Thermal Response Of Structure Research Articles

Thermostructural Responses of Metallic Lattice-Frame Sandwich Structure for Hypersonic Leading Edges

Metallic lattice-frame materials, due to excellent heat transfer performance under high heat flux and mechanical property, are regarded as the potential candidates for a vehicle leading edge. This paper presents a new-style lattice-frame sandwich panel with active heat transfer wall-plate. The heat transfer performance and thermal–structural responses are numerically studied, considering the temperature-dependent mechanical and thermal properties. The effects of geometrical characteristics of the wall-plate channel on heat exchange and hydraulic behavior are explored. The different parent materials and channel types are respectively compared based on the thermal–structural responses of sandwich structure. A relatively optimized sandwich panel is employed as the vehicle leading edge, and the effects of attack angle on heat transfer and thermostructural behavior are discussed, subjected to intense localized heat flux. The metallic lattice-frame sandwich panel with an active heat exchange wall-plate shows attractive potential for a higher- temperature leading edge, which can withstand the hypersonic thermal–mechanical environment. It can still offer a great improvement space in thermal management as leading edges for hypersonic vehicles.

Femtosecond Laser-Induced Periodic Surface Structures on 2D Ti-Fe Multilayer Condensates.

2D Ti-Fe multilayer preparation has been attracting increased interest due to its ability to form intermetallic compounds between metallic titanium and metallic iron thin layers. In particular, the TiFe compound can absorb hydrogen gas at room temperature. We applied femtosecond laser pulses to heat Ti-Fe multilayer structures to promote the appearance of intermetallic compounds and generate surface nanostructuring. The surface pattern, known as Laser Induced Periodic Surface Structures (LIPSS), can accelerate the kinetics of chemical interaction between solid TiFe and gaseous hydrogen. The formation of LIPSS on Ti-Fe multilayered thin films were investigated using of scanning electron microscopy, photo-electron spectroscopy and X-ray diffraction. To explore the thermal response of the multiple layered structure and the mechanisms leading to surface patterning after irradiating the compound with single laser pulses, theoretical simulations were conducted to interpret the experimental observations.

Different Thermal Responses of Local Structures in Pd43Cu27Ni10P20 Alloy from Glass to Liquid

Different thermal responses of local atomic packing structures in a Pd43Cu27Ni10P20 alloy from glass to liquid have been studied by in situ high-energy X-ray diffraction together with ab initio mol...

Outstanding thermo-mechanical properties of graphene-like B3C3 and C3N3

Experimentally fabricated two-dimensional (2D) carbon-based nanomaterials have received significant attention because of their ultra-high physical properties, in recent years. In this manuscript, the thermal conductivity (TC) and mechanical response of 2D B3C3 and C3N3 structures are studied in detail, using molecular dynamics (MD) simulations. Their superior mechanical properties (Young’s modulus, ultimate tensile strength and failure strain) and TC make an excellent candidate for various applications of nanodevices. The mechanical properties of these 2D structures are also examined at five various temperatures up to 900 K along with the different loading directions and various strain rates from 107 to 109 s−1. MD results demonstrate that the mechanical properties of these 2D structures gradually decrease as temperature increases, due to the weakening effect of high temprerature. Additionally, when the strain rate increases, it is revealed that the mechanical properties show an increasing trend. Furthermore, at 300 K, the failure processes of these 2D structures are studied. MD simulations results demonstrate that these structures show brittle failure mechanism. On the other hand, various types of structural defects occurs during the production process and so these defects affect the physical properties of these structures adversely. Accordingly, the effects of various atom types, such as, N, B and C, vacancy defects on the mechanical properties and TC of these structures were investigated. The existence of vacancy defects in these structures reduces the TC and mechanical properties significantly by increasing the concentrations of defects. Finally, non-equilibrium MD simulations results indicate exceptionally high TC values of these structures.

Symmetric modeling of the thermal actions in a structural fire experiment on a long-span composite floor beam in a compartment

This paper presents symmetric modeling of the thermal actions in a structural fire experiment on a 12.8 m long composite floor beam in a compartment. A quarter of the fire compartment was modeled in FDS and a portion of about 1/160 of the composite beam was modeled in ANSYS. The FDS symmetry model gave consistent results with the FDS model of the entire compartment, the differences between the predicted upper layer gas temperatures were within 2 ∘C on average. The differences between the FDS symmetry model predicted upper layer gas temperatures and the experimental data were within 7% at the steady stage. Using the thermal boundaries predicted by the FDS symmetry model, the finite element symmetry model gave good prediction of the lower flange and mid web steel temperatures of the composite beam, the differences between predicted and measured maximum lower flange and maximum mid web temperatures were within 2%. The study indicates that symmetry model might be used to predict the thermal responses of structures in realistic fires.

Adhesion layer influence on controlling the local temperature in plasmonic gold nanoholes.

Gold films do not adhere well on glass substrates, so plasmonics experiments typically use a thin adhesion layer of titanium or chromium to ensure a proper adhesion between the gold film and the glass substrate. While the absorption of light into gold structures is largely used to generate heat and control the temperature at the nanoscale, the influence of the adhesion layer on this process is largely overlooked. Here, we quantify the role of the adhesion layer in determining the local temperature increase around a single nanohole illuminated by a focused infrared laser. Despite their nanometer thickness, adhesion layers can absorb a greater fraction of the incoming infrared light than the 100 nm thick gold layer leading to a significant increase of the local temperature. Different experimental designs are explored, offering new ways to promote or avoid the temperature increase inside nanoapertures. This knowledge further expands the plasmonic toolbox for temperature-controlled experiments including single molecule sensing, nanopore translocation, polymerization, or nano-optical trapping.

Study on the performance of inflatable decelerator under hypersonic aerodynamic load

In order to understand the influence of hypersonic aerodynamic force and aerodynamic heat on the performance of flexible structure of inflatable decelerator, a unidirectional thermal-fluid-structure three field coupling model under the extreme conditions of reentry trajectory is established in this paper. The temperature distribution of thermal protection structure (TPS) and structure response are obtained. The numerical results show that the TPS has a good insulation effect, and the cooling contribution of insulation layer in TPS is up to 80.90%. The stress is concentrated at the contact position between the flexible structure and the blunt head. The stress of TPS layer fluctuates greatly.

The coupled thermal-structural response of RC beams during fire events based on nonlinear numerical simulation

In this paper and based on a previous work, a parametric study was executed to capture the crucial parameters that affect the response of reinforced concrete beams, whether the thermal response or the structural response. The aim behind the used methodology from the previous work was reaching a reliable algorithm that has the capability to simulate any reinforced concrete element under both mechanical and fire loads. This algorithm is based on connecting thermal analysis and structural analysis with coupling technique called sequential coupling technique. This technique allow taking into consideration the non-linearity for thermal material properties such as conductivity, specific heat, and density, and also the non-linearity for mechanical properties such as stress-strain relationship, and thermal expansion coefficient, beside the nonlinearity for concrete compressive strength, and rebar ultimate strength. This algorithm is achieved through detailed numerical finite element models using ANSYS program. The main parameters that had been studied in this paper are the effect of increasing concrete compressive strength, increasing concrete cover, and the effect of increasing the lateral stiffness of the beam on the total response.

Design of an Athermal Interferometer Based on Tailored Subwavelength Metamaterials for On-Chip Microspectrometry

Temperature dependence is one of the main challenges of the silicon-on-insulator platform due to the large thermo-optic coefficient of its core material. In this work, to the best of our knowledge, we propose a design of an all-passive athermal silicon-on-insulator Mach-Zehnder interferometer (MZI) with the minimal temperature sensitivity reported to date. The MZI’s temperature compensation was achieved by optimizing the relative length of its wire and subwavelength arms and by tailoring the thermal response of the subwavelength structure. Simulations of the device performance showed that the overall temperature sensitivity of 7.5 pm/K could be achieved over a 100 nm spectral range near the 1550 nm region.

Hypersonic flow characteristics and relevant structure thermal response induced by the novel combined spike-aerodome and lateral jet strategy

Huge aerodynamic drag and severe aeroheating are the inevitable challenges for hypersonic vehicles, this paper proposes a novel combined spike-aerodome and lateral jet strategy for drag reduction and thermal protection. Meanwhile, the hypersonic flow characteristics and structure thermal response are numerically investigated by an in-house code. The obtained results demonstrate that this novel strategy not only further reduces the total drag, but also provides excellent thermal protection for both the blunt body and spike rod. Then the effects of lateral jet pressure ratio, spike length and aerodome diameter on the flow properties, drag and heat reduction performance are thoroughly explored. Increasing the lateral jet pressure ratio can effectively enhance the thermal protection. Surprisingly, in a certain range, higher lateral jet pressure ratio even leads to larger pressure peak value on the blunt body. Increasing the spike length would enhance the heat transfer along the blunt body surface, and the total drag changes non-monotonically as the spike length varies. The total drag rises significantly when the aerodome diameter increases, and it can be increased by 40.1% when the aerodome diameter ratio increases from 0.15 to 0.5. Besides, increasing the aerodome diameter is beneficial to remarkably enhance thermal protection.

Combined thermal phenomena of hypersonic vehicle

The combined thermal phenomena are a series of multi-factor coupling phenomena caused by the structural thermal response under the cumulative action of aerodynamic heating. The combined thermal phenomena, which will lead to a more significant time-space coupling effect on the multiple physics of hypersonic vehicle, is an important issue in the development of long-haul hypersonic vehicle in the future. This paper describes the connotation of the combined thermal phenomena by combining with the physical link of the aircraft system coupling phenomenon. The physical essence and prediction methods of the combined thermal problem are expounded in detail. The key issues affecting the combined thermal problem such as aerodynamics, aerodynamics/structure/trajectory coupling are discussed. The new progress in the research of coupling experimental verification is introduced. The extension of the combined thermal problem such as the multi-scale effect of the new composite thermal protection materials, the multi-system optimization design based on the multi-factor coupling method, and the influence of the cabin thermal effect on the heat protection system are discussed.

Gas-kinetic unified algorithm for computable modeling of Boltzmann equation and application to aerothermodynamics for falling disintegration of uncontrolled Tiangong-No.1 spacecraft

How to solve the hypersonic aerothermodynamics around large-scale uncontrolled spacecraft during falling disintegrated process from outer space to earth, is the key to resolve the problems of the uncontrolled Tiangong-No.1 spacecraft reentry crash. To study aerodynamics of spacecraft reentry covering various flow regimes, a Gas-Kinetic Unified Algorithm (GKUA) has been presented by computable modeling of the collision integral of the Boltzmann equation over tens of years. On this basis, the rotational and vibrational energy modes are considered as the independent variables of the gas molecular velocity distribution function, a kind of Boltzmann model equation involving in internal energy excitation is presented by decomposing the collision term of the Boltzmann equation into elastic and inelastic collision terms. Then, the gas-kinetic numerical scheme is constructed to capture the time evolution of the discretized velocity distribution functions by developing the discrete velocity ordinate method and numerical quadrature technique. The unified algorithm of the Boltzmann model equation involving thermodynamics non-equilibrium effect is presented for the whole range of flow regimes. The gas-kinetic massive parallel computing strategy is developed to solve the hypersonic aerothermodynamics with the processor cores 500~45,000 at least 80% parallel efficiency. To validate the accuracy of the GKUA, the hypersonic flows are simulated including the reentry Tiangong-1 spacecraft shape with the wide range of Knudsen numbers of 220~0.00005 by the comparison of the related results from the DSMC and N-S coupled methods, and the low-density tunnel experiment etc. For un-controlling spacecraft falling problem, the finite-element algorithm for dynamic thermal-force coupling response is presented, and the unified simulation of the thermal structural response and the hypersonic flow field is tested on the Tiangong-1 shape under reentry aerodynamic environment. Then, the forecasting analysis platform of end-of-life large-scale spacecraft flying track is established on the basis of ballistic computation combined with reentry aerothermodynamics and deformation failure/disintegration.

Experimental Model Design and Preliminary Numerical Verification of Fluid–Thermal–Structural Coupling Problem

Fluid–thermal–structural interactions in hypersonic flows is an extremely complex coupling problem, which puts forward higher requirements on the coupling calculation method and computational efficiency. It is of great significance to design a fluid–thermal–structural coupled ground test to verify the effectiveness of the coupling analysis tools. However, because of the demanding requirements of testing tools and equipment capabilities, no relevant research on full-coupling test has been reported. This study aims to design a reasonable test model, including the size, material, aerodynamic shape, and structure of the model, for verification of the fluid–thermal–structural coupling analysis tools. Based on existing materials and facilities, as well as coupling test requirements, the exploratory design of the test model is carried out. The feasibility of the model design is preliminarily verified using a stainless-steel model by a 10 s short-time test in the high-temperature hypersonic wind tunnel of China Aerodynamic Research and Development Center (CARDC) and in-house FL-CAPTER (Coupled Analysis Platform for Thermal Environment and Structure Response) platform, which is developed by CARDC. The 60 s long-time test model using superalloy is also calculated, which revealed that the effects of the fluid–thermal–structural coupling problem must be considered during the design of the new generation of airbreathing hypersonic vehicles.

Phase-field modeling of metallic powder-substrate interaction in laser melting process

Understanding fusion dynamics of metallic powders and powder-substrate interactions is important for reducing the defects, and thus improving surface and bulk quality of additive manufactured (AM) parts. Albeit recent advances in AM technology, there is a great need of theoretical analysis at the powder level to quantify and predict relevant mesoscale dynamics in the manufacturing process. We present a thermodynamically consistent phase-field modeling framework to integrate relevant thermal fluid phenomena and elastic structure response, including phase transition, thermal capillarity, interfacial deformation, and thermal stress induced by spot laser heating. The 2D results show that the fusion of pure titanium powder and titanium substrate can be significantly enhanced by the capillary effect when the partially melted powder is bridging the molten substrate, whereas the thermal-elastic deformation has a longer range effect, which is primarily influenced by the heating power of the laser beam.

Two-dimensional Modelling of Thermal Responses of GFRP Profiles Exposed to ISO-834 Fire

In the past three decades, one-dimensional (1-D) thermal model was usually used to estimate the thermal responses of glass fiber-reinforced polymer (GFRP) materials and structures. However, the temperature gradient and mechanical degradation of whole cross sections cannot be accurately evaluated. To address this issue, a two-dimensional (2-D) thermo-mechanical model was developed predict the thermal and mechanical responses of rectangular GFRP tubes subjected to one-side ISO-834 fire exposure in this paper. The 2-D governing heat transfer equations with thermal boundary conditions, discretized by alternating direction implicit (ADI) method, were solved by Gauss-Seidel iterative approach. Then the temperature-dependent mechanical responses were obtained by considering the elastic modulus degradation from glass transition and decomposition of resin. The temperatures of available experimental results can be reasonably predicted. This model can also be extended to simulate the thermo-mechanical responses of beams and columns subjected to multi-side fire loading, which may occur in real fire scenarios.

Effect of fire insulation on fire resistance of hybrid-fiber reinforced reactive powder concrete beams

This paper presents the result of tests conducted on four hybrid-fiber reinforced reactive powder concrete (RPC) beams protected with fire insulation exposed to fire. The thermal fields, structural responses, fire endurance, failure modes, and crack patterns of the beams were measured and recorded during the tests. The experimental results indicate that the failure of reinforced RPC beams with fire insulation was driven by direct fire exposure and fracture of the longitudinal rebars after fall of the fire insulation on the beam. At elevated temperatures, RPC beams with fire insulation that are under-reinforced at room temperature may fail as the lightly reinforced beams. The post-fire test observation reveals that no fire-induced spalling occurred in the reinforced RPC beams (moisture content range 2.12–4.06%) under fire conditions owing to the use of hybrid fibers (2% of steel fibers and 0.2% of polypropylene fibers) and fire insulation at the same time. Furthermore, based on the test results, the effect of three significant parameters on the response of fire exposed reinforced RPC beams was investigated: cover thickness of RPC, load ratio and fire insulation thickness. Additionally, a comparison of the fire response between uninsulated and insulated RPC beams is also presented.

Effect of air-gap on response of fabricated slim floor beams in fire

PurposeThe purpose of this study is to investigate the effect of the airgap on thermal behaviour and structural response of fabricated slim floor beams (FSFBs) in fire.Design/methodology/approachA detailed analytical model is established and validated by replicating the response of FSFBs. The validated finite element modelling method is then used to perform sensitivity analysis. First, the influence of the airgap presence is analysed, and later, the effect of the airgap size on thermal behaviour and structural response of FSFBs at elevated temperatures is investigated.FindingsResults from the study demonstrate that the presence of the airgap has a considerable influence on their thermal behaviour and structural response of FSFBs. The size of the airgap, however, has no significant influence on their thermal and structural response in fire.Originality/valueNo investigations, experimental or analytical, are available in literature addressing the effect of airgap on the structural response of FSFBs in fire. The presence of airgap is helpful and beneficial; hence, the findings of this research can be used to develop designs for structural members with airgap as an efficient and inexpensive way to improve their response in fire.

Deriving temperature-dependent material models for structural steel through artificial intelligence

Structural steel undergoes significant metallurgical and physio-chemical degradation under fire conditions. This degradation is often represented by temperature-dependent material models commonly adopted in fire codes and standards. A closer look into such models reveals few surprising, and to some extent, concerning facts. For instance, presentation of temperature-induced degradation in structural steel properties substantially varies across different fire codes. This not only causes inconsistences among researchers/practitioners with regard to carrying out fire resistance analysis, but also hinders ongoing standardization efforts. Further, and despite recent advancements in material science over the past few decades, code adopted temperature-dependent material models have not been updated nor revised. In order to promote a harmonized fire assessment methodology and to ensure realistic prediction of fire performance of steel structures, this paper utilizes Artificial Intelligence (AI) and machine learning tools to derive temperature-dependent thermal and mechanical material models for structural steel. The validity of the proposed models in predicting thermal and structural response of steel structures is demonstrated through number of case studies carried out using a highly nonlinear finite element model developed in ANSYS simulation environment.

Thermal Response Analysis of Flexible Connecting Structure of Large Mesh Antenna

The thermal uniformity of large mesh antennas in orbit is influenced by the thermal encironment, which results in thermal deformation and affects the performance of the antenna.Therefore, it is the basis of improving antenna performance to accuratey predict the temperature and analyze the influence facors of the thermal stability of the antenna.In this paper, a large mesh antenna model is constructed by using the FEM analysis software to simulate the thermal response of the flexible connecting structure of the metal mesh reflector, tension cable and rib component.The analysis results show that the temperature of antenna metal mesh and rib components are sensitive to the connection of the two, and their connection to tension rope is not sensitive. The tension cable is sensitive to the connection of the metal mesh and is insensitive to the connection of the rib components. The above analysis can provide an important reference for the design of large mesh antenna connection structure.

An efficient on-line algorithm for the optimal design of multi-material structures under thermal loads

In this study, the edge-based smoothed finite element method (ES-FEM) and reduced-basis method are combined to form an efficient on-line algorithm for the optimal design of multi-material structures under thermal loads. The ES-FEM is utilized to construct the heat transfer stiffness matrix, which is much more accurate than traditional FEM. Then, the reduced-basis method is developed as a forward solver to obtain thermal responses of multi-material structures, which can significantly reduce the computational effort of each forward analysis. Finally, the genetic algorithm is employed as the inverse solver to determine appropriate value of each design variable. Several numerical examples are fully investigated and it is shown that the presented algorithm is accurate and efficient enough for the optimal design of multi-material structures.