检索结果-南通市图书馆

Thermoelectric properties of p-type (Bi_(0.15)Sb_(0.85))_2Te_3-PbTe graded thermoelectric materials with different barriers

在线全文

学校读者我要写书评

暂无评论

Journal of University of Science and Technology Beijing 2005年第4期12卷 347-350页

作者： Guiying Xu Yanping Gao Changchun Ge Weiping Shen Laboratory of Special Ceramics and Powder Metallurgy University of Science and Technology Beijing Beijing 100083 China

The p-type （Bi0.15Sb0.85）2Te3 and PbTe are typical thermoelectric materials used for low and middle temperature range and functional graded materials （FGM） is an inevitable way to widen the working temperature range. Here two segments graded thermoelectric materials （GTM） consisting of （Bi0.15Sb0.85）2Te3, PbTe and different barriers were fabricated by the common hot pressure method. Metals Fe, Mg and Ni were used as barriers between the two segments. The diffusion of different barriers between the barriers and bases were analyzed by electron microprobe analysis （EMA）. The phase and crystal structures were determined by X-ray diffraction analysis （XRD）. The thermoelectric properties were measured at 303 K along the direction parallel to the pressing direction. The results show that the compositional diffusion occurs when there is no barrier at the interface of the two segments, and the diffusion of Pb is most obvious; as the barrier material, the diffusion of metals Fe, Mg and Ni between different bases is not very obvious, and the thermoelectric properties of GTM is much better than that of the original segment.

关键词： thermoelectric parameter graded materials barrier

NONLINEAR BUCKLING CHARACTERISTIC OF graded MULTIWEB STRUCTURE OF HETEROGENEOUS materials

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2005年第11期26卷 1442-1448页

作者：李永张志民 HUANG Xiao-qing Department of Mechanics Science School Beijing Institute of Technology Beijing 100081 P. R. China Department of Mechanics Beijing University of Aeronautics and Astronautics Beijing 100083 P. R. China 不详

The graded multiweb structure of heterogeneous anisotropic materials, which makes full use of the continuous, gradual and changing physical mechanical performance of material properties, has a widespread application in aeroplane aerofoil structure and automobile lightweight structure. On the basis of laminate buckling theory, the equivalent rigidity method is adopted to establish the corresponding constitutive relation and the non-linear buckling governing equation for the graded multiweb structure. In finding the solution, the critical load of buckling under different complicated boundary conditions together with combined loads were obtained and testification of the experimental analysis shows that the calculation results can satisfy the requirements of engineering design in a satisfactory way. Results obtained from the research say that： graded materials can reduce the concentrated stress on the interface in an effective way and weaken the effect of initial defect in materials and thereby improve the strength and toughness of materials.

关键词： graded materials multiweb structure buckling heterogeneous

Growth kinetics of cubic carbide free layers in graded cemented carbides

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and materials 2012年第1期19卷 64-71页

作者： Liu-yong Shi Yi-min Liu Ji-hua Huang Shou-quan Zhang Xing-ke Zhao School of materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China College of Mechanical and Electrical engineering Hainen University Danzhou 571737 China Xiarnen Golden Egret Special Alloy Co. Ltd. Xiamen 361006 China

In order to reveal the formation mechanism of cubic carbide free layers （CCFL）, graded cemented carbides with CCFL in the surface zone were fabricated by a one-step sintering procedure in vacuum, and the analysis on microstructure and element distribution were performed by scanning electron microscopy （SEM） and electron probe micro-analyzer （EPMA）, respectively. A new physical model and ki- netic equation were established based on experimental results. Being different f^om previous models, this model suggests that nitrogen diffu- sion outward is only considered as an induction factor, and the diffusion of titanium through liquid phase plays a dominative role. The driving force of diffusion is expressed as the differential value between nitrogen partial pressure and nitrogen equilibrium pressure essentially. Simulation results by the kinetic equation are in good agreement with experimental values, and the effect of process parameters on the growth kinetics of CCFL can also be explained reasonably by the current model.

关键词： graded materials cemented carbides diffusion kinetics

Free Vibration Analysis of Functionally graded Plates with Multiple Circular and Non-circular Cutouts

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2012年第2期25卷 277-284页

作者： JANGHORBAN Maziar ROSTAMSOWLAT Iman Department of Mechanical Engineering Shiraz BranchIslamic Azad UniversityShirazIran

Cutouts are inevitable in structures due to practical *** order to investigate the free vibration of functionally graded plates with multiple circular and non-circular cutouts,finite element method is *** volume fraction of the material constituents is assumed to follow a simple power law *** parameters considered in this paper are as follows：cutout size,cutout location,number of cutouts and different boundary *** should be mentioned that free vibration for FG plates（such as rectangular？skew？trapezoidal？circular plates） with multiple cutouts has not been studied yet and hence the results out coming from this paper may be used as bench marks for future works.

关键词： graded materials rectangular?skew?trapezoidal?circular plates multiple circular/non-circular cutouts

DEGRADATION OF graded-MATERIAL BEDS IN SEDIMENT-DEFICIENT RIVERS

在线全文

学校读者我要写书评

暂无评论

International Journal of Sediment Research 1986年 39-55页

作者： M. F. Karim Assistant Research Scientist, Institute of Hydraulic Research, The University of Iowa Oity,Iowa 52242, USA John F. Kennedy Carver Professor and Director, Institute of Hydraulic Research, The University of Iowa City,Iowa 52242 USA

The unsteady channel-degradation problem is formulated for the case of graded bed material by, first, deriving a relation between degradation depth and median particle size in the bed layer that is actively participating in the transport process, and introduction of the resulting equation and an expression for sediment discharge as a function of bed slope and particle size into the sedimentcontinuity equation. The resulting second-order nonlinear partial differential equation for degradation depth is first linearized and solved in closed form, and is also solved exactly by an iterative process applied to the complete equation. The latter solutions are found to be in good agreement with data from the Colorado River downstream from Hoover Dam, and with results obtained from a numerical simulation of an idealized representation of the Missouri River.

关键词： Degradation Rivers graded materials Analytical solution Sediment transport Armoring.

Numerical Modelling and Simulation of an Internal Combustion Engine Piston with a Surface Coating

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Numerical Modelling and Simulation of an Internal Combustion...