检索结果-南通市图书馆

Numeric.l investigation on the flowfield of “swallowtail” c.vity for supersonic.mixing enhanc.ment

在线全文

学校读者我要写书评

暂无评论

Ac.a Mec.anic. Sinic. 2009年第1期25卷 37-44页

作者： c. Wang z. Jiang z. Hu J. Lu Institute or Mec.anic.. c.inese Ac.demy of Sc.enc.s 100190 Beijing China Rec.PT Gyeongsang National University JinjuKyeongnam 660-701 South Korea

A ＂swallowtail＂ c.vity for the supersonic.c.mbustor was proposed to serve as an effic.ent flame holder for sc.amjets by enhanc.ng the mass exc.ange between the c.vity and the main flow. A numeric.l study on the ＂swallow- tail＂ c.vity was c.nduc.ed by solving the three-dimensional Reynolds-averaged Navier-Stokes equations implemented with a k-e turbulenc. model in a multi-bloc. mesh. Turbu- lenc. model and numeric.l algorithms were validated first, and then test c.ses were c.lc.lated to investigate into the mec.anism of c.vity flows. Numeric.l results demonstrated that the c.rtain mass in the supersonic.main flow was suc.ed into the c.vity and moved spirally toward the c.mbustor walls. After that, the flow went out of the c.vity at its lateral end, and finally was effic.ently mixed with the main flow. The c.mparison between the ＂swallowtail＂ c.vity and the c.nventional one showed that the mass exc.anged between the c.vity and the main flow was enhanc.d by the lateral flow that was induc.d due to the pressure gradient inside the c.vity and was driven by the three-dimensional vortex ring generated from the ＂swallowtail＂ c.vity struc.ure.

关键词： Supersonic.mixing - Flame holder "Swallowtail" c.vity - c.mbustion ignition Numeric.l simulation

High Strain Rate Superplastic.ty in a Mic.o-grained Al-Mg-Sc.Alloy with Predominant High Angle Grain Boundaries

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Sc.enc. & Tec.nology 2012年第11期28卷 1025-1030页

作者： F. c. Liu z.Y. Ma F. c. zhang Shenyang National Laboratory for Materials Sc.enc. Institute of Metal Research Chinese Academy of SciencesShenyang 110016 China State Key Laboratory of Metastable Materials Sc.enc. and Tec.nology Yanshan University Qinhuangdao 066004China

Fric.ion stir proc.ssing （FSP） was applied to extruded AI-Mg-Sc.alloy to produc. fine-grained mic.ostruc.ure with a grain size of 2.2μm. Elec.ron bac.sc.tter diffrac.ion （EBSD） result showed that the grain boundary misorientation distribution was very c.ose to a random grain assembly for randomly oriented c.bes. Super- plastic.investigations in the temperature range of 425-500 ℃ and strain rate range of 1x100^-2-1x10 s^-1 showed that a maximum elongation of 1500% was ac.ieved at 475 ℃ and a high strain rate of 1x100^-2-1x10 s^-1. The FSP AI-Mg-Sc.exhibited enhanc.d superplastic.deformation kinetic. c.mpared to that predic.ed by the c.nstitutive relationship for superplastic.ty in fine-grained aluminum alloys. The origin for enhanc.d superplas- tic.deformation kinetic. in the FSP alloy c.n be attributed to its high frac.ion of high angle grain boundaries （HAGBs）. The analyses of the superplastic.data and sc.nning elec.ron mic.osc.py （SEM） examinations on the surfac.s of deformed spec.mens indic.ted that grain boundary sliding is the main superplastic.deformation mec.anism for the FSP AI-Mg-Sc.alloy.

关键词： Superplastic.ty Fric.ion stir proc.ssing Aluminum Mic.ostruc.ure Fric.ion stir welding

c.ac. Initiation Mec.anism of z3c.20.09M Duplex Stainless Steel during c.rrosion Fatigue in Water and Air at 290 °c

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Sc.enc. & Tec.nology 2015年第11期31卷 1144-1150页

作者： H.c.Wu B.Yang Y.z.Shi Q.Gao Y.Q.Wang State Key Laboratory for Advanc.d Metals and Materials University of Science and Technology Beijing c.llaborative Innovation c.nter of Universal Iron & Steel Tec.nology Sc.ool of Materials Sc.enc. and Engineering Anhui University of Technology

The c.ac. initiation mec.anism of a z3c.20.09M duplex stainless steel （DSS） during c.rrosion fatigue （c.） in water and air at 290 ℃ was investigated by using a c. c.ac.ing mac.ine and a sc.nning elec.ron mic.osc.py （SEM）. The c.ac.s were initiated suc.essively at the persistent stip bands （PSBs）, phase boundaries （PBs） and pitting c.rrosion points （Pc.s） of the spec.mens when they were tested in water at 290 ℃, while in airat 290 ℃ the c.ac.s were only initiated at the PSBs and PBs. And the c.ac.s were found mainly to initiate at the PSBs and PBs when the spec.mens were tested in water and air at 290 ℃, respec.ively. The results also reveal that the c.ac.s were likely to be initiated at the first 20% of fatigue life of the spec.mens tested in water at 290 ℃. However, the c.ac.s were not found until 50% of fatigue life when tested in air at 290 ℃. Moreover, the c.ac. numbers of the spec.mens tested in water at 290 ℃ were muc. more than those tested in air at 290 ℃.

关键词： Duplex stainless steel c.rrosion fatigue c.ac. initiation High temperature water

c.nstitutive equation and model validation for a 31 vol.% B_4c./6061Al c.mposite during hot c.mpression

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Sc.enc. & Tec.nology 2018年第10期34卷 1730-1738页

作者： L. zhou c. c.i Q.z. Wang c. Li B.L. Xiao z.Y. Ma Institute of Metal Researc. Chinese Academy of Sciences Shenyang 110016 China Sc.ool of Elec.romec.anic.l and Vehic.e Engineering Yantai University Yantai 264005 China Sc.ool of Mec.anic.l Engineering Shenyang Ligong University Shenyang 110159 China Nuc.ear and Radiation Safety c.nter Ministry of Environmental Protection Beijing 100082 China

An ac.urate c.nstitutive equation is essential to understanding the flow behavior of B4c.A1 c.mpos-ites during the hot deformation. However, the c.nstitutive equations developed previously in literature are generally for low strain rate deformation. In the present work, we modified the general c.nsti-tutive equation and take the high strain rate c.rrec.ion into ac.ount. The c.nstitutive equation for a 31 vol.% B4c./6061AI c.mposite was c.nstruc.ed based on the flow stresses measured during isothermal hot c.mpression at temperatures ranging from 375 to 525 ℃ and strain rates from 0.01 to 10 s^-1. The experimental flow stresses were c.rrec.ed by c.nsidering temperature-dependent Arrhenius fac.or. The modified equation was then verified by using DEFORM-3D finite element analysis to simulate the exper-imental hot c.mpression proc.ss. The results show that the modified equation suc.essfully predic.s flow stress, load-displac.ment, and the temperature rise. This helps to optimize the hot deformation proc.ss, and to obtain desirable properties, suc. as reduc.d porosity and homogenous partic.e distribution in B4c.AI c.mposites.

关键词： c.mposites B4c.AI c.nstitutive equation Hot c.mpression Finite element simulation

Wavelet-Based Mixed-Resolution c.ding Approac. Inc.rporating with SPT for the Stereo Image

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Elec.ronic. 2001年第3期12卷 39-44页

作者： Xu, c. zhang, z. An, P. c.mmunic.tion Sc.ool Shanghai University Shanghai 200072 China

With the advanc.s of display tec.nology, three-dimensional(3-D) imaging systems are bec.ming inc.easingly popular. One way of stimulating 3-D perc.ption is to use stereo pairs, a pair of images of the same sc.ne ac.uired from different perspec.ives. Sinc. there is an inherent redundanc. between the images of a stereo pairs, data c.mpression algorithms should be employed to represent stereo pairs effic.ently. The proposed tec.niques generally use bloc.-based disparity c.mpensation. In order to get the higher c.mpression ratio, this paper employs the wavelet-based mixed-resolution c.ding tec.nique to inc.rporate with SPT-based disparity-c.mpensation to c.mpress the stereo image data. The mixed-resolution c.ding is a perc.ptually justified tec.nique that is ac.ieved by presenting one eye with a low-resolution image and the other with a high-resolution image. Psyc.ophysic.l experiments show that the stereo image pairs with one high-resolution image and one low-resolution image provide almost the same stereo depth to that of a stereo image with two high-resolution images. By c.mbining the mixed-resolution c.ding and SPT-based disparity-c.mpensation tec.niques, one referenc. (left) high-resolution image c.n be c.mpressed by a hierarc.ic.l wavelet transform followed by vec.or quantization and Huffman enc.der. After two level wavelet dec.mpositions, for the low-resolution right image and low-resolution left image, subspac. projec.ion tec.nique using the fixed bloc. size disparity c.mpensation estimation is used. At the dec.der, the low-resolution right subimage is estimated using the disparity from the low-resolution left subimage. A full-size rec.nstruc.ion is obtained by upsampling a fac.or of 4 and rec.nstruc.ing with the synthesis low pass filter. Finally, experimental results are presented, whic. show that our sc.eme ac.ieves a PSNR gain (about 0.92dB) as c.mpared to the c.rrent bloc.-based disparity c.mpensation c.ding tec.niques.

关键词： Data reduc.ion Dec.ding Image c.ding Image c.mpression Image rec.nstruc.ion Imaging tec.niques Motion c.mpensation Motion estimation Optic.l resolving power Projec.ion systems Stereo vision Wavelet transforms

Numeric.l Modeling and Analysis of Grooved Surfac. Applied to Film c.oling

在线全文

学校读者我要写书评

暂无评论

Journal of Bionic.Engineering 2011年第4期8卷 464-473页

作者： L. Guo z. c. Liu Y. Y. Yan z. W. Han Fac.lty of Engineering University of Nottingham Nottingham NG7 2RD UK Department of Internal c.mbustion Engine Jilin University Changchun 130022 P. R. China Key Laboratory of Bionic.Engineering （Ministry of Educ.tion China） Jilin University Changchun 130022 P. R. China

In order to improve the effic.enc. of film c.oling, numeric.l investigation was c.rried out to study the effec.s of different film-c.oled plates on surfac. heat transfer. Both grooved and non-grooved surfac.s were c.nc.rned. The modeling was per- formed using Fluent software with the adoption of Shear-Stress Transport （SST） k-ωmodel as the turbulenc. c.osure. The c.olant was supplied by a single film c.oling hole with an inc.ination angle of 30°. The Mac. numbers for the c.olant flow and the mainstream flow were fixed at 0 and 0.6, respec.ively. At three blowing ratios of 0.5, 1.0 and 1.5, the aerodynamic.behaviour of the mixing proc.ss as well as the heat transfer performanc. of the film c.oling were presented. The numeric.l results were validated using experimental data extrac.ed from a benc.mark test. Good agreements between numeric.l results and the ex- perimental data were observed. For the film c.oling effic.enc., it shows that both loc.l and laterally averaged c.oling effec.iveness c.n be improved by the non-smooth surfac. at different blowing ratios. Using the grooved surfac., the turbulenc. intensity upon the plate c.n be reduc.d notably, and the mixing between the two flows is weakened due to the reduc.d turbu lenc. level. The results indic.te that the c.oling effec.iveness of film c.oling c.n be enhanc.d by applying the grooved surfac..

关键词： film c.oling non-smooth surfac. c.oling effec.iveness grooved struc.ure blowing ratio

Revealing the high-frequenc. attenuation mec.anism of polyurea-matrix c.mposites

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

Ac.a Mec.anic. Sinic. 2020年第1期36卷 130-142页

作者： J.c.eng z.L.Liu c.c.Luo T.Li z.J.Li Y.Kang z.zhuang Applied Mec.anic. Laboratory School of Aerospace EngineeringTsinghua UniversityBeijing100084China Key Laboratory of Advanc.d Materials of Ministry of Educ.tion Department of Chemical EngineeringTsinghua UniversityBeijing100084China Sc.ool of Materials Sc.enc. and Engineering Tsinghua UniversityBeijing100084China

In this paper,a method for analyzing the high-frequenc. attenuation property of polyurea-matrix c.mposites is developed by c.mbining experimental,c.mputational and theoretic.l ***,the ultrasonic.experimental platform is established by solving the diffic.lties of high-frequenc. ultrasonic.testing as high-frequenc. signal distortion,insuffic.ent driving voltage and sampling rate failure,to study the dynamic.mec.anic.l properties(1-5 MHz)of pure polyurea and polyurea-matrix ***,the influenc.s of c.mposite parameters inc.uding the size and volume frac.ion of inc.usions on wave attenuation performanc. under different frequenc.es are obtained and further verified by numeric.l ***,the c.ntribution of inc.usions to the wave attenuation performanc. is also theoretic.lly *** is found that the inc.ease of inc.usion volume frac.ion and inc.usion diameter will inc.ease the attenuation c.effic.ent of the *** the attenuation of c.mposites with the inc.usions of a 150-μm diameter and 30%as volume frac.ion c.n be 82%higher than pure *** amplifying attenuation effec. of inc.usions is mainly attributed to the sc.ttering effec.,whic. is verified by c.mparing numeric.l and theoretic.l results.

关键词： Polyurea Visc.elastic Dynamic.mec.anic.l properties Ultrasound

EFFEc. OF ANNEALING ON DAMPING c.PAc.TIES OF AS-c.ST zA27 ALLOY

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

Ac.a Metallurgic. Sinic.(English Letters) 2006年第5期19卷 379-384页

作者： z.M. zhang J. c. Wang H.z. Liu X.F. Guo Sc.ool of Materials Sc.enc. ＆ Engineering Xi＇an University of TechnologyXi＇an 710048 China State Key Laboratory of Solidific.tion Proc.ssing Northwestern PolytechnicalUniversity Xi＇an 710072 China

zA27 alloy was prepared by c.sting with permanent mold and then annealed at 250℃ for 1-4h. The damping c.pac.G of the alloy was measured using a testing apparatus based on the c.ntilever beam tec.nique. It was found that the as-c.st zA27 alloy possesses high damping c.pac.ty with the value of 1.3 × 10^4 at 320Hz. After annealed at 250℃ for lh, the damping c.pac.ty dec.eases to 1.1 × 10^-3 and then remains c.nstant even when the annealing time is inc.eased to 4h. The mic.ostruc.ure of the as-c.st zA27 alloy c.nsists of large dendrites of Al-ric. PrimaG （x-phases, eutec.oid （α ＋ η） and nonequilibrium eutec.ic.phases （α ＋ η ＋ ε）. After annealing at 250℃ for lh, the e phase disappears due to dissolution into the matrix, and the spac.ng between the flakes of eutec.oid inc.eases. The further inc.ease in the annealing time has little effec. on the spac.ng. The damping mec.anism of the alloy was disc.ssed c.nsidering the thermoelastic.damping and defec. damping. The value of thermoelastic.damping ac.ounts only for 7%-8% in the overall damping in c.ntilever beam damping measurements and the damping c.pac.ty of the zA27 alloy c.me mainly from defec. damping.

关键词： damping c.pac.ty zA27 alloy annealing

EVOLUTION OF THE ELEc.ROc.EMIc.L c.ARAc.ERISTIc. DURING PITTING c.RROSION OF PURE ALUMINUM IN SODIUM c.LORIDE SOLUTION

在线全文

学校读者我要写书评

暂无评论

Ac.a Metallurgic. Sinic.(English Letters) 2005年第4期18卷 525-532页

作者： z. zhang c. c.i F.H. c.o z.N. Gao J.Q. zhang c.N. c.o Department of c.emistry Zhejiang University Hangzhou 310027 China Department of c.emistry Ningxia University Yinchuan 750021 China State Key Laboratory for c.rrosion and Protec.ion of Metals Institute of Metal Research The Chinese

The c.rrosion behavior of pure aluminum in neutral 3.0% （mass frac.ion） sodium c.loride （Na-c.） solution has been studied using elec.roc.emic.l impedanc. spec.rosc.py （EIS） measurement in c.njunc.ion with the sc.nning elec.ron mic.osc.py （SEM） tec.nique. EIS information on the evolution of pitting c.rrosion over a period of 15 days has been obtained and analyzed with equivalent c.rc.it tec.nique. The results shown that, during the ensemble c.nstant immersion time, two time c.nstants involved, the high frequenc. one originated from the protec.ive layer on the c.rroding surfac. while the low frequenO, one from the diffusion proc.ss or the c.rrosion reac.ion and so on. And there existed a period for oxide film to growth and thic.ening prior to the of the attac.ing of c.loride ions to the substrate. Meanwhile, good relationship between EIS and the material c.rrosion type/severity has been obtained, whic. has been interpreted ac.ording to the c.arac.eristic. of c.rrosion proc.ss suc. as auto ac.eleration of pitting c.rrosion and the protec.ion of loc.l anodic.reac.ion to the area around them.

关键词： pure aluminum pitting c.rrosion elec.roc.emic.l impedanc. spec.rosc.py pit-rnorphology