Thermal Field Distribution Research Articles

Analytical heat conduction models at arc fusion welding

It is of high importance to determine the distribution of thermal fields in arc fusion welding processes due to their influence on mechanical properties and quality of welded joints. This paper presents analytical models for 2D and 3D heat conduction based on solutions of the Fourier’s heat conduction differential equation. Furthermore, authors provide simplified equations for the calculation of cooling time and cooling rate for 2D and 3D heat conduction models.

Monitoring coal fires in Datong coalfield using multi-source remote sensing data

Numerous coal fires burn underneath the Datong coalfield because of indiscriminate mining. Landsat TM/ETM, unmanned aerial vehicle (UAV), and infrared thermal imager were employed to monitor underground coal fires in the Majiliang mining area. The thermal field distributions of this area in 2000, 2002, 2006, 2007, and 2009 were obtained using Landsat TM/ETM. The changes in the distribution were then analyzed to approximate the locations of the coal fires. Through UAV imagery employed at a very high resolution (0.2 m), the texture information, linear features, and brightness of the ground fissures in the coal fire area were determined. All these data were combined to build a knowledge model of determining fissures and were used to support underground coal fire detection. An infrared thermal imager was used to map the thermal field distribution of areas where coal fire is serious. Results were analyzed to identify the hot spot trend and the depth of the burning point.

Thermal field analysis of polymer/silica hybrid waveguide thermo-optic switch

The thermal field and the temperature change of the optical waveguide core of thermo-optic (TO) switch generated by heating the Al electrode are simulated using the finite-element method (FEM), and the steady-state temperature distribution and time response of TO switch are presented. Our research covers several conditions, including different electrode heater widths, upper cladding layer thicknesses, under cladding layer materials and different structures. The results turn out that the performance of the TO switch can be improved using the polymer/silica hybrid and the air trench waveguide structures. The TO switch was fabricated and the surface thermal field distribution was measured. A good agreement between the experimental results and theory analysis has been observed.

Distribution and evolution of thermal field formed by intense pulsed ion beam on thin metal target

Intense pulsed ion beam (IPIB) is characterized by short-pulsed high power density. With the strong thermal effect in the surface as the dominating feature, IPIB is an ideal technique for flash-heating surface processing of materials, especially for metals and alloys. Thus, the understanding of formation and evolution of thermal field induced by IPIB irradiation is of great significance to their application and diagnostic techniques. Due to the short pulsed duration and high energy flux of IPIB, the study in this field was so far mainly yield to numerical simulation. In this paper, with a combination of infrared image diagnostics, numerical analysis using Monte Carlo (MC) and finite element methods (FEM), the distribution and evolution of thermal field formed by IPIB produced by a magnetically insulated diode on a thin metal target was studied. The evolution of the thermal field and its effects on applications, such as the design of calorimeters was discussed reasonably.

Study on the Thermal Field Distribution of Steel Claws for Anode in Aluminium Electrolysis Cell

The electricity consuming of aluminium electrolysis cell is affected by the voltage drop of anode steel claws during the aluminium electrolysis course. The resistivity of anode steel claws is affected by the temperature. In the present study, the thermal field distribution of anode steel claws was studied by finite element analysis. The results show that the thermal energy of anode steel claws come from anode carbon blocks and environment. The temperature of steel claws less than 1/3 height is affected by anode carbon blocks, and the other part is affected by surrounding temperature. According the results, the principle of the new anode steel claw design is proposed.

Air temperature field distribution estimations over a Chinese mega-city using MODIS land surface temperature data: the case of Shanghai

The capability of obtaining spatially distributed air temperature data from remote sensing measurements is an improvement for many environmental applications focused on urban heat island, carbon emissions, climate change, etc. This paper is based on the MODIS/Terra and Aqua data utilized to study the effect of the urban atmospheric heat island in Shanghai, China. The correlation between retrieved MODIS land surface temperature (LST) and air temperature measured at local weather stations was initially studied at different temporal and spatial scales. Secondly, the air temperature data with spatial resolutions of 250 m and 1 km were estimated from MODIS LST data and in-situ measured air temperature. The results showed that there is a slightly higher correlation between air temperature and MODIS LST at a 250m resolution in spring and autumn on an annual scale than observed at a 1 km resolution. Although the distribution pattern of the air temperature thermal field varies in different seasons, the urban heat island (UHI) in Shanghai is characterized by a distribution pattern of multiple centers, with the central urban area as the primary center and the built-up regions in each district as the subcenters. This study demonstrates the potential not only for estimating the distribution of the air temperature thermal field from MODIS LST with 250 m resolution in spring and autumn in Shanghai, but also for providing scientific and effective methods for monitoring and studying UHI effect in a Chinese mega-city such as Shanghai.

Thermal behavior analysis and thermal error compensation for motorized spindle of machine tools

The thermal error deformation of motorized spindle plays an important role in the precision machining, while error compensation has been proved to be a cost-effective way. Herein a symmetrical solution for the thermal error problem of spindle is proposed based on the thermal behavior analysis. Firstly, the heat generating and transfer mechanism are described considering the heat sources. Next, ANSYS is used to achieve the steady-state and the transient thermal field distribution as well as the related deformation with the given thermal load and boundary condition. Furthermore, the NEM is proposed to predict the thermal error under random rotating speed with no use of thermal sensors, followed by the determination of two important parameters. The verification experiment of the thermal error under random rotating speed is executed. The External Machine Zero Point Shift function of the CNC system is adopted to develop the real-time compensation system on the spindle of HDBS-63 machining center. The maximum axial thermal error is greatly reduced from 55 to 16 um, while the radial one similarly reduced from 15 to 6 um. Both are improved 73% and 63% respectively. The experiment results show that NEM method is simple but of good reliability and practicality.

Thermal-stress analysis and calculation of single and dual chip set double-sided circuit board based on three-dimensional finite element algorithm

Purpose – The purpose of this paper is to analyze and figure out the temperature field and thermal stress field with the calculation model of thermal insulation material and composite material. Design/methodology/approach – The paper adopted the three-dimensional finite element algorithm. Findings – The simulated results showed great shearing strength between the chipset and the printed circuit board. The position of chip exerts great influence on the distribution of temperature field and thermal stress field of circuit board. The reasonable distribution of chip will effectively reduce the temperature extremum and stress extremum of circuit board. Originality/value – The paper analyzes and presents a discussion of the problems relating to the density of electronic packaging. The analysis process and the method of the paper provide essential help in resolving electronic device heat problems.

Modeling of ballistic-failure mechanisms in gas metal arc welds of mil a46100 armor-grade steel

Purpose – The purpose of this paper is to discuss the recently developed multi-physics computational model for the conventional Gas Metal Arc Welding (GMAW) joining process that has been upgraded with respect to its predictive capabilities regarding the spatial distribution of the mechanical properties controlling the ballistic limit (i.e. penetration resistance) of the weld. Design/methodology/approach – The original model consists of five modules, each dedicated to handling a specific aspect of the GMAW process, i.e.: electro-dynamics of the welding-gun; radiation-/convection-controlled heat transfer from the electric arc to the workpiece and mass transfer from the filler-metal consumable electrode to the weld; prediction of the temporal evolution and the spatial distribution of thermal and mechanical fields within the weld region during the GMAW joining process; the resulting temporal evolution and spatial distribution of the material microstructure throughout the weld region; and spatial distribution of the as-welded material mechanical properties. The model is upgraded through the introduction of the sixth module in the present work in recognition of the fact that in thick steel GMAW weldments, the overall ballistic performance of the armor may become controlled by the (often inferior) ballistic limits of its weld (fusion and heat-affected) zones. Findings – The upgraded GMAW process model is next applied to the case of butt-welding of MIL A46100 (a prototypical high-hardness armor-grade martensitic steel) workpieces using filler-metal electrodes made of the same material. The predictions of the upgraded GMAW process model pertaining to the spatial distribution of the material microstructure and ballistic-limit-controlling mechanical properties within the MIL A46100 butt-weld are found to be consistent with general expectations and prior observations. Originality/value – To the authors’ knowledge, the present work is the first reported attempt to establish, using computational modeling, functional relationships between the GMAW process parameters and the mechanical properties controlling the ballistic limit of the resulting weld.

Effect of Coking Size on the Thermal Diffusion and Stress Distribution of Cr25Ni35Nb and Cr35Ni45Nb Austenitic Steels

Cr25Ni35Nb and Cr35Ni45Nb austenitic steels, used as furnace tube material in the ethylene pyrolysis furnace, generally suffer from coking during the long operation period. In the present paper, for coked Cr25Ni35Nb and Cr35Ni45Nb austenitic steel, using the finite element ABAQUS code, a sequentially coupled thermal stress procedure was developed to calculate distribution of the temperature and thermal stress field. The results show that thermal diffusion property of Cr25Ni35Nb and Cr35Ni45Nb steel deteriorates obviously with coking layer increasing. Radial bulge and rupture at local field would generate due to excess temperature for applied subsequent measurement. Maximum stress distribute along the cross-section of coking layer and metal matrix. Finally, the critical depth of coking layer of Cr25Ni35Nb and Cr35Ni45Nb austenitic steel are predicted when decoking measurement must be executed.

Analysis on the Welding Thermal Field and Residual Stress of Thick Plate

A 60mm Q345 rigid thick plate with V groove welding connection was modeled in order to simulate the welding residual stress by finite element method. Both element birth and death technique and double ellipse heat source model were introduced to simulate the welding process. The welding thermal field and residual stress of thick steel plate were analyzed by finite element simulation software ANSYS.Then the thermal field and residual stress distribution were visually demonstrated. The result shows that the thermal field shaped like a spindle during welding period and the residual stress at the mid-section in lateral, longitudinal and thickness direction of the welding joint is lower than the stress at the surface of the welding connection.

Bit-Patterned Magnetic Recording: Theory, Media Fabrication, and Recording Performance

Bit Patterned Media (BPM) for magnetic recording provide a route to densities $>1 Tb/in^2$ and circumvents many of the challenges associated with conventional granular media technology. Instead of recording a bit on an ensemble of random grains, BPM uses an array of lithographically defined isolated magnetic islands, each of which stores one bit. Fabrication of BPM is viewed as the greatest challenge for its commercialization. In this article we describe a BPM fabrication method which combines e-beam lithography, directed self-assembly of block copolymers, self-aligned double patterning, nanoimprint lithography, and ion milling to generate BPM based on CoCrPt alloys. This combination of fabrication technologies achieves feature sizes of $<10 nm$, significantly smaller than what conventional semiconductor nanofabrication methods can achieve. In contrast to earlier work which used hexagonal close-packed arrays of round islands, our latest approach creates BPM with rectangular bitcells, which are advantageous for integration with existing hard disk drive technology. The advantages of rectangular bits are analyzed from a theoretical and modeling point of view, and system integration requirements such as servo patterns, implementation of write synchronization, and providing for a stable head-disk interface are addressed in the context of experimental results. Optimization of magnetic alloy materials for thermal stability, writeability, and switching field distribution is discussed, and a new method for growing BPM islands on a patterned template is presented. New recording results at $1.6 Td/in^2$ (teradot/inch${}^2$, roughly equivalent to $1.3 Tb/in^2$) demonstrate a raw error rate $<10^{-2}$, which is consistent with the recording system requirements of modern hard drives. Extendibility of BPM to higher densities, and its eventual combination with energy assisted recording are explored.

무인항공기의 노즐 형상 변화가 Lock-on Range에 미치는 영향에 관한 연구

韓國航空宇宙學會誌 , ** , *** Agency for Defense Development**** ABSTRACT The infrared lock-on range of target aircraft plays a critical role in determining the aircraft survivability. In this investigation, the effects of various UAV engine nozzle configurations on the aircraft lock-on range were theoretically analyzed. A virtual subsonic aircraft was proposed first, based on the mission requirement a nd the engine performance analysis, and convergent-type nozzles were then designed. After determining thermal flow field and nozzle surface temperature distribution with the CFD code, an additional analysis was conducted to predict the IR signature. Also, atmospheric transmissivity for various latitude and seasons was calculated, using the LOWTRAN code. Finally, the lock-on and lethal envelopes were calculated for different nozzle configurations, assuming the sensor threshold of the given IR guided missile. It was shown that the maximum 55.3% reduction in lock-on range is possible for deformed nozzles with the high aspect ratio.

Distribution and evolution of thermal field induced by intense pulsed ion beam on thin metal target

In this paper, combined with the latest development in relevant diagnostic and modeling techniques, the intense-pulsed ion beam (IPIB) energy deposition model in solid targets is established. The power density distribution induced by IPIB is simulated by Monte Carlo method on the basis of energy balance. By taking the power density as the source term, the thermal field distribution and evolution on a 100 μm stainless steel target irradiated by IPIB are simulated using the finite element method (FEM) in a time scale of several ms. Results reveal that in a time scale of several μups after IPIB irradiation, the main feature in the induced thermal field is a thermal shock within the depth of several times of the ion range. In the time scale of ms, thermal equilibrium can be established between the front and rear surfaces of the target, and the cross-sectional temperature field profile has a similar profile to the cross-sectional energy density distribution of the ion beam. This proves that by the infrared imaging diagnostic method, high resolution cross-sectional energy density diagnostics of IPIB can be achieved with a shooting time delay in ms scale.

Mathematical modeling of temperature during laser forming using bimodal beam

Article history: Received 6 January, 2015 Accepted 15 April 2015 Available online 17 April 2015 An analytical and numerical solution is developed for a transient heat conduction equation in which a plane slab is heated by a bimodal distribution beam over the upper surface. In laser heat treatment of steel few methods are used to produce a wider and nearly uniform average irradiance profile. This may be achieved by a bimodal (TEM11) shaped laser beam. In this paper, Green function method is employed to derive an analytical solution for thermal field distribution induced by laser forming process. Then 3-D finite element modeling of a slab in the ANSYS code is used to model the thermal field of laser forming with bimodal beam distribution. The results show that bimodal beam is useful for obtaining a uniform heat intensity distribution. © 2015 Growing Science Ltd. All rights reserved.

Optimization of Gas Metal Arc Welding (GMAW) Process for Maximum Ballistic Limit in MIL A46100 Steel Welded All-Metal Armor

Our recently developed multi-physics computational model for the conventional gas metal arc welding (GMAW) joining process has been upgraded with respect to its predictive capabilities regarding the process optimization for the attainment of maximum ballistic limit within the weld. The original model consists of six modules, each dedicated to handling a specific aspect of the GMAW process, i.e., (a) electro-dynamics of the welding gun; (b) radiation-/convection-controlled heat transfer from the electric arc to the workpiece and mass transfer from the filler metal consumable electrode to the weld; (c) prediction of the temporal evolution and the spatial distribution of thermal and mechanical fields within the weld region during the GMAW joining process; (d) the resulting temporal evolution and spatial distribution of the material microstructure throughout the weld region; (e) spatial distribution of the as-welded material mechanical properties; and (f) spatial distribution of the material ballistic limit. In the present work, the model is upgraded through the introduction of the seventh module in recognition of the fact that identification of the optimum GMAW process parameters relative to the attainment of the maximum ballistic limit within the weld region entails the use of advanced optimization and statistical sensitivity analysis methods and tools. The upgraded GMAW process model is next applied to the case of butt welding of MIL A46100 (a prototypical high-hardness armor-grade martensitic steel) workpieces using filler metal electrodes made of the same material. The predictions of the upgraded GMAW process model pertaining to the spatial distribution of the material microstructure and ballistic limit-controlling mechanical properties within the MIL A46100 butt weld are found to be consistent with general expectations and prior observations.

Thermal Modelling and Design of On-board DC-DC Power Converter using Finite Element Method

Power electronic converters are widely used and play a pivotal role in electronics area. The temperature causes around 54 % of all power converters failures. Thermal loads are nowadays one of the bottlenecks in the power system design and the cooling efficiency of a system is primarily determined by numerical modelling techniques. Therefore, thermal design through thermal modelling and simulation is becoming an integral part of the design process as less expensive compared to the experimental cut-and-try approach. Here the investigation is performed using finite element method-based modelling, and also the potential of such analysis was demonstrated by real-world measurements and comparison of obtained results. Thermal modelling was accomplished using finite element analysis software COMSOL and thermo-imaging camera was used to measure the thermal field distribution. Also, the improved configuration of power converter was proposed. DOI: http://dx.doi.org/10.5755/j01.eee.20.7.8022

Numerical study of the electro–thermo-convection in an annular dielectric layer subjected to a partial unipolar injection

This article deals with the problem of electro–thermo-hydro-dynamic (ETHD) in a dielectric liquid placed between two horizontal isothermal coaxial cylinders and subjected to the simultaneous action of a thermal gradient and an electric field. The full set of equations describing the combined ETHD flow is directly solved using the control-volume method. The effect of electroconvective motion was investigated in details in the case of strong unipolar injection from the half bottom of the inner cylinder. We focused mainly on enhancing the heat transfer by unipolar injection of electric charge in the dead zone (bottom area) of the annular space.The results show the emergence of a multicellular flow in this dead zone which enhances the heat transfer up to 170%. The flow structure in terms of stream lines, distribution of electric charge density and thermal field is highlighted. The effect of various system parameters in particular the radius ratio, the electric Rayleigh number is investigated too.

Numerical Evaluation Of Effective Thermal Properties For Materials With Variable Porosity

Abstract In this paper a computational homogenization technique is applied to thermal analyses in porous materials. A volume fraction of pores on the microstructural level is the key factor that changes the macroscopic thermal properties. Thus, the distribution of thermal fields at the macroscopic level is analysed through the incorporation of the microstructural response on the representative volume element (RVE) assuming a uniform distribution of pores. For the numerical analysis the scaled boundary finite element method (SBFEM) is introduced to compute the thermal response of RVE. The SBFEM combines the main advantages of the finite element method (FEM) and the boundary element method (BEM). In this method, only the boundary is discretized with elements leading to the reduction of spatial dimension by one, similarly as in the BEM. It reduces computational efforts in the mesh generation and CPU time. The proposed method is used to study square RVE with a circular and elliptic pore under the thermal load. Dimensions of the pore are varied to obtain different volume fractions of matrix material. Numerical results for effective thermal conductivities obtained via SBFEM modelling show an excellent agreement with the finite element analysis using commercial software COMSOL Multiphysics.

The Thermal Stress Analysis of Concrete Bridge Tower

Based on a 125 - days natural environment temperature changing observation of one cable-stayed bridge in zhejiang province and the reasonable simplification of the thermal field and stress distribution of concrete bridge tower, the bridge tower thermal stress finite element analysis is done through the first kind boundary condition and the third kind boundary condition. It is confirmed that the deviation of thermal stress between the first kind boundary condition and the third kind boundary condition is below 6% because the outside temperature change range is limited in the practical engineering case. Using the first kind boundary condition can meet the accuracy requirement of the project at the same time greatly simplify the calculation process.