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Interfacial Instability of Two Bonded Elastic Bodies Driven by Interface or Bulk Residual Stress

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Acta Mechanica Solida Sinica 2023年第6期36卷 914-920页

作者： c.q.Ru Department of Mechanical Engineering University of AlbertaEdmonton T6G 2G8Canada

Inspired by recent research interest in the interface wrinkling of bonded materials in diverse areas of 3D printing,the present work studies the interfacial instability of two bonded elastic bodies driven by negative interfacial tension or compressible bulk residual *** interfacial instability modes decaying exponentially with distance from the interface,the present model is formulated for two bonded elastic half-spaces with a planar interface under plane *** explicit expression is given for the wavenumber of interfacial instability driven by negative interfacial tension,and a critical condition is derived for interfacial instability driven by compressive bulk residual *** derived results are validated with comparison to known results on surface instability of an elastic half-space,and the role of shear modulus ratio and Poisson’s ratios of two bonded elastic bodies in interfacial instability,an issue to be addressed in literature,is studied with specific reference to material parameters used in some areas of 3D printing.

关键词： Interfacial tension Surface tension Interfacial instability 3D printing Interface wrinkling

A simple criterion for finite time stability with application to impacted buckling of elastic columns

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Applied Mathematics and Mechanics(English Edition) 2018年第3期39卷 305-316页

作者： c.q.RU Department of Mechanical Engineering University of Alberta

The existing theories of finite-time stability depend on a prescribed bound on initial disturbances and a prescribed threshold for allowable responses. It remains a challenge to identify the critical value of loading parameter for finite time instability observed in experiments without the need of specifying any prescribed threshold for al- lowable responses. Based on an energy balance analysis of a simple dynamic system, this paper proposes a general criterion for finite time stability which indicates that finite time stability of a linear dynamic system with constant coefficients during a given time interval [0, tf] is guaranteed provided the product of its maximum growth rate （determined by the maximum eigen-root pl 〉0） and the duration tf does not exceed 2, i.e., pltf 〈2. The proposed criterion （pltf=2） is applied to several problems of impacted buckling of elastic columns：（i） an elastic column impacted by a striking mass, （ii） longitudinal impact of an elastic column on a rigid wall, and （iii） an elastic column compressed at a constant speed （＂Hoff problem＂）, in which the time-varying axial force is replaced approximately by its average value over the time duration. comparison of critical parameters predicted by the proposed criterion with available experimental and simulation data shows that the proposed criterion is in robust reasonable agreement with the known data, which suggests that the proposed simple criterion （pltf---2） can be used to estimate critical parameters for finite time stability of dynamic systems governed by linear equations with constant coefficients.

关键词： finite time stability, buckling impact, elastic column, Hoff problem, dy-namic buckling, stability criterion

Rationally designing S/Ti3c2Tx as cathode material with an interlayer for highrate and long-cycle lithium-sulfur batteries

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Rationally designing S/Ti3C2Tx as cathode material with an i...

Measurement and Prediction of Insertion Force for the Mosquito Fascicle Penetrating into Human Skin

中国化学会第三届中国能源材料化学研讨会

作者： q.jin N.Zhang c.c.Zhu H.Gao X.T.Zhang School of Physics and Electronic Engineering Harbin Normal University Key Laboratory for Photonic and Electronic Bandgap Materials Ministry of Education

Lithium-sulfur batteries suffer from poor cycling stability and inferior rate capability,mainly caused by the low conductivity and lithium polysulfides *** tackle these problems,this work demonstrates that Ti

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Journal of Bionic Engineering 2009年第2期6卷 143-152页

作者： X q Kong c W Wu State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering MechanicsDalian University of Technology

Mosquitoes are exceptional in their ability to pierce into human skin with a natural ultimate painless microneedle, named fascicle. Here the structure of the Aedes albopictus mosquito fascicle is obtained using a Scanning Electron Microscope (SEM), and the whole process of the fascicle inserting into human skin is observed using a high-speed video imaging technique. Direct measurements of the insertion force for mosquito fascicle to penetrate into human skin are reported. Results show that the mosquito uses a very low force (average 18 μN) to penetrate into the skin. This force is at least three orders of magnitude smaller than the reported lowest insertion force for an artificial microneedle with an ultra sharp tip to insert into the human skin. In order to understand the piercing mechanism of mosquito fascicle tip into human multilayer skin tissue, a numerical simulation is conducted to analyze the insertion process using a nonlinear finite element method. A good agreement occurs between the numerical results and the experimental measurements.

关键词： biomimetic microneedle mosquito fascicle mechanics penetration

SIMULATION OF LARGE TURBINE ROTOR'S HEAT TREATMENT PROcESS

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Acta Metallurgica Sinica(English Letters) 2005年第6期18卷 768-772页

作者： c. Jiang Y.B. chen B.S. Wu q.L. jin Beijing Research Institute of Mechanical and Electrical Technology Beijing 100083 China

Temperature field numerical simulation about he heat treatment process curve of large turbine rotor is presented. With simulation software Deform3D in according to the heat treatment processing of china First Heavy Machinery, the details of temperature change at the different location of the rotor is to be found. Once knowing the temperature field change, the duplex grain defect long time existed in large forgings can be solved with a quantitative analysis instead of only the qualitative one. Precondition for small metal samples is brought to simulate microstructare and grain size change of large rotor according to the numerical simulation result. Also, consistent feature with real manufacture is showed from the physical experiment, so that the simulation can be used to not only improve the products process but also prevent wasting unnecessary energy and shorten process periods. The rotor quality is controlled thoroughly with plenty of experiments data.

关键词： temperature field numerical simulation grain size

Elastoplastic homogenization of particulate composites complying with the Mohr–coulomb criterion and undergoing isotropic loading

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Acta Mechanica Sinica 2015年第3期31卷 392-405页

作者： D.Yang q.c.He School of Mechanical Engineering Southwest Jiaotong University Université Paris-Est Laboratoire Modélisation et Simulation Multi Echelle UMR 8208 CNRS

This work aims at determining the overall response of a two-phase elastoplastic composite to isotropic loading. The composite under investigation consists of elastic particles embedded in an elastic perfectly plastic matrix governed by the Mohr-coulomb yield criterion and a non-associated plastic flow rule. The composite sphere assemblage model is adopted, and closed-form estimates are derived for the effective elastoplastic properties of the composite either under tensile or compressive isotropic loading. In the case when elastic particles reduce to voids, the composite in question degenerates into a porous elastoplastic material. The results obtained in the present work are of interest, in particular, for soil mechanics.

关键词： composite Porous medium. Elastoplasticity Mohr-coulomb yield criterion Non-associated flow rule Homogenization

Stability and local bifurcation of parameter-excited vibration of pipes conveying pulsating fluid under thermal loading

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Applied Mathematics and Mechanics(English Edition) 2015年第8期36卷 1017-1032页

作者： Demin ZHAO Jianlin LIU c.q.WU Department of Mechanics College of Pipeline and Civil Engineering China University of Petroleum Department of Mechanical and Manufacturing Engineering University of Manitoba

The parametric excited vibration of a pipe under thermal loading may occur because the fluid is often transported heatedly. The effects of thermal loading on the pipe stability and local bifurcations have rarely been studied. The stability and the local bifurcations of the lateral parametric resonance of the pipe induced by the pulsating fluid velocity and the thermal loading are studied. A mathematical model for a simply supported pipe is developed according to the Hamilton principle. Two partial differential equations describing the lateral and longitudinal vibration are obtained. The singularity theory is utilized to anMyze the stability and the bifurcation of the system solutions. The transition sets and the bifurcation diagrams are obtained both in the unfolding parameter space and the physical parameter space, which can reveal the relationship between the thermal field parameter and the dynamic behaviors of the pipe. The frequency response and the relationship between the critical thermal rate and the pulsating fluid velocity are obtained. The numerical results demonstrate the accuracy of the single-mode expansion of the solution and the stability and local bifurcation analyses. It also confirms the existence of the chaos. The presented work can provide valuable information for the design of the pipeline and the controllers to prevent the structural instability.

关键词： thermal load parameter excited local bifurcation,unfolding parameterspace physical parameter space

Effects of chemical pressure on diluted magneticsemiconductor(Ba,K)(Zn,Mn)_2As_2

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chinese Physics B 2019年第5期28卷 288-292页

作者： Y Peng S Yu G q Zhao W M Li J F Zhao L P cao X c Wang q q Liu S J Zhang R Z Yu Z Deng X H Zhu c q.jin college of Materials Science & Engineering Sichuan University Beijing National Laboratory for condensed Matter Physics and Institute of Physics Chinese Academy of Sciences School of Physics University of Chinese Academy of Sciences collaborative Innovation center of quantum Matter

chemical pressure induced by iso-valent doping has been widely employed to tune physical properties of materials. In this work, we report effects of chemical pressure by substitution of Sb or P into As on a recently discovered diluted magnetic semiconductor(Ba,K)(Zn,Mn)_2 As_2, which has the record of reliable curie temperature of 230 K due to independent charge and spin doping. Sb and P are substituted into As-site to produce negative and positive chemical pressures, respectively.X-ray diffraction results demonstrate the successful chemical solution of dopants. Magnetic properties of both K-underdoped and K-optimal-doped samples are effectively tuned by Sb-and P-doping. The Hall effect measurements do not show decrease in carrier concentrations upon Sb-and P-doping. Impressively, magnetoresistance is significantly improved from7% to 27% by only 10% P-doping, successfully extending potential application of(Ba,K)(Zn,Mn)_2 As_2.

关键词： chemical pressure (Ba,K)(Zn,Mn)2As2 diluted magnetic semiconductor iso-valent doping

Nodal superconducting gap in LiFeP revealed by NMR:contrast with LiFeAs

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chinese Physics B 2021年第4期30卷 113-118页

作者： A F Fang R Zhou H Tukada J Yang Z Deng X c Wang c q.jin Guo-qing Zheng Department of Physics Beijing Normal UniversityBeijing 100875China Institute of Physics Chinese Academy of Sciencesand Beijing National Laboratory for Condensed Matter PhysicsBeijing 100190China Songshan Lake Materials Laboratory Dongguan 523808China Department of Physics Okayama UniversityOkayama 700-8530Japan

Identifying the uniqueness of FeP-based superconductors may shed new lights on the mechanism of superconductivity in ***,we report nuclear magnetic resonance(NMR) studies on LiFeP and LiFeAs which have the same crystal structure but different pnictogen *** NMR spectrum is sensitive to inhomogeneous magnetic fields in the vortex state and can provide the information on the superconducting pairing symmetry through the temperature dependence of London penetration depth λ_(L).We find that λ_(L) saturates below T~0.2 T_(c) in LiFeAs,where T_(c) is the superconducting transition temperature,indicating nodeless superconducting ***,by using a two-gaps model,we simulate the temperature dependence of λ_(L) and obtain the superconducting gaps of LiFeAs,as Δ_(1)=1.2 kB T_(c) and Δ_(2)=2.8 k_(B)T_(c),in agreement with previous result from spin-lattice *** LiFeP,in contrast,λ_(L) does not show any saturation down to T~0.03 T_(c),indicating nodes in the superconducting gap ***,we demonstrate that strong spin fluctuations with diffusive characteristics exist in LiFeP,as in some cuprate high temperature superconductors.

关键词： iron-based superconductor nuclear magnetic resonance superconducting pairing symmetry spin fluctuations