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High-Speed Friction Stir Welding of T6-Treated B4Cp/6061Al Composite

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Acta Metallurgica Sinica(English Letters) 2020年第1期33卷 67-74页

作者： y.Z.Li y.N.Zan Q.Z.Wang B.L.Xiao Z.y.Ma Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China University of Science and Technology of China Shenyang 110016China

T6-treated 20 wt% B4 Cp/6061 Al sheets were joined under welding speeds of 400–1200 mm/min by friction stir welding(FSW) with a threaded cermet pin. The macro-defect-free FSW joints could be achieved at high welding speeds up to 1200 mm/min, but larger plunge depth was required at the welding speeds of 800 and 1200 mm/min to eliminate the tunnel defect. In the nugget zone(NZ) of the joints, the B4 C particles were broken up and uniformly redistributed. The NZ exhibited lower hardness than the base metal(BM), and the hardness value almost did not change with increasing welding speed, attributable to the dissolution of precipitates. Compared with the BM, the joints showed lower tensile strength. As the welding speed increased from 400 to 800 mm/min, the joint efficiencies were nearly the same and up to ~ 73%. When the welding speed increased up to 1200 mm/min, the tensile strength significantly decreased, due to the occurrence of kissing bond defect at the bottom of the NZ. With increasing welding speed, the fracture location of the joints transferred gradually from the heat-affected zone to the NZ due to the kissing bond defects.

关键词： Metal-matrix composites Microstructures Mechanical properties Friction stir welding High-speed welding

Multi-place physics and multi-place nonlocal systems

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Communications in Theoretical Physics 2020年第5期72卷 120-132页

作者： S y Lou School of Physical Science and Technology Ningbo UniversityNingbo315211China

Multi-place nonlocal systems have attracted attention from many *** this paper,we mainly review the recent progresses on two-place nonlocal systems(Alice-Bob systems)and four-place nonlocal ***-place systems can firstly be derived from many physical problems by using a multiple scaling method with a discrete symmetry group including parity,time reversal,charge conjugates,rotations,field reversal and exchange *** nonlocal systems can also be derived from the symmetry reductions of coupled nonlinear systems via discrete symmetry *** the other hand,to solve multi-place nonlocal systems,one can use the symmetry-antisymmetry separation approach related to a suitable discrete symmetry group,such that the separated systems are coupled local *** using the separation method,all the known powerful methods used in local systems can be applied to nonlocal *** this review article,we take two-place and four-place nonlocal nonlinear Schr?dinger(NLS)systems and Kadomtsev-Petviashvili(KP)equations as simple examples to explain how to derive and solve *** types of novel physical and mathematical points related to the nonlocal systems are especially emphasized.

关键词： multi-place physics multi-place nonlocal systems symmetries integrable systems parity and time reversal soliton theory classical prohibitions

A novel supercapacitor-fuel cell hybrid cell

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Rare Metals 2006年第z1期25卷 12-18页

作者： WANG y ZHENG Jim P Department of Electrical and Computer Engineering Florida A&M University and Florida State University Tallahassee FL 32310 USA Department of Electrical and Computer Engineering Florida A&M University and Florida State University Tallahassee FL 32310 USA

A monolithic hybrid fuel cell (MHFC) with a novel configuration was proposed in an effort to improve the fuel cell performance during instantaneous power changes. A modified direct methanol fuel cell (DMFC) with a layer of hydrous ruthenium dioxide (RuO2·xH2O) sandwiched between the anode catalyst layer and membrane was used to demonstrate the principle of the MHFC. Experimental results indicate that the RuO2·xH2O layer is equivalent to a resistor-capacitor transmission line and functions similar to a capacitor in parallel with the anode electrode. The improvement in dynamic response of the MHFC was experimentally confirmed under step current change and square current pulse operating. The ionic conductivity of the RuO2·xH2O layer was also obtained.

关键词： hybrid devices direct methanol fuel cells hydrous ruthenium dioxide dynamic response

Neumann＇s method for boundary problems of thin elastic shells

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Applied Mathematics and Mechanics(English Edition) 2017年第4期38卷 543-556页

作者： y. S. NEUSTADT Department of Civil Engineering Samara State Architectural and Building University Samara 443001 Russia

The possibility of using Neumann＇s method to solve the boundary problems for thin elastic shells is studied. The variational statement of the static problems for the shells allows for a problem examination within the distribution space. The convergence of Neumann＇s method is proven for the shells with holes when the boundary of the domain is not completely fixed. The numerical implementation of Neumann＇s method normally requires significant time before any reliable results can be achieved. This paper suggests a way to improve the convergence of the process, and allows for parallel computing and evaluation during the calculations.

关键词： boundary problem thin elastic shell theory Neumann's method variational principle Korn's inequality distribution embedding theorem Green tensor

THEORy OF WATER WAVES IN AN ELASTIC VESSEL

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Acta Mechanica Sinica 2000年第2期16卷 97-112页

作者： D. y. Hsieh Division of Applied Mathematics Brown University USA

Recent experiments related to the Dragon Wash phenomena showed that axisymmetric capillary waves appear first from excitation, and circumferential capillary waves appear after increase of the excitation strength. Based on this new finding, a theory of parametric resonance is developed in detail to explain the on- set of the prominent circumferential capillary waves. Numerical computation is also carried out and the results agree generally with the experiments. Analysis and nu- merical computation are also presented to explain the generation of axisymmetric low-frequency gravity waves by tile high-frequency external excitation.

关键词： water waves elastic vessel Dragon Wash

STRUCTURAL TRANSFORMATION INDUCED By MECHANICALLy DRIVEN ALLOyING AND SUBSEQUENT MAGNETIC PROPERLIESOF THE Fe-Cu SySTEM

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Acta Metallurgica Sinica(English Letters) 1998年第2期11卷 128-136页

作者： y.Z.yang y.HLuo Q.S.Li y.L.Zhu X.M.Ma y.D.Dong y.Z.Chuang Guangdong Univ of Technology Guangzhou China

The structural transformation in Fe-Cu powder induced by mechanically driven alloying has been monitored by the lattice constant measurements and Mossbauer spectroscopy. For the samples with Cu higher than 75at.% Mossbauer the spectra show a broad paramagnetic doublet; for samples with 50 and 60at.%Cu a new broad ferromagnetic sextet; for those with less than 30at.%Cu similar to those of α-Fe. The main peaks of the hyperfine field distribution significantly broaden and shift to a lower position with increasing Cu content due to the complex environments of iron atoms in the solid solutions and the reduction in the nearest neighbor Fe of a cental Fe atom, respectively. The saturation magnetization of Fe-Cu alloys monotonously decreases with Cu content. The complex composition dependence of coercive field for the milled samples is discussed with respect to the solid dissolution, grain size, interfacial state etc.. The increase of lattice constants with the solute content in the two terminal solid solutions has been explained by the volume-size factor theory or magnetovolume effect.

关键词： mechanical alloying Mossbauer effect Fe-Cu alloy magnetic measurement

Ab Initio Study on the Thermal Isomerization from 1,2-Butadiene to1,3-Butadiene

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Chinese Chemical Letters 1997年第1期8卷 71-72页

作者： Feng, WL Lei, M Wang, y Qian, y BEIJING NORMAL UNIV DEPT CHEMBEIJING 100875PEOPLES R CHINA BEIJING IND UNIV DEPT ENVIRONM & ENGNBEIJINGPEOPLES R CHINA

Ab initio UHF/6-31G** method has been employed to study the mechanism of the thermal isomerization from 1,2-butadiene to 1,3-butadiene. The energies were corrected at MP2//6-31G**+ZPE(zero-point energy) level. The results indicate that it is a stepwise reaction via a radical intermediate. The calculated activation barriers are 65.01 and 64.16 kcal./mol., respectively.

关键词： Ab Initio Study on the Thermal Isomerization from 1,2-Butadiene to1,3-Butadiene

Microstructural analysis of EN-GJS-450-10 ductile cast iron via vibrational casting

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China Foundry 2020年第4期17卷 272-278页

作者： Caglar yüksel Atatürk University Department of Metallurgical and Materials EngineeringErzurumTurkey

EN-GJS-450-10 ductile cast iron was produced with and without vibration to evaluate microstructural features. To investigate the effect of vibration, a reference, and two different castings having amplitudes of 0.9 mm and 1.8 mm were cast with a fixed vibration frequency of 50 Hz. The nodule count (density), form (type), size distribution, nodularity, and the fraction of graphite, percentages of both ferrite and pearlite phases, length of ferrite shell, and pore, were evaluated via optical microscopy using an image analysis software. It is observed that the microstructure of the cast iron is more uniform by vibrational casting than that by non-vibrational casting. Additionally, mechanical vibration enhances nodule count and nodularity, also, more ferritic matrix could be obtained after the application of vibration. Nodule count and nodularity of vibrational casting with 1.8 mm amplitude increased from 226 nodule per mm2 and 80% to 311 nodule per mm2 and 86.5% of non-vibrational casting. Percentages of ferrite and graphite area dramatically improved from 24% and 16.5% for non-vibrational casting to 57% and 22.3% for vibrational casting with 1.8 mm amplitude, whereas the percentages of pearlite and pores decreased significantly from 56.1% and 5% to 20% and 1%, respectively.

关键词： mechanical vibration spheroidal cast iron ductile iron nodularity image analysis amplitude

Low temperature oxidation of Cr-alloyed MoSi_2

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中国有色金属学会会刊：英文版 2007年第6期17卷 1282-1286页

作者： E. Strom y. Cao y. M. yao Kanthal AB Box 502 SE-734 27 Hallstahammar Sweden Department of Materials and Manufacturing Technology Chalmers University Technology SE-412 96 Gothenburg Sweden

Cr-alloyed MoSi2 was compared with monolithic MoSi2 with respect to oxidation at 450 ℃ for 456 h. Phases formed on Cr-alloyed MoSi2 after exposure are Cr2(MoO4)3, MoO3, and cristobalite (SiO2) according to X-ray diffraction results. Monolithic MoSi2 forms MoO3 and mainly amorphous SiO2. X-ray photoelectron spectroscopy indicates that the main oxidation product on the outermost surface is SiO2 for all studied samples. The samples form a relatively loose oxide but the oxide adherence improves with increasing Cr content. It is indicated that Cr addition can benefit pesting control in MoSi2.

关键词：钼硅化合物合金有害物氧化作用