An exact analysis for heat conduction in laminated infinite cylindrical arches subjected to Dirichlet boundary conditions

The temperature field within a layered arch subjected to Dirichlet Boundary Conditions is investigated based on the exact heat conduction theory. An analytical method is shown to obtain the temperature field in the arch. Because of the complex of the temperature boundary conditions, the temperature field is divided into two parts with the linear superposition principle. The first part is a temperature filed from the temperature boundary conditions on the lateral surfaces. The second part is from the temperature conditions on the outside surfaces expect the influence from the two edges. The temperature solution of the first part is constructed directly according to the temperature boundary conditions on the lateral surfaces. The temperature solution of the second part is studied with transfer matrix method. The convergence of the solutions is checked with respect to the number of the terms of series. Comparing the results with those obtained from the finite element method, the correctness of the present method is verified. Finally, the influences of surface temperature and the thickness-radius ratio h∕r0 on the distribution of temperature in the arch are discussed in detail.

Analysis of multi-cavity molding of parts with different geometries

In the industrial processes of injection molding, one of the basic requirements is a uniform temperature filed within workpiece and the mold cavities. In the case of simple geometry of workpiece and mold with single cavity achieving a uniform temperature field is not a critical issue. However, if one deals with parts of complex geometries, multi-cavity molds and asymmetric layout of different forms in the mold additional analyses of the runner and cooling system are necessary in order to obtain the required quality and accuracy of end the products. Disposition and dimensions of both runners and cooling channels are directly related to the geometry of finished parts and material properties. In that sense, virtual models and numerical simulations of injection molding processes based on the finite element method are very effective tool which enable accurate prediction of potential problems and significant reduction of trial and error procedure. In this paper, FEM software package Moldex3D was employed for simulation and analyses of injection molding process in which pipe fittings Ø75/45o and Ø75/90o are produced using a mold with two asymmetric cavities.

Effect of deformation temperature on mechanical properties and microstructure of TWIP steel for expansion tube

According to the downhole temperature filed, the mechanical behavior of TWIP steel for expansion tube was studied in the temperature range from 25°C to 300°C. Meanwhile, the phase and microstructure changes before and after deformation were investigated by X-ray diffractometer (XRD), optical microscope (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that yield strength, tensile strength and elongation decrease with temperature increasing. The TWIP steel is single-phase of austenite before and after deformation. Analysis on the microstructure shows that the deformation twins gradually decrease with increasing temperature. The deformation process cannot benefit from the deformation twins, which is responsible for the decreased ductility. In addition, due to the increased temperature, the stacking fault energy becomes high enough to restrain twinning, thus dislocation glide becomes the main deformation mechanism.

Damage Evolution of RC Beams Under Simultaneous Reinforcement Corrosion and Sustained Load

To accurately obtain the performance of concrete structures in coastal regions, it is necessary to correctly understand the damage evolution law of reinforced concrete (RC) members under real working conditions. In this paper, four RC beams, subjected to different levels of corrosion and sustained load, are first tested. Reinforcement corrosion coupled with sustained load increases the number and width of cracks at the soffit of beams but decreases their loading capacities. Crack width of the corroded beam under 50% of designed load is two times of that under 30% of designed load. Residual loading capacities of the corroded beams subjected to 30% and 50% of designed load are 87.5% and 81.8% of the control beam. A finite element model is developed for the corroded RC beams. Due to less confinement, concrete below and at the sides of reinforcements is subjected to a higher stress, compared to concrete above the reinforcements. Corrosion expansion of reinforcements is successfully modelled by a temperature-filed method, as it properly simulates the damage evolution of the corroded RC beams. As a result, concrete cracking, caused by the reinforcement corrosion, is well captured. Coupling reinforcement corrosion with sustained load significantly increases the damage level in RC beams, particularly for those subjected to a high sustained load. The whole damage evolution process of concrete cracking due to corrosion expansion under the coupling effect of sustained loading and environment can be simulated, thus providing a reference for the durability evaluation, life prediction, and numerical simulation of concrete structure.

Evaluating the Ability of SLW Model in Numerical Simulation of Radiative Turbulent Reacting Flow in Industrial Application

In this paper, the turbulent reacting flow in an industrial furnace is numerically simulated using the RANS equations. The two-equation standard k-ε and the eddy dissipation models are used respectively to close the turbulent closure problem and to consider the turbulence-chemistry interaction. The radiation transfer equation is solved using the discrete ordinates method (DOM). To calculate the radiation absorption coefficient in participating combustion gases, we use the spectral line-based weighted sum of grey gases (SLW) model and compare the achieved results with famous gray-based model, i.e., the weighted-sum-of-gray-gases (WSGG) model. The results of this research show that using the SLW model, the predicted heat transfer from the flame to the furnace walls is reduced due to the thermal radiation. So, the predicted temperature filed increases up to 5% near the outlet of furnace in comparison with the results of WSGG model, which is in more agreement with the experimental data. These results indicate that if one wishes to accurately predict the temperature field and the temperature sensitive quantities such as the NOx emission, one should use the spectral-based models to calculate the radiation absorption coefficient. The details are discussed in the results section.

The transient temperature field simulation of the micro-grid inverter

For the power electronics devices with the insulated gate bipolar transistors, the thermal management is very important and necessary for the devices reliability. In this paper, power losses of the inverter were evaluated based on its electro-thermal model and control logic. Accordingly, its thermal management system using forced air cooling is designed and simulated. The transient temperature filed simulation results showed that the thermal management system is feasible and can guarantee the working temperature of the inverter. Experimental results were also obtained to verify the simulation results in this paper.

RESEARCH OF NON-STATIONARY THERMAL FIELD IN RESERVOIRAND WELLBORE WITH MULTIPHASE FILTRATION

In the paper the mathematical formulation of a task of temperature filed in the wellbore and reservoir sys-tem with multiphase fluid filtration is considered. The mathematical models of two-phase non-isothermal filtration of fluid in porous media are described, which take into account non-stationary thermo hydrodynamic processes, barothermic effect, oil degassing when reservoir pressure lowers below saturation pressure. The mathematical models are developed for two-phase flow in vertical wellbore. The paper shows the results of numerical solution of formation of temperature field in reservoir and wellbore system and testing results on analytical solutions.

Analytical Solution of Transient Three-Dimensional Temperature Field in a Rotating Cylinder Subject to a Localized Laser Beam

Laser-assisted machining (LAM) is a growing trend in machining of hard to cut materials. In most experimental cases, LAM is carried out in two stages; first, laser and machine parameters are tuned to adjust the temperature at the material removal point (Tmr), and second, the cutting tool is engaged to cut the points that have already been heated by the laser. Alternatively, an analytical model for the prediction of temperature filed can replace lengthy experimentation needed for tuning the material removal temperature. This paper presents an analytical solution to the transient temperature field in a rotating cylinder subject to a localized laser heat source based on Green's functions. The analytical solution is validated by comparing the surface point temperatures to thermal experiments on DIN 1.7225 steel, which shows good agreement in trend and values. Furthermore, a finite element model is developed and verified by the results of the same experiments, providing a more detailed investigation on the performance of the analytical model. The developed analytical scheme can be used to readily calculate pointwise temperatures on workpiece surface and internal points which can be used as a tool for designing machining conditions.