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MECHANISM OF SOUND GENERATION By FLOW OVER TWO CAVITIES IN TWO DIMENSIONS

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Journal of Hydrodynamics 2001年第1期13卷 58-63页

作者： Liu, X.z. Liu, y.z. Miao, G.P. Sch. of Naval Archit. and Ocean Eng. Shanghai Jiaotong Univ. Shanghai 20030 China

The mechanism of sound generation by flow over two cavities in two dimensions is studied by examining the evolution of vorticity, pressure level, spectra and directivity of the generated sound. The study shows that the sound pressure level for two cavities is higher than that for a single cavity. When the distance between the two cavities is large, the interaction between vortices caused by cavities is weak enough to be negligible, so that the results from the acoustic analogy approach coincide with those from the superposition principle. When the distance between the two cavities is relatively small, however, the interaction between vortices becomes stronger and the results from acoustic analogy approach are then larger than those from the superposition principle. Regarding the nonlinear interaction of sound waves in the far field, high harmonic waves can occur when the dimensions of the two cavities are equal, while the sum and difference frequency waves besides the high harmonic waves appear when the dimensions of the two cavities are different.

关键词： Cavitation Computer simulation Hydrodynamics

RELIABILITy ANALySIS FOR AN AERO ENGINE TURBINE DISK UNDER LOW CyCLE FATIGUE CONDITION

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Acta Metallurgica Sinica(English Letters) 2004年第4期17卷 514-520页

作者： C.L.Liu z.z.Lü y.L.Xu School of Aviation Northwestern Polytechnical University Xi'an 710072 ChinaSchool of Aviation Northwestern Polytechnical University Xi'an 710072 ChinaChina Aviation Research Institute 608 Zhuzhou 412002 China

Reliability analysis methods based on the linear damage accumulation law (LDAL) and load-life interference model are studied in this paper. According to the equal probability rule, the equivalent loads are derived, and the reliability analysis method based on load-life interference model and recurrence formula is constructed. In conjunction with finite element analysis (FEA) program, the reliability of an aero engine turbine disk under low cycle fatigue (LCF) condition has been analyzed. The results show the turbine disk is safety and the above reliability analysis methods are feasible.

关键词： low cycle fatigue life reliability analysis load-life interference model recurrence method aero engine turbine disk

STRUCTURAL TRANSFORMATION INDUCED By MECHANICALLy DRIVEN ALLOyING AND SUBSEQUENT MAGNETIC PROPERLIESOF THE Fe-Cu SySTEM

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Acta Metallurgica Sinica(English Letters) 1998年第2期11卷 128-136页

作者： y.z.yang y.HLuo Q.S.Li y.L.zhu X.M.Ma y.D.Dong y.z.Chuang Guangdong Univ of Technology Guangzhou China

The structural transformation in Fe-Cu powder induced by mechanically driven alloying has been monitored by the lattice constant measurements and Mossbauer spectroscopy. For the samples with Cu higher than 75at.% Mossbauer the spectra show a broad paramagnetic doublet; for samples with 50 and 60at.%Cu a new broad ferromagnetic sextet; for those with less than 30at.%Cu similar to those of α-Fe. The main peaks of the hyperfine field distribution significantly broaden and shift to a lower position with increasing Cu content due to the complex environments of iron atoms in the solid solutions and the reduction in the nearest neighbor Fe of a cental Fe atom, respectively. The saturation magnetization of Fe-Cu alloys monotonously decreases with Cu content. The complex composition dependence of coercive field for the milled samples is discussed with respect to the solid dissolution, grain size, interfacial state etc.. The increase of lattice constants with the solute content in the two terminal solid solutions has been explained by the volume-size factor theory or magnetovolume effect.

关键词： mechanical alloying Mossbauer effect Fe-Cu alloy magnetic measurement

Pinless Friction Stir Spot Welding of Mg-3Al-1zn Alloy with zn Interlayer

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Journal of Materials Science & Technology 2016年第1期32卷 76-88页

作者： R.z.Xu D.R.Ni Q.yang C.z.Liu z.y.Ma College of Materials Science and Engineering Shenyang Aerospace University Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences

With the addition of a thin zn interlayer, 2.4 mm thick Mg-3AI-1zn alloy sheets were friction stir spot welded （FSSW） using a pinless tool with fiat, convex and concave shoulder shapes. The results showed that an alloying reaction took place between the Mg substrate and zn interlayer during FSSW, forming a discontinuous intermetallics layer composed of dispersive （α-Mg ＋ Mgzn） eutectic structure under- neath the shoulder and a Mg-zn intermetallics bonding zone at the outside of the joints. This alloying reaction increased the bonded area and eliminated the hook defects, thereby producing sound FSSWjoints with a shallow keyhole without hook defects. The increase of plunge depth was beneficial to the Mg-zn diffusion, thereby increasing the tensile-shear load of the joints. However, excessive plunge depths re- sulted in a decrease of the effective sheet thickness, reducing the strength of the joints. At a small plunge depth, the convex and concave shoulders were more beneficial to the interface reaction than the fiat shoul- der. The maximum joint load of 6.6 kN was achieved by using the concave shoulder at a plunge depth of 1.0 mm. A post-welding heat treatment promoted the dissolution of the discontinuous reaction layer in the joints; however, it led to the occurrence of void defects, influencing the bonding strength.

关键词： Friction stir spot welding Magnesium alloys zn interlayer Hook defects

Effects of Growth Temperature on Structural and Electrical Properties of Li-N-H Codoped znO

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Journal of Materials Science & Technology 2013年第2期29卷 154-156页

作者： y.F. Lu z.z. ye L.P. zhu y.J. zeng J.y. Huang B.H. zhao State Key Laboratory of Silicon Materials Department of Materials Science and Engineering Zhejiang University

Effects of growth temperature on the structural and electrical properties of Li-N-H codoped znO thin films grown by DC reactive magnetron sputtering were investigated. Scanning electron microscopy and X-ray diffraction results showed that increasing growth temperature could improve the crystalline quality. But Hall measurement results showed that growth temperature had a nonlinear influence on the electrical property. The variation of electrical properties with the growth temperature was found to be related to the activated concentration of N in znO and the evaporation of Li during the growth process, derived from the Hall measurement and the second ion mass spectroscopy measurement.

关键词： znO Codoped Growth temperature Structural property Electrical property

Transition of deformation mechanisms from twinning to dislocation slip in nanograined pure cobalt

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Journal of Materials Science & Technology 2022年第26期121卷 124-129页

作者： y.W.Qi z.P.Luo X.y.Li K.Lu Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China

Deformation mechanisms of nanograined and submicron-grained pure cobalt processed by means of high strain rate shear deformation at cryogenic temperatures were *** analysis revealed a transition of governing deformation mechanism from deformation twinning and dislocation slip in submicron-grains to and dislocations slip in *** tests illustrated that the Hall-Petch relation slope changes consequently with the transition of deformation mechanism.

关键词： Nanograin Cobalt Deformation mechanism Hall-Petch relation

Evolution of the Microstructure and Strength in the Nugget zone of Friction Stir Welded SiCp/Al-Cu-Mg Composite

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Journal of Materials Science & Technology 2014年第1期30卷 54-60页

作者： D.Wang B.L.Xiao Q.z.Wang z.y.Ma Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences University of Science and Technology of China

A 6 mm-thick SiCp/2009AI composite plate was successfully joined by friction stir welding （FSW） using an ultrahard material tool to investigate the evolution of the microstructure and the strength in the nugget zone （Nz）. While some SiC particles were broken up during FSW, most of them rotated in the matrix. Large compound particles on the interfaces were broken off during FSW, whereas the amorphous layer and small compound particles remained on the interfaces. The dynamically recrystallized AI grains nucleated on the surface of fractured SiC particles during FSW, forming nano-sized grains around the SiC particles. The yield strength of the Nz decreased slightly due to the variation in the size, shape, and distribution of the SiC particles. The clean interfaces were beneficial to the load transfer between SiC particles and AI matrix and then increased the ultimate tensile strength of the Nz.

关键词： Metal-matrix composites Friction stir welding Microstructure Mechanical properties

Dislocation ordering and texture strengthening of naturally aged Al-Cu-Mg alloy

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Journal of Materials Science & Technology 2022年第23期118卷 1-14页

作者： F.Liu z.y.Liu G.y.He L.N.Ou School of Materials Science and Engineering Central South UniversityChangsha 410083China Key Laboratory of Nonferrous Metal Materials Science and Engineering Ministry of EducationCentral South UniversityChangsha 410083China National Key Laboratory of Science and Technology on High-Strength Structural Materials Central South UniversityChangsha 410083China

Stability of grain structure,dislocation ordering and strengthening mechanisms of the naturally aged AlCu-Mg alloy after solution treatment are investigated by using optical microscope(OM),scanning electron microscope(SEM),electron back-scattered diffraction(EBSD),X-ray diffraction(XRD) and transmission electron microscope(TEM).Results show that {100},{100},{110} and {110}slip systems can be activated after solution treatment,which can promote the formation of {110}Goss *** combination effect of T-Al_(20)Cu_(2) Mn_(3) phase and Goss-oriented grains with large Taylor factor makes the solution-treated alloys display excellent stability of grain *** enhanced yield strength of the alloy is ascribed to grain-refine strengthening,dispersed particles strengthening,dislocation strengthening and texture *** coarsening of the second phase is responsible for softening of the alloy after annealing at 400 ℃+solution treatment at 475 ℃.

关键词： Al-Cu-Mg alloy Dislocation ordering Goss texture Grain structure stability Texture strengthening

Microstructural Evolution and Mechanical Properties of Laminated CuAl Composites Processed by Accumulative Roll-Bonding and Annealing

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Acta Metallurgica Sinica(English Letters) 2021年第7期34卷 925-931页

作者： H.R.Lin y.z.Tian S.J.Sun z.F.zhang Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education) School of Materials Science and EngineeringNortheastern UniversityShenyang 110819China Research Center for Metallic Wires Northeastern UniversityShenyang 110819China

Nano structured Cu-/Al-laminated composites were processed by accumulative roll-bonding(ARB)technique for four *** evolutions inside the Cu and Al layers and the interfacial reactions were revealed after annealing at different *** and recrystallization occurred in the Cu and Al layers at low annealing temperatures,and three kinds of intermetallic compounds formed near the *** mechanical properties of these composites after annealing were investigated by tensile tests,and the variation of strength-ductility synergy was comprehensively discussed by considering the roles of constituent and the intermetallic compounds.

关键词： CuAl composites Accumulative roll-bonding(ARB) Annealing Intermetallic compounds Ductility