Applied Mechanics and Materials Vols. 217-219

Abstract: Heat transfer performance of the heat-pipe grinding wheel (HPGW) is mainly depended on the heat pipe in the wheel. In this paper, a basal body of HPGW was developed and a heat transfer experiment was performed to study the effect of the parameters of the heat pipe such as liquid filling ratio and rotating speed on the heat transfer performance of the HPGW. Results show that the heat transfer performance decreases if the liquid filling rate is too large or too small under the same heat source intensity and the optimal liquid filling rate is about 35% of the volume inside the heat pipe. The heat transfer performance of the HPGW is enhanced with the increasing of the rotating speed. The analysis of the results also shows that the heat pipe in the HPGW can play a great role on enhancing the heat transfer in the grinding zone with suitable processing parameters.

Abstract: The magnitudes of heat flux for both isotropic materials and anisotropic materials can be determined from Fourier’s law. But the mechanism of heat transfer in anisotropic materials is quite different from that in isotropic materials. The thermal conductivities at one point are not equal in all directions for anisotropic materials. The magnitude of heat transfer rate of anisotropic material in one direction is not only relevant to the temperature gradient in this direction, but also relevant to the temperature gradient which is normal to the direction. Basing on one-dimensional unsteady state heat conduction problem in isotropic materials which can be solved by separation-of-variables method, the performance of unsteady state heat conduction in anisotropic materials was analyzed. And the unsteady state temperature field of the anisotropic plane wall was obtained. The results will provide help for the energy conservation of anisotropic materials.

Abstract: This paper presents a successive approximation approach (SAA) designing optimal controllers for a class of nonlinear heat equations with a quadratic performance index. By using the SAA, the optimal control problem for nonlinear heat equations is transformed into a sequence of nonhomogeneous linear differential Riccati operator equations. The optimal control law obtained consists of an accurate linear feedback term and a nonlinear compensation term which is the limit of an adjoin vector sequence. By using the finite-step iteration of the nonlinear compensation sequence, we can obtain a suboptimal control law.

Abstract: Based on the Joule heating nuclear waste treatment technology, a series of numerical simulations have been studied to predict transient flow and heat transfer.The physical model is a rectangular cavity filled with fluid, the direct current contributes heat for heating the process medium by a pair of plate electrodes. For Pr=1 fluid, the thermally driven stable convection and the electromagnetically driven stable flow can be observed respectively or both gravitationally and electromagnetically driven stable convection exhibit. The threshold Hartmann number for the flow transition from an asymmetric 2 cells steady flow to a steady non- asymmetric state 1 roll flow is 159.687, where the Nusselt number exhibits a minimum value. And the second transition from non- asymmetric state 1 roll flow to a steady asymmetric 2 rolls flow is fixed at 178.88 with Ra=1.0×105. The results can provide some guidelines for conceptual thermal control for Joule heated ceramic melter technology.

Abstract: Microstructures of precursor-derived amorphous SiCN ceramics under conditions of vacuum and high temperature (1300°C, 1900°C) were observed by transmission electron microscopy. The gas phase reaction crystallization mechanisms of amorphous SiCN in vacuum was investigated based on thermodynamic calculation. The results indicate vacuum heat treatment can promote decomposition, induces gaseous species (SiO, CO and Si vapor) production. Gas phase reaction between Si(g), SiO(g) and C induces SiC nucleation inside amorphous ceramic network. Free Si- and N- can not form Si-N-enriched regions and N- is discharged in the form of N2. The crystallization of amorphous SiCN in vacuum displays significant difference to that in N2 and Ar.

Abstract: The higher order two-scale finite element errors of the thermoelastic problem in perforated composites with boundary layer are presented, and the two-scale finite element method coupled with boundary layer is built for analyzing the coupling problem. The numerical results show that the basic configuration and the local temperature strongly affect local strains and local stresses.

Abstract: Aiming at the problem that thermal boundary resistance (TBR) has an effect on heat transportation of superconducting magnet when Superconducting Magnetic Energy Storage (SMES) is cooled directly, from perspective of numerical calculation, truncated cone, circular arc and triangular models are used to simulate the solid to solid contact surface, and finite element method is adopted to carry on numerical simulation calculation for thermal boundary resistance. With comparison and analysis of the calculation results of the three models, knowing that the value calculated with the triangular model when its control angle is 30° is close to the measured value and its relative error is 17%. Meanwhile, the error source is analyzed. This dissertation can be a good reference to the research on superconducting magnet heat transportation.

Abstract: Stiffness and strength of the electric power steering structure were analyzed based on Catia, HyperMesh and ANSYS. Then, the influence of temperature on the stiffness of every component was also studied. The results indicate that the maximum deformations of the worm and worm wheel occur in the centre of the tooth top and their shape approximate ellipse. The deformation of the tail end of the worm-wheel shaft is large, and the limited groove area contracting the splined shaft and the steel ball bears large stress. The temperature load has some impact on the stress and deformation of components. The deformations of the components gradually enlarge with the increasing of the temperature, but the variations are not large. The stiffness and strength of steering can meet the design requirements.

Abstract: It is beneficial to keep low superheat and constant speed continuous casting with tundish heating technology which can improve the control of molten steel temperature and bloom quality. The application of tundish heating technology at home and abroad is investigated, and the temperature of molten steel and bloom quality in Panzhihua steel are analyzed. On the basis of investigation and analysis, it is necessary to apply tundish heating technology in Panzhihua steel.

Abstract: With the development of electronic packaging technology, the time criterion and the space criterion of heat transfer have been becoming smaller and smaller, which results in the stronger Non-Fourier effect．Using the classical Fourier model to analyze the heat transfer of the substrate will inevitably make the result deviate from the actual conditions greatly. However, using the Non-Fourier model could closely describe the real situation. This paper regards the Fourier model and the Non-Fourier model separately, sets up their own mathematics-physics equations to the heat-transfer model of three-dimension multi-chip module(MCM) substrate，adopts finite difference method(FDM) to solve the corresponding equations，and get the temperature field of the three-dimensional substrate model. To test the accuracy of the results, meanwhile, the thermal analysis software ANSYS ICEPAK is used to calculate the same model. The results indicate that，compared with the classical Fourier model，the results of Non-Fourier model have great advantages：the temperature value is higher, the time is longer for temperature field to enter the stable state, changing of the temperature is faster and the phenomenon of thermal coupling is stronger too.