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Analysis on membrane wrinkling using stress extremum method

Journal of Harbin Institute of Technology(New Series) 2012年第1期19卷 34-39页

作者：李云良鲁明宇谭惠丰谭忆秋 School of Transportation Science and Engineering Harbin Institute of Technology Post-doctoral Research Center in Civil Engineering Harbin Institute of Technology Dept. of Mechanical Engineering The Hong Kong Polytechnic University Center for Composite Materials and Structure Harbin Institute of Technology

A stress extremum method is developed based on Von Karman equations for analysis of membrane wrinkles in this paper. A mechanical model is also established for analyzing shear membrane wrinkles. Expressions of wrinkling wavelength,amplitude and angle are obtained in terms of the stress extremum method. A numerical analysis approach-directly disturbing method is proposed to analyze the configuration parameters of shear membrane wrinkles by introducing out-of-plane disturbing forces to trigger wrinkle formation,while it timely removes the applied forces in order to eliminate the effect of disturbing forces on analytical results. The simulation results agree well with analytical results,which demonstrate that the proposed approach is capable for analyzing the membrane wrinkles with good accuracy.

关键词： membrane wrinkle stress extremum method

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Chemical Changes in LiNi1/3Mn1/3Co1/3O2 Lithium-Ion-Battery Cathodes during Electrochemical Cycling

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ECS Meeting Abstracts 2013年第4期MA2013-01卷

作者： Hanshuo Liu Mark J.R. Dunham Kristopher J. Harris Jian Liu Xifei Li Xueliang Andy Sun Meng Jiang Yan Wu Gillian R Goward Gianluigi A. Botton Dept. of Materials Science and Engineering McMaster University Dept. of Chemistry McMaster University Dept. of Mechanical and Materials Engineering Western University GM R&D Center McMaster University Department of Material Science and Engineering McMaster University

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Stabilization of explicit flow solvers using a proper orthogonal decomposition technique 50

Stabilization of explicit flow solvers using a proper orthog...

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50th AIAA Aerospace sciences Meeting Including the New Horizons Forum and Aerospace Exposition

作者： Ekici, Kivanc Hall, Kenneth C. Huang, Huang Dept. of Mechanical Aerospace and Biomedical Engineering University of Tennessee Knoxville TN 37996-2030 United States Dept. of Mechanical Engineering and Materials Science Duke University Durham NC 27708-0300 United States

ISBN: (数字)9781600869365

A new numerical technique for the stabilization of explicit computational fluid dynamic (CFD) solvers is presented. When using CFD codes to solve practical problems, one sometimes finds the solution fails to converge due to the presence of a small number of eigenvalues of the flow solver outside the unit circle. In this paper, we use the proper orthogonal decomposition technique to estimate the unstable eigenvalues and eigenmodes of the flow solver as the solution diverges for linear problems, or exhibits limit cycle oscillations for nonlinear problems. We use the resulting eigen-information to construct a preconditioner that repositions the unstable eigenvalues from outside the unit circle to a point inside the unit close to the origin, resulting in a stable flow solver. In this work, the proposed method is applied to a nonlinear steady cascade solver. However, the technique can be easily applied to external flow solvers, and to unsteady frequency-domain (time-linearized and harmonic balance) flow solvers. Copyright © 2012 by Kivanc Ekici, Kenneth C. Hall and Huang Huang.

关键词： Stabilization

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A comparative study on conventional electrospinning and emulsion electrospinning of PLLA nanofibers

A comparative study on conventional electrospinning and emul...

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20th International Symposium on Processing and Fabrication of Advanced materials, PFAM XX

作者： Zhang, Xin Wang, Min Yuan, Xiao-Yan Kang, Jia-Chen Dept. of Mechanical Engineering University of Hong Kong Pokfulam Road Hong Kong Hong Kong School of Materials Science and Engineering Tianjin University Tianjin 300072 China

ISBN: (纸本)9783037853160

Electrospinning is investigated by many groups around the world for constructing fibrous tissue engineering scaffolds. Incorporating biomolecules such as growth factors in fibers is becoming common for enhancing the biological performance of electrospun scaffolds. However, biomolecules may lose bioactivity if they are exposed to organic solvent during electrospinning. In emulsion electrospinning, an aqueous biomolecule solution is emulsified and water-in-oil emulsions are then electrospun into core-shell structured fibers, with biomolecules being contained in the core of fibers, which helps to avoid biomolecule-solvent contact and also reduce the initial burst release. In this investigation, for a comparative study, poly(L-lactic acid) was made into solid and core-shell structured fibers via conventional electrospinning and emulsion electrospinning, respectively. The two electrospinning techniques and resultant fibers were compared in terms of processing parameters (polymer concentration, applied voltage, working distance, etc.) and fiber characteristics (morphology, diameter, structure, etc.). Solvent properties such as conductivity and volatility affected fiber morphology and diameter. The polymer concentration range usable for emulsion electrospinning was narrower than that for conventional electrospinning owing to changes in viscosity.

关键词： Nanofibers

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Optimization of power generation from shrouded wind turbines

Optimization of power generation from shrouded wind turbines

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42nd AIAA Fluid Dynamics Conference and Exhibit 2012

作者： Foote, Tudor Agarwal, Ramesh K. Dept. of Mechanical Engineering and Materials Science Washington University in St. Louis 1 Brookings Drive MO 63130 United States

ISBN: (纸本)9781600869334

In recent years, a number of studies have shown that shrouded wind turbines can generate greater power compared to bare turbines. The objective of this study is to determine the potential of shrouded wind turbines for increased power generation by employing numerical simulations. An analytical/computational study is performed by employing the commercial Computational Fluid Dynamics (CFD) software FLUENT. An actuator disc model is used to model the turbine. The incompressible Navier-Stokes equations and a two equation realizable k - Ε model are employed in the calculations. Power coefficient and generated power are calculated for a large number of cases for horizontal axis wind turbines (HAWT) of various diameters and wind speeds for both bare and shrouded turbines. The design of the shroud is optimized by employing a single objective genetic algorithm;the objective being the maximization of the generated power and power coefficient Cp (power generated by the turbine/kinetic energy of the wind facing the turbine swept area). It was found that the shroud indeed increases the generated power and Cp beyond the Betz's limit;this effect is consistent with that found in the recent literature that the shrouded wind-turbines can generate greater power than the bare turbines. The optimized shape of the shroud or diffuser further increases the generated power and Cp. © 2012 by Tudor Foote and Ramesh K. Agarwal.

关键词： Navier Stokes equations

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Corrigendum “Temperature control of a cabin in an automobile using thermal modeling and fuzzy controller” [Applied Energy 97 (2) (2012) 860–868]

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Applied Energy 2013年 103卷 721-721页

作者： Sepehr Sanaye Masoud Dehghandokht Navid Kashaninejad Amir Fartaj Energy Systems Improvement Laboratory (ESIL) Department of Mechanical Engineering Iran University of Science and Technology (IUST) Iran Dept. of Mechanical Engineering Damavand Branch Islamic Azad University Damavand Iran School of Mechanical and Aerospace Engineering Nanyang Technological University Singapore Dept. of Mechanical Automotive and Materials Engineering (MAME) University of Windsor Canada

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Effect of hydrogen content on hydrogen embrittlement of API X70 steel

Effect of hydrogen content on hydrogen embrittlement of API ...

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20th IMEKO World Congress 2012

作者： Bae, Dong-Su Sung, Chi-Eun Jeon, Hyeon-Jee Lee, Sang-Pill Lee, Jin-Kyung Baek, Un-Bong Nahm, Seung-Hoon Dept. of Advanced Materials Engineering Dong-Eui Univ. Busan Korea Republic of Dept. of Mechanical Engineering Dong-Eui Univ. Busan Korea Republic of Korea Research Institute of Standards and Science Center for Materials Measurements Daejeon Korea Republic of

ISBN: (纸本)9781627481908

The effect of hydrogen content on hydrogen embrittlement of high toughness API X70 line-pipe steels was studied. The hardness of conventional API X70 steel was measured before and after hydrogen charging. The various hydrogen contents for API X70 steel were charged at 10MPa gas pressure. The tensile test for hydrogen charged API steel was conducted at room temperature. The hardness increased slightly with hydrogen content. The fracture surfaces were changed from dimple type to quasicleavage type with hydrogen content. And external cracks were observed just only at 100% hydrogen content. Copyright © (2012) by the International Measurement Federation (IMEKO).

关键词： Hardness

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Multiscale technique for localized strain investigation of aluminum alloy and carbon fiber composite based on data of strain gauging, digital image correlation and acoustic emission

Multiscale technique for localized strain investigation of a...

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2012 7th International Forum on Strategic Technology, IFOST 2012

作者： Panin, S.V. Burkov, M.V. Byakov, A.V. Lyubutin, P.S. Laboratory of Polymer Composite Materials ISPMS SB RAS Tomsk Russia Dept. of Material Science in Mechanical Engineering National Research Tomsk Polytechnic University Tomsk Russia

ISBN: (纸本)9781467317702

A combined method to investigation of localized deformation processes in notched aluminum alloy as well as carbon fiber reinforced composite specimens is applied in order to reveal characteristic stages of strain and fracture. Stress concentrators have the shape of a circular hole and edge crack of various sizes. Carbon fiber reinforced composites (CFRC) with notches of different size were also tested in order to illustrate the difference in deformation behavior between metal and reinforced polymeric composites specimens. Use of simultaneous strain data registration has allowed us to register and compare parameters under analysis during entire time of the experiments. The reasons of similarity and difference of the results are shown and discussed. It is offered to apply the obtained results for the aims of non-destructive testing of structural materials being based on revealing characteristic stages of strain development and a particularly prefracture stage. © 2012 IEEE.

关键词： Image correlation

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Ab initio model of intrinsic defects in Sc2O3 for thermionic cathode systems

Ab initio model of intrinsic defects in Sc2O3 for thermionic...

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2012 IEEE 9th International Vacuum Electron Sources Conference, IVESC 2012

作者： Jacobs, Ryan M. Morgan, Dane Booske, John H. Materials Science Program University of Wisconsin-Madison 1415 Engineering Dr. Madison WI 53706 United States Materials Science and Engineering University of Wisconsin-Madison 1415 Engineering Dr. Madison WI 53706 United States Electrical and Computer Engineering Dept. University of Wisconsin-Madison 1415 Engineering Dr. Madison WI 53706 United States

ISBN: (纸本)9781467303699

A defect model for Sc2O3 was developed using quantum mechanical modeling and evaluated under cathode operating conditions to determine the electronic properties of Sc2O3 used in cathode experiments. We find that Sc2O3 can conduct well enough with a sub-ppm impurity concentration such that the limiting step of emission is not conduction through bulk Sc2O3. © 2012 IEEE.

关键词： Scandium compounds

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Elastic properties of aligned carbon nanotube polymer nanocomposites with controlled morphology

Elastic properties of aligned carbon nanotube polymer nanoco...

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53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and materials Conference 2012

作者： Handlin, D. de Villoria, R. Guzmán Chan, S.H. Takahashi, K. Cebeci, H. Williams, M. Parsons, E.M. Socrate, S. Wardle, B.L. Massachusetts Institute of Technology Dept. of Aeronautics and Astronautics Cambridge MA 02139 United States Dept. of Aeronautics and Astronautics IMDEA - Materials Institute C/Professor Arunguren s/n 28040 Madrid Spain Center for Materials Science and Engineering Dept. of Materials Science and Engineering University of Pennsylvania United States Dept. of Aeronautics and Astronautics Dept. of Mechanical and Aerospace Engineering University of California Los Angeles United States Department of Aeronautics and Astronautics Department of Aeronautical Engineering Istanbul Technical University Maslak 34469 Istanbul Turkey Department of Aeronautics and Astronauti United States Institute for Soldier Nanotechnologies United States

ISBN: (纸本)9781600869372

The theoretical elastic properties of aligned carbon nanotube polymer nanocomposites (A-PNCs) have been predicted by standard composite theory, however, a complete experimental characterization of their (presumed) transversally isotropic properties has not been presented to date. High volume fraction A-PNCs are fabricated by biaxial mechanical densification of the CNTs, followed by polymer infiltration via capillarity-assisted wetting using an aerospace-grade epoxy. Because of the dimensions of the samples (~1mm3), only bulk compression or nanomechanical tests have been attempted previously. Here, optical strain mapping is used in conjunction with simple mechanical loadings (here simple uniaxial dogbone specimens) in order to characterize the linear elastic constitutive relations of this material. Elastic stiffness is in agreement both with prior experimental nanoindentation measurements and finite element calculations that include the effects of waviness of the reinforcing CNT 'fibers'. © 2012 by the American Institute of Aeronautics and Astronautics, Inc.

关键词： Yarn

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