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HEAT TREATMENT sTRENGTHENING EFFECTs OF RARE EARTHs ON Mg-9Al ALLOy

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Acta Metallurgica sinica(English Letters) 2003年第1期16卷 8-14页

作者： y.s.wang J.Z.yu Q.D.wang W.J.Ding shanghai Cosmopolitan Automobile Accessory Co. LTD Shanghai 200083 China school of Materials science and Engineering Shanghai Jiao Tong University Shanghai 200030 China

Mg-9Al-xRE magnesium alloys were studied, where, x is 0, 0.4. 0.8. 1.2 and 1.6% (in weight percent, wt%), respectively. Influence of rare earths (RE) on micro structure. and strength in both T4 (solute heat treatment) and T6 (solute heat treatment and artificial ageing treatment) were investigated. strength of specimen was tested at ambient temperature. The micro structure was analyzed by optical microscopy, scanning electron microscopy (sEM) and X-ray diffraction analysis. RE additions improved T4 tensile strength of the treated alloys. small addition (0.4wt%) of RE greatly improved the strength of ageing treated (T6) Mg-9Al alloy, but further additions caused decreasing.

关键词： Mg-Al alloy rare earth (RE) heat treatment mechanical property strength

Engine valve and seat insert wear study with a simulator

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science China Mathematics 2001年第S1期44卷 235-241页

作者： y.s.wang s.Narasimhan Eaton Corp. Engine Components Operations 19218 B Drive SouthMarshall MI 49068

The demands on higher performance and the increasing use of alternative fuels chal-lenge engine valves now with greater wear problems than before. A seat wear simulator was builtto evaluate the compatibility and wear of valve and seat insert. The rig test results have been suc-cessfully correlated with engine test results. In this study, intake valves made from sil 1 materialwere treated with salt bath nitride processes and tested against six different insert materials. Wearresistance of these combinations was ranked and compared to the sil 1 valve without *** test results demonstrate that nitriding improved valve seat wear resistance. In the total valveseat recession ranking, the combination of nitrided sil 1 valve against T 400 insert exhibited theleast total recession among the nineteen combinations of valve and insert tested. The results indi-cate that the valve seat wear mechanisms are a complex combination of adhesion and shearstrain. The nitrides in the compound layer of nitrided valves gave strong atomic bonding, higherhardness, compressive residual stresses, and possible low friction, thus resulted in the superiorwear performance.

关键词： engine valve nitride seat insert valve scat wear mechanism wear simulation

MODELING OF AUsTENITE GRAIN sIZE IN LOW-ALLOy sTEEL WELD METAL

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Acta Metallurgica sinica(English Letters) 2004年第2期17卷 147-154页

作者： A.G.Huang y.s.wang Z.y.Li J.G.Xiong Q.Hu school of Materials science & Engineering,Huazhong University of science and Technology,Wuhan 430074,China school of Materials science & Engineering Huazhong University of Science and Technology Wuhan 430074 China

The size of austenite grain has significant effects on components and proportions ofvarious ferrites in low-alloy steel weld metal. Therefore, it is important to determinethe size of austenite grain in the weld metal. In this paper, a model based upon thecarbon diffusion rate is developed for computing austenite grain size in low-alloy steelweld metal during continuous cooling. The model takes into account the effects of theweld thermal cycles, inclusion particles and various alloy elements on the austenitegrain growth. The calculating results agree reasonably with those reported experimentalobservations. The model demonstrates a significant promise to understand the weldmicrostructure and properties based on the welding science.

关键词： low-alloy steel anstenite mathematical model diffusion

Large Bandgaps of Two-Dimensional Phononic Crystals with Cross-like Holes

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Large Bandgaps of Two-Dimensional Phononic Crystals with Cro...

The 16th Annual Conference of Hong Kong society of Theoretical and Applied Mechanics 2012、The 1st Mainland-Hong Kong youth Forum on Mechanics 2012、The 8th shanghai-Hong Kong Forum on Mechanics and Its Application 2012

作者： y.F.wang y.s.wang Institute of Engineering Mechanics Beijing Jiaotong University

Phononic crystal(PC) is an artificial periodic elastic/acoustic structure with acoustic or elastic bandgaps within which the propagation of elastic/acoustic waves is fully *** PC may have potential applications in acoustic filtering,noise suppression,vibration isolation,and design of new acoustic devices,***,a certain degree of interests is being generated on the PCs with periodic holes(vacuum or filled with air) with their bandgaps mainly determined by the geometric *** of the reports are focused on the systems with convex holes(circular or regular polygon holes).But,the difference between convex and non-convex holes may lead to evident change of *** motivates the investigation on bandgaps of PCs with non-convex *** this paper,the finite element method(FEM) based on the Comsol Multiphysics software is used to study the effects of geometric parameters on the bandgaps of 2D systems in a square lattice with cross-like(a kind of non-convex) holes which are denoted as the "+"-hole and "x"-hole respectively.

关键词： Large Bandgaps of Two-Dimensional Phononic Crystals with Cross-like Holes

Complete Band Gaps in sandwich Phononic Crystal Plates

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Complete Band Gaps in Sandwich Phononic Crystal Plates

作者： X.F.Liu y.s.wang Institute of Engineering Mechanics Beijing Jiaotong University

Using the finite element method,the propagation of Lamb waves in sandwich phononic crystal plates(sPCP) is *** structure is composed of a two-dimensional phononic crystal plate coated with two substrates on both *** phononic crystal plate(PCP) is constituted by a square array of gold cylinders arranged in an epoxy matrix,and the substrates are made of *** is evidenced that some complete phononic band gaps(PBGs) are opened up by changing the thickness of PCP,and the width of the first PBG becomes larger as the thickness *** influence of substrates' thickness and material on the width of PBG is discussed as *** to the results,one can notice that the thickness of PCP and substrates plays a key role in tuning the band gaps of the sPCPs,and could estimate the best configuration of these two parameters in the application of vibration control and noise reduction.

关键词： sandwich Complete Band Gaps in sandwich Phononic Crystal Plates

Bandgap Calculation for Phononic Crystals with Nanosized Inclusions by Dirichlet-to-Neumann Map

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Bandgap Calculation for Phononic Crystals with Nanosized Inc...

作者： N.Zhen y.s.wang C.Zhang Institute of Engineering Mechanics Beijing Jiaotong University Department of Civil Engineering University of Siegen

Phononic crystals are composed of periodic arrays of two or more materials with different mass densities and elastic *** of the distinguishing features of phononic crystals is the presence of band gap(energy or frequency gap) where waves cannot propagate through the system. Phononic crystals have received considerable attention in the last decades because of their potential applications in noise reduction,vibration damping,design of new acoustic devices,*** has been demonstrated that the surface/interface effects play an important role in the mechanical behaviors of nanosized structures,therefore the surface/interface effects on the dispersion relations of the nanosized phononic crystals should be an interesting *** this paper,we develop a new method based on the Dirichlet-to-Neumann map to study phononic crystals with nanosized circular inclusions. We consider a transverse wave polarized in the z-direction propagating in a phononic crystal composed of nanosized cylinders in a square *** of the interface effects,the boundary condition on the interface between the cylinder and matrix of the nanosized structures is different from the perfectly bonded interface *** the displacements in a unit cell as cylindrical wave expansions and imposing the well known young-Laplace equation on the interface,we build a map from the displacement to its normal derivative at the boundary of the unit *** based on the Bloch theory,the wave equations are transferred to an eigenvalue problem which can be solved to obtain the band *** calculate the band structures of the phononic crystals composed of aluminum cylinders embedded in tungsten matrix with and without the interface effect,with the filling fraction of *** results show that the influence of the interface effect cannot be *** lowest band gap will become wider with the first band descending *** should be considered carefully in practical applicat

关键词： Neumann Dirichlet Bandgap Calculation for Phononic Crystals with Nanosized Inclusions by Dirichlet-to-Neumann Map

Topology Optimization of Two-Dimensional Phononic Crystals Using FEM and Genetic Alogrithm

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Topology Optimization of Two-Dimensional Phononic Crystals U...

作者： H.W.Dong X.X.su y.s.wang Institute of Engineering Mechanics Beijing Jiaotong University school of Electronic and Information Engineeing Beijing Jiaotong University

Because of the potential application of the phononic crystals(PCs)(noise reduction, acoustic filtering and waveguiding,etc) and with the in-depth development of this field,the topological optimization and inverse design of PC structures have provoked certain degree of interests within the community in recent *** the present work,we carry out the band gap optimization of the two-dimensional(2D) solid binary-component *** finite element method(FEM) and the genetic algorithm(GA) are used as the forward calculation method and optimization scheme, *** forward FEM calculation of the band structures is accomplished by the standard software *** the calculation,the parameter modeling is realized by modifying the input file and running the scriptlet;and we choose iterative method Lanzcos for to calculate the eigenfrequencies corresponding to each of the selected Bloch wave ***,with the scriptlet of Abaqus,the considered 2D PC is extracted from the obtained band *** the GA optimization sheme,we encode the materials distribution by dividing the unit cell into N×N elements;then the genetic operators(selection,crossover andmutation are applied to create children replacing their parent in the next *** generation after another is created in such a manner until a convergence criterion is *** elitist selection scheme is applied in the *** the best one of the new generation is not more excellent than that of the parent generation,the latter one will replace a chromosome of the new generation *** last,the materials distribution parameters of chromosome are transferred to Abaqus by using the Python language which can call the Abaqus kernel to make pretreatment and post-processing. some preliminary numerical results are *** component materials are Pb and *** the initial population,the seed chromosome corresponds to a PC stucture with the maximum relative width is *** the optimization process,GA beg

关键词： FEM Topology Optimization of Two-Dimensional Phononic Crystals Using FEM and Genetic Alogrithm

Effects of Poisson's Ratio on Band Gaps of Two-Dimensional solid/solid Phononic Crystals

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Effects of Poisson's Ratio on Band Gaps of Two-Dimensional S...

作者： T.X.Ma X.X.su y.F.wang y.s.wang Institute of Engineering Mechanics Beijing Jiaotong University school of Electronic and Information Engineering Beijing Jiaotong University

since the 1990s,there has been a great deal of work devoted to the study of phononic crystals(PCs).The existence of a phononic band gap(PBG) where the propagation of the acoustic or elastic waves is forbidden leads to many engineering *** the PBG tuning mechanism is always an important aspect of the theoretical studies of PCs. In this paper,we study the effects of the Poisson's ratios on the PBGs in two-dimensional(2D) solid-solid square-latticed *** to the theoretical importance and practical application of the auxetic material,the effect of negative Poisson's ratio is also considered in the present work. For the in-plane wave mode,the material parameters determining PBGs include the velocity ratio,the acoustic impedance ratio and the Poisson's ratios of the two component materials[1].We investigate the influences of the Poisson's ratio on 2D square-latticed PCs with given values of the velocity ratio and acoustic impedance *** different combinations of the velocity ratio and acoustic impedance ratio correspond to the large impedance ratio with small mismatch in the transverse wave velocities,small velocity ratio with small mismatch in the acoustic impedances and small impedance ratio with small mismatch in the wave *** PBGs between the 2nd and 3rd,3rd and 4th bands are *** are usually the first or second PBGs. For the PCs with large impedance ratio and small mismatch in the wave velocities,the PBG is influenced slightly by the Poisson's ratio of the host,but significantly by that of the inclusion when its value is *** the PCs with small velocity ratio and small mismatch in the acoustic impedances,the PBGs between the 3rd and 4th bands are sensitive to the Poisson's ratios of both the host and inclusion;those between the 2nd and 3rd bands are influenced significantly by the Poisson's ratio of the inclusion and become wider as the Poisson's ratio of the inclusion *** the PCs with small impedance rati

关键词： Poisson Effects of Poisson's Ratio on Band Gaps of Two-Dimensional solid/solid Phononic Crystals

China’s participation in the international RRT for I_(c) measurement of superconducting cables organized by IEC/TC90

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superconductivity 2022年第1期1卷 27-33页

作者： J.Li y.shi G.M.Zhang L.W.Jing J.X.Zheng C.L.Liu W.yuan y.s.wang M.song y.J.Xia X.H.Zong y.W.Han D.N.Zheng X.J.Zhou T.Matsushita G.Nishijima The Institute of Physics Chinese Academy of SciencesBeijing 100190China The Institute of Electrical Engineering Chinese Academy of SciencesBeijing 100190China The Institute of Plasma Physics Chinese Academy of SciencesHefei 230031China Eastern superconductor science&Technology(suzhou)Co LtdSuzhou 215299China Guangdong Power Grid Corporation Guangzhou 510630China shanghai International superconductor Technology Co LtdShanghai 200444China Department of Computer science and Electronics Kyushu Institute of Technology Iizuk1Japan National Institute for Materials scienc5 Tsukuba 305-0003Japan

Currently,IEC/TC90 is working on standardizing the method for measuring critical current(Ic)in superconducting *** the end of 2020,an international round robin test(RRT)was organized,in which five Chinese institutions participated,and four accomplished the *** electric-field versus current(E-I)curves obtained by each institution are highly *** obtained by different institutions are nearly identical after appropriate curve averaging,indicating high reproducibility,except the last participant's inner core *** discrepancy was later determined to be the result of sample cable *** excluding highly deviated data,it is determined that the maximum relative standard uncertainty in I_(c) is 0.7%,and the maximum relative standard uncertainty in n-value is 12.8%.The I_(c)values are comparable to Japan's domestic RRT results,but the n-values are significantly *** test results support the DC four-terminal method as a recommended test method,with a target relative uncertainty of less than 2%for the Ic value.

关键词： superconducting cable Round robin test standardization