Papers by Keyword: Thermal Effect

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Authors: Kyoung Jin Kim, Ho Sang Kwak, Jin Su Choi
Abstract: In manufacturing optical fibers, there has been intense research efforts of continually increasing fiber drawing speed to improve productivity. However, higher speed fiber drawing poses new challenge in many areas of optical fiber manufacturing. In this paper, thermal effects on coating resin flow in an unpressurized coating applicator are studied numerically. Present simulation results found that higher fiber drawing speed leads to severe viscous heating in coating resin flow and significant increase of resin temperature, which in turn leads to substantial viscosity decrease. These thermal effects profoundly alter the resin flow patterns and velocity profiles in the coating die and they should be considered in controlling the final coating thickness.
1080
Authors: S. Boubendir, Salah Larbi, Rachid Bennacer
Abstract: In this work the influence of thermal effects on the performance of a finite porous journal bearing has been investigated using a thermo-hydrodynamic analysis. The Reynolds equation of thin viscous films is modified taking into account the oil leakage into the porous matrix, by applying Darcy’s law to determine the fluid flow in the porous media. The governing equations were solved numerically using the finite difference approach. Obtained result show a reduction in the performance of journal bearings when the thermal effects are accounted for and, this reduction is greater when the load capacity is significant.
618
Authors: Chun Sheng Xu, Yang Li, Hong Xian Zhong, Xiu Hui Gao
Abstract: Data fitting approach based on test data is commonly adopted on analyzing of thermal effect due to the thruster plume impingement on communication satellites, however, the existing methods are only available for the appendages which are regularly shaped or could be formulated. In this paper, a plume impingement analyzing approach for irregularly shaped appendages is present. The STL (Stereo Lithographic) data is firstly derived from the three-dimensional model of the appendages. Then the STL data are made a kind of interpolation to get small particle size in order to obtain a precise analyzing result. Finally, the normal vector and the location of each triangle grid are obtained from the STL data to form a new model for plume impingement analyzing on irregularly shaped appendages. The new method is proved correct by comparing with PLUME software and the method given in [4].The application range of analyzing exhaust plume impingement on communication satellites can be widely extended by the proposed method.
3542
Authors: Lu Ming Shen, Zhen Chen
Abstract: To better understand the responses of ultrananocrystalline diamond (UNCD) under extreme working conditions, a numerical study is performed to investigate the size, loading rate and thermal effects on the material properties of UNCD films. A combined kinetic Monte Carlo (KMC) and molecular dynamics (MD) method is first applied to simulate the growth of polycrystalline UNCD films. The responses of the resulting UNCD films with various grain sizes are then investigated by applying displacement–controlled tensile loading with different rates and temperatures in the MD simulations. The preliminary results presented in this paper provide a better understanding of the combined size, rate and thermal effects on the material properties of UNCD.
621
Authors: Otto T. Bruhns
Abstract: Recently it has been demonstrated that the classical Prandtl/Reuss theory based on the additive split of the deformation rate contrary to what is believed so far is possible to establish a consistent Eulerian rate formulation for finite elastoplasticity. Here, we attempt to place this Eulerian formulation on the thermodynamic grounds by extending it to a general case with thermal effects.
787
Authors: Jing Liu, Tao Tao Shui, Fei Ma
Abstract: In order to investigate natural cross-ventilation in buildings driven by combined wind and thermal buoyancy forces, computational fluid dynamics (CFD) with the DES model is applied. The aim of this paper is to investigate the influence of thermal buoyancy force on natural ventilation in buildings under different heating conditions. The simulation results indicate that the thermal effect has a significant impact on airflow structure and airflow rate of building at low Froude numbers, however, the thermal effect can be neglected when Froude number value is greater than 6.
3001
Authors: Bao Ming Wang, Xia Lun Yun, Xing Yao Liao, Xue Song Mei
Abstract: Based on the theory of point contact thermal elastohydrodynamic lubrication (EHL),the mathematical models for the thermal EHL of high-speed angular contact ball bearing are established. Multi-grid method and multigrid integration method are respectively used to calculate out the film pressure and film thickness respectively,and the column-by-column scanning method is used to calculate temperature rise of isothermal EHL and thermal EHL. The calculation results show that, under the pure rolling condition, temperature rise of oil film temperature is mainly caused by the compression work and shear heat at inlet and the heat in contact zone mainly comes from the inlet and the heat conduction around; the temperature rise results in oil viscosity lower and the lubricating film thinner ,in this way it reduces the lubrication performance in contact pair.
443
Authors: Niu Jing Ma
Abstract: According to the common girder with side main rib section of PC cable-stayed bridge with double cable planes, a computational model of two-dimension temperature field is presented. Temperature gradient of main rib, small longitudinal rib, top plate and flange plate was computed respectively, and then the stress and strain of each section are derived through plane cross-section assumption. For the cable-stayed bridge, member structure FEM is applied to compute node equivalent load and displacement, which resulted from both sunshine and seasonal thermal difference. Finally, a case study is analyzed, the results showed: computed and measured deflection of girder that result from thermal effect are very close, therefore, this method is feasible.
495
Authors: Xiao Chun Ma, Ji Hui Yin
Abstract: The thermal effect has pronounced influence on deformation behavior of materials at nanoscale due to small length scale. In current paper, shear deformation of single crystal copper is simulated by molecular dynamics simulation, and special attention is paid to the thermal effect on the deformation behavior of material and mechanical response. The result shows that the plastic deformation of material during shear deformation is dominated by dislocation activities. Both the yield strength and shear strength have strong dependence on temperature due to thermal effect.
155
Authors: Zheng Yuan, Yi Fan Dai, Hao Yu, Xu Hui Xie, Lin Zhou
Abstract: During ion beam figuring process, most heat energy is absorbed by optics surface, heating the workpiece surface un-uniformly, called thermal effect. Thermal effect leads to distortion even cracking of the optical figure due to high temperature and temperature gradients, especially for the temperature sensible materials such as BK7, KDP and CaF2. One of the methods on decreasing thermal effect is decreasing total dwelling time and dwelling time gradients. According to the ability of ion beam correction, It is proposed that a new surface error distribution is obtained by filtered by a low pass filter from the initial surface error distribution measured by interferometer, and then it is used to calculate the dwelling time function. It is indicated by simulation that this measured decreases the total dwelling time and dwelling time gradients, reduces the temperature peak and heat stress. At last, a flat surface with the surface accuracy of 0.002λ rms is obtained from the initial surface error of 0.006λ rms, proving that high precision surface can be achieved with the surface after low pass filtering. So it is of great signification for actual application on ion beam figure temperature sensible materials.
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