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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

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

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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

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

Allelopathic effect of Acorus tatarinowii upon algae

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Journal of Environmental Sciences 2001年第4期13卷 481-484页

作者： He, c.-q. Wang, c.-k. Dept. of Environmental Science/Eng. Shanghai University Shanghai 200072 China

Besides competing with algae for light and mineral nutrients (i. e. N, P, etc.), the root system of Acorus tatarinowii excretes some chemical substances, which injure and eliminate alga cells, to inhibit the growth of the algae. When the algae cells were treated in 'A. tatarinowii water', some of the chlorophyll a were destroyed and the photosynthetic rate of algae decreased markedly and the ability of alga cells to deoxidize triphenyltetrazolium chloride (TTc) reduced greatly. Then alga cells turned from bright red to bluish green under fluorescence microscope. These showed that the allelopathic effects of A. tatarinowii on algae were obvious and planting A. tatarinowii can control some green algae. The experiment on the extractions of the secretions of the root system showed that the inhibitory effect had a concentration effect. If the concentration of the root secretion was below 30 μl/disc, the inhibitory rate was negative; if it was over 45 μl/disc, the inhibitory rate was positive. This proved that the influence of the root secretion on the same acceptor was a kind of concentration effect. When the concentration of the root secretion was low, it promoted the growth of algae; when the concentration reached a definite threshold value, it restrained the growth of algae. In present case, the threshold value was between 30 μl/disc and 45 μl/disc.

关键词： Algae cells chlorophyll concentration (process) Deoxidants Photosynthesis

Gene Transfer to Dendritic cells Induced a Protective Immunity against Melanoma

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cellular & Molecular Immunology 2005年第4期2卷 281-288页

作者： Pat Metharom Kay A.o. Ellem Ming q. Wei queensland Institute of Medical Research Herston Department of Medicine University of Queensland Prince Charles Hospital Brisbane Australia

Lentiviral vectors have shown promises for efficient gene transfer to dividing as well as nondividing cells. In this study, we explored lentiviral vector-mediated, the entire mTRP-2 gene transfer and expression in dendritic cells （Dcs）. Adoptive transfer of Dcs-expressing mTRP-2 （Dc-HR＇cmT2） into c57BL/6 mouse was also assessed. Dendritic cells were harvested from bone marrow and functional Dcs were proved by allogeneic mixed lymphocyte reaction. Lentiviral vectors were produced by transient transfection of 293T cells. Transduction of Dcs was proved by marker gene expression and PcR and RT-PcR amplification. Implantation of the transduced Dcs, depletion of immune cells as well as the survival of the mice after tumour challenge were investigated. High efficiency of gene transfer into mature Dcs was achieved. The high level expression of the functional antigen （TRP-2） and induction of protective immunity by adoptive transfer of TRP-2 gene modified Dcs were demonstrated. In vivo study showed a complete protection of mice from further melanoma cell challenge. In comparison, only 83% of mice survived when mTRP-2 peptide-pulsed Dcs were administered, suggesting the generation of specific protection. Together, these results demonstrated the usefulness of this gene transfer to Dc approach for immunotherapy of cancer and indicated that using tumour associated antigens （TAAs） for gene transfer may be potentially beneficial for the therapy of melanoma.

关键词： lentiviral vector gene transfer dendritic cell tumour antigen melanoma

Reduction effect of final-pass heavy reduction rolling on the texture development,tensile property and stretch formability of ZWK100 alloy plates

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Journal of Materials Science & Technology 2022年第16期111卷 211-223页

作者： B.q.Shi L.Y.Zhao X.L.Shang B.H.Nie D.c.chen c.q.Li Y.q.cheng School of Materials Science and Hydrogen Energy Foshan UniversityFoshan 528000China School of Materials and Energy Guangdong University of TechnologyGuangzhouGuangdong 510006China GD Midea Air-conditioning Equipment co. Ltd.Foshan 528311China Guangdong Key Laboratory of Hydrogen Energy Technology Foshan 528000China YunFu(Foshan)R&D center of Hydrogen Energy Standardization Yunfu 527326China

obviously planar anisotropy due to‘TD split’orthotropic texture(TD indicates Transverse direction)always exist in the Rare-earth(RE)or ca containing Mg alloy sheets,which is likely caused by the lowreduction rolling(and annealing)as revealed in our previous *** this work,the as-cast billets of a ZWK100 alloy were subjected to final-pass heavy reduction rolling(FHRR)at 500°c with different reductions(30%-70%)after rough rolling,aiming to investigate the reduction effect on the microstructure and texture *** results show that FHRR with higher reductions above 50%is in favor of shear banding formation but has little effect on the as-deformed texture components,and the excellent formability with single-pass reduction up to 70%is mainly ascribed to the activation of prismatic *** with reduction above 50%and annealing can generate uniform grain structures of~10μm and symmetrical‘oblique-line split’texture in(0001)pole figures,with basal poles tilting by about 50°from ND(Normal direction)towards some oblique-line of TD and RD(Rolling direction)as well as uniform distribution of counter lines as an annular shape,resulting in excellent elongation to failure of~50%and ultra-low planar anisotropyΔr_of~0.1 and high stretch formability(Erichsen value:8.1).The formation‘oblique-line split’texture in(0001)pole figures is mainly correlated with the preferred growth tendency of grains with■//RD,which was suggested to relate to the high mobility of some special boundaries such as 40°-45°■.The influences of starting textures on the mechanical properties,planar anisotropy and related deformation modes,as well as their correlations with the stretch formability were comparatively investigated with the‘TD split’orthotropic texture as a counterpoint.

关键词： Magnesium alloys Texture Plane anisotropy Stretch formability Rolled sheets

Modeling the Newtonian dynamics for rotation curve analysis of thin-disk galaxies

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Research in Astronomy and Astrophysics 2011年第12期11卷 1429-1448页

作者： James q.Feng c.F.Gallo Superconix Inc 2440 Lisbon AvenueLake ElmoMN 55042USA

We present an efficient, robust computational method for modeling the Newtonian dynamics for rotation curve analysis of thin-disk galaxies. With appropriate mathematical treatments, the apparent numerical difficulties associated with singularities in computing elliptic integrals are completely removed. Using a boundary element discretization procedure, the governing equations are transformed into a linear algebra matrix equation that can be solved by straightforward Gauss elimination in one step without further iterations. The numerical code implemented according to our algorithm can accurately determine the surface mass density distribution in a disk galaxy from a measured rotation curve （or vice versa）. For a disk galaxy with a typical flat rotation curve, our modeling results show that the surface mass density monotonically decreases from the galactic center toward the periphery, according to Newtonian dynamics. In a large portion of the galaxy, the surface mass density follows an approximately exponential law of decay with respect to the galactic radial coordinate. Yet the radial scale length for the surface mass density seems to be generally larger than that of the measured brightness distribution, suggesting an increasing mass-tolight ratio with the radial distance in a disk galaxy. In a nondimensionalized form, our mathematical system contains a dimensionless parameter which we call the ＂galactic rotation number＂ that represents the gross ratio of centrifugal force and gravitational force. The value of this galactic rotation number is determined as part of the numerial solution. Through a systematic computational analysis, we have illustrated that the galactic rotation number remains within 4-10% of 1.70 for a wide variety of rotation curves. This implies that the total mass in a disk galaxy is proportional to V02 Rg, with V0 denoting the characteristic rotation velocity （such as the ＂flat＂ value in a typical ro- tation curve） and Rg the radius of the galacti

关键词： galaxy: disk -- galaxies: general -- galaxies: kinematics and dynamics -- galaxies: structure -- methods: numerical and analytical