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INFlUENCE OF lOCAl BRITTlE ZONE ON ThE FRACTURETOUGhNESS OF hIGh-STRENGTh lOW-AllOYEDMUlTIPASS WElD METAlS

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Acta Metallurgica Sinica(English letters) 1998年第2期11卷 87-92页

作者： Z.l.Zhou S.h.liu Dalian Railway Inst Dalian China

In this paper, toughness properties and microstructurc of low-alloyed multipass welds with yield strength above 700MPa have 6een studied using the weld thermal simulation and throughout thickness CTOD fracture mechanics tests. Impact testing of thermal simulated specimens showed that the primary weld metal and the fine gmmed weld metal had good toughness, while the coarse grained weld metal had the lowest toughness value as the local brittle zone (lBZ) in multipass weld metals. Cleavage fracture in CTOD testing of thick multipass weld metals was initiated from martensite-austenite (MA) phases in the lBZ. MA phases were distributed at the prior austenite grain boundaries and around ferrite grains. As the size of the local brittle zone along the fatigue crack front increases, CTOD frncture toughness of multipass weld metals decreases. The weakest link theory was used to evaluate effect of the local brittle zone on fracture toughness of thick multipass weld metals. The estimated curves agree well with the eaperimental data.

关键词： multipass weld metal local brittle zone weld thermal simulation CTOD fracture toughness

MEChANISM ANAlYSIS OF ThICKNESS EFFECT ON MIXED MODE Ⅰ/Ⅱ FRACTURE OF lC4-CS AlUMINUM AllOY

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Acta Metallurgica Sinica(English letters) 2004年第3期17卷 255-262页

作者： h.R. Dong W.l. Guo The State Key laboratory of Mechanical Structural Strength and Vibration Xi'an Jiaotong UniversityXi'an 710049 China The Engineering Institute Air Force Engineering University Xi'an 710038 ChinaThe State Key Laboratory of Mechanical Structural Strength and Vibration Xi'an Jiaotong UniversityXi'an 710049 China Department of Aircraft Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

Mixed mode Ⅰ/Ⅱ fracture erperiments of lC4-CS aluminum alloy were conductedby using tension--shear specimens with thicknesses of 2, 4, 8 and 14mm. Fracturemechanisms of thickness effect on mixed mode Ⅰ/Ⅱ fracture were first examined fromfracture surface morphology to correlate with the macroscopic fracture behavior andstress state. It is found that specimen thickness has a strong influence on mixed modefracture. As thickness varies from thin to thick the macroscopic fracture surfacesappear the characteristics of plane stress state (2mm, 4mm--thick specimen), three--dimensional stress state (8mm--thick specimens), and plane strain state (14mm--thickspecimens), respectively. The specimens of all kinds of thicknesses are typical of ten-sile type failure under mode Ⅰ loading condition and shear type failure under mode Ⅱloading condition. Two distinct features coexist on the fracture surfaces under mixedmode loading conditions, and the corresponding proportion varies with loading mix-ity. Void--growth processes are the failure mechanism in both predominately tensile-and shears--type fractures. The size and depth of dimples on the fracture surface varygreatly with thickness. Therefore, it is extraordinary necessary to take into accountthe thickness effect when a mixed mode fracture criterion is being established.

关键词： lC4-CS aluminum alloy mixed mode Ⅰ/Ⅱ fracture thickness effect macroscopic fracture appearance SEM

Economic optimization of resource-constrained project scheduling:a two-phase metaheuristic approach

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Journal of Zhejiang University-Science C(Computers and Electronics) 2010年第6期11卷 481-494页

作者： Angela h.l.ChEN Chiuh-Cheng ChYU Department of Industrial Engineering and Management Yuan Ze University Department of Finance Nanya Institute of Technology

This paper deals with the problem of project scheduling subject to multiple execution modes with non-renewable resources, and a model that handles some of monetary issues in real world *** objective is to schedule the activities to maximize the expected net present value(NPV) of the project, taking into account the activity costs, the activity durations, and the cash flows generated by successfully completing an *** to the combinatorial nature of this problem, the current study develops a hybrid of branch-and-bound procedure and memetic algorithm to enhance both mode assignment and activity *** for the makespan minimization problem have been made through a set of benchmark problem *** performance is rated on the maximization of the project NPV and computational results show that the two-phase hybrid metaheuristic performs competitively for all instances of different problem sizes.

关键词： Memetic algorithm(MA) Branch and bound(B&B) algorithm Net present value(NPV) Project scheduling problem

EFFECT OF TESTING ENVIRONMENT ON FRACTURING BEhAVIOR OF Fe_3Si BASED AllOY

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Acta Metallurgica Sinica(English letters) 2003年第2期16卷 104-109页

作者： J.h.Peng G.l.Chen National Key laboratory for Nuclear Fuel&Materials China Nuclear Power InstituteChengdu 610041ChinaState Key Laboratory for Advanced Metal MaterialsUniversity of Science&Technology BeijingBeijing 100083China

The mechanical behavior of Fes Si based alloy with B2 structure was studied by tension and fracture toughness test in various testing media. The fracture strength σb of Fe3Si alloy decreased in the following order: oxygen, air and hydrogen respectively. The fracture toughness in different testing environment showed that KIC in oxygen is 11.5±0.3MPa·m1/2, and is 8.6±0.4MPa·ml/2 in distilled water. The reduction of fracture toughness is contributed to the environmental reaction of Si with water. Addition of Al element in Fe3Si is not beneficial to improve the intrinsic ductility of Fe-14Si-3Al alloy. The scattering phenomenon of fracture strength was found, and explained by fracture mechanics. It was found by means of SEM that the fracture mode changed from transgranular in oxygen to intergranular in hydrogen gas and distilled water.

关键词： Fe3Si intermetallic mechanical behavior environmental em- brittlement

Ab initio STUDIES ON MAGNETISM OF 3d TRANSITION METAl DIMERS

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Acta Metallurgica Sinica(English letters) 2007年第5期20卷 341-346页

作者： J.h. Gu Z.l. Zhu School of Physical Engineering and Material Physics laboratory Zhengzhou University Zhengzhou 450052 China

Ab initio calculations with the self-consistent full-potential linearized augmented-plane-wave method （FlAPW）, under generalized gradient approximation, have been carried out to describe the electronic and magnetic properties of 3d transition metal dimers. It predicted the antiferromagneticity of Cr2 and ferromagneticity of other species. The Mn2 dimer was shown to be ferromagnetic coupling with a local magnetic moment of 5μB. retaining the value of its free atom state. The V2 and Ni2 exhibited low spin-polarization with local magnetic moment of only 1μB per atom. On the other hand, Fe2 and Co2 were highly spin-polarized with local magnetic moments of 3 and 2μB.

关键词： magnetism 3d transition metal dimer ab initio calculation

Influences of residual stress and micro-deformation on microstructures and mechanical properties for Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy produced by laser powder bed fusion

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Journal of Materials Science & Technology 2021年第16期75卷 174-183页

作者： C.C.Zhang h.l.Wei T.T.liu l.Y.Jiang T.Yang W.h.liao National Joint Engineering Research Center of NC Forming Technology and Equipment School of Mechanical EngineeringNanjing University of Science and TechnologyNanjing 210094China

laser powder bed fusion(lPBF)yields unique advantages during the fabrication of titanium *** the present work,Ti-6.5 Al-3.5 Mo-1.5 Zr-0.3 Si alloy specimens with excellent mechanical performances were fabricated by *** as-built specimens displayed relatively high strength and ductility under modest volume energy densities(VEDs),whereas they manifested high strength with low ductility under high *** investigate the key reason of this phenomenon,the specimens were designed with two VEDs ranges of 60 J/mm^(3) and 85 J/mm^(3).Special attention was paid to the influences of residual stress and micro-deformation on microstructures and mechanical properties for the first *** results indicated that the residual stresses and relative density of the 60 J/mm^(3) range specimens were higher than that of the 85 J/mm3 range *** multiplication and dislocation movement promoted by the residual stress were hindered by the initialα’phase grain boundary(prior-α’GB),leading to the formation ofα’metastable *** mean tensile strength and elongation of the 60 J/mm^(3) range specimens were 1248.1 MPa and 12.3%,respectively,whereas the corresponding values for the 85 J/mm^(3) range specimens were 1405.3 MPa,5.0%,*** deformation,the strength and ductility of the specimens were first improved by lamellar structures generated from prior-α’phases,and then effectively enhanced by the interaction between the{10–12}twins and ***,pores significantly reduced the ductility;hence,high VED specimens with large twins and numerous large pores increased the strength and reduce the ductility.

关键词： laser powder bed fusion Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy Residual stress Twin Mechanical properties

Interlayer distance effects on absorption coefficient and refraction index change in p-type double-δ-doped GaAs quantum wells

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Chinese Physics B 2019年第12期28卷 186-190页

作者： h Noverola-Gamas l M Gaggero-Sager O Oubram Instituto de Investigaciones en Ciencias Básicas y Aplicadas Universidad Autónoma del Estado de Morelos MorelosCuernavaca 62209Mexico Division Academica de Ingeniería y Arquitectura Universidad Juárez Autonoma de TabascoCunduacan 8660Mexico Centro de Investigación en Ingeniería y Ciencias Aplicadas Universidad Autónoma del Estado de MorelosCuernavaca 62209Mexico Facultad de Ciencias Químicas e Ingeniería Universidad Autónoma del Estado de MorelosCuernavaca 62209Mexico

In the framework of the Thomas–Fermi(TF) approach, a model for the p-type double-δ-doped(DDD) system in Ga As is presented. This model, unlike other works in the literature, takes into account that the Poisson equation associated with the system is nonlinear. The electronic structure is calculated for heavy and light holes. The changes in the electronic structure result of the distance d between the doped layers are studied. In particular, the relative absorption coefficient as well as the relative refractive index change is calculated as a function of the incident photon energy for heavy holes. The effect of the interlayer distance exhibits, in the absorption coefficient, a red shift of the peak position and a decrease in amplitude when the distance increases. In addition, the relative refractive index change node has a red shift as well as the interlayer distance increases. The calculations show that the effect of the separation between layers has a greater influence on the linear terms. These results are very important for theoretical calculations and engineering of optical and electronic devices based in δ-doped Ga As.

关键词： double delta-doping p-type GaAs layers electronic structure Thomas–Fermi approach nonlinear optical properties

Direct joining of oxygen-free copper and carbon-fiber-reinforced plastic by friction lap joining

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Journal of Materials Science & Technology 2018年第1期34卷 192-197页

作者： l.h. Wu K. Nagatsuka K. Nakata Joining and Welding Research Institute Osaka University 11-1 Mihogaoka Ibaraki Osaka 567-0047 Japan

Oxygen-flee copper （Cu） was successfully joined to carbon-fiber-reinforced thermoplastic （CFRTP, polyamide 6 with 20wt% carbon fiber addition） by friction lap joining （FlJ） at joining speeds of 200-1600 mm/min with a constant rotation rate of 1500 rpm and a nominal plunge depth of 0.9 ram. It is the first time to report the joining of CFRTP to Cu by FlJ. As the joining speed increased, the tensile shear force （TSF） of joints increased first, and decreased thereafter. The maximum TSF could reach 2.3 kN （ 15 mm in width）. hydrogen bonding formed between the amide group of CFRTP and the thin Cu20 layer on the Cu surface, which mainly contributed to the joint bonding. The influence factors of the TSF of the joints at different joining speeds were discussed. The TSF was mainly affected by the joining area, the degradation of the plastic matrix and the number and the size of bubbles. As the joining speed increased, the influence factors varied as follows： the joining area increased first and then decreased; the degra- dation of the plastic matrix and the number and the size of bubbles decreased. The maximum TSF was the comprehensive result of the relatively large joining area, small degradation of the plastic matrix and small number and sizes of bubbles.

关键词： Friction lap joining Metal Plastic Carbon-fiber reinforced thermoplastic Dissimilar materials joining

Assets and tactics in a mating market： Economic models of negotiation offer insights into animal courtship dynamics on the lek

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Current Zoology 2011年第2期57卷 225-236页

作者： Gail l. PATRICEllI Alan h. KRAKAUER Richard MCElREATh Department of Evolution and Ecology University of California Davis CA 95616 USA Department of Anthropology University of California Davis CA 95616 USA

Economists study negotiation as a series of events--partner choice, information gathering, bargaining, etc.--with each step of the process affecting the outcome of the next, and the optimal decision at each stage depending on the player＇s bargaining power. The context in which these negotiations occur--the market--is critical, since players can adjust their behaviors in response to outside offers. Animals similarly are faced with sequential decisions regarding courtship： who to court, how to approach a potential mate, at what level to display, when to give up, etc. Thus economic models of negotiation in a market provide a framework in which we can view not just the outcome of courtship （assortative mating）, but also the process, where each sex can use tactics to improve their negotiating outcome, using the assets that they have available. here we propose to use negotiation as a conceptual framework to explore the factors promoting tactical adjustments during sequential stages of courtship in lekking species. Our goal is to discuss the utility of negotiation as a heuristic tool, as well as the promise and peril of co-opting game theoretic models from economics to understand animal interactions. We will provide a brief overview of a few areas where we see promise for using negotiation as a framework to understand animal courtship dynamics： choice of a display territory, tactical partner choice for negotiation, approaching a potential partner and courtship haggling .

关键词： Bargaining Game theory lek Sexual selection Signaling Negotiation