检索结果-南通市图书馆

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

在线全文

学校读者我要写书评

暂无评论

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

作者： CHENG Zhanqi1,2.& ZHONG Zheng1 1. school of Aerospace engineering and Applied mechanics, {2. University, shanghai 2.0092, china 2. College of Civil engineering, Zhengzhou University, Zhengzhou 450002. china school of Aerospace engineering and Applied mechanics Tongji University Shanghai China College of Civil engineering Zhengzhou University Zhengzhou 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

Two-dimensional thermoelasticity solution for functionally graded thick beams

在线全文

学校读者我要写书评

暂无评论

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 engineering, Zhejiang University, Hangzhou 31002., china 2. Key Laboratory of Solid Mechanics of Ministry of Education, {2. of Aerospace engineering and Ap- plied Mechanics, tongji University, shanghai 2.0092, china Department of Civil engineering Zhejiang University Hangzhou China Key Laboratory of Solid Mechanics of Ministry of Education School of Aerospace Engineering and Applied Mechanics Tongji University Shanghai 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.

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

在线全文

学校读者我要写书评

暂无评论

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 100871, china 2. Laboratory of Marine Geology, {2. University, shanghai 2.0092, china school of Earth and Space Sciences Peking University Beijing China Laboratory of Marine Geology Tongji University 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, 2.7, 2.1, 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 1146.

Homogenization-based multi-scale damage theory

在线全文

学校读者我要写书评

暂无评论

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 school of Civil engineering, {2. University, shanghai 2.0092, china 2.State Key Laboratory of Disaster Reduction in Civil engineering, shanghai 2.0092, china school of Civil engineering Tongji University Shanghai China State Key Laboratory of Disaster Reduction in Civil engineering Shanghai 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

An accessibility measure for the combined travel demand model

在线全文

学校读者我要写书评

暂无评论

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

作者： YANG Chao & HE ShuLin school of transportation {2., tongji University, shanghai 2.1804, china school of transportation {2. Tongji University Shanghai 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

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

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

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

作者： YANG QingShan 1 &WANG XiaoFeng 2.1 school of Civil engineering,Beijing Jiaotong University,Beijing 100044,{2. 2.College of Civil engineering,tongji University,shanghai 2.0092.china school of Civil engineering Beijing Jiaotong University Beijing China College of Civil engineering Tongji University Shanghai 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

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

在线全文

学校读者我要写书评

暂无评论

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. shanghai Baosteel Research Institute, shanghai 2.0431, {2. 2. school of Material Science and engineering, shanghai Jiao Tong University, shanghai 2.02.0, {2.) shanghai Baosteel Research Institute Shanghai China school of Material Science and engineering Shanghai Iiao Tong University Shanghai China

The microstructure and mechanical properties evolution of AISI 301LN metastable austenitic stainless steels during cold rolling were investigated. A wide range of cold thickness reduction (10%-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 3.17.

关键词： metastable austenitic stainless steel cold rolling reduction strength

Interaction Theory of Asphalt and Rubber

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2010年第5期25卷 853-855页

作者：高英 transportation school Southeast University

Through scanning electron microscope （SEM）, spectral analysis, and component analysis tests, the interaction theory between asphalt and rubber was discussed. It is concluded that rubber powder become soft and bond together with each other after being mixed with asphalt. The asphalt changes from a smooth homogeneous matter to a continuous mixing system which is composed of rubber powder and asphalt. The interaction is mainly physical diffusion, but there are some chemical reactions in the process, especially at long reaction time.

关键词： crumb rubber asphalt rubber interaction theory physical diffusion chemical reactions

Effect of Pozzolanic Reaction Products on Alkali-silica Reaction

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2006年第3期21卷 168-171页

作者：魏风艳 shanghai K. Wah Concrete Co.Ltd Shanghai 200030China

The effect of fly ash on controlling alkail-silica rection （ASR） in simudated alkali solution was studied. The expausion of mortar bars and the content of Ca（ OH）2.in cement paste cured at 80 °G for 91 d were measured. Traasmission electron microscopy （TEM） and high-resolution transmission electron microscot9 （HRTEM） were employed to study the microstructure of C-S-H. TEM/ energy dispersive spectroscopy （EDS） leas then used to determine the composition of C-S-H. The pore structure of the paste was analyzed by mercury intntsion porosimetry （MIP）. The results show that the contents of fly ash of 30% and 45% can well inhibit ASR. And the content of Ca（OH） 2.decreases with the increase of fly ash. That fly ash reacted with Ca（OH）2.to produce C-S-H with a low Ca/Si molar ratio could bind more Na^＋ and K^＋ ious, and produce a reduction in the amount of soluble alkali available for ASR. At the same time, the C- S- H produced by pozzolanic reaction converted large pores to snudler ones （ gel pores smaller than 10 nm ） to deusify the pore structure. Perhaps that could inhibit alkali trausport to aggregate for ASR.

关键词： alkali Ca/ Si molar ratio C-S-H alkali-silica reaction