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FINITE ELEMENT ANALySIS OF VISCOUS FLOW PAST A ROTATING SPHERE

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Journal of Hydrodynamics 2001年第2期13卷 80-85页

作者： Wang, y.x. Lu, x.y. Zhuang, L.x. Dept. of Modern Mech. Univ. of Sci. and Technol. of China Hefei 230026 China

Viscous flow past a rotating sphere with a constant rotating speed about an axis aligned with the free stream was investigated numerically by solving the three-dimensional Navier-Stokes equations using the finite element method. To elucidate the character of this flow in the near wake, the flow structures at different Reynolds numbers and rotating speeds are examined. The axisymmetric and non-axisymmetric flow structures were observed at Re=200 and 250, respectively, which rotate as a whole around the rotating axis steadily. At Re=300, the vortex shedding appears and the wake becomes more complicated. At low rotating speeds, the flow is dominated by the vortex shedding at higher Reynolds numbers. As the rotating speed increases, the rotating effect gets stronger and the interaction between the rotating action and the vortex shedding results a swirling vortex pattern in the near wake of the sphere.

关键词： Finite element method Navier Stokes equations Numerical methods Three dimensional

MESHFREE METHOD BASED ON POINT COLLOCATION FOR METAL FORMING SIMULATION

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Acta Metallurgica Sinica(English Letters) 2006年第2期19卷 79-84页

作者： H.y. Wen x.H. Dong x.y. Ruan Department of Plasticity Forming Engineering Shanghai Jiaotong University Shanghai 200030 China

A meshfree method based on reproducing kernel approximation and point collocation is presented for analysis of metal ring compression. The point collocation method is a true meshfree method without the employment of a background mesh. It is shown that, in a point collocation approach, the remesh problem because of the mesh distortion in FEM （finite element method） and the low efficiency in Galerkin-based meshfree method are avoided. The corrected kernel functions are introduced to the stabilization of free-surface boundary conditions. The solution of symmetric ring compression problem is compared with a conventional finite element solution, and reasonable results have been obtained.

关键词： meshfree method RKPM (reproducing kernel particle method) point collocation metal forming frictional contact

Thermal stability of nanograins with grain boundary relaxation in microalloyed Cu-Sb and Cu-Fe

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Journal of Materials Science & Technology 2023年第24期155卷 66-71页

作者： R.J. Zhu x.Zhou x.y. Li Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China School of Materials Science and Engineering University of Science and Technology of China Shenyang 110016 China

Grain refinement into nanoscale significantly enhances the strength and hardness of metallic materials but generally reduces the thermal stability by the introduced strong tendency for grain boundary(GB)*** nanograins through GB relaxation had been proven as an effective way in several metals recently when the grain size is below a critical ***,we discovered that the abnormally enhanced thermal stability induced by GB relaxation can be realized in 0.5%Sb or Fe doped Cu,similar to that in pure *** observed critical grain sizes for GB relaxation in the two Cu alloys are almost the same as pure ***,the GB relaxation effect on thermal stability is kind of suppressed compared to pure Cu with similar grain sizes because of the segregation/precipitation of Sb/Fe during the annealing process,which accelerates the detwinning and the failure of relaxed GBs.

关键词： Thermal stability Grain boundary relaxation Nanograined Cu alloy Segregation Precipitate

METASTABLE PHASE SEPARATION OF Fe_(50)Cu_(50) HyPOPERITECTIC ALLOy UNDER SPACE SIMULATION CONDITIONS

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维普期刊数据库

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Acta Metallurgica Sinica(English Letters) 1999年第2期12卷 198-204页

作者： Lu, x.y. Cao, C.D. Wei, B.B. Northwestern Polytechnical Univ Xi'an China

A 3m drop-tube was used to investigate the solidification of Fe50Cu50 hypoperitectic alloy. The falling droplets solidified as spheres and splats. The obtained particles range from 1000μm to 80μm in diameter. It was found that the phase separation occurred if the Fe-Cu liquid was undercooled to a certain extent before *** the big particles macroscopic separation of Fe-rich phase always appeared in the cented of the particles, and in the small ones the Fe-rich phase usually solidified as little spheres. In the flakes the Fe-rich and Cu-rich layers alternatively displayed from top to bottom.

关键词： peritectic alloy phase separation dendrite growth drop tube

STUDy ON PROPERTIES OF PULSE ELECTRODEPOSITED RE-Ni-W-P-SiC COMPOSITE COATINGS

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Acta Metallurgica Sinica(English Letters) 2007年第2期20卷 111-116页

作者： Z.C. Guo x.y. Zhu R.D. xu Faculty of Materials and Metallurgical Engineering Kunming University of Science and Technology Kunming 650093 China

The effects of pulse frequency f and duty cycle r on the deposition rate, composition, morphology, and hardness of pulse electrodeposited RE （rare earth）-Ni-W-P-SiC composite coatings have been studied. The results indicate that pulse current can improve the deposition rate of RE-Ni-W-P-SiC composite coatings; W, P, and SiC contents in the coating decrease with the increase of pulse frequency and reach the lowest value at f = 33Hz, whereas the RE content in the composite coatings increases with the increase of pulse frequency. SiC content decreases with the increase of duty cycle, W content reaches the lowest value, and P content reaches the highest value at r = 0.4; pulse current and RE can lead to smaller size of the crystalline grains; however, the effects of different pulse frequency and duty cycle on the morphologies of RE-Ni-W-P-SiC composite coatings are not obvious. The hardness of RE-Ni-W-P-SiC composite coatings is the highest when the duty cycle is at 0.6 and 0.8 and pulse frequency is at 50Hz. At the same pulse frequency, the hardness of RE-Ni-W-P-SiC composite coatings at r= 0.8 is higher than that at r= 0.6.

关键词： frequency duty cycle electrodeposition RE-Ni-W-P-SiC composite coating

MODELING OF MICROSTRUCTURAL EVOLUTION IN MICROALLOyED STEEL DURING HOT FORGING PROCESS

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Acta Metallurgica Sinica(English Letters) 2006年第4期19卷 279-286页

作者： J. Wang J. Chen Z. Zhao x.y. Ruan National Die ＆. Mold CAD Engineering Research Center Shanghai Jiaotong University Shanghai 200030 China

The microstractural evolution of microalloyed steel during hot forging process was investigated using physical simulation experiments. The dynamic recrystallized fraction was described by modifying Avrami＇s equation, the parameters of which were determined by single hit compression tests. Double hit compression tests were performed to model the equation describing the static recrystallized fraction, and the obtained predicted values were in good agreement with the measured values. Austenitic grain growth was modeled as： Dinc^5 = D0^5 ＋ 1.6 × 10^32t·exp （ -716870/RT ） using isothermal tests. Furthermore, an equation describing the dynamic recrystallized grain size was given as Ddyn=3771·Z^-0.2. The models of microstructural evolution could be applied to the numerical simulation of hot forging.

关键词： microalloyed forging steel flow stress recrystallized fraction grain size

RELATIONSHIP AMONG EVAPORATION FLUx OF GROUNDWATER, DEPTH OF WATER TABLE AND NEGATIVE PRESSURE HEAD IN BARE SOIL

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Journal of Hydrodynamics 2000年第4期12卷 52-58页

作者： Qian, J.Z. Zhu, x.y. Zhou, N.Q. Li, G.y. Dep. of Earth Sci. Nanjing Univ. Nanjing 210093 China

Evaporation of ground water is a part of moisture circulation in the field. And it is a main natural form in which water transmits from the ground water to the soil water and atmosphere water. According to the simulated experiments, we study the relationship among the evaporation, depth of groundwater table and negative pressure. By theoretical analysis of the experimental results, the main conclusions are drawn as follows. There are two abrupt points in every Q-H curve. The locations of the abrupt points are separately in step with the height of top of the capillary fringe and the height of maximal capillary rise in the soil section. When the depth of water table H is small, the evaporation flux of ground water is large. While the depth of water table exceeds the maximal capillary rise of media in vadose zone, the capillary rise breaks up and evaporation flux of groundwater is small. The water content ratio in ground surface tends to be zero and the surface of soil tends to be drought. These conclusions show that the maximal capillary rise of media in vadose zone is an important value in regulating rational depth of ground water to reduce the evaporation of ground water and to increase effective quantity of water resources. In the meantime, these conclusions are of important theoretical and practical significance to reduce the evaporation of ground water, to prevent and cure the salinization of soil, and to make full use of and protect water resources in the northern plains in China.

关键词： Capillarity Evaporation Soils

RHEOLOGy FEATURE OF SIMPLE METAL MELT

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Acta Metallurgica Sinica(English Letters) 2007年第3期20卷 181-186页

作者： C.J. Sun H.R. Geng y.S. Shen x.y. Teng Z.x. yang Key Laboratory of Liquid Structure and Heredity of Materials Ministry of Education Shandong University Jinan 250061 China School of Material Science and Engineering Jinan University Jinan 250022 China

The rheology feature of Sb, Bi melt and alloys was studied using coaxial cylinder high-temperature viscometer. The results showed that the curve of torsion-rotational speed for Sb melt presents a linear relation in all measured temperature ranges, whereas for the Bi melt, the curve presents obvious non-Newtonian feature within the low temperature range and at relative high shear stress. The rheology feature of Sb80Bi20 and Sb20Bi80 alloy melts was well correlated with that of Sb and Bi, respectively. It is considered that the rheology behavior of Sb melt plays a crucial role in Sb80Bi20 alloy and that of Bi melt plays a crucial role in Sb20Bi80 alloy.

关键词： Newtonian liquid rheology melt Bi Sb

Propagation behavior of elastic waves in one-dimensional piezoelectric/piezomagnetic phononic crystal with line defects

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Acta Mechanica Sinica 2014年第5期30卷 703-713页

作者： y.pang F.-y.Jiao J.-x.Liu Department of Engineering Mechanics Shijiazhuang Tie Dao University School of Mathematics and Physics University of Science and Technology Beijing

Using a stiffness matrix method, we in- vestigate the propagation behaviors of elastic waves in one-dimensional （1D） piezoelectric/piezomagnetic （PE/PM） phononic crystals （PCs） with line defects by calculating energy reflection/transmittion coefficients of quasi-pressure and quasi-shear waves. Line defects are created by the re- placement of PE or PM constituent layer. The defect modes existing in the first gap are considered and the influences on defect modes of the material properties and volume fraction of the defect layers, the type of incident waves, the location of defect layer and the number of structural layers are discussed in detail. Numerical results indicate that defect modes are the most obvious when the defect layers are inserted in the middle of the perfect PCs; the types of incidence wave and material properties of the defect layers have important effects on the numbers, the location of frequencies and the peaks of defect modes, and the defect modes are strongly de- pendent on volume fraction of the defect layers. We hope this paper will be found useful for the design of PE/PM acoustic filters or acoustic transducer with PCs structures.

关键词： 1D phononic crystal Piezoelectric/piezomag- netic. Elastic wave Line defect Stiffness matrix method