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Fracture analysis of a functionally graded interfacial zone between two dissimilar homogeneous materials

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Science china(Physics,Mechanics & Astronomy) 2006年第5期49卷 540-552页

作者： CHENG Zhanqi1.2.& ZHONG Zheng1.1. {1. of Aerospace engineering and Applied mechanics, {2. University, shanghai 200092, china 2. College of Civil engineering, Zhengzhou University, Zhengzhou 450002. china 1. school of Aerospace {1. and Applied mechanics Tongji University Shanghai 200092 China 2. College of Civil {1. Zhengzhou University Zhengzhou 450002 China

In this paper the plane elasticity problem for a functionally graded interfacial zone containing a crack between two dissimilar homogeneous materials has been considered. It is assumed that in the interfacial zone the reciprocal of the shear modulus is a linear function of the coordinate, while Possion’s ratio keeps constant. By utilizing the Fourier transformation technique and the transfer matrix method, the mixed boundary problem is reduced to a system of singular integral equations that are solved numerically. The influences of the geometric parameters and the graded parameter on the stress intensity factors are investigated. The numerical results show that the graded parameters, the thickness of interfacial zone, the crack size and location have significant effects on the stress intensity factors.

关键词： functionally graded material interfacial zone fracture stress intensity factor

Homogenization-based multi-scale damage theory

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Science china(Physics,Mechanics & Astronomy) 2010年第4期53卷 690-698页

作者： LI Jie 1.2.& REN XiaoDan 1.1.{1. of Civil engineering, {2. University, shanghai 200092, china 2.State Key Laboratory of Disaster Reduction in Civil engineering, shanghai 200092, china 1. school of Civil {1. Tongji University Shanghai 200092 China2. State Key Laboratory of Disaster Reduction in Civil Engineering Shanghai 200092 China

The research of modern mechanics reveals that the damage and failure of structures should be considered on different scales. The present paper is dedicated to establishing the multi-scale damage theory for the nonlinear structural analysis. Starting from the asymptotic expansion based homogenization theory, the multi-scale energy integration is proposed to bridge the gap between the micro and macro scales. By recalling the Helmholtz free energy based damage definition, the damage variable is represented by the multi-scale energy integration. Hence the damage evolution could be numerically simulated on the basis of the unit cell analysis rather than the experimental data identification. Finally the framework of the multi-scale damage theory is established by transforming the multi-scale damage evolution into the conventional continuum damage mechanics. The agree- ment between the simulated results and the benchmark results indicates the validity and effectiveness of the proposed theory.

关键词： Multi-scale damage representation asymptotic method constitutive model numerical simulation

Two-dimensional thermoelasticity solution for functionally graded thick beams

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Science china(Physics,Mechanics & Astronomy) 2006年第4期49卷 451-460页

作者： Lü Chaofeng1. CHEN Weiqiu1.& ZHONG Zheng2.1. Department of Civil {1., Zhejiang University, Hangzhou 31.02., china 2. Key Laboratory of Solid Mechanics of Ministry of Education, {2. of Aerospace {1. and Ap- plied Mechanics, tongji University, shanghai 200092, china Department of Civil engineering Zhejiang University Hangzhou 310027 China Key Laboratory of Solid Mechanics of Ministry of Education School of Aerospace Engineering Applied Mechanics Tongji University Shanghai 200092 China

Two-dimensional thermoelasticity analysis of functionally graded thick beams is presented using the state space method coupled with the technique of differential quadrature. Material properties vary continuously and smoothly through the beam thickness, leading to variable coefficients in the state equation derived from the elasticity equations. Approximate laminate model is employed to translate the state equation into the one with constant coefficients in each layer. To avoid numerical instability, joint coupling matrices are introduced according to the continuity conditions at interfaces in the approximate model. The differential quadrature procedure is applied to discretizing the beam in the axial direction to make easy the treatment of arbitrary end conditions. A simply-supported beam with exponentially varying material properties is considered to validate the present method. Numerical examples are performed to investigate the influences of relative parameters.

关键词： state equation differential quadrature approximate laminate model joint coupling matrices thermal stresses.

A geometrical and physical nonlinear finite element model for spatial thin-walled beams with arbitrary section

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Science china(Technological Sciences) 2010年第3期53卷 829-838页

作者： YANG QingShan 1.&WANG XiaoFeng 2.1.{1. of Civil engineering,Beijing Jiaotong University,Beijing 1.0044,{2. 2.College of Civil engineering,tongji University,shanghai 200092,{2. 1. school of Civil {1. Beijing Jiaotong University Beijing 100044 China2. College of Civil Engineering Tongji University Shanghai 200092 China

Based on the theories of Bernoulli-Euler beams and Vlasov's thin-walled members,a new geometrical and physical nonlinear beam element model is developed by applying an interior node in the element and independent interpolations on bending angles and warp,in which factors such as traverse shear deformation,torsional shear deformation and their coupling,coupling of flexure and torsion,and second shear stress are all ***,geometrical nonlinear strain in total Lagarange(TL) and the corresponding stiffness matrix are *** plastic model is applied to physical nonlinearity to comply with the yield rule of Von Mises and incremental relationship of *** stiffness matrix is derived by numerical integration on the basis of the finite segment *** show that the developed model is feasible in analysis of thin-walled structures with high accuracy.

关键词： Spatial beams thin-walled structures geometrical and physical nonlinearity finite element arbitrary section

Paleoceanographic evolution recorded in the northern South china Sea since 4 Ma

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Science china Earth Sciences 2005年第12期48卷 2166-2173页

作者： HUANG Baoqi1.2. JIAN Zhimin2.& WANG Pinxian2.1. school of Earth and Space Sciences, Peking University, Beijing 1.0871. china 2. Laboratory of Marine Geology, {2. University, shanghai 200092, china 1. school of Earth and Space Sciences Peking University 100871 Beijing China 2. Laboratory of Marine Geology Tongji University 200092 Shanghai China

Upper water structure over the last 4 million years in the northern South china Sea (SCS) was reconstructed by sea surface temperature (SST) and primary productivity estimated by changes in the abundance of planktonic foraminifer, planktonic foraminifer transfer function, and the accumulation rate of benthic foraminifera. Results of SST and primary productivity show that SST gradually decreased since 4 Ma, but differential seasonal temperature and primary productivity increased in steps mainly at about 3.1. {1.7, {1.1. 1.6, 0.9 and 0.5 Ma. Comparison with tectonics and orbital variations indicates that phased rising of the Tibet since 3.6 Ma, closing of Panama and Indonesian seaways, and orbital changes were responsible for the changes of upper water structure in the SCS, respectively.

关键词： northern South china Sea, upper water structure, Late Pliocene, planktonic foraminifer, ODP 1.46.

Synthesis and Properties of Water-soluble CdSe/ZnS Nanocrystals with the Type-I Core/Shell Structure

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Journal of Wuhan University of Technology(Materials Science) 2008年第5期23卷 600-605页

作者：王德平 school of Material Science and {1. Tongji University

The synthesis of CdSe/ZnS core/shell nanocrystals though aqueous phase using the coprecipitation method was reported. The influences of factors such as injection methods and dosages of precursors, reaction duration of water-bathing and the initial CdSe：ZnS molar ratio were discussed. In comparison to the CdSe plain core nanocrystals, the CdSe/ZnS core/shell nanocrystals show much brighter photoluminescence demonstrated by the photoluminescence spectra. The epitaxial growth of the core/shell structures was verified by TEM and XRD.

关键词： nanocrystals CdSe/ZnS core/shell synthesis of aqueous phase fluorescence

Fold-Hopf bifurcation in a simplified four-neuron BAM (bidirectional associative memory) neural network with two delays

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Science china(Technological Sciences) 2010年第3期53卷 633-644页

作者： GE JuHong & XU Jian school of Aerospace {1. and Applied Mechanics,{2. University,shanghai 200092,china 1. school of Aerospace {1. and Applied Mechanics Tongji University Shanghai 200092 China

The bidirectional associative memory (BAM) neural network with four neurons and two delays is considered in the present paper.A linear stability analysis for the trivial equilibrium is firstly employed to provide a possible critical point at which a zero and a pair of pure imaginary eigenvalues occur in the corresponding characteristic equation.A fold-Hopf bifurcation is proved to happen at this critical point by the nonlinear *** coupling strength and the delay are considered as bifurcation parameters to investigate the dynamical behaviors derived from the fold-Hopf *** dynamical behaviours are qualitatively classified in the neighbourhood of the fold-Hopf bifurcation point by using the center manifold reduction (CMR) together with the normal *** bifurcating periodic solutions are expressed analytically in an approximate *** validity of the results is shown by their consistency with the numerical simulation.

关键词： codimension-two bifurcation time delay solution classification unfolding centre manifold

An accessibility measure for the combined travel demand model

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Science china(Information Sciences) 2010年第2期53卷 299-306页

作者： YANG Chao & HE ShuLin school of {1. {2., tongji University, shanghai 2.1.04, china 1. school of {1. {2. Tongji University Shanghai 201804 China

The accessibility-oriented transport planning method is critical for many high population density cities in china. Most definitions of accessibility only consider spatial separation and ignore the influence of traveler choice on accessibility. In this paper, the combined travel demand model is employed in transport planning. The travelers’ choice behavior of the model is based on the random utility theory. The model overcomes inconsistence problem of the sequential four-step model on travel behavior and congestion effects. Based on the same random utility theory, an accessibility measure is proposed, which can be integrated into the combined travel demand model. The accessibility measure can reflect the traveler’s choices at different stages (travel choice, destination choice, mode choice and route choice). The properties of the accessibility measure are discussed through a numerical example.

关键词： accessibility random utility theory combined travel demand model urban transport planning

Effect of Cold Rolling on Microstructure and Mechanical Properties of AISI 301.N Metastable Austenitic Stainless Steels

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Journal of Iron and Steel Research International 2012年第10期19卷 59-63页

作者： HUANG Jun-xia1. YE Xiao-ning1. XU Zhou2.(1. {1. Baosteel Research Institute, {1. 2.0431. {2. 2. school of Material Science and engineering, {1. Jiao Tong University, {1. 2.02.0, {2.) [a] shanghai Baosteel Research Institute Shanghai 200431 China [b] school of Material Science and {1. Shanghai Jiao Tong University Shanghai 200240 China

The microstructure and mechanical properties evolution of AISI 301.N metastable austenitic stainless steels during cold rolling were investigated. A wide range of cold thickness reduction (1.%-80%) was carried out in a four-high rolling mill at ambient temperature. The X-ray and Feritscope MP30 were used to identify the strain-induced α′-martensite phase and its volume fraction, respectively. The microstructure was observed by optical micrograph and the mechanical properties were determined by tensile tests and microhardness. The results show that the strain-induced α′-martensite nucleated at the shear bands intersections and the growth of α′-martensite occurred by the repeated nucleation of new embryos. The volume fraction of strain-induced α′-martensite increased with increasing the cold rolling reduction. In addition, the percentage increased in the tensile strength is the same as that of hardness. The ratio between the average tensile strength and the average microhardness was found to range between 2.82.and 3.1..

关键词： metastable austenitic stainless steel cold rolling reduction strength