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Conception of tooling adapted to thixoforging of high solid fraction hot-crack-sensitive aluminium alloys

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Transactions of Nonferrous Metals Society of China 2010年第9期20卷 1712-1718页

作者： g.vaneetveld A.RASSILI J.C.PIERRET J.LECOMTE-BECKERS Thixo Unit B56University of Liège Special Metallic Materials B52University of Liège

Thixoforging is a type of semi-solid metal processing at high solid fraction (0.7<φs<1), which involves the processing of alloys in the semi-solid *** has to be adapted to this particular process to benefit shear thi... 详细信息

Thixoforging is a type of semi-solid metal processing at high solid fraction (0.7g of alloys in the semi-solid *** has to be adapted to this particular process to benefit shear thinning and thixotropic behaviour of such semi-solid *** parameters, such as the forming speed and tool temperature, have to be accurately controlled because of their influence on thermal exchanges between material flow and *** thermal exchanges influence the high-cracking tendency and the rheology of the semi-solid material during forming, which affects parts properties and therefore their *** tests show how thermal exchanges influence quality of thixoforged parts made of 7075 aluminium alloys at high solid fraction by modifying process parameters like forming speed, tool temperature and tool thermal *** an optimum in terms of thermal exchanges has to be found between surface quality and mechanical properties of the part.A direct application is the evaluation of surface quality of thixoforged thin wall parts made of 7075 aluminium alloy.

关键词： thixoforging solid fraction near-net-shaping tooling 7075 aluminium alloys

Characterization of thixoforming process of 100Cr6 steel

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中国有色金属学会会刊：英文版 2010年第S3期20卷 916-920页

作者： K.P.SOLEK A.RASSILI J.C.PIERRET g.vaneetveld AgH University of Science and Technology av.Mickiewicza 3030-059 KrakówPoland Thixo-Unit ULg PiMW(B56)University of L iègeBd de Colonster 4B-4000 LiègeBelgium

The main goal of this work is to analyze the semi-industrial process of steel *** process was carried out using industrial *** equipment consists of a heating device,industrial robots and a hydraulic *** globular microstructure ensuring thixotropic properties was obtained using the SIMA *** is one of the simplest and cheapest methods which could be easy applied in the case of steel *** this work,the hot forged rods,commercially produced from 100Cr6 steel,were *** first part of the work concerned the determination of the proper temperature range,for thixoforming of 100Cr6 ***,some heating tests were carried out in order to obtain as uniform temperature distribution as *** process was executed using inductive *** analysis of heated samples reveals globular particles surrounded by liquid *** last,the thixoforming process was carried out using closed-die forming *** filled die cavity and good microstructure of the part show that applied process parameters were properly selected.

关键词： thixoforming globular microstructure rheological properties physical modeling numerical modeling

X38CrMoV5 hot-work tool steel as tool material for thixoforging of steel:Numerical and experimental evaluation

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中国有色金属学会会刊：英文版 2010年第S3期20卷 713-718页

作者： A.RASSILI J.C.PIERRET g.vaneetveld J.H ALLEUX g.WALMAg J.LECOMTE-BECKERS Thixo Unit ULg Department of Aerospace and Mechanica l EngineeringUniversity of Liège

Although thixoforming of low melting point alloys as aluminum or magnesium is now an industrial reality,thixoforming of high melting point alloys as steel is still at the research *** working temperature,die wearing and production rate are problems that must be solved and are under *** aim of this work is to evaluate the thermal and mechanical loadings applied to the tools during the steel thixoforging process in order to determine whether classical hot-work tool steel can be an appropriate tool *** evaluation has been realized thanks to experimental trials and to simulations on the finite elements code Forge2008.The effect of the loadings on the tool's failure modes are highlighted and compared with the ones observed in classical hot *** this,the failure modes of hot-work tool steel,the X38CrMoV5 or H11,were presented.

关键词： thixoforging steel high melting point tool material

Thixoextrusion of A357 aluminium alloy

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中国有色金属学会会刊：英文版 2010年第S3期20卷 1005-1009页

作者： A.FORN g.vaneetveld J.C.PIERRET S.MENARgUES M.T.BAILE M.CAMPILLO A.RASSILI Light Alloys and Surfaces Treatment Design Centre(CDAL) Universitat Politècnica de Catalunya(UPC)Rambla de l'Exposició 2408800 Vilanova i la Geltrú(Barcelona)Spain ThixoUnit University of Liège4Boulevard de Colonster4000 LiègeBelgium

The aim of this work is to attempt the application of A357 Al-Si-Mg cast alloy in the thixoextrusion process,evaluating the different forming parameters *** offers several advantages compared with traditional hot-extrusion such as lower pressure,minor friction forces,higher material fluidity and longer tool *** type of semi-solid process requires high solid fraction(0.7gh strength,ductility and corrosion *** is commonly used for cast production of automotive components and it is also suitable for semi-solid process,due to its wide range of solidification.A357 aluminium alloy was used as a feedstock for thixoextrusion in order to investigate thixoformability at high solid fraction.A357 alloy with high solid fraction(>0.85) is less sensitive to temperature drops and allows more stable material flow at higher *** know the forming parameters that improve the mechanical properties of thixoextruded parts,some extrusion tests were carried *** results were used as the main criteria for assessing the thixoforming viability of the A357 alloy.

关键词： thixoextrusion A357 aluminium alloy solid fraction semi-sold

Challenges and opportunities in the production of magnesium parts by directed energy deposition processes

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Journal of Magnesium and Alloys 2024年第5期12卷 1663-1686页

作者： gürel Cam Ali günen Iskenderun Technical University Faculty of Engineering and Natural SciencesDepartment of Mechanical Engineering31200 Iskenderun-HatayTurkey Iskenderun Technical University Faculty of Engineering and Natural SciencesDepartment of Metallurgy and Materials Engineering31200 Iskenderun-HatayTurkey

Mg-alloys have gained considerable attention in recent years for their outstanding properties such as lightweight,high specific strength,and corrosion resistance,making them attractive for applications in medical,aerospace,automotive,and other transport ***,their widespread application is hindered by their low formability at room temperature due to limited slip *** Mg-alloys have low mechanical properties due to the presence of casting defects such as porosity and anisotropy in addition to the high *** casting methods benefit from established process optimization techniques for these problems,additive manufacturing methods are increasingly replacing casting methods in Mg alloys as they provide more precise control over the microstructure and allow specific grain orientations,potentially enabling easier optimization of anisotropy properties in certain *** metal additive manufacturing(MAM)technology also results in some manufacturing defects such as inhomogeneous microstructural evolution and porosity and additively manufactured Mg alloy parts exhibit lower properties than the wrought parts,they in general exhibit superior properties than the cast ***,MAM is a promising technique to produce Mg alloy *** energy deposition processes,particularly wire arc directed energy deposition(WA-DED),have emerged as an advantageous additive manufacturing(AM)technique for metallic materials including magnesium alloys,offering advantages such as high deposition rates,improved material efficiency,and reduced production costs compared to subtractive ***,the inherent challenges associated with magnesium,such as its high reactivity and susceptibility to oxidation,pose unique hurdles in the application of this *** review paper delves into the progress made in the application of DED technology to Mg-alloys,its challenges,and ***,the predominant imperfections,notably inhomo

关键词： Additive manufacturing DED processes Arc-DED Wire arc additive manufacturing(WAAM) 3-D printing High deposition rate

Recent research in mechanical properties of geopolymer-based ultrahigh-performance concrete:A review

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Defence Technology（防务技术） 2024年第2期32卷 67-88页

作者： g.Murali Division of Research&Innovation Uttaranchal UniversityDehradun 248007India

Due to the growing need for sustainable and ultra-high-strength construction materials,scientists have created an innovative ultra-high-performance concrete called geopolymer based ultra-highperformance concrete(gUHPC).Besides,in the last few decades,there have been a lot of explosions and ballistic attacks around the world,which have killed many civilians and fighters in border *** this context,this article reviews the fresh state and mechanical properties of ***,the ingredients of gUHPC and fresh properties such as setting time and flowability are briefly ***,the review of compressive strength,flexure strength,tensile strength and modulus of elasticity of fibrous ***,the blast and projectile impact resistance performance was ***,the microstructural characteristics were reviewed using the scanning electron microscope and X-ray Powder *** review outcome reveals that the mechanical properties were increased when 30%silica fume was added to a higher dose of steel fibre to improve the microstructure of *** is hypothesized that the brittleness of gUHPC was mitigated by adding 1.5%steel fibre reinforcement,which played a role in the decrease of contact explosion cratering and *** the need for cement in gUHPC was a key factor in the review,indicating a promising potential for lowering carbon ***,gUHPC research is still in its early stages,so more study is required before its full potential can be utilized.

关键词： Mechanical properties Blast Projectile impact Fibre geopolymer Silica fume Alkaline activators

Nitrogen mineralization in the oldest climax communities in the eastern Mediterranean region

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Journal of Forestry Research 2024年第1期35卷 213-228页

作者： Fatma Selcen Sakar gürcan güleryüz Department of Biology Section Ecology GörükleGraduate School of Natural and Applied ScienceUniversity of Bursa Uludağ16059 NilüferBursaTurkey Department of Biology Section Ecology GörükleFaculty of Science and ArtsUniversity of Bursa Uludağ16059 NilüferBursaTurkey

In this study,we investigated how tree species affect N mineralization in connection to some soil properties and seconder metabolite levels of litter,in the soil of the old-est native forest *** the oldest pure communi-ties of Pinus nigra(PN),Fagus orientalis(FO),and Abies bornmuelleriana(AB)in the mountain range of Mount Uludağ,Bursa,Turkey,annual net yield and N mineraliza-tion in the 0-5-and 5-20-cm soil layers were determined in a field incubation study over 1 *** locations were chosen from 1300 to 1600 m a.s.l.,and moisture content(%),pH,water-holding capacity(%),organic C,total N,and C/N ratio,and annual net mineral N yield of the soil and hydro-lyzed tannic acid and total phenolic compounds in litter were compared for these forest *** had the highest annual net Nmin yield(43.9±4.8 kg ha^(-1) a^(-1)),*** the lowest(30.5±4.2 kg ha^(-1) a^(-1)).Our findings show that in the oldest forest ecosystems,the seasonal soil moisture content and tree species play an essential role in N cycling and that hydrolyzed tannic acids and total phenolic compounds effectively control N *** acid and total phenolics in the litter were found to inhibit nitrification,but total phenolics were found to stimulate ammonification.

关键词： Oldest forest communities Nitrogen mineralization Nitrification Tannic acid Total phenolic Litter

Shell-model representations of the microscopic version of the Bohr-Mottelson collective model

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Communications in Theoretical Physics 2024年第8期76卷 79-90页

作者： H g ganev Joint Institute for Nuclear Research DubnaRussia Institute of Mechanics Bulgarian Academy of SciencesSofiaBulgaria

The structure of the irreducible collective spaces of the group Sp(12,R),which many-particle nuclear states are classified according to the chain Sp(12,R)⊃U(6)⊃SO(6)⊃SU_(pn)(3)⊗SO(2)⊃SO(3)of the proton-neutron symplectic model(PNSM),is considered in *** chain of the PNSM was recently shown to correspond to a microscopic shell-model version of the Bohr-Mottelson collective *** construction of the relevant shell-model representations of the Sp(12,R)group along this chain is considered for three nuclei with varying collective properties and from different mass *** is shown that the SU_(pn)(3)basis states of the Sp(12,R)representations belonging to the SO(6)irreps with seniorityυ≥υ0,withυ0 denoting the maximal seniority SO(6)irrep contained in the Sp(12,R)bandhead,are always Pauli allowed,but organized in a different way into different SO(6)*** is in contrast to the case of filling the levels of the standard three-dimensional harmonic oscillator and using the plethysm *** the SU_(pn)(3)multiplets withinυ<υ0 are not all Pauli forbidden,it is safe to discard *** results obtained in the present work are important for the practical application of the microscopic version of the Bohr-Mottelson collective model.

关键词： microscopic shell-model version of the Bohr-Mottelson model proton-neutron symplectic model Sp(12,R)dynamical algebra shell-model representations

Harmonics in the Squirrel Cage Induction Motor Analytic Calculation Part III: Influence on the Torque-speed Characteristic

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CES Transactions on Electrical Machines and Systems 2024年第1期8卷 86-102页

作者： g.Kovács the ganz Electric Works BudapestHungary

The harmonics that appear in the squirrel cage asynchronous machine have been discussed in great detail in the literature for a long time. However, the systematization of the phenomenon is still pending, so we made an attempt to fill this gap in the previous parts of our study by elaborating formulas for calculation of parasitic torques. It was a general demand among those who work in this field towards the author to verify his formulas with measurements. In the literature, it seems,only one detailed, purposeful series of measurements has been published so far, the purpose of which was to investigate the effect of the number of rotor slots on the torque-speed characteristic curve of the machine. The main goal of this study is to verify the correctness of the formulas by comparing them with the referred series of measurements. Relying on this, the expected synchronous parasitic torques were developed for the frequently used rotor slot numbers-as a design guide for the ***, together with our complete table for radial magnetic pull published in our previous work, the designer has all the principles, data and formulas available for the right number of rotor slots for his given machine and for the drive system. This brings this series of papers to an end.

关键词： Asynchronous parasitic torques Induction motor Squirrel cage rotor Space harmonics Synchronous parasitic torques