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PROBABILISTIC MODELING Of.BRITTLE f.ACTURE WITH PRIOR DUCTILE CRACK EXTENSION

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Acta Metallurgica Sinica(English Letters) 2000年第1期13卷 98-102页

作者： H. y. Jing L. X. Huo y. f. zhang and f. Minami( 1) College of.Material Science, Tianjin University. Tianjin 300072,China 2) Osaka University. Japan)

A computation f.amework f.r brittle f.acture which incorporates weakest link statistics and a microme- chanics model ref.ecting ref.ecting local damage of.the material is *** Weibull stress W emerges as a probabilistic f.acture parameter to def.ne the condition leading material f.ilure. Unstable crack propa- gation occurs at a critical value of.W which may.be attained paior to or f.llowing some amount of.duc- tile crack extension. A realistic model of.ductile crack growth using the computation cell methodology.is used to def.ne the evolution of.near tip stress f.elds during crack extension. An application of.proposed f.amework to predict the measured geometry.and ductile tearing ef.ects on the statistical distributio of.f.acture toughness f.r the pipe line steel welded joint is described.

关键词： f.acture toughness ductile crack extension brittle f.acture

Cutter Accessibility.Map and Its Application f.r 5-axis Milling Tool-path Generation

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武汉理工大学学报 2006年第S1期28卷 40-47页

作者： L. L. Li,y. f. zhang (Department of.Mechanical Engineering,National University.of.Singapore 9 Engineering Drive 1,Singapore 117576) Department of.Mechanical Engineering National University of Singapore 9 Engineering Drive 1Singapore 117576

In tool-path generation process f.r 5-axis f.ce milling,the specif.cation of.cutter posture is one of.the critical issues that contribute to the computation load. In this paper,a quick algorithm is presented to specif.0}the cutter posture at a surf.ce point based on the cutter’s accessibility.maps (A-maps) at all the sampled points,obtained during cutter selection. Integrated with this quick algorithm,an ef.icient approach is proposed to generate a set of.iso-planar tool-paths f.r f.nishing a given surf.ce withmaximum machining ef.iciency.without violating the desirable prof.le and scallop height tolerance. One example is given to conf.rm the validity.of.the quick algorithm f.r cutter posture and the ef.iciency.of.the algorithm f.r tool-path generation.

关键词： cutter accessibility map tool-path generation machining strip width step-over

Thermo-kinetic characteristics on stabilizing hetero-phase interf.ce of.metal matrix composites by.cry.tal plasticity.f.nite element method

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Journal of.Materials Science & Technology 2024年第2期169卷 53-67页

作者： y.B.zhang S.J.Song f.Liu State Key.Laboratory.of.Solidif.cation Processing Northwestern Polytechnical UniversityXi’an 710072China Analy.ical&Testing Center Northwestern Polytechnical UniversityXi’an 710072China

Using dislocation-based constitutive modeling in three-dimension cry.tal plasticity.f.nite element(3D CPf.)simulations,co-def.rmation and instability.of.hetero-phase interf.ce in dif.erent material sy.tems were herein studied f.r poly.ry.talline metal matrix composites(MMCs).Local stress and strain f.elds in two ty.es of.3lay.r MMCs such as f.c/f.c Cu-Ag and f.c/bcc Cu-Nb have been predicted under simple compressive ***,more severe strain-induced interf.ce instability.can be observed in the f.c/bcc sy.tems than in the f.c/f.c sy.tems upon ref.ning to metallic nanolay.red composites(MNCs).By.detailed analy.is of.stress and strain localization,it has been demonstrated that the interf.ce instability.is alway. accompanied by.high-stress concentration,i.e.,thermody.amic characteristics,or high strain prevention i.e.,kinetic characteristics,at the hetero-phase *** then f.llows that the thermody.amic driving f.rceG and the kinetic energy.barrier Q during dislocation and shear banding can be adopted to classif.0}the def.rmation modes,f.llowing the so-called thermo-kinetic *** by.inserting a high density.of.high-energy.interf.ces into the Cu-Nb composites,such thermo-kinetic integration at the hetero-phase interf.ce allows a successf.l establishment of.MMCs with the high△G-high Q def.rmation mode,which ensures high hardening and unif.rm strain distri-bution,thus ef.iciently.suppressing the shear band,stabilizing the hetero-phase interf.ce,and obtaining an exceptional combination in strength and *** hetero-phase interf.ce chosen by.a couple of.thermody.amics and kinetics can be def.ned as breaking the thermo-kinetic correlation and has been proposed f.r artif.cially.designing MNCs.

关键词： Thermody.amics and kinetics Phy.ics-based constitutive modeling Hetero-phase interf.ce Cry.tal plasticity.f.nite element

STUDy.ON THE PREDICTIVE METHOD Of.BUCKLING DEf.RMATIONS Of.THIN-PLATE WELDED STRUCTURES

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Acta Metallurgica Sinica(English Letters) 2000年第1期13卷 178-186页

作者： X. Q. y.ng L. X. Huo y. f. zhang and J. X. y.n (School of.Material Science and Engineering, Tianjin University. Tianjin 300072, China)

The buckling f.rmation and inf.uence f.ctors during welding thin - plated structures were investigated based on f.nite element methods, An engineering treatment method f.r prdicating the buckling distor- tion was proposed in here. It was used the equivalent applied thermal - load to simulate the welding residual stress,theref.re the calculation of.complex welding distoriton can be transf.rmed into 3D elas- tic structural applied- load analy.es, which can reduce the quantities of.calculating works ef.ectively. The validation of.the method was verif.ed by.comparison of.the numerical simulation and experimental results. The simulation of.buckling distorition f.r side - walled structrues of.paseenger train was per- f.rmed and the calculation was in agreement with measuring results in general. It was shown that the main f.ctors f.r producing the buckling were the intermittent f.llet and ping the during welding the stif.ened beams and columns to the *** existence of.the f.ee edge of.panels would reduce the crit- ical buckling stress and enlarge the def.ection obviously.but the continuous weld in closed f.ames didn' t degrade the buckling situation.

关键词： welding buckling distortion equivalent applied thermal-lood,numerical simulation

Nanoscale electrical properties of.individual GeSi quantum dots and quantum rings studied by.scanning probe microscopy

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Nanoscale electrical properties of individual GeSi quantum d...

Microstructure evolution and shape memory.behaviors of.Ni_(47)Ti_(44)Nb_(9)alloy.subjected to multistep thermomechanical loading with dif.erent prestrain levels

第18届国际真空大会

作者： S. H. Zhao, y. f. zhang, y. Lv, and X. J.y.ng* Surf.ce Phy.ics Laboratory. f.dan University. Shanghai 200433, China

The electrical properties of.self.assembled GeSi quantum dots (QDs) and quantum rings (QRs) have attracted intense interests f.r their promising applications. Scanning probe microscopy.of.ers an ef.ective way.to study.the electrical properties of.individual GeSi QDs and QRs. However many.ef.ects will inf.uence the measured results, such as morphology. composition distribution, dot/ring size. To dis-tinguish these ef.ects, Si QDs and QRs with dif.erent sizes were f.bricated by.using nano-sphere tech-niques. The electrical properties of.Si QDs and QRs were investigated by.CAf., SKM and SCM, and the ef.ects of.morphology.and size are studied. By.comparing the electrical properties of.Si QDs/QRs with GeSi’s counterparts, the compositional ef.ect on the electrical properties is discussed. Together with the compositional inf.rmation of.GeSi QDs/QRs obtained by.atomic f.rce microscopy.with selective chemical etching, the possible mechanisms f.r nano-scale electrical properties of.GeSi QDs and QRs are suggested.

关键词： GeSi quantum dots/quantum rings CAf./SKM/SCM electrical property

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Journal of.Materials Science & Technology 2024年第4期171卷 80-93页

作者： y.H.zhang H.Li Z.W.y.ng X.Liu Q.f.Gu State Key.Laboratory.of.Solidif.cation Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi’an 710072China Shaanxi Key.Laboratory.of.High-Perf.rmance Precision f.rming Technology.and Equipment Northwestern Polytechnical UniversityXi’an 710072China

Ni_(47)Ti_(44)Nb_(9)shape memory.alloy.SMA)is a promising material in the aerospace f.eld due to its wide transf.rmation *** application of.shape memory.ef.ect depends on multistep thermomechan-ical loading,viz.,low-temperature def.rmation and subsequent heating to ***-temperature def.rmation prestrain play. a pivotal role in shape memory.properties tailoring of.SMA ***,microstructure evolution and def.rmation mechanisms of.Ni_(47)Ti_(44)Nb_(9)SMA subjected to vari-ous prestrain levels are still *** this end,microstructure evolution and shape memory.behaviors of.Ni_(47)Ti_(44)Nb_(9)alloy.subjected to multistep thermomechanical loading with prestrain levels of.8%-16%at-28℃(M_(s)+30℃)were *** results demonstrate that the stress-strain curve of.the specimen exhibits f.ur distinct stages at a maximal prestrain of.16%.Whereas stageⅡand stageⅢend at prestrains of.8%and∼12%,*** stageⅡ,the stress-induced martensitic transf.rmation is accompanied by.the dislocation slip of.the NiTi matrix andβ-Nb *** stageⅢ,in addition to the higher density.of.dislocations and f.rther growth of.stress-induced martensite variants(SIMVs),(001)compound twins are introduced as a result of.the(001)def.rmation twinning in stress-induced ***{20-1}martensite twins are gradually.introduced in stageⅣ.Correspondingly.af.er subsequent unloading and heating,a higher density.of.114}austenite twins f.rm in the specimen with a larger prestrain of.16%.With increasing prestrain f.om 8%to 16%,the recoverable strainε_(re)^(T)upon heating increases f.rst and then ***ε_(re)^(T)obtains a maximum of.7.03%at 10%prestrain and de-creases to 6.17%at 16%*** increase of._(re)^(T)can be attributed to the f.rmation of.new SIMVs,the f.rther growth of.existing SIMVs,and the recoverable(001)compound *** the decrease of._(re)^(T)is mainly.associated with the irrecoverable strain by.20−1}martensite *** ef.e

关键词： Ni_(47)Ti_(44)Nb_(9)shape memory.alloy Wide transf.rmation hy.teresis Thermomechanical loading Microstructure evolution Shape memory.behaviors Stress-induced martensitic transf.rmation Def.rmation twinning

Electron kinetic ef.ects in back-stimulated Raman scattering bursts driven by.broadband laser pulses

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Matter and Radiation at Extremes 2024年第4期9卷 54-67页

作者： Q.K.Liu L.Deng Q.Wang X.zhang f.Q.Meng y.P.Wang y.Q.Gao H.B.Cai S.P.Zhu Graduate School China Academy of Engineering PhysicsBeijing 100088China Institute of.Applied Phy.ics and Computational Mathematics Beijing 100094China School of.Nuclear Science and Technology University of Science and Technology of ChinaHefei 230026China Shanghai Institute of.Laser Plasma Shanghai 201800China HEDPS Center for Applied Physics and TechnologyPeking UniversityBeijing 100871China School of.Phy.ics Zhejiang UniversityHangzhou 310027China

We examine electron kinetic ef.ects in broadband-laser-driven back-stimulated Raman scattering(BSRS)bursts using particle-in-cell *** bursts occur during the nonlinear stage,causing ref.ectivity.spikes and generating large numbers of.hot ***-duration simulations are perf.rmed to observe burst events,and a simplif.ed model is developed to eliminate the interf.rence of.the broadband laser’s random intensity.*** the simplif.ed model,we isolate and characterize the spectrum of.electron plasma *** spectrum changes f.om a sideband structure to a turbulence-like structure during the burst.A signif.cant asy.metry.in the spectrum is *** asy.metry.is amplif.ed and transf.rred to electron phase space by.high-intensity.broadband laser pulses,leading to violent vortex-merging and generation of.hot *** proportion of.hot electrons increases f.om 6.76%to 14.7%during a single violent burst *** demonstrate that kinetic ef.ects prof.undly.inf.uence the BSRS evolution driven by.broadband lasers.

关键词： scattering kinetic simplif.ed

Ef.ect of.Nitrogen Source on Anaerobic Hy.rogen f.rmentation

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Effect of Nitrogen Source on Anaerobic Hydrogen Fermentation

Asy.metric reversible structural switching of.a diene coordination poly.er promoted by.UV-visible light

2004年国际氢能大会

作者： y. f. zhang G Z. Liu & J. Q. Shen Institute of.Chemistry.the Chinese Academy.of.Sciences Zhongguancun Beijing 100080 P. R. China

＜正＞Anaerobic batch cultures were established to assess the ef.ect of.dif.erent nitrogen source on hy.rogen production. The experiment was conducted in non-sterile conditions using a mixed anaerobic hy.rogen-producing bacteria and sucrose-mineral salts solution at 35 癈. The sy.tems were added with try.tone and NH4HCO3 as nitrogen source, respectively. The concentrations of.nitrogen source ranged f.om 0 to 4000 mg l-1. There are obvious dif.erences between the two sy.tems. The specif.c hy.rogen production y.eld varied hardly.any.f.r the sy.tems with try.tone f.om 0 to 4000 mg l-1, while it decreased all along f.r the sy.tems with NH4HCO3 at the same time. The biomass production y.eld increased with increasing try.tone concentrations, however, it kept steadily.f.r the sy.tems with NH4HCO3. The ultimate pH value kept about 4.7 f.r the f.rmer, but increased f.om 4.6 to 7.7 f.r the latter. The sucrose degradation ef.iciencies were over 99% f.r both of.the two sy.tems.

关键词： sucrose f.rmentation nitrogen source hy.rogen production

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Science China Chemistry 2024年第2期67卷 536-541页

作者： y.ng Wang Qiaoqiao zhang y.ng-y.ng Cao Qi Liu Brendan f.Abrahams Jian-Ping Lang College of.Chemistry Chemical Engineering and MaterialsSoochow UniversitySuzhou215123China State Key.Laboratory.of.Organometallic Chemistry Shanghai Institute of Organic ChemistryChinese Academy of SciencesShanghai200032China College of.Biological Chemical Science and EngineeringJiaxing UniversityJiaxing314001China School of.Chemistry University of MelbourneVictoria3010Australia

In natural and artif.cial sy.tems,reversible reactions are commonly.asy.metric with respect to the time scale and nature of.the stimuli which drive the f.rward and backward *** applications f.r which switching behavior is required,it is desirable that the reversible reaction goes as close to sy.metric as possible;however,such sy.tems are ***,we report an example of.ultraviolet(UV)-visible light-regulated asy.metric reversible structural switching involving a diene-based coordination poly.er,CP1 and its monocy.lobutane product,*** is possible to cy.le at least ten times through a f.rward [2+2] photocy.loaddition reaction and the reverse,photocleavage reaction.A single cy.le can be completed within a f.w *** transf.rmation is accompanied by.f.st and distinct f.uorescence changes,arising f.om optimisation of.the reaction *** f.nctional theory.calculations allow rationalisation of.the asy.metric reversible transf.rmation between CP1 and CP1a rather than between CP1 and its dicy.lobutane product *** work provides a clear illustration of.reversible structural switching which approaches sy.metric behaviour with respect to reaction rate and *** insights gained f.om this work also assist in the design of.f.st,reversible switching materials.

关键词： asy.metrical reversible structural switching coordination poly.er photocy.loaddition UV-visible light-controlled f.uorescence switching