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Hot Deformation Behavior and Dynamic Recrystallization Characteristics in a Low-Alloy High-Strength Ni–Cr–Mo–V Steel

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Acta Metallurgica Sinica(English Letters) 2018年第9期31卷 963-974页

作者： chuan wu Shuang Han National-Local Joint Engineering Laboratory of Intelligent Manufacturing Oriented Automobile Die & Mould College of Mechanical EngineeringTianjin University of Technology and Education College of Mechanical Engineering Yanshan University

This study presented a quantitative investigation of deformation behavior and dynamic recrystallization of low-alloy high- strength Ni-Cr-Mo-V steels during hot deformation. A series of isothermal compression experiments were performed at temperatures ranging from 800 to 1200 ℃ and strain rates from 0.01 to 10 s^-1 with a height reduction of 60%. A complete Arrhenius constitutive model and processing maps were developed. The results showed that the constitutive model had the ability to predict the flow stress with an average absolute relative error of 〈 5.7%. The processing maps constructed at strains of 0.2, 0.4, and 0.8 showed that flow instability was prone to occur at higher strain. Dynamic recrystallization tended to take place at higher temperatures （900-1200 ℃） and lower strain rates （0.01^-1 s^-1）. The critical strain for the onset of dynamic recrystallization was determined, and a kinetics model was developed. The predicted results for recrystaUization volume fraction and flow stress were compared with the experimental data, which indicated that the model was accurate and reliable.

关键词： Deformation behavior Dynamic recrystallization Constitutive equation Processing map Critical strain RecrystaUization kinetics

A hybrid DEM/CFD approach for solid-liquid flows

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Journal of Hydrodynamics 2014年第1期26卷 19-25页

作者：邱流潮 wu chuan-yu College of Water Resources and Civil Engineering China Agricultural University Department of Chemical and Process Engineering University of SurreyGuildfordSurrey

A hybrid scheme coupling the discrete element method （DEM） with the computational fluid dynamics （CFD） is developed to model solid-liquid flows. Instead of solving the pressure Poisson equation, we use the compressible volume-averaged continuity and momentum equations with an isothermal stiff equation of state for the liquid phase in our CFD scheme. The motion of the solid phase is obtained by using the DEM, in which the particle-particle and particle-wall interactions are modelled by using the theoretical contact mechanics. The two phases are coupled through the Newton＇s third law of motion. To verify the proposed method, the sedi-mentation of a single spherical particle is simulated in water, and the results are compared with experimental results reported in the literature. In addition, the drafting, kissing, and tumbling （DKT） phenomenon between two particles in a liquid is modelled and rea-sonable results are obtained. Finally, the numerical simulation of the density-driven segregation of a binary particulate suspension in-volving 10 000 particles in a closed container is conducted to show that the presented method is potentially powerful to simulate real particulate flows with large number of moving particles.

关键词： discrete element method (DEM) computational fluid dynamics (CFD)

Preparation and characterization of Pt-WO_3/C catalysts for direct ethanol fuel cells

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Rare Metals 2010年第3期29卷 255-260页

作者： wu Feng LIU Yanhong wu chuan School of Chemical Engineering and Environment Beijing Institute of Technology Beijing 100081 China National Development Center for High Technology Green Materials Beijing 100081 China

Three co-impregnation/chemical reduction methods in acidic solutions of pH 〈 1,including ethylene glycol （EG）,NaBH4,and HCOOH,were compared for Pt-WO3/C ***-WO3/C catalysts containing 10 wt.% and 20 wt.% platinum per carbon were prepared by the three methods; their morphology and electrocatalytic activities were *** 20 wt.% Pt-WO3/C catalyst prepared by the co-impregnation/EG method presented the optimal dispersion with an average particle size of 4.6 nm and subsequently the best electrocatalytic activity,and so,it was further *** anodic peak current density for ethanol oxidation from linear sweep voltammetry （LSV） is 7.9 mA·cm^-2,which is 1.4 and 5.2 times as high as those of the catalysts prepared by co-impregnation/NaBH4 and co-impregnation/ HCOOH reduction methods,2.1 times as high as that of the 10 wt.% Pt-WO3/C catalyst prepared by co-impregnation/EG method,respectively.

关键词： direct ethanol fuel cells catalysts preparation method characterization ethanol electrooxidation

Preparation of Pt/C Nanocatalysts by Ethylene Glycol Method in Weakly Acidic Solutions

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Journal of Materials Science & Technology 2010年第8期26卷 705-710页

作者： Feng wu Yanhong Liu chuan wu School of Chemical Engineering and Environment Beijing Institute of Technology Beijing 100081 China National Development Center for High Technology Green Materials Beijing 100081 China

Pt/C catalysts were prepared by ethylene glycol （EG） method in weakly acidic solutions adjusted by sodium citrate （NasCit）, sodium acetate （NaAc） and sodium hydroxide （NaOH）, separately. The effects of alkalizing agent, pH and temperature were investigated by transmission electron microscopy （TEM） and CV. The composition and structure of Pt/C catalyst prepared at optimal conditions of 140℃ and pH=6.7 adjusted by NasCit was further characterized by X-ray photoelectron microscopy （XPS） and X-ray diffraction （XRD）, respectively. The average particle size of Pt/C catalyst prepared using Na3Cit is 2.1 nm, smaller than that of Pt/C catalyst （2.9 nm） prepared using NaAc, much smaller than that of Pt/C catalyst （100 nm） prepared using NaOH. The electrocatalytic activity of Pt/C catalysts prepared using Na3Cit and NaAc for ethanol oxidation are 456.6 and 419.2 mA/mgPt, comparative to those of Pt/C catalyst prepared by typical EG method and commercial E-TEK Pt/C catalyst. Finally, the size control mechanism of Pt nanoparticles was discussed.

关键词： Platinum Nanocatalyst Formation mechanism Fuel Cell

Numerical simulation for the comparison of thermal and plastic material flow behavior between symmetrical and asymmetrical boundary conditions during friction stir welding

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Advances in Manufacturing 2023年第1期11卷 143-157页

作者： Hao Su chuan-Song wu MOE Key Lab for Liquid-Solid Structure Evolution and Materials Processing Institute of Materials JoiningShandong UniversityJinan250061People’s Republic of China

An accurate description of the contact condition between the tool and the workpiece material is one of the most important issues for expounding the underlying multi-physics coupled mechanism during friction stir welding(FSW)*** the present study,a novel asymmetrical boundary condition around the tool-workpiece contact interface is proposed for the FSW of AA2024-T4 alloy.A three-dimensional computational fluid dynamics model is employed for the comparison of the coupled thermal and plastic material flow behavior between asymmetrical and symmetrical boundary *** results of heat generation,temperature distribution,tunnel defect formation and material flow streamline during the welding process are quantitatively ***,various experimental measuring methods are utilized to obtain information about temperature,thermal cycle,tool torque and horizontal cross-section around the exiting *** is revealed that the modeling results of heat flux density and temperature distribution around the pin,as well as material flow characteristics all change significantly for the two models with different boundary ***,the asymmetrical boundary condition is more capable of predicting temperature fluctuation,plastic material flow along the vertical direction,as well as tunnel defect formation during ***,the superiority of the model with asymmetrical boundary condition over the symmetrical one during the numerical simulation of FSW is elucidated.

关键词： Friction stir welding(FSW) Numerical simulation Heat generation Plastic material flow Asymmetrical boundary condition

A privacy-preserving group encryption scheme with identity exposure

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Frontiers of Computer Science 2022年第5期16卷 237-238页

作者： chuan-Kun wu School of Information Science and Engineering Linyi UniversityLinyi 276000China

1 Introduction At the end of December 2019,a new kind of contagious disease known as COVID-19 was found and spread *** event reflects that early whistleblowing is ***,the fear of potential over-responsibility could cause hesitation of some discoverers of potential critical events to blow the whistle at the earliest possible *** is noticed that,to set up a platform accepting anonymous messages from public as whistleblowing messages is not a good approach,because there might be a considerable amount of *** way to achieve this property is the anonymous authentication mechanism,such as group signature[1]and ring signature[2].However,whistleblowing with privacy protection has more security requirements that cannot be provided by group signatures and ring signatures.

关键词： signature preserving scheme

Microstructural evolution of a steam-turbine rotor subjected to a water-quenching process: numerical simulation and experimental verification

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Advances in Manufacturing 2019年第1期7卷 84-104页

作者： chuan wu Qing-Ling Meng National-Local Joint Engineering Laboratory of Intelligent Manufacturing Oriented Automobile Die & Mould College of Mechanical Engineering Tianjin University of Technology and Education Tianjin 300222 People's Republic of China College of Civil Engineering Tianjin University Tianjin 300072 People's Republic of China

Cr-Ni-Mo-V steam-turbine rotors have been widely used as key components in power plants. In this study, a coupled thermomechano-metallurgical model was proposed to simulate the phase transformation and transformation-induced plasticity (TRIP) of a 30Cr2Ni4MoV steam-turbine rotor during a water-quenching process, which was solved using a user defined material mechanical behavior (UMAT) subroutine in ABAQUS. The thermal dilation, heat generation from plastic work, transformation latent heat, phase transformation kinetics, and TRIP were considered in the model. The thermomechanical portion of the model was used to predict the evolution of temperature, strain, and residual stress in the rotor. The phase transformation that occurred during the quenching process was considered. Constitutive models of phase transformations (austenite to pearlite, austenite to bainite, and austenite to martensite) and TRIP were developed. Experimental data were adopted and compared with the predicted results to verify the accuracy of the model. This demonstrates that the model is reliable and accurate. Then, the model was utilized to predict the temperature variation, dimensional change, minimum austenitization time, residual stress, TRIP, and volume fractions of each phase. It is concluded that this model can be a useful computational tool in the design of heat-treatment routines of steam-turbine rotors.

关键词： Thermomechano-metallurgical model user defined material mechanical behavior (UMAT) subroutine Microstructural evolution Transformation-induced plasticity (TRIP)- Residual stress

Toward better electrode/electrolyte interfaces in the ionic-liquid-based rechargeable aluminum batteries

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Journal of Energy Chemistry 2020年第6期29卷 98-102,I0004页

作者： Haoyi Yang Feng wu Ying Bai chuan wu Beijing Key Laboratory of Environmental Science and Engineering and School of Materials Science and EngineeringBeijing Institute of TechnologyBeijing 100081China Collaborative Innovation Center of Electric Vehicles in Beijing Beijing 100081China

The past decade has witnessed the germination of rechargeable aluminum batteries(RABs)with the colossal potential to enact as a device for the large scale energy storage and *** Majority of investigations are dedicated to the exploration of suitable cathode materials,while less is known about the electrode/electrolyte interfaces that determine the electrochemistry of *** this perspective,we will highlight the significance of electrode/electrolyte interface for RABs,in overall kinetics and capacity *** will be laid on the complicated yet basic understandings of the phenomena at the interfaces,including the dendrite growth,surface Al2O3 and solid–electrolyte-interphase(SEI).And we will summarize the reported practice in effort to build better electrode/electrolyte interfaces in *** the end,outlook regarding to the challenges,opportunities and directions is presented.

关键词： Electrochemistry Interface Rechargeable aluminum battery

New secondary batteries and their key materials based on the concept of multi-electron reaction

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Chinese Science Bulletin 2014年第27期59卷 3369-3376页

作者： Feng wu chuan wu Beijing Key Laboratory of Environmental Science and Engineering School of Chemical Engineering and the EnvironmentBeijing Institute of Technology

Facing the significant applications in energy field, this paper introduces how to construct new high specific energy secondary batteries based on the concept multi-electron reaction and by designing multi-electron electrode materials. Recent progress on those new secondary batteries and their key materials based on the theory of multi-electron reaction are overviewed. Representative multi-electronic electrode materials, such as metal borides,metal fluorides, sulfur composite electrode materials and ferrates are briefly introduced, as well as the new secondary battery systems constructed with these materials. Thus gives the significance of the development based on multielectron reaction mechanism of secondary batteries and their key materials for new chemical battery systems and related energy materials.

关键词：复合电极材料二次电池反应机制电子金属氟化物能源领域高比能量高铁酸盐