrossRef F. A. Sala, M. A. Karpierz, "Modeling of molecular reorientation and beam propagation in chiral and non-chiral nematic liquid crystals", Opt. Express 20, 13923-13938 (2012) CrossRef F. A. Sala, "Design of false color palettes for grayscale reproduction", Displays, 46, 9-15 (2017) CrossRef
29
Sanchis, E., L. Testi, A. Natta, S. Facchini, C. F. Manara, A. Miotello, B. Ercolano et al. "Measuring the ratio of the gas and dust emission radii of protoplanetary disks in the Lupus star-forming region". Astronomy & Astrophysics 649 (28 aprile 2021): A19. http://dx.doi.org/10.1051/0004-6361/202039733.
Testo completoAbstract (sommario):
We performed a comprehensive demographic study of the CO extent relative to dust of the disk population in the Lupus clouds in order to find indications of dust evolution and possible correlations with other disk properties. We increased the number of disks of the region with measured RCO and Rdust from observations with the Atacama Large Millimeter/submillimeter Array to 42, based on the gas emission in the 12CO J = 2−1 rotational transition and large dust grains emission at ~0.89 mm. The CO integrated emission map is modeled with an elliptical Gaussian or Nuker function, depending on the quantified residuals; the continuum is fit to a Nuker profile from interferometric modeling. The CO and dust sizes, namely the radii enclosing a certain fraction of the respective total flux (e.g., R68%), are inferred from the modeling. The CO emission is more extended than the dust continuum, with a R68%CO/R68%dust median value of 2.5, for the entire population and for a subsample with high completeness. Six disks, around 15% of the Lupus disk population, have a size ratio above 4. Based on thermo-chemical modeling, this value can only be explained if the disk has undergone grain growth and radial drift. These disks do not have unusual properties, and their properties spread across the population’s ranges of stellar mass (M⋆), disk mass (Mdisk), CO and dust sizes (RCO, Rdust), and mass accretion of the entire population. We searched for correlations between the size ratio and M⋆, Mdisk, RCO, and Rdust: only a weak monotonic anticorrelation with the Rdust is found, which would imply that dust evolution is more prominent in more compact dusty disks. The lack of strong correlations is remarkable: the sample covers a wide range of stellar and disk properties, and the majority of the disks have very similar size ratios. This result suggests that the bulk of the disk population may behave alike and be in a similar evolutionary stage, independent of the stellar and disk properties. These results should be further investigated, since the optical depth difference between CO and dust continuum might play a major role in the observed size ratios of the population. Lastly, we find a monotonic correlation between the CO flux and the CO size. The results for the majority of the disks are consistent with optically thick emission and an average CO temperature of around 30 K; however, the exact value of the temperature is difficult to constrain.
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Krokhalev, A. V., V. O. Kharlamov, S. V. Kuzmin e V. I. Lysak. "FUNDAMENTALS OF WEAR-RESISTANT COATING PRODUCTION FROM CHROMIUM CARBIDE POWDER MIXTURE WITH BINDER METAL BY EXPLOSIVE COMPACTION". Izvestiya Vuzov Tsvetnaya Metallurgiya (Proceedings of Higher Schools Nonferrous Metallurgy, n. 3 (14 giugno 2018): 68–83. http://dx.doi.org/10.17073/0021-3438-2018-3-68-83.
Testo completoAbstract (sommario):
The article presents experimental data on explosive compaction of chromium carbide (Cr3C2) powder mixtures with metals (Ti, Ni, Cu) provided with theoretical explanations. These data were used as a basis for stating science-based principles of composition selection and technology development to produce antifriction wear-resistant chromium carbide hard alloys and coatings by explosion. Explosive compaction of powder mixtures was carried out according to a scheme using a normally incident plane detonation wave in a wide range of loading parameters (powder heating temperature in shock waves varied from 200 to1000 °Cand maximum shock compression pressure varied from 4 to 16 GPa during experiments). Phase transformation analysis was carried out by the numerical thermodynamic modeling of phase equilibrium using the Thermo-Calc software. Microstructure, chemical and phase compositions were studied using optical («Axiovert 40МАТ» by CarlZeiss,Germany), scanning («Versa 3D» and «Quanta 3D FEG» byFEI,USA), transmission («BS 540» byTesla,Czech Republic, «Titan 80-300» and «Tecnai G2 20F» byFEI,USA) electron microscopes and «Solver Pro» atomic force microscope (LLC «NT-MDT», Zelenograd). Temperature stability and oxidation resistance at elevated temperatures of the materials obtained by explosion was studied using thermogravimetric analysis (TGA) using the «STA 449 F3 Jupiter» instrument (NETZSCH, Germany) in the synthetic air environment when heated to1500 °C. Tribological tests were carried out on the MI-1M friction machine (MEZIMiV,Moscow) according to the pin-on-ring scheme with plunging in distilled water environment. The mechanisms of consolidation and formation of strong boundaries between powder material particles during explosive compaction are described. It is shown that hard alloys of chromium carbide with titanium bond obtained by explosion retain their phase compositions without any changes and resist to oxidation up to600 °C, and also have significantly better anti-friction properties and wear resistance than the SGP-0,5 and KHN-20 materials used in water-lubricated friction couples until the present time.
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Stober, Jörg, Martin Schubert, Mireille Schneider, Severin S. Denk, Rainer Fischer, Emanuele Poli, Dirk Stieglitz, Matthias Willensdorfer, Alberto Loarte e Daria Ricci. "Quantification of X3 absorption for ITER L-mode parameters in ASDEX Upgrade". EPJ Web of Conferences 277 (2023): 02007. http://dx.doi.org/10.1051/epjconf/202327702007.
Testo completoAbstract (sommario):
For an early H-mode access in hydrogen, ITER considers operating at 1/3 of the full field using 170 GHz X-Mode for heating at the 3rd harmonic. The optical thickness for such a heating scheme depends on Te2. It is rather low in the ohmic phase (with Te about 1-2 keV), but reaches high single pass absorption for the strongly EC heated plasma with Te exceeding 10 keV. Launching ECRH into an ohmic plasma may trigger a boot-strap process on Te if the additional power absorption due to increasing Te exceeds the additional power losses due to increased transport (which often tends to increase with input power). In this contribution we present measurements of the X3 absorption for the parameter range relevant for ITER, i.e. ne 2 1019 m−3, Te 2 keV in order to back up theoretical estimates used for the modeling so far. In ASDEX Upgrade (AUG) such low densities cannot be reached in H-mode such that dominant heating with NBI is not an option. For moderate Te, it is also not an option to use X3 heating as main heating, due to the excessive stray radiation threatening in-vessel components. This dilemma is solved with the 2-frequency EC system of AUG. The main central heating is done with the lower frequency of 105 GHz at the 2nd harmonic and full single pass absorption. Up to 3.5 MW of ECRH are used at that frequency to vary Te. Two other gyrotrons are used at 140 GHz to probe the X3 interaction close to the plasma center with a sequence of short blips. The expected values of single pass absorption are calculated with TORBEAM and vary from 7% to 70%. Below 40% single pass absorption the non-absorbed power triggers an arc in the tile gaps of the inner heat shield which screens the thermo-couples from the incoming beam such that they cannot be used. Between 40% and 80% single pass absorption, the predictions and measurements agree within the uncertainty of the measurement, unless we have clear evidence for non-linear interactions, which are not described by TORBEAM and which are not expected in ITER, but are due to some specific experimental choices for an isolated subset of our results.
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Myhre, G., e A. Grini. "Modelling of nitrate particles: importance of sea salt". Atmospheric Chemistry and Physics Discussions 6, n. 1 (22 febbraio 2006): 1455–80. http://dx.doi.org/10.5194/acpd-6-1455-2006.
Testo completoAbstract (sommario):
Abstract. A thermo dynamical model for treatment of gas/aerosol partitioning of semi volatile inorganic aerosols has been implemented in a global chemistry and aerosol transport model (Oslo CTM2). The sulphur cycle and sea salt particles have been implemented earlier in the Oslo CTM2 and the focus of this study is on whether nitrate particles are formed as fine mode ammonium nitrate or react on existing sea salt particles. The model results show that ammonium nitrate particles play a non-negligible role in the total aerosol composition in certain industrialized regions and therefore have a significant local radiative forcing. On a global scale the aerosol optical depth of ammonium nitrate is relatively small due to limited availability of ammonia and reaction with sea salt particles. Inclusion of sea salt in the calculations reduces the aerosol optical depth and burden of ammonium nitrate particles by 25% on a global scale but with large regional variations.
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Heim, Dariusz, Dominika Knera e Anna Machniewicz. "Modelling of Thermo-optical Properties of Amorphous and Microcrystalline Silicon Semitransparent PV Layer". Energy Procedia 78 (novembre 2015): 430–34. http://dx.doi.org/10.1016/j.egypro.2015.11.688.
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Aussavy, Delphine, Rodolphe Bolot, François Peyraut, Ghislain Montavon e Serge Selezneff. "Thermomechanical Properties of CoNiCrAlY-BN-Polyester Composite Coatings Elaborated by Atmospheric Plasma Spraying". Key Engineering Materials 606 (marzo 2014): 167–70. http://dx.doi.org/10.4028/www.scientific.net/kem.606.167.
Testo completoAbstract (sommario):
This study concerns the mechanical properties of CoNiCrAlY-BN-Polyester composite coatings elaborated by Atmospheric Plasma Spray (APS) and used as abradable seals in the aeronautic industry. The objective is to determine the influence of the diameter of the plasma torch on the coating micrograph morphologies and on the resulting coating thermal and mechanical effective properties. The thermo-mechanical effective properties were then estimated by Finite Element modelling (thanks to the multipurpose finite element software ANSYS) based on coating microstructures captured by Scanning Electron Microscopy (SEM) and Optical Microscopy (OM)
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Kim, Hansung, Da Xu, Ciby John e Yaqiong Wu. "Modeling Thermo-Mechanical Stress of Flexible CIGS Solar Cells". IEEE Journal of Photovoltaics 9, n. 2 (marzo 2019): 499–505. http://dx.doi.org/10.1109/jphotov.2019.2892531.
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van Driel, W. D., G. Q. Zhang, J. H. J. Janssen e L. J. Ernst. "Response Surface Modeling for Nonlinear Packaging Stresses". Journal of Electronic Packaging 125, n. 4 (1 dicembre 2003): 490–97. http://dx.doi.org/10.1115/1.1604149.
Testo completoAbstract (sommario):
The present study focuses on the development of reliable response surface models (RSM’s) for the major packaging processes of a typical electronic package. The major objective is to optimize the product/process designs against the possible failure mode of vertical die cracks. First, the finite element mode (FEM)-based physics of failure models are developed and the reliability of the predicted stress levels was verified by experiments. In the development of reliable thermo-mechanical simulation models, both the process (time and temperature) dependent material nonlinearity and geometric nonlinearity are taken into account. Afterwards, RSM’s covering the whole specified geometric design spaces are constructed. Finally, these RSM’s are used to predict, evaluate, optimize, and eventually qualify the thermo-mechanical behavior of this electronic package against the actual design requirements prior to major physical prototyping and manufacturing investments.
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Carmona, M., S. Marco, J. Samitier, M. C. Acero, J. A. Plaza e J. Esteve. "Modeling the Thermal Actuation in a Thermo-Pneumatic Micropump". Journal of Electronic Packaging 125, n. 4 (1 dicembre 2003): 527–30. http://dx.doi.org/10.1115/1.1604154.
Testo completoAbstract (sommario):
The analysis of a thermo-pneumatic actuation unit for its use in a micropump has been carried out. Coupled thermo-mechanical simulations by finite element method (FEM) (with ANSYS software) were required because of the complexity of the device. The simulation results were validated by thermal and mechanical experimental results, showing a good agreement. FEM results have been used to extract a high level model of the actuation unit that can be used to estimate the maximum performance of the micropump operation with this actuation unit. In order to identify the best frequency of operation for the pump, a quality parameter has been defined based on the thermal dynamics of the actuation unit.
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Górecki, Krzysztof, e Przemysław Ptak. "Compact Modelling of Electrical, Optical and Thermal Properties of Multi-Colour Power LEDs Operating on a Common PCB". Energies 14, n. 5 (26 febbraio 2021): 1286. http://dx.doi.org/10.3390/en14051286.
Testo completoAbstract (sommario):
This paper concerns the problem of modelling electrical, thermal and optical properties of multi-colour power light-emitting diodes (LEDs) situated on a common PCB (Printed Circuit Board). A new form of electro-thermo-optical model of such power LEDs is proposed in the form of a subcircuit for SPICE (Simulation Program with Integrated Circuits Emphasis). With the use of this model, the currents and voltages of the considered devices, their junction temperature and selected radiometric parameters can be calculated, taking into account self-heating phenomena in each LED and mutual thermal couplings between each pair of the considered devices. The form of the formulated model is described, and a manner of parameter estimation is also proposed. The correctness and usefulness of the proposed model are verified experimentally for six power LEDs emitting light of different colours and mounted on an experimental PCB prepared by the producer of the investigated devices. Verification was performed for the investigated diodes operating alone and together. Good agreement between the results of measurements and computations was obtained. It was also proved that the main thermal and optical parameters of the investigated LEDs depend on a dominant wavelength of the emitted light.
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Jiang, Jianliang, Ulrich Hilleringmann e Xiaoping Shui. "Electro-thermo-mechanical analytical modeling of multilayer cantilever microactuator". Sensors and Actuators A: Physical 137, n. 2 (luglio 2007): 302–7. http://dx.doi.org/10.1016/j.sna.2007.03.012.
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Papingiotis, Theodoros, Dimitrios N. Korres, Irene Koronaki e Christos Tzivanidis. "Energetical and Exergetical Analyses of a Concentrating PV/T Collector: A Numerical Approach". Applied Sciences 13, n. 19 (25 settembre 2023): 10669. http://dx.doi.org/10.3390/app131910669.
Testo completoAbstract (sommario):
The specific work presents an optical and thermal investigation of a hybrid thermo-photovoltaic solar collector with an asymmetrical compound parabolic mirror. Such collectors offer an innovative and sustainable approach to address both the thermal and electrical demands of residents on islands using renewable sources of energy and thus reducing the dependency on fossil fuels. The main goal of this investigation involves an analysis of the prementioned type of solar collector, incorporating an innovative and cost-effective numerical modelling technique aiming to enhance comprehension of its energy and exergy performance. The optical performance of the collector was calculated first with ray tracing for the month of June, and the ideal slope was determined for the same month. After the optical analysis, the energy and exergy performance were both estimated by implementing a novel numerical method in both COMSOL and SolidWorks. Based on the optical analysis, it was determined that the most favorable inclination angle for achieving optimum optical efficiency on the mean day of June is 10°. The thermal analysis, focusing on thermal efficiency, showed a maximum deviation of 5.3% between the two solutions, which indicates the reliability of the method. The collector achieved a maximum thermal efficiency of 58.55% and a maximum exergy efficiency of 16.94%.
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Shen, Y. L. "Thermo-mechanical stresses in copper interconnects – A modeling analysis". Microelectronic Engineering 83, n. 3 (marzo 2006): 446–59. http://dx.doi.org/10.1016/j.mee.2005.11.009.
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Trajin, Baptiste, e Paul-Etienne Vidal. "Bond graph multi-physics modeling of encapsulating materials in power electronic modules". European Physical Journal Applied Physics 89, n. 2 (febbraio 2020): 20902. http://dx.doi.org/10.1051/epjap/2020180287.
Testo completoAbstract (sommario):
This paper focuses on multi-physics modeling of encapsulating gels in power electronic modules for transient and steady-state simulation. With the emergence of wide-bandgap semiconductors such as SiC or GaN, operating at a higher temperature than conventional Si power chips, this passive element of the packaging appears as a few studied element sensitive to thermal and mechanical stresses. A thermo-mechanical coupled modeling of the material, based on bond graph representation, is presented. This approach allows to establish, under the same formalism, an analogy between the different physical domains. From this analogy, a multi-physical nonlinear state space representation is built, allowing transient simulation of the thermo-mechanical behavior of the material. This way of modeling and simulating is particularly adapted for a preliminary study during the upstream phases of design of the power electronic modules. It quickly establishes the maximum temperature and mechanical strains experienced by the gel.
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Boutelier, D., e O. Oncken. "3-D thermo-mechanical laboratory modelling of plate-tectonics". Solid Earth Discussions 3, n. 1 (18 febbraio 2011): 105–47. http://dx.doi.org/10.5194/sed-3-105-2011.
Testo completoAbstract (sommario):
Abstract. We present an experimental apparatus for 3-D thermo-mechanical analogue modelling of plate-tectonics processes such as oceanic and continental subductions, arc-continent or continental collisions. The model lithosphere, made of temperature-sensitive elasto-plastic with softening analogue materials, is submitted to a constant temperature gradient producing a strength reduction with depth in each layer. The surface temperature is imposed using infrared emitters, which allows maintaining an unobstructed view of the model surface and the use of a high resolution optical strain monitoring technique (Particle Imaging Velocimetry). Subduction experiments illustrate how the stress conditions on the interplate zone can be estimated using a force sensor attached to the back of the upper plate and changed because of the density and strength of the subducting lithosphere or the lubrication of the plate boundary. The first experimental results reveal the potential of the experimental set-up to investigate the three-dimensional solid-mechanics interactions of lithospheric plates in multiple natural situations.
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Venkatachalam, A., W. T. James e S. Graham. "Electro-thermo-mechanical modeling of GaN-based HFETs and MOSHFETs". Semiconductor Science and Technology 26, n. 8 (8 giugno 2011): 085027. http://dx.doi.org/10.1088/0268-1242/26/8/085027.
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Luzi, Giovanni, Seunghyeon Lee, Bernhard Gatternig e Antonio Delgado. "An Asymptotic Energy Equation for Modelling Thermo Fluid Dynamics in the Optical Fibre Drawing Process". Energies 15, n. 21 (25 ottobre 2022): 7922. http://dx.doi.org/10.3390/en15217922.
Testo completoAbstract (sommario):
Microstructured optical fibres (MOFs) are fibres that contain an array of air holes that runs through the whole fibre length. The hole pattern of these fibres can be customized to manufacture optical devices for different applications ranging from high-power energy transmission equipment to telecommunications and optical sensors. During the drawing process, the size of the preform is greatly scaled down and the original hole pattern result might be modified, potentially leading to unwanted optical effects. Because only a few parameters can be controlled during the fabrication process, mathematical models that can accurately describe the fibre drawing process are highly desirable, being powerful predictive tools that are significantly cheaper than costly experiments. In this manuscript, we derive a new asymptotic energy equation for the drawing process of a single annular capillary and couple it with existing asymptotic mass, momentum, and evolution equations. The whole asymptotic model only exploits the small aspect ratio of a capillary and relies on neither a fitting procedure nor on any empirical adjustable parameters. The numerical results of the simplified model are in good accordance with experimental data available in the literature both without inner pressurization and when internal pressure is applied. Although valid only for annular capillaries, the present model can provide important insights towards understanding the MOF manufacturing process and improving less detailed approaches for more complicated geometries.
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Ramdane, Brahim, Didier Trichet, Mohamed Belkadi e Javad Fouladgar. "3-D Numerical Modeling of the Thermo-Inductive Technique Using Shell Elements". IEEE Transactions on Magnetics 46, n. 8 (agosto 2010): 3037–40. http://dx.doi.org/10.1109/tmag.2010.2044022.
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Woliński, Tomasz, Sławomir Ertman, Katarzyna Rutkowska, Daniel Budaszewski, Marzena Sala-Tefelska, Miłosz Chychłowski, Kamil Orzechowski, Karolina Bednarska e Piotr Lesiak. "Photonic Liquid Crystal Fibers – 15 years of research activities at Warsaw University of Technology". Photonics Letters of Poland 11, n. 2 (1 luglio 2019): 22. http://dx.doi.org/10.4302/plp.v11i2.907.
Testo completoAbstract (sommario):
Research activities in the area of photonic liquid crystal fibers carried out over the last 15 years at Warsaw University of Technology (WUT) have been reviewed and current research directions that include metallic nanoparticles doping to enhance electro-optical properties of the photonic liquid crystal fibers are presented. Full Text: PDF ReferencesT.R. Woliński et al., "Propagation effects in a photonic crystal fiber filled with a low-birefringence liquid crystal", Proc. SPIE, 5518, 232-237 (2004). CrossRef F. Du, Y-Q. Lu, S.-T. Wu, "Electrically tunable liquid-crystal photonic crystal fiber", Appl. Phys. Lett. 85, 2181-2183 (2004). CrossRef T.T. Larsen, A. Bjraklev, D.S. Hermann, J. Broeng, "Optical devices based on liquid crystal photonic bandgap fibres", Opt. Express, 11, 20, 2589-2596 (2003). CrossRef T.R. Woliński et al., "Tunable properties of light propagation in photonic liquid crystal fibers", Opto-Electron. Rev. 13, 2, 59-64 (2005). CrossRef M. Chychłowski, S. Ertman, T.R. 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Rożek, A., S. C. Lowry, B. Rozitis, S. F. Green, C. Snodgrass, P. R. Weissman, A. Fitzsimmons et al. "Physical model of near-Earth asteroid (1917) Cuyo from ground-based optical and thermal-IR observations". Astronomy & Astrophysics 627 (luglio 2019): A172. http://dx.doi.org/10.1051/0004-6361/201834162.
Testo completoAbstract (sommario):
Context. The near-Earth asteroid (1917) Cuyo was subject to radar and light curve observations during a close approach in 1989, and observed up until 2008. It was selected as one of our ESO Large Programme targets, aimed at observational detections of the Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect through long-term light curve monitoring and physical modelling of near-Earth asteroids. Aims. We aim to constrain the physical properties of Cuyo: shape, spin-state, and spectroscopic and thermo-physical properties of the surface. Methods. We acquired photometric light curves of Cuyo spanning the period between 2010 and 2013, which we combined with published light curves from 1989 to 2008. Our thermal-infrared observations were obtained in 2011. Rotationally resolved optical spectroscopy data were acquired in 2011 and combined with all available published spectra to investigate any surface material variegation. Results. We developed a convex light curve-inversion shape of Cuyo that suggests the presence of an equatorial ridge, typical for an evolved system close to shedding mass due to fast rotation. We determine limits of YORP strength through light curve-based spin-state modelling, including both negative and positive acceleration values, between − 0.7 × 10−8 and 1.7 × 10−8 rad day−2. Thermo-physical modelling with the ATPM provides constraints on the geometric albedo, pV = 0.24 ± 0.07, the effective diameter, Deff = 3.15 ± 0.08 km, the thermal inertia, Γ = 44 ± 9 J m−2 s−1∕2 K−1, and a roughness fraction of 0.52 ± 0.26. This enabled a YORP strength prediction of ν = (−6.39 ± 0.96) × 10−10 rad day−2. We also see evidence of surface compositional variation. Conclusions. The low value of YORP predicted by means of thermo-physical analysis, consistent with the results of the light curve study, might be due to the self-limiting properties of rotational YORP, possibly involving movement of sub-surface and surface material. This may also be consistent with the surface compositional variation that we see. The physical model of Cuyo can be used to investigate cohesive forces as a way to explain why some targets survive rotation rates faster than the fission limit.
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Babilotte, Philippe. "Simulation of multiwavelength conditions in laser picosecond ultrasonics". SIMULATION 97, n. 7 (25 marzo 2021): 473–84. http://dx.doi.org/10.1177/0037549721996451.
Testo completoAbstract (sommario):
Complete numerical simulations are given under SciLab® and MATLAB® coding environments, concerning propagative acoustic wavefronts, for laser picosecond ultrasonics under multiwavelength conditions. Simulations of the deformation field and its propagation into bulk material are given under different wavelength configurations for optical pump and probe beams, which are used to generate and to detect the acoustic signal. Complete insights concerning the dynamics of the acoustic waves are given, considering the absence of carrier diffusions into the material. Several numerical approaches are proposed concerning both the functions introduced to simulate the wavefront ( Heaviside or error) and the coding approach (linear/vectorized/ Oriented Object Programming), under the pure thermo-elastic approach.
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Bui, Huu Kien, Guillaume Wasselynck, Didier Trichet, Brahim Ramdane, Gerard Berthiau e Javad Fouladgar. "3-D Modeling of Thermo Inductive Non Destructive Testing Method Applied to Multilayer Composite". IEEE Transactions on Magnetics 49, n. 5 (maggio 2013): 1949–52. http://dx.doi.org/10.1109/tmag.2013.2241037.
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