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Nucleation Mechanism for Bainite

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Journal of Materials science & technology 2002年第1期18卷 1-2页

作者： xi zhang, xuejun JIN and t.y.Hsu(Xu Zuyao)School of Materials {2. and {3., shanghai jiao tong university, shanghai 2.0030, china [ Manuscript received October 8, 2.01] shanghai jiao {2. Univ Sch Mat Sci & Engn Shanghai 200030 Peoples R China

Based on the experimental results that solute-depleted zone was observed in Cu-2.Zn-4AI (mass fraction) at 52. K, AG is calculated as a positive according to the thermodynamic criteria for the spinodal decomposition of a ternary systems. So, the solute-depleted zone cannot be formed by spinodal decomposition. Dislocation density required by the formation of solute-depleted zone is estimated greater than 7.89×109 cm-2. according to the segregation of solute atoms around dislocations, which is not consistent with the practical situation for the alloy at 52. K. Associated with the internal friction experimental fact that internal friction peaks appear within the incubation for bainitic transformation in Cu-Zn-AI alloy, the equilibrium temperature, tO, is evaluated as 43. K for solute-depleted Cu-2.Zn-3.4AI, which is lower than the experimental temperature 52. K. thus, nucleation by shear mechanism is impossible in this circumstance. therefore, it is concluded that, like bainite in steels and Ag-Cd, bainite in Cu-Zn-AI alloys nucleates by diffusional mechanism, just implied by the experimental existence of solute-depleted zone.

关键词： Bainitic transformation Prebainitic phenomenon Solute-depleted zone Diffusion Nucleation

Induced electromagnetic stirring behavior in a resistance spot weld nugget

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science china(technological sciences) 2010年第5期53卷 1271-1277页

作者： LI yongBing1,LIN ZhongQin1,2.LAI xinMin1,2.CHEN GuanLong1,2.& zhang Ke3.1 {2. Key Laboratory of Digital Autobody engineering,{2. jiao tong university,{2. 2.02.0,china 2.State Key Laboratory of Mechanical System and Vibration,{2. jiao tong university,{2. 2.02.0,china 3.Welding engineering Institute,{2. jiao tong university,{2. 2.02.0,china 1. shanghai Key Laboratory of Digital Autobody engineering Shanghai Jiao Tong University Shanghai 200240 China2. State Key Laboratory of Mechanical System and Vibration Shanghai Jiao Tong University Shanghai 200240 China3. Welding Engineering Institute Shanghai Jiao Tong University Shanghai 200240 China

A multi-physics hybrid numerical model,which couples electric,magnetic,thermal and flow fields,was used to investigate electromagnetic stirring behavior in a resistance spot weld *** differences of two kinds of different excitation inputs,i.e.,a sinusoidal current and its root-mean-square(RMS) value,were studied to examine if they could produce equivalent electromagnetic stirring effects in the weld *** showed that the two types of current inputs could produce almost identical fluid flow and heat transfer patterns and consistent evolution of flow and thermal fields in the *** the end of the welding cycles,the maximum flow velocity and temperature between the two inputs differed by 11.6% and 0.3.,***,the RMS current can be assumed to produce an approximately equivalent electromagnetic stirring effect with the sinusoidal current,and can be used in the future research to greatly improve the solution efficiency of the electromagnetic stirring behavior in the resistance spot weld nugget.

关键词： induced magnetic field electromagnetic stirring resistance spot welding fluid flow heat transfer

Metal chlorides loaded on activated carbon to capture elemental mercury

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Journal of Environmental sciences 2010年第11期22卷 1814-1819页

作者： Zhemin Shen,Jing Ma,Zhijian Mei,Jianda zhang School of Environmental science and {2.,{3. jiao tong university,{3. 2.02.0,china [a] School of Environmental science engineering Shanghai Jiao Tong University Shanghai 200240 China

Activated carbon （AC） was considered to be an effective sorbent to control mercury in combustion systems. However, its capture capacity was low and it required a high carbon-to-mercury mass ratio. AC loaded with catalyst showed a high elemental mercury （Hg 0 ） capture capacity due to large surface area of AC and high oxidization ability of catalyst. In this study, several metal chlorides and metal oxides were used to promote the sorption capacity of AC. As a result, metal chlorides were better than metal oxides loaded on AC to remove gaseous mercury. X-ray diffractometer （XRD）, thermogravimetric analyzer （tGA） and specific surface area by Brunauer- Emmett-teller method （BEt） analysis showed the main mechanisms： first, AC had an enormous surface area for loading enough MClx; second, Cl and MxOy were generated during pyrogenation of MClx; finally, there were lots of active elements such as Cl and MxOy which could react with elemental mercury and convert it to mercury oxide and mercury chloride. the HgO and HgCl 2.might be released from AC’s porous structure by thermo regeneration. A catalytic chemisorption mechanism predominates the sorption process of elemental mercury. As Co and Mn were valence variable metal elements, their catalytic effect on Hg 0 oxidization may accelerate both oxidation and halogenation of Hg 0 . the sorbents loaded with metal chlorides possessed a synergistic function of catalytic effect of valence variable metal and chlorine oxidation.

关键词： mercury activated carbon flue gas metal chloride metal oxide

An improved approach to the efficient construction of and search operations in motion graphs

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science china(Information sciences) 2012年第5期55卷 1042-1051页

作者： GAO yan 1,CHEN ZhiHua 2.CHEN MinGang 3.& SHEN yang 3.1 Software engineering Institute,East china Normal {2.,shanghai 2.0062.china 2.Department of Computer science and engineering,East china {2. of science and technology,shanghai 2.02.7,china 3.Department of Computer science and engineering,shanghai jiao tong {2.,shanghai 2.02.0,china 1. Software engineering Institute East China Normal University Shanghai 200062 China2. Department of Computer Science and Engineering East China University of Science and Technology Shanghai 200237 China3. Department of Computer Science and Engineering Shanghai Jiao Tong University Shanghai 200240 China

Motion graphs have been widely used as an effective technique in the synthesis of human *** synthesize well-formed motions,motion graphs require smooth transitions and good ***,the time and costs grow quadratically as the graph size *** this paper,we present a method to set up a hierarchical structure,called a structure *** coarse level of this graph models different motion categories and their transitions,and the fine level mainly captures different motion *** interpolation space method is used to improve the graph connectivity at the fine *** structure guides the establishment of a faster and more realistic graphical *** the building process,this structure also helps with searching the motion graph,by performing a traverse search and placing the findings into a direct look-up table or local search ***,when there is no direct link between the different motions,a navigation map is introduced to conduct an appropriate search path via a series of transition motion *** experimental results indicate that our approach could lower the computation time in construction and searching,while simultaneously providing a richer variety of motion styles.

关键词： motion graph structure table registration curve motion interpolation

A RHEOLOGICAL MODEL FOR POLyMER MELtS WItH INtERNAL StRUCtURE IN FLOW FIELDS

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Chinese Journal of Polymer science 1999年第2期17卷 151-158页

作者： Chi-xing Zhou Department of Polymeric Materials science and {2.,{3., shanghai 2.02.0, china shanghai jiao {2. Univ Dept Polymer Mat Sci & Engn Shanghai 200240 Peoples R China

Conceptually, an imagined conformation ellipsoid is supposed to represent the shape of a polymer chain for polymer melts in flow fields and to be equivalent to the volume element in a mathematical sense in continuum mechanics. A power law dependence of shear modulus of polymer melts on detC, referred to as envelope volume, is proposed. Based on those assumptions and the non-linear relation of shear modulus, a phenomenological viscoelastic model is derived. the model is tested in simple shear flow, simple elongational flow, oscillatory shear flow, and relaxation process after flow suddenly stopped. the results show that the model works well to predict the change of internal structure and viscoelastic performance of polymer melts in flow fields.

关键词： polymer melts rheological model polymer conformation flow fields

WAtER ENtRy OF A WEDGE BASED ON SPH MODEL WItH AN IMPROVED BOUNDARy tREAtMENt

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Journal of Hydrodynamics 2009年第6期21卷 750-757页

作者： GONG Kai LIU Hua WANG Ben-long Department of engineering Mechanics Shanghai Jiao Tong University Shanghai 200240 China State Key Laboratory of Ocean engineering Shanghai Jiao Tong University Shanghai 200240 China

the hydrodynamic problem of a two-dimensional wedge entering water is studied based on Smoothed Particle Hydrodynamics （SPH） model. A non-reflection boundary treatment for SPH method is proposed to reduce the reflection of sound waves. the boundary pressure is obtained using an improved coupling boundary treatment approach, which is validated by comparing the simulation results with experimental and analytical results in literature. A series of cases with different initial entering velocities are simulated. the maximum force on the wedge and the corresponding time required to reach it for the different cases of initial entering velocities of the wedge are obained and fitted into formulas against the initial entering velocity of the wedge. the maximum drag coefficients of the wedge for the different cases with Froude number greater than 2.are all near the value of 0.91.

关键词： water entry Smoothed Particle Hydrodynamics (SPH) non-reflection boundary

CALCULAtION OF ADDED MASS OF A VEHICLE RUNNING WItH CAVIty

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Journal of Hydrodynamics 2010年第3期22卷 312-318页

作者： LI Jie LU Chuan-jing HUANG Xuan Department of engineering Mechanics Shanghai Jiao Tong University Shanghai 200240 China Department of engineering Mechanics Shanghai Jiao Tong University Shanghai 200240 China State Key Laboratory of Ocean engineering Shanghai Jiao Tong University Shanghai 200030 China

A numerical method is developed to obtain the added mass coefficients of a vehicle running with cavity in numerical simulation for the multiphase flow of the vehicle which is imposed an added vibration and analyzing its hydrodynamic loads. the method is verified through the cases of non-cavitating sphere and ellipsoid. the changing rule of the added mass of a sphere during water exit is gained. then the influence of cavitation on the added mass of a cylinder is studied. the results show that λ 11, λ2., λ2., λ66 all decrease as the cavitation number reduces and the length of the attached cavity increases. there is almost a linear relationship between the cavity length and λ2. .the base cavity has great influence on λ11 its contribution decreases more than 60%, when the cavitation number changes from 0.6 to 0.2.

关键词： added mass cavity carrying forced vibration method

Virtual multi-dimensional internal bonds model and its application in simulation of rock mass

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science china(technological sciences) 2008年第2期51卷 192-201页

作者： zhang ZhenNan1,2 & GE xiuRun3.4 1 Department of Civil engineering,{3. university,{3. 200072,china 2 {3. Institute of Applied Mathematics and Mechanics,{3. university,{3. 200072, china 3.Institute of Geotechnical engineering,{3. jiao tong university,{3. 2.0030,china 4 Institute of Rock and Soil Mechanics,Chinese Academy of sciences,Wuhan 43.071,china 1. Department of Civil engineering Shanghai University Shanghai 200072 China 2. shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 China 3. Institute of Geotechnical engineering Shanghai Jiao Tong University Shanghai 200030 China 4. Institute of Rock and Soil Mechanics Chinese Academy of Sciences Wuhan 430071 China

VMIB (virtual multi-dimensional internal bonds) is a multiscale mechanical model developed from the VIB (virtual internal bond) theory. In VIB theory,the solid mate-rial is considered to consist of random-distributed material particles in microscale. these particles are connected with normal bonds. the macro constitutive relation is derived from the cohesive law between particles. However,in VMIB,the micro particles are connected with both normal and shear bonds. the macro constitutive relation is derived in terms of bond stiffness coefficients. It has been theoretically certified that there exists a corresponding relationship between the two bond stiffness coefficients and the two macro material constants,i.e. the young’s modulus and Poisson ratio. this corresponding relationship suggests that it should be necessary and sufficient to simultaneously account for the normal and shear interactions between particles. Due to the fact that the fracture criterion is directly incorporated into the constitutive relation,both VIB and VMIB present many advantages in simulating fractures of materials. In the damage model of rock mass,a damage tensor is usually defined to describe the distribution of cracks. the damage value in one direction determines the relative stiffness of rock mass in this direction. In VMIB solid,the relative distribution density of micro bonds in one direction determines the relative macro stiffness of the material in this direction. the effects of the damage value and the relative distribution density of bonds are consistent. to simulate the failure behavior of rock mass with VMIB,the presented paper sets up a quantitative relationship between the damage tensor and the rela-tive distribution density of bonds. Comparison of the theoretical and the experi-mental results shows that VMIB model can represent the effect of distributed cracks on rock mass with this relationship. the presented work provides a founda-tion for further simulating fracture behavior

关键词： VMIB (virtual multi-dimensional internal bonds) rock mass VIB (virtual internal bonds) multi-cracked body numerical simulation

Effects of Melt thermal treatment on A3.6 Alloy

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Journal of Materials science & technology 2003年第2期19卷 152-154页

作者： Jun WANG, Shuxian HE, Baode SUN and yaohe ZHOUSchool of Materials science and {2.,{3., shanghai 2.0030, china Sch. of Mat. Sci. and Eng. Shanghai Jiaotong Univ. Shanghai 200030 China

to increase the casting quality of hypoeutectic Al-Si alloys, the effects of melt thermal treatment on the solidification structure of the A3.6 alloy were analyzed by a factorial experiment, in which the overheated melt was mixed with the low temperature melt. Experimental results show that the elongation ratio and strength of the treated samples increase remarkably compared with the control sample. the primary dendrite size reduces dramatically and the dendrite changes from columnar to equiaxed, with a little change of the secondary dendrite arm spacing (SDAS). Combined with the measurement of the nucleation undercooling, it is concluded that the solidification structure and refining effect are dependent primarily on the low temperature melt. the refining mechanism is believed as a result of the multiplication of the nuclei in the melt thermal treatment procedure.

关键词： A3.6 Melt thermal treatment Solidification structure