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RISS 인기검색어
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- 저자 : Changjiang Song (검색결과 5 건)
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Nonlinear aerodynamic stability analysis of orthotropic membrane structures with large amplitude
Zhoulian Zheng,Yunping Xu,Changjiang Liu,Xiaoting He,Weiju Song 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.37 No.4
The aerodynamic stability of orthotropic tensioned membrane structures with rectangular plane is theoretically studied under the uniform ideal potential flow. The aerodynamic force acting on the membrane surface is determined by the potential flow theory in fluid mechanics and the thin airfoil theory in aerodynamics. Then, based on the large amplitude theory and the D'Alembert's principle, the interaction governing equation of wind-structure is established. Under the circumstances of single mode response, the Bubnov-Galerkin approximate method is applied to transform the complicated interaction equation into a system of second order nonlinear differential equation with constant coefficients. Through judging the stability of the system characteristic equation, the critical divergence instability wind velocity is determined. Finally, from different parametric analysis, we can conclude that it has positive significance to consider the characteristics of orthotropic and large amplitude for preventing the instability destruction of structures.
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Nonlinear aerodynamic stability analysis of orthotropic membrane structures with large amplitude
Zheng, Zhoulian,Xu, Yunping,Liu, Changjiang,He, Xiaoting,Song, Weiju Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.37 No.4
The aerodynamic stability of orthotropic tensioned membrane structures with rectangular plane is theoretically studied under the uniform ideal potential flow. The aerodynamic force acting on the membrane surface is determined by the potential flow theory in fluid mechanics and the thin airfoil theory in aerodynamics. Then, based on the large amplitude theory and the D'Alembert's principle, the interaction governing equation of wind-structure is established. Under the circumstances of single mode response, the Bubnov-Galerkin approximate method is applied to transform the complicated interaction equation into a system of second order nonlinear differential equation with constant coefficients. Through judging the stability of the system characteristic equation, the critical divergence instability wind velocity is determined. Finally, from different parametric analysis, we can conclude that it has positive significance to consider the characteristics of orthotropic and large amplitude for preventing the instability destruction of structures.
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Conghui Hu,Jianlei Zhang,Yunhu Zhang,Ke Han,Changjiang Song,Qijie Zhai 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.2
High-entropy alloys (HEAs) are novel multi-element alloys based on five or more constituent elements in a range of 5–35 at%. Here we present a method to improve strength of a body-centered cubic (bcc) matrix HEA without loss of ductility. Theimprovement was achieved by phase modulation combined other strengthening effect of interstitial carbon addition. Carbonaddition can enhance strength and retain good ductility in some steels because carbon increases the volume fraction offace-centered cubic (fcc) phase. We used the same principle to design and fabricate a set of Al8(FeCuCrMn)92Cx (x = 0, 1,2, 3, 4 at%) HEAs under near-rapid solidification. Our results showed that carbon addition modulated constituent phases byincreasing the volume fraction of fcc phase and carbides. As a result, addition of carbon increased yield strength of this bccmatrix HEA. But the ductility decreased, especially when carbon content was higher than 3 at%, which was ascribed to unevendistribution of Cu-rich fcc phase and carbides precipitated in bcc phase region. After annealing at 1173 K for 2 h, additionof 1 at% carbon improved yield strength without compressive fracture. It demonstrated that a proper carbon content additionwith annealing can enhance the yield strength without loss of ductility for this bcc matrix HEA. Thus, interstitial carbon additionis a meaningful method to improve the mechanical properties by phase modulation combined other strengthening effect.
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Jianlei Zhang,Yueshan Jiang,Conghui Hu,Gang Ji,Changjiang Song,Qijie Zhai 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.11
The influence of Cr on the microstructural evolution of austenite in Fe-20Mn-9Al-1.2C-xCr (wt%, x = 0, 3 and 6) low-densitysteels during isothermal aging at 650 °C for various durations was systematically investigated. With the isothermal agingprocessed, the 0Cr and 3Cr samples underwent the divorced eutectoid transformation followed by the eutectoid transformation,while only the eutectoid transformation was observed in the 6Cr sample. Meanwhile, increasing Cr content changedthe eutectoid transformation products from ferrite + κ-carbide in the 0Cr sample to ferrite + κ-carbide + M23C6carbide in the3Cr sample, and to ferrite + M7C3carbide in the 6Cr sample. The Cr addition significantly increased the A1 temperature (655°C) of the 0Cr sample to 712 °C of the 3Cr sample, and to 841 °C of the 6Cr sample. As a result, the temperature differencebetween the A1 temperature and experimental phase transformation temperature (650 °C) was enlarged, which provided agreater driving force for the eutectoid transformation and accelerated the transformation rate of eutectoid transformation. Inaddition, the Cr addition had a significant effect on the diffusion of constituent elements, decreased the interlayer spacingof pearlite structure from 625 ± 30 nm in the 0Cr sample to 385 ± 25 nm in the 3Cr sample, and to 150 ± 20 nm in the 6Crsample, refining the eutectoid structure. These findings revealed the mechanism regarding the effect of Cr addition on theeutectoid transformation of austenite, offering valuable insights into the microstructure design of high-performance lowdensitysteels.
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Monte Carlo Simulation on Kinetics of Batch and Semi-Batch Free Radical Polymerization
Jing Shao,Peng Chen,Wei Tang,Ru Xia,Xiaoshuang Feng,Jiasheng Qian,Changjiang Song 한국고분자학회 2015 Macromolecular Research Vol.23 No.11
Based on Monte Carlo simulation technology, we proposed a hybrid routine which combines reaction mechanism together with coarse-grained molecular simulation to study the kinetics of free radical polymerization. By comparing with previous experimental and simulation studies, we showed the capability of our Monte Carlo scheme on representing polymerization kinetics in batch and semi-batch processes. Various kinetics information, such as instant monomer conversion, molecular weight, and polydispersity etc. are readily calculated from Monte Carlo simulation. The kinetic constants such as polymerization rate kp is determined in the simulation without of “steady-state” hypothesis. We explored the mechanism for the variation of polymerization kinetics those observed in previous studies, as well as polymerization-induced phase separation. Our Monte Carlo simulation scheme is versatile on studying polymerization kinetics in batch and semi-batch processes.
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