Papers by Keyword: Stress

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Authors: Yoshitaka Umeno, Kuniaki Yagi, Hiroyuki Nagasawa
Abstract: We carry out ab initio density functional theory calculations to investigate the fundamental mechanical properties of stacking faults in 3C-SiC, including the effect of stress and doping atoms (substitution of C by N or Si). Stress induced by stacking fault (SF) formation is quantitatively evaluated. Extrinsic SFs containing double and triple SiC layers are found to be slightly more stable than the single-layer extrinsic SF, supporting experimental observation. Effect of tensile or compressive stress on SF energies is found to be marginal. Neglecting the effect of local strain induced by doping, N doping around an SF obviously increase the SF formation energy, while SFs seem to be easily formed in Si-rich SiC.
Authors: Yan Ping Sun, De Chen Zhang, Ming Yang, Yuan Li
Abstract: In this paper, iron ladle stress and deformation has been accurately calculated using finite element analysis software ANSYS based on 260t iron ladle in standing, lifting, tipping working conditions. Distribution of stress field was obtained. The stiffness and strength of the iron ladle has been evaluated. The results show that the iron ladle in the standing, lifting and tipping working conditions, structural deformation is small, the strength and stiffness meet the requirements. This research extends the working life of 260t iron ladle. It provides theoretical basis for producing and using of the iron ladle and further optimal designing.
Authors: Andrea Canino, Andrea Severino, Nicolò Piluso, Francesco La Via, Stefania Privitera, Alessandra Alberti
Abstract: 3C-SiC shows encouraging physical properties for the development of low cost high power compatible silicon based technology. The fundamental capability of grown 3C-SiC on silicon substrates leads to the possibility of a full integration of Si based process technologies. This is the driving force for the efforts for development a high quality heteroepitaxial film. The fundamental issue is the reduction of defects and stress due to the lattice mismatch between the 3C-SiC epilayer and the Silicon substrate. In this paper we show a way to reduce macroscopic structural features and to enhance the material quality and the surface quality by simply using a process based on a multilayer (ML) buffer structure with n++ and n doping alternation. This process leads to an evident improvement of both surface roughness, morphology and crystal quality.
Authors: Vladimír Křístek, Lukáš Kadlec
Abstract: Due to increase of requirements on accuracy of structural analyses, practically applicable computational tools for reliable determination of the real structural performance of bridges are needed. A method is proposed for the true full 3D analysis which can be applied to achieve the real spatial behaviour of concrete bridge structures taking into account rheological phenomena and changes of structural systems. Particularly, the effects of shear lag, shear performance of webs of box girders, warping torsion, warping of cross-sections, distortional effects, state of stresses in the singular regions, the real prestress loss, etc., can be correctly determined. The method combines conventional approaches (based on the elementary beamtype assumptions) for calculating the time development of the internal forces due to rheological phenomena and changes in the structural system during construction and routine commercial FEM software intended for calculating spatial shell structures. The method is capable to give the true 3D prediction of structure behaviour by using only commercially available software. The primary advantage of the proposed method is its ease of application which allows the true 3D performance to be determined from simple calculations. The method offers the designers of concrete bridge girders an ideal design tool. The correct 3D simulation can lead to more efficient and economical designs.
Authors: Gui Rong Liu, Shi Hai Xiang, Xiao Ke Li, Shun Bo Zhao
Abstract: Under the background of engineering application, a 3-D FE analysis was carried out to evaluate the loading performance of a two-hole pair-arch tunnel under-across the main canal of South-to-North Water Transfer Project. In fact, the tunnel was constructed in integral longitudinally without obeying the design requirement of parting within certain length. The analysis showed that the vertical deformation and tensile stress along the longitudinal axis are obviously affected by the loads from main canal, moreover, the tensile stress exceeds the limit of tensile strength of concrete, which may lead thoroughly cracks on top plate of tunnel. This analysis determined the crack zone which should be dealt with.
Authors: Min You, Jia Ling Yan, Xiao Ling Zheng, Ding Feng Zhu, Jing Rong Hu
Abstract: The effect of the adhesive thickness and elastic modulus on the stress distribution in the mid-bondline of the adhesively-bonded steel/steel joint under impact loading is analyzed using 3-D finite element method (FEM). The results show that the stress distributed in bondline near the interface was significantly affected by the adhesive thickness and the elastic modulus. When the thickness increased from 1 mm to 2 mm, the values of all the stress components increased evidently along the upper edge of the adhesive but decreased significantly along the lower edge near the loading face. When the elastic modulus of the adhesive was increased, all the stresses increased along either the upper or the lower edge. It is clear that the suitable thickness and the elastic modulus of the adhesive are very important when the adhesively bonded joints subjected to the impacting load.
Authors: J.R. Słowik, L.M. Kasprzyczak, Ewald Macha
Abstract: Unreliable and inflexible analog control systems of fatigue test stands applied in laboratories are being replaced by systems enabling easy development and implementation of new test ideas. This paper presents a digital control system applied in the fatigue test stand SHM 250b. It is based on a new electronic system and the I/O board RT-DAQ4/PCI with the software Matlab/Simulink used for communication with the board. The control system for the fatigue test stand SHM 250b gives the possibility of performing fatigue tests under controlled strain ε(t), stress σ(t) and energy parameter W(t) which is calculated from the stress and strain signals. The applied control system is now used, depending on the performed fatigue tests, and can be developed for specific needs of material strength analysis.
Authors: Kouichi Yasuda, Tadachika Nakayama, Satoshi Tanaka
Abstract: A mechanical model is proposed to estimate internal stress during sintering of ceramic multiphase laminates. A symmetrical multi-layered laminate is assumed, and one-dimensional elastic analysis is carried out on the change in stress of each layer during sintering, based on the differences in sintering strain, thermal expansion strain and phase transformation strain between the layers. By taking a limit such that the thickness of each layer approaches infinitesimally small, the internal stress expression can be extended into the case of the materials with continuous compositional change (viz. functionally gradient materials).
Authors: Kouichi Yasuda, Pei Ling Lv
Abstract: This paper proposes a model for estimating stress history during sintering of ceramic laminates. A symmetrical 3-layered laminate is assumed, and one-dimensional elastic calculation gives the stress change of each layer during heating, keeping at the sintering temperature, and cooling, respectively. How to get the stress history is actually shown by incorporating data of mechanical and thermal expansion properties of calcined monolayers. The validity of this model is discussed with a preliminary experiment on dense alumina / porous alumina laminates.
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