检索结果-南通市图书馆

Role of fragmentation in as-cast structure:numerical study and experimental validation

在线全文

学校读者我要写书评

暂无评论

China Foundry 2017年第5期14卷 321-326页

作者： Yong-jian Zheng Meng-huai Wu A.Kharicha A.Ludwig Chair of simulation and Modelling of metallurgical processes Montanuniversitaet Leoben Christian Doppler Laboratory for Advanced Process simulation of Solidification and Melting Department of Metallurgy University of Leoben

A volume average solidification model is extended to incorporate fragmentation as the source of equiaxed crystals during mixed columnar-equiaxed solidification. This study is to use this model to analyze the role of fragmentation in the formation of as-cast structure. Test simulations are made for the solidification of a model alloy(Sn-10wt.%Pb) with two different geometries. The first one is a 2D rectangular domain(50 × 60 mm^2) as cooled from the top boundary. Solidification starts unidirectionally as columnar structure from the top. The solute(Pb) enriched interdendritic melt is heavier than the bulk melt, and sinks downwards, hence leads to solutal convection. Fragmentation phenomenon occurs near the columnar tip front. The fragments are transported out of the columnar region, and they continue to grow and sink, and finally settle down and pile up at the bottom. The growing columnar structure from the top and pile-up of equiaxed crystals from the bottom finally lead to a mixed columnar-equiaxed structure, in turn leading to a columnar-to-equiaxed transition(CET). The second geometry is a 3D plate, 100 × 60 ×10 mm^3, as cooled laterally from one side. It was cast experimentally and analyzed for the as-cast structure. The equiaxed fragments are produced in the solidification front and transported into the bulk melt, leading to a special pattern of as-cast structure: columnar structure in the cool wall side and equiaxed structure in the upper left corner near the hot wall side, extending downwards to the middle bottom region. Numerically calculated as-cast structures agree with the experiment results.

关键词： macrostructure interdendritic fluid flow fragmentation

Investigation of effect of electrode polarity on electrochemistry and magnetohydrodynamics using tertiary current distribution in electroslag remelting process

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2021年第12期28卷 1551-1561页

作者： E.Karimi-Sibaki A.Kharicha A.Vakhrushev M.Wu A.Ludwig J.Bohacek Christian-Doppler Laboratory for metallurgical Applications of Magnetohydrodynamics Montanuniversitaet of LeobenLeobenA-8700Austria Chair of simulation and modeling of metallurgical processes Montanuniversitaet of LeobenLeobenA-8700Austria Heat Transfer and Fluid Flow Laboratory Faculty of Mechanical EngineeringBrno University of TechnologyTechnicka 2896/261669BrnoCzech Republic

Transport phenomena including the electromagnetic,concentration of ions,flow,and thermal fields in the electroslag remelting(ESR)process made of slag,electrode,air,mold,and melt pool are computed considering tertiary current ***-Planck equations are solved in the bulk of slag,and faradaic reactions are regarded at the metal-slag *** at exploring electrochemical effects on the behavior of the ESR process,the calculated field structures are compared with those obtained using the classical ohmic approach,namely,primary current distribution whereby variations in concentrations of ions and faradaic reactions are ***,the influence of the earth magnetic field on magnetohydrodynamics in the melt pool and slag is *** impact of the polarity of electrode,whether positive,also known as direct current reverse polarity(DCRP),or negative,as known as direct current straight polarity(DCSP),on the transport of oxygen to the ingot of ESR is *** obtained modeling results enabled us to explain the experimental observation of higher oxygen content in DCSP than that of DCRP operated ESR process.

关键词： Electroslag remelting Electrochemistry Calcium fluoride Calcium oxide Ion transport Electro-migration

Norton-Hoff model for deformation of growing solid shell of thin slab casting in funnel-shape mold

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2022年第1期29卷 88-102页

作者： Alexander Vakhrushev Abdellah Kharicha Menghuai Wu Andreas Ludwig Gerald Nitzl Yong Tang Gernot Hackl Josef Watzinger Christian M.G.Rodrigues Christian-Doppler Laboratory for metallurgical Applications of Magnetohydrodynamics Montanuniversitat Leoben8700 LeobenAustria Primetals Technologies 4031 LinzAustria Chair of simulation and modeling of metallurgical processes Department of MetallurgyMontanuniversit?t Leoben8700 LeobenAustria RHI Magnesita GmbH 1120 ViennaAustria RHI Magnesita GmbH 8700 LeobenAustria

A funnel-type mold is commonly used to provide necessary clearance for the submerged entry nozzle in the thin slab casting(TSC).The partially solidified shell is subjected to the mechanical deformations,which can lead to the defects formation and,as a results,to a ***,the results of the flow simulation,performed by the finite volume method(FVM),are fed to the external package for the finite element analysis of stress and strain.A coupled model was assembled using“creeping solid”approach by blending the Norton-Hoff viscoplastic stress for the solidifying shell with the Newtonian viscous stress of the liquid *** FVM was used to combine both liquid and solid stress models within a single *** iterative procedure based on the improved both side diffusion method was introduced to treat the nonlinear relation between the viscoplastic stress and the strain *** modeled shell thickness was verified by previously published breakout measurements and the simulation *** distribution,obtained during the TSC simulation,dominantly corresponds to the viscoplastic *** numerical approach is robust and has direct industrial application.

关键词： Solid shell Viscoplastic stress Solidification Norton-Hoff model Thin slab Continuous casting Improved both side diffusion method OpenFOAM

F）remature melt solidification during mold filling and its nfluence on the as-cast structure

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Mechanical Engineering 2018年第1期13卷 53-65页

作者： M. WU M. AHMADEIN A. LUDWIG Chair for simulation and modeling of metallurgical processes University of Leoben Leoben A-8700 Austria Christian-Doppler Laboratory for Advanced Process simulation ofSolidification and Melting Department of Metallurgy University ofLeoben Leoben A-8700 Austria Production Engineering and Mechanical Design Department Faculty ofEngineering Tanta University Tanta 31111 Egypt

Premature melt solidification is the solidifica- tion of a melt during mold filling. In this study, a numerical model is used to analyze the influence of the pouring process on the premature solidification. The numerical model considers three phases, namely, air, melt, and equiaxed crystals. The crystals are assumed to have originated from the heterogeneous nucleation in the undercooled melt resulting from the first contact of the melt with the cold mold during pouring. The transport of the crystals by the melt flow, in accordance with the so- called ＂big bang＂ theory, is considered. The crystals are assumed globular in morphology and capable of growing according to the local constitutional undercooling. These crystals can also be remelted by mixing with the super- heated melt. As the modeling results, the evolutionary trends of the number density of the crystals and the volume fraction of the solid crystals in the melt during pouring are presented. The calculated number density of the crystals and the volume fraction of the solid crystals in the melt at the end of pouring are used as the initial conditions for the subsequent solidification simulation of the evolution of the as-cast structure. A five-phase volume-average model for mixed columnar-equiaxed solidification is used for the solidification simulation. An improved agreement between the simulation and experimental results is achieved by considering the effect of premature melt solidification during mold filling. Finally, the influences of pouring parameters, namely, pouring temperature, initial mold temperature, and pouring rate, on the premature melt solidification are discussed.

关键词： premature solidification mold filling as-caststructure modeling

Numerical microstructure prediction for an aluminium casting and its experimental validation

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

China Foundry 2011年第3期8卷 331-336页

作者： Unterreiter Guenter Ludwig Andreas Wu Menghuai Materials Center Leoben Forschung GmbH Leoben Austria Chair for simulation and Modelling of metallurgical processes Department of Metallurgy University of Leoben Leoben Austria

Virtual manufacturing based on through-process modelling becomes an evolving research area which aims at integrating diverse simulation tools to realize computer-aided design, analysis, prototyping and manufacturing. Numerical prediction of the as-cast microstructure is an initial and critical step in the whole through- process modelling chain for engineering components. A commercial software package with the capability of calculating important microstructure features for aluminium alloys is used to simulate a G-AISi7MgCu0.5 laboratory casting. The simulated microstructure, namely grain size, secondary dendrite arm spacing and diverse phase fractions are verified experimentally. Correspondence and discrepancies are reported and discussed.

关键词： numerical microstructure prediction aluminium casting through-process modelling

Numerical simulation for macrosegregation in direct-chill casting of 2024 aluminum alloy with an extended continuum mixture model

在线全文

学校读者我要写书评

暂无评论

Transactions of Nonferrous Metals Society of China 2018年第5期28卷 1007-1015页

作者： Hai-jun LUO Wan-qi JIE Zhi-ming GAO Yong-jian ZHENG State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi＇an 710072 China Chair of simulation and modeling of metallurgical processes Montan Universitaet Leoben 8700 Leoben Austria

An extended continuum mixture model for macrosegregation is applied to predicting Cu and Mg segregation in large-size ingot of 2024 aluminum alloy during direct chill casting（DC）. A microsegregation model using the approximate phase diagram data was coupled with macroscopic transport equations for macrosegregation profiles. Then, the impacts of transport mechanisms on the formation of macrosegregation were discussed. It is found that copper and magnesium have a similar segregation configuration from the billet center to surface. Negative segregation is observed in the centerline and subsurface, whereas positive segregation is obtained in the surface and somewhat underestimated positive segregation in the middle radius. Further, the discrepancy between the predicted and experimental results was discussed in detail. The results show that the magnesium to some extent alleviates the copper segregation in ternary alloy, compared with that in binary alloy. The predicted results show good agreement with measured experimental data obtained from literatures.

关键词： direct-chill casting macrosegregation numerical simulation continuum model 2024 aluminum alloy

基于热溶质对流及晶粒运动的柱状晶-非球状等轴晶混合三相模型

在线全文

学校读者我要写书评

暂无评论

金属学报 2016年第9期52卷 1096-1104页

作者：李军葛鸿浩 WU Menghuai LUDWIG Andreas 李建国上海交通大学材料科学与工程学院上海200240 simulation and modeling of metallurgical processes University of Leoben Christian-Doppler Lab for Advanced Process simulation of Solidification and Melting University of Leoben

基于Eulerian-Eulerian方法,阐述了简化枝晶状等轴晶、柱状晶以及金属液三相完全混合的凝固模型.模型考虑了等轴晶的移动及柱状晶对等轴晶的捕获,跟踪了柱状晶尖端的位置并考虑了等轴晶和柱状晶的相互竞争生长,因此该模型具备了预测柱... 详细信息

基于Eulerian-Eulerian方法,阐述了简化枝晶状等轴晶、柱状晶以及金属液三相完全混合的凝固模型.模型考虑了等轴晶的移动及柱状晶对等轴晶的捕获,跟踪了柱状晶尖端的位置并考虑了等轴晶和柱状晶的相互竞争生长,因此该模型具备了预测柱状晶向等轴晶转变(CET)的能力;为了在不过量增加计算量的前提下提高模型的精度,模型对等轴晶采取了简单的枝晶化处理,即采用简化方法描述等轴晶包络线内固相分数.分别模拟了3.25和25 t钢锭的凝固过程,成功预测了大型钢锭凝固过程所形成的底部锥形负偏析、"类-A型"偏析以及CET等现象.分析认为长细形状铸锭中出现的顶部负偏析区,是由于凝固后期所形成的局部小钢锭及等轴晶在其内部的沉积聚集而成.

关键词：数值模拟宏观偏析钢锭晶粒运动 CET

CFD simulation of impeller shape effect on quality of mixing in two-phase gas–liquid agitated vessel

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2020年第11期28卷 2733-2745页

作者： Amir Heidari Process simulation and modeling Laboratory(PSMlab) Faculty of ChemicalPetroleum and Gas EngineeringSemnan UniversitySemnan ***Iran

Mixing efficiency in two-phase gas–liquid agitated vessel is one of the important challenges in the industrial *** fluid dynamics technique(CFD)was used to investigate the effect of four different pitched blade impellers,including 15°,30°,45°and 60°,on the mixing quality of gas–liquid agitated *** multiphase flow behavior was modeled by Eulerian–Eulerian multiphase approach,and RNG k-εwas used to model the *** CFD results showed that a strong global vortex plays the main role on the mixing quality of the gas phase in the *** on the standard deviation criterion,it was observed that the axial distribution of the gas phase in the 30°impeller is about 55%better than the *** addition,the results showed that the 30°impeller has a uniform radial distribution over the other impellers and the maximum gas phase holdup in the *** of the power consumption of the impellers showed that the 30°impeller has the highest power consumption among the other pitched blade ***,examine the effect of same power condition for pitched blade impellers showed that the 30°impeller has the best mixing quality in this condition.

关键词： Pitched blade impeller Mixing CFD Multiphase flow RNG k-εmodel

simulation on solidification of an Al-Ni alloy under electromagnetic stirring

在线全文

学校读者我要写书评

暂无评论

China Foundry 2012年第3期9卷 258-262页

作者： Sha Minghong Wang Tongmin Bai Fudong Li Jun Li Tingju School of Materials and Metallurgy University of Science and Technology LiaoningAnshan 114051China School of Materials Science and Engineering Dalian Uaiversity of TechnologyDalian 116085China Sinopec Fushun Research Institute of Petroleum and Petrochemicals Fushun 113001China simulation and modeling of metallurgical processes Department of MetallurgyUniversity of LeobenA-8700 LeobenAustria

The microstructure of AI-Ni alloy has a significant influence on its performance, while electromagnetic stirring is one of the most effective methods for control of solidification structure of AI alloy. To investigate the effect of electromagnetic stirring on the solidification of the ingot, the solidification of the Al-50Ni alloy in vacuum with electromagnetic stirring was described by numerical simulation in this paper; and a three dimensional mathematical model was established. The electromagnetic field was simulated by ANSYS software and the thermal-flow field was simulated by FLUENT software. The coupling between the electromagnetic field and the thermal-flow field was implemented by user-defined subroutines. It is found that the current intensity has significant influences on the fluid flow and the microstructure of the alloy. The simulation results agree well with the experimental results, and the optimum current intensity under the exprimental conditions is 80 A, while the frequency is 50 Hz.

关键词： electromagnetic stirring numerical simulation Al-Ni alloy solidification