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Journal of Materials Science & Technology 2020年第7期42卷 220-228页

作者： R.z.Xu q.Yang D.R.Ni B.L.Xiao C.z.Liu z.Y.Ma Institute of Metal Research Chinese Academy of SciencesShenyang110016China College of Material Science and Engineering Shenyang Aerospace UniversityShenyang110136China Department of Materials Science and Engineering University of Illinois at Urbana-Champaign1304 W Green StUrbanaIL61801United States Fredrick Seitz Materials Research Laboratory University of Illinois at Urbana-Champaign104 S Goodwin AveUrbanaIL61801United States

Al-free zK60 magnesium (Mg) alloy sheet was selected as substrate material of Mg-steel pinless friction stir spot welding (FSSW), avoiding the effect of the Al element in the substrate on the alloying reaction of Mg-iron (Fe) interface. The sound FSSW joint of zK60 Mg alloy and q235 steel with a hot-dipped aluminum (Al)-containing zinc (zn) coating was successfully realized. The detailed microstructural examinations proved that Al5Fe2 phase at the Mg-Fe interface came from the pre-existing Al5Fe2 phase in the coating and acted as the transition layer for promoting the metallurgical bonding of Mg and Fe. The interfaces with well-matched lattice sites among Fe, Al5Fe2 and Mg were formed during FSSW. A low energy interface with good match of lattice sites ((002)Al5Fe2//(110)Fe, [110]Al5Fe2//[113]Fe) between Al5Fe2 and Fe was identified. For the interface between Al5Fe2 and Mg, an orientation relationship of (622)Al5Fe2//(3112)Mgand[158]Al5Fe2//[2423]Mg was observed. The tensile-shear load of the zK60-steel joint could reach 4.6 kN. Moreover, the joint fracture occurred at the interface between the Al5Fe2 layer and the Mg alloy substrate, suggesting the brittle fracture characteristic.

关键词： Dissimilar welding Friction stir spot welding Magnesium alloys Steels zinc coating

Soft computing approach for prediction of surface settlement induced by earth pressure balance shield tunneling

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Underground Space 2021年第4期6卷 353-363页

作者： W.G.zhang H.R.Li C.z.Wu Y.q.Li z.q.Liu H.L.Liu Key Laboratory of New Technology for Construction of Cities in Mountain Area Chongqing UniversityChongqing 400045China National Joint Engineering Research Center of Geohazards Prevention in the Reservoir Areas Chongqing UniversityChongqing 400045China School of Civil Engineering Chongqing UniversityChongqing 400045China Norwegian Geotechnical Institute(NGI) Sognsveien 720855 OsloNorway

Estimating surface settlement induced by excavation construction is an indispensable task in tunneling,particularly for earth pressure balance(EPB)shield *** this study,predictive models for assessing surface settlement caused by EPB tunneling were established based on extreme gradient boosting(XGBoost),artificial neural network,support vector machine,and multivariate adaptive regression *** from three tunnel construction projects in Singapore were used,with main input parameters of cover depth,advance rate,earth pressure,mean standard penetration test(SPT)value above crown level,mean tunnel SPT value,mean moisture content,mean soil elastic modulus,and grout *** performances of these soft computing models were evaluated by comparing predicted deformation with measured *** demonstrate the acceptable accuracy of the model in predicting ground settlement,while XGBoost demonstrates a slightly higher *** addition,the ensemble method of XGBoost is more computationally efficient and can be used as a reliable alternative in solving multivariate nonlinear geo-engineering problems.

关键词： EPB Surface settlement Soft computing XGBoost Multivariate adaptive regression spline

FATIGUE PROPERTIES OF AUSTEMPERED DUCTILE IRON(ADI)IN WATER ENVIRONMENT

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Acta Metallurgica Sinica(English Letters) 2004年第2期17卷 122-130页

作者： q.z.Cai B.K.Wei Y.Tanaka StateKeyLabofPlasticFormingSimulation＆Dies／MouldTechnology FacultyofMaterialsScienceandEngineeringHuazhongUniversityofScienceandTechnologyWuhan430074China DepartmentofMechanicalSystemsEngineering MuroranInstituteofTechnologyMuroran050-8585Japan

The acicular ferrite in austempered ductile iron (ADI) matrix around graphite wascorroded preferentially in wet condition, promoting crack origination and propagationand resulting in the disappearance of ADI fatigue limit. ADI fatigue strength wasgradually reduced with increasing the time of test and was reduced by 50% in wetcondition at 10~7 cycles compared with the fatigue limit in dry condition. The fatiguestrength variation of ferritic ductile iron in wet condition was similar to that of ADI.The ferritic ductile iron, however, has better corrosion resistance so that the fatiguestrength was lowered only by 10% in wet condition at 10~7 cycles compared with thefatigue limit in dry condition. On the other hand, the fatigue limits of ADI and ferriticductile iron were dropped by 32% and 25% in tap water dipping 480h/dry conditionrespectively compared with those in dry condition. The reduction of fatigue limit wasattributed to corrosion pits formation correlated with stress concentration, resultingin origination and propagation of fatigue crack.

关键词： anstempered ductile iron water environment corrosion fatigue crack fatigue strength

Modified spherical cavity-expansion model for projectile penetration into concrete targets

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Acta Mechanica Sinica 2019年第3期35卷 518-534页

作者： Y.Peng H.Wu q.Fang X.z.Kong College of Liberal Arts and Sciences National University of Defense TechnologyChangsha 410073China Key Laboratory of Performance Evolution and Control for Engineering Structures Tongji UniversityShanghai 200092China Research Institute of Structural Engineering and Disaster Reduction College of Civil EngineeringTongji UniversityShanghai 200092China State Key Laboratory for Disaster Prevention and Mitigation of Explosion and Impact PLA Amy Engineering UniversityNanjing 210007China

A modified spherical cavity-expansion model is developed in this paper.(1) We introduce a piecewise hyperbolic yield criterion suitable for pressure less than fc/3 to describe the mechanical behavior in the elastic region for the elastic-plastic response and modify the crack occurrence condition for the elastic-cracked-plastic response.(2) The hyperbolic yield criterion and a piecewise equation of state (EOS) are adopted for a better description of the plastic behavior of concrete material. Then, the modified model is validated by several projectile penetration tests in both the normal strength concrete (NSC) and ultra-high performance cement-based composite (UHPCC) targets. Finally, the hydrostatic pressure of the targets under rigid ogive-nosed projectile penetrations is found to be nearly within (0, 1.6 GPa), which usually exceeds the range that the shear strength-pressure test data covered. The influence of yield criterion on depth of penetration is discussed and it is recommended that the pressure should arrive at least 400 MPa in the related triaxial compression tests.

关键词： Dynamic cavity-expansion model Projectile Penetration Concrete Depth of penetration

CALCULATION OF THE DAMPING OF THE zn-27Al ALLOY BASED ON THE MICRO INTERFACE SLIDING MODEL

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Acta Metallurgica Sinica(English Letters) 2006年第3期19卷 228-234页

作者： Y.z. zhao q. Gao Y.C. Liu School of Civil Engineering Southwest Jiaotong University Chengdu 610031 China Department of Applied Mechanics and Engineering Southwest Jiaotong University Chengdu 610031 China

The microstructures of the zn-27Al alloy after modification, solid-solution treatment, and natural aging were studied. It was clarified why the damping properties of zn-27Al alloys, after treatment, had advanced most on the basis of analyzing the microstructures. Approximate expressions have been educed, which can be used to quantificationally work out the damping of the zn-27Al alloy on the basis of the micro interface sliding model. By comparing the testing damping properties of the foundry zn-27Al alloys and the zn-27Al alloys after modification, solid solution, and natural aging, it was shown that the expressions were rational.

关键词： modification solid solution and aging damping micromechanism micro interface sliding model

On-Load Voltage Distortion Compensation Method Using Disturbance Observer for SPM Machines with Closed Slot

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Chinese Journal of Electrical Engineering 2015年第1期1卷 58-69页

作者： Beomseok Lee z.q.zhu D.Wu Department of Electronic and Electrical Engineering University of SheffieldSheffieldS13JDUK

This paper proposes an on-load voltage distortion compensation method,in which the voltage distortion is mainly produced in the surface-mounted permanent magnet machines having closed *** from the voltage distortions caused by the inverter,such as dead time and inverter non-linearity,the on-load voltage distortion has relatively large magnitude dependent of machine *** a result,it causes a significant distortion of current waveforms and deteriorates control ***,a voltage disturbance compensation method using a disturbance observer is proposed and *** on the machine model,the disturbance observer is chosen which helps to observe a voltage disturbance,while the error between measured and estimated currents is *** disturbance observer only compensates the sixth-multiple harmonic components of the inverter voltage in synchronous reference *** harmonic compensator with multiple narrow-band pass based adaptive filter is proposed and implemented in the feedback loop with current *** observed voltage disturbances are compensated to the reference *** addition,robust performance of the proposed method is shown against the parameter *** effectiveness of the proposed compensation scheme is validated by the experiments.

关键词： Closed slot disturbance observer inverter non-linearity on-load voltage distortion surface-mounted permanent magnet(SPM)machines

STUDY ON THE SHOCK WAVE CRYSTALLIzATION OF AMORPHOUS ALLOYS BY DSC

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Acta Metallurgica Sinica(English Letters) 2002年第5期15卷 431-438页

作者： H. Y. zhao, H. wang, q.J. Liu, J.D. Kan and z.q. LiuDepartment of Materials Science and Engineering, Yunnan University, Kunming 650091, China Department of Materials Science and Engineering Yunnan University

Shock wave and annealing crystallization of amorphous alloys FeSiB, FeMoSiB and FeCuNbSiB were studied by isothermal and non-isothermal DSC technique. It was found that the shock wave crystallization is very perfect, the fraction crystallized is very close to 100%, though the period of crystallization is very short, only about 10-4-10-6s. Their produced phases differ from the parent phase in structure and composition. The high velocity of the transformation is very difficult to explain by the diffusion theory of solid state phase transition.

关键词： amorphous alloy nano-crystallization shock wave crystalliza-tion

Mechanical Properties of a Low-thermal-expansion Aluminum/Silicon Composite Produced by Powder Metallurgy

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Journal of Materials Science & Technology 2014年第4期30卷 417-422页

作者： Y.q.Liu S.H.Wei J.z.Fan z.L.Ma T.zuo National Engineering & Technology Research Center for Nonferrous Metal Matrix Composites Beijing General Research Institute for Nonferrous Metals

AI matrix composite containing high volume fraction silicon has been promising candidate for lightweight and low-thermal-expansion components. Whereas, optimization of its mechanical properties still is an open challenge. In this article, a flexile powder metallurgy processing was used to produce a fully dense AI-4.0Cu （wt%） alloy composite reinforced with 65 vol.% Si particles. In this composite, Si particles were homogenously distributed, and the particle size was refined to the range of 3-15 μm. Tensile and flexural strength of the composite were 282 and 455 MPa, respectively, about 100% and 50% higher than the best properties reported in literature. The measured fracture toughness of the composite was 4.90 MPa m1/2. The improved strength of 65%Si/AI was attributed to the optimized particle characteristics and matrix properties. This investigation is expected to provide a primary understanding of the mechanical behaviors of Si/AI composites, and also promote the structural applications of this low-thermal-expansion material.

关键词： Aluminum matrix composite Powder metallurgy Mechanical properties Coefficient of thermal expansion Fracture

Enhancing strength and ductility in the nugget zone of friction stir welded 7Mn steel via tailoring austenitic stability

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Journal of Materials Science & Technology 2024年第18期185卷 174-185页

作者： Y.q.wang F.Y.Li J.X.Su R.H.Duan z.A.Luo G.M.Xie State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China School of Materials Science and Engineering Jiangsu University of Science and TechnologyZhenjiang 212003China

The martensite often appears in the nugget zone(Nz)of friction stir welding(FSW)7 wt.%Mn steel due to low austenite stability,deteriorating ductility and *** this work,a 7 wt.%Mn steel was sub-jected to FSW,and preheating was used to tailor the austenitic stability to greatly improve the strength-ductility combination of the *** austenitic deformation behavior and strain hardening mechanism in the Nz were systematically *** microstructure of the as-welded Nz was composed of ultrafine blocky ferrite,austenite,and small amounts of martensite,whereas the as-preheated Nz con-tained ultrafine blocky ferrite and austenite,and the concentration of Mn in austenite was increased from 8.4 wt.%to 10.7 wt.%.This enhanced the austenitic stability,resulting in a significant increase in the volume fraction of austenite in the as-preheated Nz from 37.3%to 66.4%.The product of strength and elongation(PSE)in the as-preheated Nz increased dramatically from 42.6 GPa%to 67.1 GPa%,depending on a persistent high strain hardening rate(SHR).Multiple strain-hardening mechanisms were *** austenite with enhanced stability can provoke sustained transformation-induced plasticity(TRIP)and twinning-induced plasticity(TWIP)effects,and massive dislocation multiplication occurs during tension,resulting in strong strain hardening.

关键词： Friction stir welding Medium Mn steel Preheating Transformation-induced plasticity Twinning-induced plasticity

The role of melt cooling rate on the interface between 18R and Mg matrix in Mg_(97)zn_(1)Y_(2) alloys

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Journal of Magnesium and Alloys 2023年第8期11卷 2883-2890页

作者： q.q.Jin X.H.Shao J.M.Li z.z.Peng M.Lv B.zhang Y.M.Li X.L.Ma Materials Science and Engineering Research Center Guangxi University of Science and TechnologyLiuzhou 545006China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering Hebei University of Science and TechnologyShijiazhuangHebei 050018China

The role of melt cooling rate on the interface morphology and dislocation configuration between 18R long-period stacking ordered(LPSO)structure and Mg matrix in Mg_(97)zn_(1)Y_(2)(at.%)alloys was investigated by atomic-scale HAADF-STEM *** 18R/Mg interface is step-like both in the near-equilibrium alloy and non-equilibrium *** cooling rate makes the step size more regular and *** 54R structure can be observed at the interface in the near-equilibrium alloy,and the dislocations are highly ordered.54R and 54R′structure sandwiched by b1 and b2+b3 dislocation arrays,and new dislocation configuration can be detected at the interface in the non-equilibrium alloy,but the dislocations are less ordered.18R/Mg interface containing 54R or 54R′in equilibrium width,parallel to the(010)plane,should be most stable based on elastic *** segregation of solute atoms and its strong interaction with dislocations dominate the LPSO/Mg interface via diffusion-displacive transformation.

关键词： Magnesium alloys Long-period stacking ordered phases Dislocations Interface structure