检索结果-南通市图书馆

A structural topological optimization meth.d for multi-displacement constraints and any initial topology configuration

在线全文

学校读者我要写书评

暂无评论

Acta Mech.nica Sinica 2010年第5期26卷 735-744页

作者： j. h. Rong j. h. Yi Sch.ol of Automotive and Mech.nical Engineering Changsha University of Science and TechnologyChangsha 410076 China

In density-based topological design, one expects th.t th. final result consists of elements eith.r black （solid material） or wh.te （void）, with.ut any grey areas. Moreover, one also expects th.t th. optimal topology can be obtained by starting from any initial topology configuration. An improved structural topological optimization meth.d for multidisplacement constraints is proposed in th.s paper. In th. proposed meth.d, th. wh.le optimization process is divided into two optimization adj.stment ph.ses and a ph.se transferring step. Firstly, an optimization model is built to deal with.th. varied displacement limits, design space adj.stments, and reasonable relations between th. element stiffness matrix and mass and its element topology variable. Secondly, a procedure is proposed to solve th. optimization problem formulated in th. first optimization adj.stment ph.se, by starting with.a small design space and advancing to a larger deign space. Th. design space adj.stments are automatic wh.n th. design domain needs expansions, in wh.ch.th. convergence of th. proposed meth.d will not be affected. Th. final topology obtained by th. proposed procedure in th. first optimization ph.se, can approach.to th. vicinity of th. optimum topology. Th.n, a h.uristic algorith. is given to improve th. efficiency and make th. designed structural topology black/wh.te in both.th. ph.se transferring step and th. second optimization adj.stment ph.se. And th. optimum topology can finally be obtained by th. second ph.se optimization adj.stments. Two examples are presented to sh.w th.t th. topologies obtained by th. proposed meth.d are of very good 0/1 design distribution property, and th. computational efficiency is enh.nced by reducing th. element number of th. design structural finite model during two optimization adj.stment ph.ses. And th. examples also sh.w th.t th.s meth.d is robust and practicable.

关键词： Topological optimization Displacement constraint Continuum structure Design space adj.stment Rational approximation material model

Acoustic Measurements for Determination of th. Materials Damping Using A Sound Source Localisation System

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English.Letters) 2013年第2期26卷 113-121页

作者： j. Gken j. Swiostek h. h.rdelbrink U. Keil Faculty of Maritime Studies University of Applied Sciences Emden/Leer Bergmannstr. 36 26789 LeerGermany Stalomax TM Company of High-Precision Mechanics ul. Parkingowa 45 37450 Stalowa WolaPoland

Noise measurements are especially a problem wh.n th. obj.ct under investigation is largely dimensioned and can only be measured from th. distance. To obtain information about th. location of noise generation, a measurement tech.ique wh.ch.makes sound visible in order to introduce furth.r specific tech.ical measures is advantageous. Th. question is if th. time dependence of th. signal got from such.a non touch.ng and non destructive acoustic meth.d h.s th. potential to calculate th. materials damping from. Using a small sound source localization system （Microflown^TM probe）, specimens of magnesium alloys with.different grain sizes obtained by h.drostatic extrusion were investigated. It h.s been demonstrated th.t th. fine grained microstructure led to a lower damping and its dependence on th. strain was reduced. In th.s context, acoustic measurements by a sound source localisation system wh.ch.makes materials ch.racterization possible could be used as a quality tool to detect ch.nges in h.gh.y stressed components. Th.s approach.allows to promote a selective substitution of conventional materials by more innovative ones. Th. offsh.re sector is considered to be a field of application： Wind turbines produce noise emission wh.ch.stems mainly from turbulences at th. tips of th. rotor blades and vibrations of components inside th. nacelle （e.9. gearbox, generator, ...）. If th. vibration amplitudes are too h.gh. microcracks of components can lead to failure over th. long term. Th. monitoring of microstructural ch.nges using a larger type of a sound source localisation system is considered as an innovative tech.ical approach.with.respect to maintenance activities.

关键词： Magnesium Noise measurements MicroflownTM Damping

Simulating canopy stomatal conductance of winter wh.at and its distribution using remote sensing information

在线全文

学校读者我要写书评

暂无评论

j.urnal of Environmental Sciences 2001年第4期13卷 439-443页

作者： Zh.ng, j.-h. Fu, C.-b. Kanzawa, h. START Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

Th. canopy stomatal movement, a plant ph.siological process, generally occurs with.n leaves but its influence on exch.nge of CO2, water vapor, and sensible h.at fluxes between atmosph.re and terrestrial ecosystem. Many studies h.ve documented th.t th. interaction between leaf ph.tosynth.sis and canopy stomatal conductance is obvious. Th.s, information on stomatal conductance is valuable in climate and ecosystem models. In current study, a newly developed model was adopted to calculate canopy stomatal conductance of winter wh.at in h.ang-h.ai-h.i (h.h.h. Plain of Ch.na (31.5 - 42.7°N, 110.0 - 123.0°E). Th. remote sensing information from NOAA-AVh.R and meteorological observed data were used to estimate regional scale stomatal conductance distribution. Canopy stomatal conductance distribution pattern of winter wh.at on March.18, 1997 was also presented. Th. developed canopy stomatal conductance model migh. be used to estimate canopy stomatal conductance in land surface sch.mes and seems can be acted as a boundary condition in regional climatic model runs.

关键词： Carbon dioxide Data reduction Ecosystems h.at flux Meteorology Ph.tosynth.sis Ph.siology Plants (botany) Remote sensing Vapors

Exact solution and transient beh.vior for torsional vibration of functionally graded finite h.llow cylinders

在线全文

学校读者我要写书评

暂无评论

Acta Mech.nica Sinica 2009年第4期25卷 555-563页

作者： h. M. Wang C. B. Liu h. j. Ding Department of Mech.nics Zhejiang University Department of Civil Engineering Zhejiang University

Exact solutions are obtained for transient torsio- nal responses of a finitely long, functionally graded h.llow cylinder under th.ee different end conditions, i.e. free-free, free-fixed and fixed-fixed. Th. cylinder with.its external surface fixed is subj.cted to a dynamic sh.aring stress at th. internal surface. Th. material properties are assumed to vary in th. radial direction in a power law form, wh.le keep invariant in th. axial direction. With.expansion in th. axial direction in terms of trigonometric series, th. governing equations for th. unknown functions about th. radial coordinate r and time t are deduced. By applying th. variable substitution tech.ique, th. superposition meth.d and th. separation of variables consecutively, series-form solutions of th. equations are obtained. Natural frequencies and th. transient torsional responses are finally discussed for a functionally graded finite h.llow cylinder.

关键词： Exact solution Functionally graded material Finite h.llow cylinder Transient torsional vibration

h.brid finite-discrete element modelling of asperity degradation and gouge grinding during direct sh.aring of rough.rock j.ints

在线全文

学校读者我要写书评

暂无评论

International j.urnal of Coal Science & Tech.ology 2016年第3期3卷 295-310页

作者： h. Y. Liu h.oyu h.n h. M. An j. j. Sh. Sch.ol of Engineering and ICT University of TasmaniaHobart TAS 7001 Australia Sch.ol of Civil & Environmental Engineering University ofScience and Technology Beijing Beijing China

A h.brid finite-discrete element meth.d was implemented to study th. fracture process of rough.rock j.ints under direct sh.aring. Th. h.brid meth.d reproduced th. j.int sh.ar resistance evolution process from asperity sliding to degradation and from gouge formation to grinding. It is found th.t, in th. direct sh.ar test of rough.rock j.ints under constant normal displacement loading conditions, h.gh.r sh.aring rate promotes th. asperity degradation but constraints th. volume dilation, wh.ch.th.n results in h.gh.r peak sh.ar resistance, more gouge formation and grinding, and smooth.r new j.int surfaces. Moreover, it is found th.t th. j.int rough.ess affects th. j.int sh.ar resistance evolution th.ough.influencing th. j.int fracture micro mech.nism. Th. asperity degradation and gouge grinding are th. main failure micro-mech.nism in sh.aring rough.r rock j.ints with.deeper asperities wh.le th. asperity sliding is th. main failure micro-mech.nism in sh.aring smooth.r rock j.ints with.sh.llower asperities. It is concluded th.t th. h.brid finite-discrete element meth.d is a valuable numerical tool better th.n traditional finite element meth.d and discrete element meth.d for modelling th. j.int sliding, asperity degradation, gouge formation, and gouge grinding occurred in th. direct sh.ar tests of rough.rock j.ints.

关键词： h.brid FEM-DEM Rock j.int Asperity sliding Asperity sh.aring Fragment grinding

Traj.ctory Generation for Autonomous Soaring UAS

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International j.urnal of Automation and computing 2012年第3期9卷 248-256页

作者： j. h. A. Clarke W. h. Ch.n Department of Aeronautical and Automotive Engineering Loughborough University

As unmanned aerial veh.cles are expected to do more and more advanced tasks, improved range and persistence is required. Th.s paper presents a meth.d of using sh.llow layer cumulus convection to extend th. range and duration of small unmanned aerial veh.cles. A simulation model of an X-models XCalubur electric motor-glider is used in combination with.a refined 4D parametric th.rmal model to simulate soaring fligh.. Th. parametric th.rmal model builds on previous successful models with.refinements to more accurately describe th. weath.r in north.rn Europe. Th. implementation of th. variation of th. MacCready setting is discussed. Meth.ds for generating efficient traj.ctories are evaluated and recommendations are made regarding implementation.

关键词： Unmanned aerial veh.cles (UAV) unmanned aerial systems (UAS) soaring traj.ctory th.rmal optimal h.uristic

Investigations on th. Corrosion Beh.viour and Structural Ch.racteristics of Low Temperature Nitrided and Carburised Austenitic Stainless Steel

在线全文

学校读者我要写书评

暂无评论

材料热处理学报 2004年第5期25卷 311-315页

作者： D. Mnter h.-j. Spies h. Biermann Ch.. Eckstein Department of Materials Engineering Technische Universitat Bergakademie Freiberg 09599 Freiberg/ GermanyDepartment of Materials Engineering Technische Universitat Bergakademie Freiberg 09599 Freiberg/ GermanyDepartment of Materials Engineering Technische Universitat Bergakademie Freiberg 09599 Freiberg/ GermanyCorrosion laboratory Steel-Centre-Freiberg (SZF) Research centre of the Technische Universitat Bergakademie Freiberg 09599 Freiberg/ Germany

Th. wear resistance of austenitic stainless steels can be improved by th.rmo-ch.mical surface treatment with.nitrogen and carbon. h.wever, it is possible th.t th. corrosion resistance will be impaired by th. precipitation of ch.omiumnitrid or -carbide. Th. present contribution deals with.investigations of th. corrosion beh.viour and structural ch.racteristics of a low temperature nitrided and carburised austenitic stainless steel. Th. material investigated was AISI 316L (X2CrNiMol7-12-2) austenitic stainless steel. A commercial plasma-nitriding unit (pulsed dc) was used for th. nitriding and carburising process. Additional samples were treated by th. gasoxinitriding process for a comparison between plasma- and gasoxinitriding. Th. nitrided and carburised layer of austenitic stainless steel consists of th. nitrogen or carbon S-ph.se (expanded austenite), respectively. X-ray diffraction investigations sh.w th. typical sh.ft of th. peaks to lower angles, indicating expansion of th. fee lattice. Also th. X-ray diffraction tech.ique was employed to study th. residual stresses in th. nitrogen and carbon S-ph.se. Th. corrosion beh.viour of surface engineered samples was investigated with.electroch.mical meth.ds. Anodic potentiodynamic polarisation curves were recorded for testing th. resistance against general corrosion (in h.SO4) and pitting corrosion (in NaCl).

关键词：奥氏体不锈钢腐蚀低温渗氮低温渗碳残留应力

FLOW STRESS MODEL FOR h.RD MACh.NING OF AISI h.3 WORK TOOL STEEL

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English.Letters) 2005年第6期18卷 741-748页

作者： h. Yan j. h.a R. Sh.vpuri Sch.ol of Mech.nical-Electrical Engineering Nanchang University Nanchang 330029China Th. Oh.o State University Columbus OH 43210 USA

An approach.is presented to ch.racterize th. stress response of workpiece in h.rd mach.ning, accounted for th. effect of th. initial workpiece h.rdness, temperature, strain and strain rate on flow stress. AISI h.3 work tool steel was ch.sen to verify th.s meth.dology. Th. proposed flow stress model demonstrates a good agreement with.data collected from publish.d experiments. Th.refore, th. proposed model can be used to predict th. corresponding flow stress-strain response of AISI h.3 work tool steel with.variation of th. initial workpiece h.rdness in h.rd mach.ning.

关键词： flow stress model h.rd mach.ning AISI h.3 work tool steel

Glass formation for iron-based alloys by combining kinetic and th.rmodynamic parameters

在线全文

学校读者我要写书评

暂无评论

j.urnal of Central South.University 2013年第2期20卷 293-300页

作者： j. h. Willy 王刚刘仲武 Sch.ol of Materials Science and Engineering South China University of Technology

Th. glass formation was intensively studied for Fe-based alloys. Parameters defining kinetics and th.rmodynamic beh.vior of crystallization were calculated using calorimetric measurements and ph.sical properties of constituent elements. It is found th.t th. critical cooling rate Rc estimated by combining kinetic and th.rmodynamic parameters h.gh.y correlates with.measured Rc found in literatures with.correlation coefficient R2=0.944, and alloy compositions with.h.gh.melting enth.lpy Ah. can easily form glass even with.ut h.gh.undercooling and h.gh.value of th. ,β-parameter of Tumbull＇s th.ory, revealing th.t th. glass formation in th.s group of alloys is mostly controlled by growth.limitation. Th.s combination of kinetic and th.rmodynamic parameters can be used to determine alloy composition with.good glass forming ability in Fe-based alloys j.st using ph.sical properties of alloying elements and calorimetric measurements.

关键词： metallic glass glass-forming ability iron-based alloys critical cooling rate