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3D thermoelasticity solutions for functionally graded thick plates
Ji YING, Chao-feng LÜ, C. W. LIM
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(3): 327-336.
https://doi.org/10.1631/jzus.A0820406
Thermal-mechanical behavior of functionally graded thick plates, with one pair of opposite edges simply supported, is investigated based on 3D thermoelasticity. As for the arbitrary boundary conditions, a semi-analytical solution is presented via a hybrid approach combining the state space method and the technique of differential quadrature. The temperature field in the plate is determined according to the steady-state 3D thermal conduction. The Mori-Tanaka method with a power-law volume fraction profile is used to predict the effective material properties including the bulk and shear moduli, while the effective coefficient of thermal expansion and the thermal conductivity are estimated using other micromechanics-based models. To facilitate the implementation of state space analysis through the thickness direction, the approximate laminate model is employed to reduce the inhomogeneous plate into a homogeneous laminate that delivers a state equation with constant coefficients. The present solutions are validated by comparisons with the exact ones for both thin and thick plates. Effects of gradient indices, volume fraction of ceramics, and boundary conditions on the thermomechanical behavior of functionally graded plates are discussed.
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3D wind-induced response analysis of a cable-membrane structure
Jun-jie LUO, Da-jian HAN
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(3): 337-344.
https://doi.org/10.1631/jzus.A0820430
Wind loading is a dominant factor for design of a cable-membrane structure. Three orthogonal turbulent components, including the longitudinal, lateral and vertical wind velocities, should be taken into account for the wind loads. In this study, a stochastic 3D coupling wind field model is derived by the spectral representation theory. The coherence functions of the three orthogonal turbulent components are considered in this model. Then the model is applied to generate the three correlated wind turbulent components. After that, formulae are proposed to transform the velocities into wind loads, and to introduce the modified wind pressure force. Finally, a wind-induced time-history response analysis is conducted for a 3D cable-membrane structure. Analytical results indicate that responses induced by the proposed wind load model are 10%~25% larger than those by the conventional uncorrelated model, and that the responses are not quite influenced by the modified wind pressure force. Therefore, we concluded that, in the time-history response analysis, the coherences of the three orthogonal turbulent components are necessary for a 3D cable-membrane structure, but the modified wind pressure force can be ignored.
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New method of improving parts accuracy by adding heat balance support in selective laser sintering
Bing LIU, Li-chao ZHANG, Jian-hua MO, Bo QIAN
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(3): 361-369.
https://doi.org/10.1631/jzus.A0820226
In order to improve parts accuracy, a method of adding heat balance support (HBS) was proposed, and the detailed algorithm for generating HBS was developed. A number of experiments and a comparison between similar softwares, showed that the algorithm is efficient and feasible. Moreover, different features of HBS were studied for different kinds of materials, such as PS and nylon. The research findings indicate that automatically adding HBS can significantly improve the accuracy of the parts, and that the algorithm for generating HBS is efficient and precise.
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Filament geometrical model and nozzle trajectory analysis in the fused deposition modeling process
Yu-zhen JIN, Jia-fan ZHANG, Ying WANG, Zu-chao ZHU
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(3): 370-376.
https://doi.org/10.1631/jzus.A0820346
The geometrical model of the filament during the fused deposition modeling (FDM) process was firstly proposed based on three different models, tractrix, parabola, and catenary. Comparing with the actual measured filament curves on the Stratasys 1600 FDM machine, it is indicated that the tractrix model had the best agreement with the actual measured curves. With the analytical simulation, the nozzle trajectories in the straight-line deposition road, circle road, and arbitrary continuous curve road were deduced, according to the traxtric based geometrical model of the filament.
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Mechanical analysis and reasonable design for Ti-Al alloy liner wound with carbon fiber resin composite high pressure vessel
Chuan-xiang ZHENG, Fan YANG, Ai-shi ZHU
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(3): 384-391.
https://doi.org/10.1631/jzus.A0820025
To consider the internal pressure loaded by both the cylindrical Ti-Al alloy liner and the carbon fiber resin composite (CFRC) wound layers, two models are built. The first one is a cylinder loaded with the internal pressure in the hoop direction only. In this model, the total hoop direction load is distributed over all layers under the internal pressure. The second one is a cylinder loaded with the internal pressure in the axial direction only. In this model, the total axial load is distributed over all cylinders under the internal pressure. Taking the boundary conditions of the continuous displacement between layers into account, a group of equations are built. From these equations, we get the solutions of stresses in both hoop direction and axial direction loaded by every layer under internal pressures. After the stresses are obtained, a reasonable design can be done. An example is given in the final section of this study.
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Liquid film dryout model for predicting critical heat flux in annular two-phase flow
Bo JIAO, Li-min QIU, Jun-liang LU, Zhi-hua GAN
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(3): 398-417.
https://doi.org/10.1631/jzus.A0820322
Gas-liquid two-phase flow and heat transfer can be encountered in numerous fields, such as chemical engineering, refrigeration, nuclear power reactor, metallurgical industry, spaceflight. Its critical heat flux (CHF) is one of the most important factors for the system security of engineering applications. Since annular flow is the most common flow pattern in gas-liquid two-phase flow, predicting CHF of annular two-phase flow is more significant. Many studies have shown that the liquid film dryout model is successful for that prediction, and determining the following parameters will exert predominant effects on the accuracy of this model: onset of annular flow, inception criterion for droplets entrainment, entrainment fraction, droplets deposition and entrainment rates. The main theoretical results achieved on the above five parameters are reviewed; also, limitations in the existing studies and problems for further research are discussed.
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Absorption of NO2 into Na2S solution in a stirred tank reactor
Xiang GAO, Rui-tang GUO, Hong-lei DING, Zhong-yang LUO, Ke-fa CEN
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(3): 434-438.
https://doi.org/10.1631/jzus.A0820657
To understand the absorption mechanism of nitrogen dioxide into a sodium sulfide solution, a stirred tank reactor with a plane gas-liquid interface was used to measure the chemical absorption rate of diluted nitrogen dioxide into sodium sulfide solution. The absorption rates under various experimental conditions were measured and the effects of experimental conditions on nitrogen dioxide absorption rate were discussed. The results show that, in the range of this study, nitrogen dioxide absorption rate increases with increasing sodium sulfide concentration, nitrogen dioxide inlet concentration, and flue gas flow rate, but decreases with increasing reaction temperature and oxygen content in flue gas.
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Investigation of migration of pollutant at the base of Suzhou Qizishan landfill without a liner system
Hai-jian XIE, Yun-min CHEN, Liang-tong ZHAN, Ren-peng CHEN, Xiao-wu TANG, Ru-hai CHEN, Han KE
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(3): 439-449.
https://doi.org/10.1631/jzus.A0820299
We investigated migration of pollutant at the base of the Suzhou landfill after it had been operated for 13 years. The investigation was carried out by performing chemical analyses on the soil samples taken from the silty clay deposit. Concentrations of chloride, chemical oxygen demand (COD) and the heavy metals in the soil samples were determined using the standard methods. The experimental data showed that the maximum migration depth of chloride was more than 10 m, while the maximum migration depth of COD varied between 1 and 3.5 m. It is believed that the difference is attributed to the variation in diffusion rate and leachate-soil interaction. The chloride profiles also indicated that advection may be the dominant contaminant transport mechanism at this site. The total contents of Cu, Pb and Cr are very close to the background levels and the concentration values of these metals mainly are lower than the threshold values specified by the Chinese soil quality standard and the European one. The water-extractable concentrations of COD in the surface of the silty clay generally exceed the limit value specified by the Chinese standard. The concentrations of copper and chromium in pore water are 1~2 orders of magnitude less than the total concentrations of these heavy metals within the soils, implying that heavy metals are mainly adsorbed by the soil particles. Finally, remediation methods were suggested for this landfill site.
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Manganese removal from the Qiantang River source water by pre-oxidation: A case study
Jian-wen ZHU, Zhen ZHANG, Xiao-min LI, Xin-hua XU, Da-hui WANG
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(3): 450-457.
https://doi.org/10.1631/jzus.A0820409
We evaluated several different pre-oxidation treatments, namely the introduction of either potassium permanganate (KMnO4), chlorine (Cl2), or both to remove manganese (Mn) from the Qiantang River source water. Our results showed that Mn removal percentages were 12.7%, 71.0%, 17.4% and 58.7% when none of the oxidants, KMnO4 only, Cl2 only, or both oxidants were added, respectively. Furthermore, a field study showed that when the available Mn concentration in the source water was 0.14 mg/L, it could be reduced to less than 0.05 mg/L when a solution of KMnO4 (0.47 mg/L) was added as the oxidant.
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Preparation of AlN thin films for film bulk acoustic resonator application by radio frequency sputtering
Kan LI, Hao JIN, De-miao WANG, Yi-fei TANG
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2009, 10(3): 464-470.
https://doi.org/10.1631/jzus.A0820572
Aluminum nitride (AlN) thin films with high c-axis orientation have been prepared on a glass substrate with an Al bottom electrode by radio frequency (RF) reactive magnetron sputtering. Based on the analysis of Berg’s hysteresis model, the improved sputtering system is realized without a hysteresis effect. A new control method for rapidly depositing highly c-axis oriented AlN thin films is proposed. The N2 concentration could be controlled by observing the changes in cathode voltage, to realize the optimum processing condition where the target could be fixed stably in the transition region, and both stoichiometric film composition and a high deposition rate could be obtained. Under a 500 W RF power of a target with a 6 cm diameter, a substrate temperature of 450 °C, a target-substrate distance of 60 mm and a N2 concentration of 25%, AlN thin film with preferential (002) orientation was deposited at 2.3 μm/h which is a much higher rate than previously achieved. Through X-ray diffraction (XRD) analysis, the full width at half maximum (FWHM) of AlN (002) was shown to be about 0.28°, which shows the good crystallinity and crystal orientation of AlN thin film. With other parameters held constant, any increase or decrease in N2 concentration results in an increase in the FWHM of AlN.
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18 articles
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