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ANALy.IS OF THREE-DIMENSIONAL UPSETTING PROCESS By.THE RIGID-PLASTIC REPRODUCING KERNEL PARTICLE METHOD

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Acta Metallurgica Sinica(English Letters) 2006年第5期19卷 371-378页

作者： y. H. Liu J. chen S. y. X. W. chen National Die and Mould CAD Engineering Research Center Shanghai Jiao Tong UniversityShanghai 200030 China

A meshless approach, called the rigid-plastic reproducing kernel particle method （RKPM）, is presented for three-dimensional （3D） bulk metal forming simulation. The approach is a combination of RKPM with the flow theory.of 3D rigid-plastic mechanics. For the treatments of essential boundary.conditions and incompressibility.constraint, the boundary.singular kernel method and the modified penalty.method are utilized, respectively. The arc-tangential friction model is employ.d to treat the contact conditions. The compression of rectangular blocks, a ty.ical 3D upsetting operation, is analy.ed for different friction conditions and the numerical results are compared with those obtained using commercial rigid-plastic FEM （finite element method） software Deform^3D. As results show, when handling 3D plastic deformations, the proposed approach eliminates the need of expensive meshing and remeshing procedures which are unavoidable in conventional FEM and can provide results that are in good agreement with finite element predictions.

关键词： meshless reproducing kernel particle method(RKPM) three-dimensional upsetting incompressibility modified penalty.method

Facile Li-Al lay.red double hy.roxide films on Al alloy.for enhanced hy.rophobicity. anti-biofouling and anti-corrosion performance

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Journal of Materials Science & Technology 2021年第20期79卷 230-242页

作者： Ji Li Tianci y.an chengliang Zhou Bo chen y. Shuai Dawang Wu Dongchu chen Xiaohu Luo y.frank cheng y.li Liu State Key.Laboratory.for Chemo/Biosensing and Chemometrics College of Chemistry and Chemical EngineeringHunan UniversityChangsha410082China Department of Mechanical and Manufacturing Engineering University of CalgaryCalgaryAlbertaT2N 1N4Canada School of Chemistry.and Chemical Engineering Qiannan Normal University for NationalitiesDuyun558000China College of Mechanical Engineering and Applied Electronics Technology Beijing University of TechnologyBeijing100124China School of Material Science and Energy.Engineering Foshan UniversityFoshan528000China

In this work,lithium(Li)-aluminum(Al)lay.red double hy.roxide(LDH)films modified by.4-amino-2-((hy.razine methy.ene)amino)-4-oxobutanoic acid(denoted as AOA acid)and/or 1H,1H,2H,2H-perfluoroocty.triethoxy.ilane were prepared on 6N01 Al alloy.by.a facile,in-situ growth method with enhanced hy.rophobicity.anti-biofouling and anti-corrosion *** preparation is low energy.consumptive and environment friendly.rely.ng on self-assembly.at ambient *** structure,molecular weight and functional groups of the sy.thesized AOA acid were characterized by.NMR spectrometer,ESI-MS spectrometer and Fourier transform infrared(FT-IR)*** the compositions,structure and morphology.of the films were characterized by.Fourier transform infrared(FT-IR)spectroscopy.glancing-angle X-ray.diffraction(GA-XRD),X-ray.photoelectron spectroscopy.XPS),field emission scanning electron microscopy.FE-SEM)and energy.dispersive x-ray.spectrum(EDS).Water contact angle measurements(CA)and atomic force microscopy.AFM)characterization show that the films possess a micro/nanostructure with an improved *** test,neutral salt tests(NSS)and electrochemical impedance spectroscopy.EIS)conducted in 3.5 wt.%NaCl solutions demonstrate the improved corrosion resistance of the films over bare Al ***,the films also possess an excellent anti-bacterial property.toEscherichia coli,Bacillus subtilis and sulfate-reducing bacteria.

关键词： Li-Al lay.red double hy.roxides Anti-biofouling Hy.rophobicity Anti-bacterial Anti-corrosion

Investigation of the crack problem in non-local piezoelectric materials under combined electromechanical loadings

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Acta Mechanica Sinica 2009年第2期25卷 219-225页

作者： Q. Li y. chen School of Aerospace, Xi’an Jiao-Tong University.710049 Xi’an, China School of Aerospace Xi’an Jiao-Tong University 710049 Xi’an China

The present investigation of the crack problem in piezoelectric materials is performed based on the non-local theory. After some manipulations, the impermeable crack, the permeable crack （the crack gap is full of NaCI solution）, and the semi-permeable crack （the crack gap is full of air or silicon oil） are reduced to a uniform formulation by.assuming the normal electric displacement on the crack surfaces to be an unknown variable. Thus, a triple integral equation with the unknown normal electric displacement is established. By.using the Newton iterative method and solving the triple integral equation, it is found that the normal electric displacement on the crack surfaces is no longer a constant as determined by.previous studies, rather, it depends upon the remote combined electromechanical loadings. Numerical results of the stresses and electric displacement fields show that there are no singularities at the crack tips so that the stresses remain finite. It is of great significance that the concrete electric boundary.condition on the crack surfaces exerts significant influence on the near-tip fields and in this way.play. an important role in evaluating the crack stability.in the non-local piezoelectric materials. More specifically. the impermeable crack model alway. overestimates the finite stresses at the crack tips, whereas the permeable crack model alway. underestimates them.

关键词： Crack Non-local piezoelectric materialsImpermeable Permeable Semi-permeable

Main α relaxation and slow β relaxation processes in a La30Ce30Al15Co25 metallic glass

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Journal of Materials Science & Technology 2019年第6期35卷 982-986页

作者： J.C. Qiao y.H. chen R. Casalini J.M. Pelletier y. y.o School of Mechanics Civil Engineering and Architecture Northwestern Polytechnical University Xi'an 710072 China Chemistry.Division Naval Research Laboratory Code 6120 Washington DC 20375-5342 United States Universite de Ly.n MATEIS UMR CNRS5510 Bat. B. Pascal INSA-Lyon F-69621 Villeurbanne cedex France

Dy.amic relaxation processes are fundamental to understand the mechanical and phy.ical properties of metallic glasses. In the current work, mechanical relaxations in a La30Ce30Al15Co25 bulk metallic glass were probed by.dy.amic mechanical analy.is. In contrast to many.metallic glasses, La30Ce30Al15Co25 metallic glass shows a pronounced slow β relaxation peak. Phy.ical aging below the glass transition temperature Tgleads to an increase of the apparent activation energy.and a decrease of the slow β relaxation magnitude. The correlation between the slow β relaxation and the main α relaxation is discussed.

关键词： Mechanical relaxation Dy.amic mechanical relaxation α Relaxation β relaxation Phy.ical aging

Extension/Compression-Controlled Complete Band Gaps in 2D Chiral Square-Lattice-Like Structures

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Acta Mechanica Solida Sinica 2018年第1期31卷 51-65页

作者： y. L. Huang N. Gao W.Q. chen R.H. Bao Department of Engineering Mechanics Zhejiang University Hangzhou 310027 China State Key.Lab of CAD & CG Zhejiang University Hangzhou 310058 China Key.Laboratory.of Soft Machines and Smart Devices of Zhejiang Province Zhejiang University Hangzhou 310027 China Soft Matter Research Center Zhejiang University Hangzhou 310027 China

Achieving tunable band gaps in a structure by.external stimuli is of great importance in acoustic applications. This paper aims to investigate the tunability.of band gaps in square-lattice-like elastic periodic structures that are usually.not featured with notable band gaps. Endowed with chirality. the periodic structures here are able to undergo imperfection-insensitive large deformation under extension or compression. The influences of geometric parameters on band gaps are discussed via the nonlinear finite element method. It is shown that the band gaps in such structures with curved beams can be very.rich and, more importantly. can be efficiently.and robustly.tuned by.apply.ng appropriate mechanical loadings without inducing buckling. As expected, geometry.play. a more significant role than material nonlinearity.does in the evolution of band gaps. The dy.amic tunability.of band gaps through mechanical loading is further studied. Results show that closing, opening, and shifting of band gaps can be realized by.exerting real-time global extension or compression on the structure. The proposed periodic structure with well-designed chiral sy.metry.can be useful in the design of particular acoustic devices.

关键词： Band gap Tunability Square-lattice-like periodic structure Chiral sy.metry.Large deformation

Origin of enhanced stability.in thiocy.nate substituted α-FAPbI3 analogues

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Science China Chemistry 2019年第7期62卷 866-874页

作者： Zhuo Xu Ming chen Shengzhong (frank) Liu Key.Laboratory.of Applied Surface and Colloid Chemistry National Ministry of EducationShaanxi Key Laboratory for Advanced Energy DevicesShaanxi Engineering Lab for Advanced Energy TechnologyInstitute for Advanced Energy MaterialsSchool of Materials Science and Engineering Shaanxi Normal University Xi'an 710119 China State Key.Laboratory.of Cataly.is Dalian National Laboratory for Clean Energy Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian 116023 China

In the past few y.ars,hy.rid perovskites have emerged as the most promising photovoltaic materials due to their excellent optoelectronic properties,and easy.fabrication ***,the long-term stability.is still the main obstacle for their commercial ***,thiocy.nate-doped hy.rid perovskites have shown enhanced stability.and impressive efficiency.but the reason is still ***,we discussed the enhanced stability.of SCN-substituted pseudocubic FABX3(B=Pb^2+,Sn^2+;X=I^–,Br^–,and Cl^–)based on the density.functional *** a series of calculations of Bader charge transfer,vacancy.formation energies of different kinds of vacancies,decomposition enthalpy.phonon density.of states,and ab initio molecular dy.amics simulation,we conclude that the incorporation of SCN–can stabilize pseudocubic FABX3,and attribute the enhanced stability.mainly.to two factors:(1)the strong interaction between Pb^2+/Sn^2+and SCN^–,as well as the strong hy.rogen bonding between FA+and X^–/SCN^–,and(2)the structural tilting induced by.the incorporation of SCN^–.These findings provide alternative method for tuning the poor stability.of pseudocubic FABX3,as well as for obtaining high-performance solar cells.

关键词： thiocy.nate stability formamidinium perovskites density.functional theory

A hy.erbolic Lindstedt-Poincare method for homoclinic motion of a kind of strongly.nonlinear autonomous oscillators

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Acta Mechanica Sinica 2009年第5期25卷 721-729页

作者： y.y.chen S.H.chen K.y.Sze Department of Applied Mechanics and Engineering Sun y.t-sen University Department of Mechanical Engineering The University of Hong Kong Department of Applied Mechanics and Engineering Sun Yat-sen University

A hy.erbolic Lindstedt-Poincare method is presented to determine the homoclinic solutions of a kind of nonlinear oscillators, in which critical value of the homoclinic bifurcation parameter can be determined. The generalized Lienard oscillator is studied in detail, and the present method＇s predictions are compared with those of Runge-Kutta method to illustrate its accuracy.

关键词： Lindstedt-Poincare method Hy.erbolic function Nonlinear autonomous oscillator - Homoclinic orbit

DEFORMATION BEHAVIOR OF AA6063 ALUMINIUM ALLOy.AFTER REMOVING FRICTION EFFECT UNDER HOT WORKING CONDITIONS

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Acta Metallurgica Sinica(English Letters) 2008年第6期21卷 451-458页

作者： Z. y. chen S. Q. Xu X.H. Dong National Die ＆ Mold CAD Engineering Research Center Shanghai Jiaotong University Shanghai 200030 China College of Materials Science and Engineering Taiyuan University of Technology Taiyuan 030024 China

The hot deformation behavior of AA6063 aluminium alloy.has been investigated by.means of compression tests at temperatures between 400 and 520℃, and strain rates ranging from 2.5 to 10 s^-1. Owing to the barreling, the theoretical model on the basis of Hills general method is used to calculate the flow stress of a cy.indrical specimen under uniaxial simple compression so as to consider the friction effect at the die-specimen interface. A method of evaluating the friction coefficient by.combining compression tests with the finite element method is presented. The real flow behavior of AA6063 aluminium alloy.can be described with sinh-Arrhenius equation. The hot deformation activation energy.Q derived from the corrected stress and strain data is 232. 350 kJ/mol.

关键词： Barreling Compression test Friction Flow stress Aluminium alloy Activation energy

Kruppel-like factors and vascular wall homeostasis

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Journal of Molecular Cell Biology 2017年第5期9卷 352-363页

作者： y.nbo Fan Haocheng Lu Weny.ng Liang Wenting Hu Jifeng Zhang y. Eugene chen Cardiovascular Center Department of Internal Medicine University of Michigan Medical Center Ann Arbor MI 48109 USA

Cardiovascular diseases （CVDs） are major causes of death worldwide. Identification of promising targets for prevention and treatment of CVDs is paramount in the cardiovascular field. Numerous transcription factors regulate cellular function through modulation of spe- cific genes and thereby.are involved in the phy.iological and pathophy.iologicai processes of CVDs. Although Kriippel-like factors （KLFs） have a similar protein structure with a conserved zinc finger domain, they.possess distinct tissue and cell distribution patterns as well as biological functions. In the vascular sy.tem, KLF activities are regulated at both transcriptional and posttranscriptional levels. Growing in vitro, in vivo, and genetic epidemiology.studies suggest that specific KLFs play.important roles in vascular walt biology. which further affect vascular diseases. KLFs regulate various functional aspects such as cell growth, differentiation, activa- tion, and development through controlling a whole cluster of functionally.related genes and modulating various signaling pathway. in response to pathological conditions. Therapeutic targeting of selective KLF family.members may.be desirable to achieve distinct treatment effects in the context of various vascular diseases. Further elucidation of the association of KLFs with human CVDs, their underly.ng molecular mechanisms, and precise protein structure studies will be essential to define KLFs as promising targets for therapeutic interventions in CVDs.

关键词： endothelial cells vascular smooth muscle cells inflammation shear stress atherosclerosis vascular injury drugdevelopment