Thermal Coupling Analysis Research Articles

Numerical Simulation and Investigation of High Frequency Tube Welding Process

Welding processes and installations used nowadays are mainly developed on practical experience and analytical calculations. Nevertheless, high frequency induction tube welding is a very complex three-dimensional dynamic process, where the electromagnetic and thermal characteristics are distributed not only in space but in time as well. A more profound detailed investigation of the induction tube welding process can be only done by numerical modeling. Full and local three-dimensional transient numerical models of induction tube welding process with continuous movement of the welded tube have been developed and tested. Coupled electromagnetic and thermal analyses are carried out at each time step of simulation for correction of temperature dependent material properties. Voltage or current of the induction coil can be individually input into electromagnetic analysis at each time step. This approach allows simulating “quasi” steady-state and transient operation modes.

Concentration photovoltaic–thermal energy co-generation system using nanofluids for cooling and heating

New designs of dual concentration photovoltaic–thermal (CPV/T) systems can provide both electrical and thermal energy, while reducing solar cell material usage via optical techniques. The overall system efficiency can be improved by using advanced dual-purpose liquids with enhanced heat transfer characteristics, such as nanofluids. In this paper the use of nanofluids, i.e., dilute nanoparticle suspensions in liquids, are considered for improved efficiency of a CPV/T system for the first time. Specifically, a 2-D model coupling thermal analysis and computational fluid dynamics simulations has been developed to calculate efficiencies of individual subsystems as well as the overall system. A new thermal conductivity model for nanofluids, which was validated with experimental data sets, was employed. The electrical and thermal performances of the system were evaluated for different climatic conditions. The results show that using nanofluids improves the electrical and total efficiencies of the system, especially when using silicon solar cells. For example, if the nanofluid outlet temperature of the solar cell is set to 62°C via a controlled flow rate, the system overall efficiency could reach 70% with electrical and thermal contributions amounting to 11% and 59%, respectively. In summary, a nanofluid-based system is preferable to water-based systems in the long run.

Study on the Stiffness of Positioning Platform with Large Trip and High Precision under Thermal to Structure Coupling

Thermal influences the stiffness, and then affects dynamic characteristics of the platform. The paper appoints a method to calculate the global stiffness of the positioning platform with large trip and high precision, and find the rule that the platform stiffness changing with the temperature to follow. The rule provides a fundamental basis for establishing vibration model of the platform. The main method to collect analysis data is finite element. Firstly, choose a number of points from the surfaces of the platform. Through the experiment data of thermal stress coupling analysis on the platform and a degree of grey incidence, the degree of correlation between all concerned points and thermal displacement can be solved. The key points are confirmed the one which have large degree of grey incidence which also have large influence on the stiffness, and will be the input value of stiffness model of the platform. Calculate the global stiffness value of positioning platform under different temperature using the finite element method analysis. Establish the stiffness model using BP neural network.

Simulation of Non-Destructive Testing on Weld Surface Crack of Metal Structure by Electromagnetically Stimulated Infrared Thermography

With the wider use of metal welded structure in engineering machine, on-line inspection on weld crack is of great significance. This paper reports an emerging nondestructive approach----electromagnetically stimulated infrared thermography technique, for the detection and characterization of surface cracks. According to the electromagnetic thermal coupling analysis theory, different abnormal temperature field distributions caused by various crack dimensions , coil lifting heights, stimulated frequencies and paint film thickness were obtained, via 3D finite element analysis (FEA).The results show that the weld surface crack detectability are greatly influenced by the crack width and the paint layer thickness, with coil life-off height decreasing and electromagnetic excitation frequency increasing, the maximum abnormal temperature difference increases. There is a certain reference value for further research on the design of the electromagnetically stimulated control device.

Interfacial shear strength of reduced graphene oxide polymer composites

Interfacial shear strength (IFSS) between particle and matrix in particulate polymer composites is a critical property in determining the mechanical behaviors since it is directly related to not only their Young’s modulus or specific strength, but also energy absorbing capability. However, the conventional techniques often present a technical challenge to accurately measure the IFSS between fillers and matrix in the composites. This is more apparent in graphene particulate composites due to their nano-scale dimensions as well as the platelet-shaped geometry. Here, the focus of this study is to use a semi-empirical approach to determine the IFSS of graphene particulate composites by combining experiments with finite element (FE) modeling. The materials of interest are reduced graphene oxide (RGO) and polycarbonate (PC). The tensile testing was performed to characterize the mechanical properties, while simultaneously monitoring the acoustic emission events in order to measure the global debonding stress (GDS) in the composites. By coupling thermal stress analysis and deformation analysis with the GDS as input to a FE model, the IFSS of the RGO particulate PC composites was successfully estimated by about 136MPa, avoiding unnecessary assumptions and uncertainties which are seem to be inevitable with the conventional techniques for the IFSS measurement.

Inserts thermal coupling analysis in hexagonal honeycomb plates used for satellite structural design

Mechanical joints and fasteners are essential elements in joining structural components in mechanical systems. The thermal coupling effect between the adjacent inserts depends to a great extent on the thermal properties of the inserts and the clearance. In this paper the Finite-Element Method (FEM) has been employed to study the insert thermal coupling behaviour of the hexagonal honeycomb panel. Fully coupled thermal analysis was conducted in order to predict thermal coupling phenomena caused by the adjacent inserts under extreme thermal loading conditions. Detailed finite elements models for a honeycomb panel are developed in this study including the insert joints. New approach of the adhesive joint is modelled. Thermal simulations showed that the adjacent inserts cause thermal interference and the adjacent inserts are highly sensitive to the effect of high temperatures. The clearance and thermal interference between the adjacent inserts have an important influence on the satellite equipments (such as the electronics box), which can cause the satellite equipments failures. The results of the model presented in this analysis are significant in the preliminary satellites structural dimensioning which present an effective approach of development by reducing the cost and the time of analysis.

Preparation and Characterization of Methyl Substituted Maleic Anhydride: Modified Collagens Destined for Medical Applications

Porous modified collagens with vinyl groups were synthesized by reaction with 2,3-dimethylmaleic anhydride or citraconic anhydride. The structure of modified collagen was assessed by analytical determination of the amino groups in collagen and spectroscopic methods (Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance (1H NMR)). The amount of protonated amino groups and carboxylic acid moieties of the samples have been determined by potentiometric titration. The dependence of the viscosity of diluted collagen solutions on the concentration and temperature was followed to determine their denaturation transitions. The increased average molecular weight, particle size, and second virial coefficient of modified collagen solutions with respect to the unmodified one proved that modification took place. Coupled thermal analyses (TG/DTG/DTA/FT-IR/MS) also indicated the collagen modification by increased thermal stability and new volatile compounds formed during decomposition. The adhesion test...

Dedicated thermal emulator for analysis of thermal coupling in many-core processors

This paper discusses the problem of thermal coupling in many-core processors manufactured in non-planar FinFET technologies. Our work focuses on two research goals. Firstly, the results obtained from the thermal simulations allow the investigation of mutual thermal influence between neighboring cores in such processors, what can be used to develop thermal models of such architectures. Secondly, we describe a test integrated circuit designed specifically to mimic the thermal behavior of microprocessors manufactured in various technologies. In particular, this paper describes its design and presents selected simulation results obtained using Green׳s function-based thermal software.

Synthesis and electrochemical behavior of Li2CoSiO4 cathode with pyrrolidinium-based ionic liquid electrolyte for lithium ion batteries

Li2CoSiO4, a silicate olivine cathode for lithium rechargeable batteries, is synthesized for the first time by sol–gel method using polyacrylic acid (PAA) as the chelating agent. Coupled thermal and vibrational analysis of the gel and also the X-ray diffraction pattern confirms the formation of the sample at 800 °C. 1-Butyl-1-methyl pyrrolidinium bis(trifluoromethanesulfonyl)imide (BMPyTFSI) solutions of lithium bis(trifuloromethansulfonyl)imide (LiTFSI) having a concentration of 0.2 mol kg−1 is used as electrolyte. The electrochemical stability window of this electrolyte is found to be >5 V by linear sweep voltammetry technique. The compatibility of Li2CoSiO4 with 0.2 mol kg−1 LiTFSI-BMPyTFSI electrolyte is tested by charge–discharge cycles which show charging and discharging capacities of about 204 and 32 mAh g−1, respectively, in the first cycle.

Coupled Thermal Analysis on Carbide Anvil of Cubic Press

Based on finite element analysis software ANSYS, the 3D contact finite element model of carbide anvil, steel ring and cushion block were built to make heat transfer analysis, and the temperature field distribution was obtained. The indirect coupling thermal analysis of carbide anvil, steel ring and cushion block were made regarding as a whole, the Von Mises stress nephogram of them and the shear stress nephogram of carbide anvil were displayed. The stress nephogram revealed that it was liable to fracture on the edge of top surface under high pressure status, and it was also proven that the main reason of fracture was the yield of internal material defects under the action of shear stress.

Coupled Fluid, Thermal and Structural Analysis of Nozzle in Solid Rocket Motor

A coupled fluid, thermal and structure analysis model was established for solid rocket motor nozzle. Based on a steady flow simulation and a transient thermal simulation, a transient structure analysis simulation was executed. The model took a frictional coefficient 0.3 into account to simulate a rub action between the parts of the nozzle. Result showed that with a frictional coefficient, Von Mises stress could be released which gives a constructive recommendation for a structure simulation of a nozzle. Also, the model was more close to the actual. A more dependable approach was introduced and it could contribute to designing department.

Flow blockage accident or loss of flow accident by using comparative approach of NK/TH coupling codes and RELAP5 code

This paper deals with the comparison and safety studies of the neutron kinetics and thermal hydraulic coupling analysis of small nuclear reactor core. In this study, first the coupling between neutron kinetics and thermal hydraulics has been achieved for the small nuclear reactor core. The coupling approach is done by using the lattice physics code (HELIOS), neutron kinetic code (REMARK) and thermal hydraulic code (THEATRe). After finalizing the NK/TH coupling, power distribution of reactor core has been acquired. The loss of flow accident or coolant blockage accident is considered for the safety analysis of the reactor core. The comparison studies were accomplished by comparing the results from coupled codes (HELIOS, REMARK & THEATRe) and thermal hydraulic system code RELAP5. The simulated results from both codes agree well conforming the accuracy of the NK/TH coupling approach. The purpose of the research is to corroborate the NK/TH coupling by safety pre-assessment of nuclear reactor core.

The Coupling Thermal and Mechanical Analysis of Machining Aluminum Alloy Work-Piece Based on FEM

The Cutting force and cutting temperature are the important factors which can affect the quality and accuracy of the aluminum alloy work-pieces. Based on the theoretical analysis of the cutting force and cutting temperature, the three-dimensional Finite Element Model (FEM) with the overall tool is established. The corresponding results of the digital simulation were researched, and the cutting force and cutting temperature were analyzed. The cutting temperature and cutting force changes were compared by altering the axial depth of cut and the feed rate. Keywords: Oblique cutting model, Finite Element Method (FEM), Cutting temperature, Cutting force, Aluminum alloy work-piece

Coupled thermal analysis of novel alumina nanofibers with ultrahigh aspect ratio

The phase conversions and morphological changes of commercial alumina nanofibers (ANF) with 7 and 40nm in diameter during heat treatment were investigated. These super-high aspect ratio (length-to-diameter ratio is ∼107) fibers are mostly composed of partially hydrated (2–6wt.%) gamma-alumina phase. The transformations of the ANF during heating up to 1480°C were studied simultaneous coupled thermal analysis (TG-DSC-FTIR) supported by XRD and SEM examinations. It was found that for ANF gamma-phase starts to transform into stable α-alumina from ∼1250°C, but the water releases during most of the heating time at least in two stages. The behavior of the material and observed changes are discussed and compared with literature date for different alumina materials.

Selecting of the Temperature Measurement Points for Positioning Platform with Large Trip and High Precision Thermally Induced Error Compensation Model

In the technology of thermal error compensation in positioning platform with large trip and high precision, selecting the temperature measurement points rationally is particular important for successfully establishing the model of compensation. The method uses simulation to track platform heat distribution and thermal deformation under various thermal conditions. Temperature variables are grouped by different surfaces of the platform. Then a degree of grey incidence from grey system theory is introduced to identify the key temperature measurement points of each surface. Through the experiment data of thermal stress coupling analysis on the platform, the degree of correlation between all temperature measurement points and thermal displacement can be solved. The key temperature measurement points are confirmed by the largest value of the degree of correlation of each surface.

Study of bat flight behavior by combining thermal image analysis with a LiDAR forest reconstruction

The nature of forest structure plays an important role in the study of foraging behaviors of bats. In this study, we demonstrate a new combined methodology that uses both thermal imaging technology and a ground-based LiDAR system to record and reconstruct Eptesicus fuscus (big brown bats) flight trajectories in three-dimensional (3-D) space. The combination of the two 3-D datasets provided a fine-scale reconstruction of the flight characteristics adjacent to and within the forests. A 3-D forest reconstruction, assembled from nine Echidna Validation Instrument LiDAR scans over the 1 ha site area, provided the essential environmental variables for the study of bat foraging behaviors, such as the canopy height, terrain, location of the obstacles, and canopy openness at a bat roosting and maternity site in Petersham, Massachusetts. Flight trajectories of 24 bats were recorded over the 25 m × 37.5 m region within the LiDAR forest reconstruction area. The trajectories were reconstructed using imaging data from multiple FLIR ThermoVision SC8000 cameras and were co-registered to the 3-D forest reconstruction. Twenty-four of these flight trajectories were categorized into four different behavior groups according to velocity and altitude analysis of the flight trajectories. Initial results showed that although all bats were guided by echolocation and avoided hitting a tree that was in all of their flight paths, different bats chose different flight routes. This study is an initial demonstration of the power of coupling thermal image analysis and LiDAR forest reconstructions. Our goal was to break ground for future ecological studies, where more extensive flight trajectories of bats can be coupled with the canopy reconstructions to better establish responses of bats to different habitat characteristics and clutter, which includes both static (trees) and dynamic (other bats) obstacles.

Synthesis and solid-state structure of thermally stable linear bi-pyrazoles

The long and rigid bi-pyrazolyl-based ligands 2,6-bis[4-(1H-pyrazol-4-yl)phenyl]pyrrolo[3,4-f]isoindole-1,3,5,7(2H,6H)-tetrone, L1, and 2,5-bis[4-(1H-pyrazol-4-yl)phenyl]thiazolo[5,4-d]thiazole, L2, were isolated in pure form, with satisfying yields, as very insoluble polycrystalline materials. Their thermal behavior was investigated by coupling thermal analyses and variable-temperature X-ray powder diffraction measurements. Their crystal structures were unraveled from powder diffraction data by a rather unconventional structure determination approach, without the a priori knowledge of the unit cell parameters. Inline with shorter analogues, successfully employed in the formation of porous MOFs with intriguing functional properties, L1 and L2 are promising to construct higher-porosity materials, potentially capable of hosting nano-sized guests.

Coupled Electromagnetic and Thermal Analysis of Single-Phase Insulated High-Current Busducts and GIL Systems

This paper presents a mathematical model for the coupled electromagnetic and thermal analysis of the single-phase insulated high-current busducts of circular cross-section geometry and of gas-insulated transmission lines (GIL). The mathematical model, accompanied by a numerical solution procedure, features an exact current distribution in phase conductors and shields of the busduct or GIL system, accounting for the skin and proximity effects, and including the complete electromagnetic coupling between phase conductors and shields. The current distribution is based on the conductor filament method in combination with the mesh-current method. The mathematical model further couples the analysis of current distribution with the computation of (Joule) power losses and subsequent temperature increase in the high-current busducts or GIL systems, accounting for the material properties (electrical conductivity, thermal emission and convection coefficients) as well as for the surrounding ambient properties (ambient temperature, wind and solar radiation influences).

2109 電磁場-熱流体連成解析向け物理量マッピング技術の開発

In design phase, it is difficult to evaluate the influence of heat density distribution by non-uniform current density on temperature distribution of conductive parts. Therefore, we are developing an electromagnetic field ? thermal flow coupling analysis system. In this research, we developed a physical quantity mapping technique for electromagnetic field - thermal flow coupling analysis. Conventionally, temperature distribution of conductive parts is evaluated by thermal flow analysis under the condition of uniform heat density. In this research, heat density is calculated by finite element method, and thermal fluid field is calculated by voxel method. We developed a technique of mapping heat density onto thermal fluid field. In the technique, defining points and units of finite element are converted to defining points and units of voxel. We compared temperature evaluated by thermal flow analysis under the condition of non-uniform heat density with uniform heat density. As a result, it is confirmed that we can evaluate the influence of heat density distribution on temperature distribution of conductive parts.

2110 ナレッジ融合型電磁場-熱流体連成解析システムの開発

We developed electromagnetic field - thermal fluid coupling analysis system integrated knowledge for designers. Previously, only expert designers which are familiar with both of electromagnetic field and thermal fluid could be used the analysis system. There was further improvement of usability and automation. Therefore, we developed the analysis condition setting integrated knowledge technique and automatic analysis model generation technique added-on 3D-CAD. As the result, operations of the analysis model generation work become simple and analysis model become high reliability. Designers which are unfamiliar with the analyses could be utilized with the high reliability analysis models. We demonstrated the analysis model generation work time reduced from 155 minutes to 11 minutes by applying this technique.