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CONCAVE BIOLOGICAL SURFACES FOR STRONG WET ADHESION

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Acta Mechanica Solida Sinica 2009年第6期22卷 593-604页

作者： Yewang Su Baohua Ji Yonggang Huang kehchih hwang Department of Engineering Mechanics Tsinghua University Beijing 100084 China Department of Applied Mechanics Beijing Institute of Technology Beijing 100081 China Department of Civil and Environmental Engineering Northwestern University Evanston IL 60208 USA

Plant leaves, insects and geckos are masters of adhesion or anti-adhesion by smartly designed refined surface structures with micro- and nano- ＇technologies＇. Understanding the basic principles in the design of the unique surface structures is of great importance in the manufacture or synthesis of micro- and nano- devices in MEMS or NEMS. This study is right inspired by this effort, focusing on the mechanics of wet adhesion between fibers having concave tips and a flat substrate via capillary forces. We show that the concave surface can effectively enhance the wet adhesion by reducing the effective contact angle of the fiber, firmly pinning the liquid bridge at its circumferential edge. A critical contact angle is identified below which the adhesion strength can achieve its maximum, being insensitive to the contact angle between the fiber and liquid. The analytical expression for the critical angle is derived. Then a tentative design for the profile of concave surfaces is proposed, considering the effects of chamfering size, deformation and buckling, etc. The effect of liquid volume on the wet adhesion of multiple-fiber system is also discussed.

关键词： biological surface wet adhesion contact shape concave surface robustness ad- hesion force

STEADY GROWTH OF CRACKS IN COMPRESSIBLE ELASTIC-PLASTIC MEDIA

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Acta Mechanica Sinica 1989年第1期5卷 60-69页

作者： Luo Xuefu hwang kehchih (Department of Engineering Mechanics,Tsinghua University) Department of Engineering Mechanics Tsinghua University China

Based on the theoretical framework for crack growth analysis provided by Gao and hwang, the 5-sector soiution of near-tip fields of mode-I cracks growing quasi-statically and steadily in compressible elastic perfectly plastic materials is *** Poisson's ratio v tends to 1/2,the 5-sector solution degener- ates to the 4-sector solution of near-tip fields of crack growth in incompressible elastic perfectly plastic materials.

关键词： compressible materials elastic perfectly plastic medium growing crack near-tip fields

THE LIMIT ANALYSIS OF CYLINDRICAL SHELL WITH HEMISPHERICAL ENDS

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Acta Mechanica Sinica 1985年第1期1卷 59-70页

作者： Cheng Li Xu Bingye Huang Kezhi (hwang kehchih)(Tsinghua University) Tsinghua University China

The present paper is concerned with the limit analysis of a thin cylindrical shell withhemispherical ends under internal *** cases of collapse mechanisms for various geometryparameters are examined and the complete solution for each mechanism is *** range of val-idity for each mechanism is also *** is proved that the solutions obtained from the sevenmechanisms are complete.

关键词： limit analysis collapse mechanism limit load

A MICROMECHANICS CONSTITUTIVE THEORY FOR FORWARD TRANSFORMATION PLASTICITY WITH SHEAR AND DILATATION EFFECT:I,NONPROPORTIONAL LOADING HISTORY

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Acta Mechanica Sinica 1990年第4期6卷 324-332页

作者： hwang kehchih Sun Qingping Yu Shouwen (Department of Engineering Mechanics,Tsinghua University,Beijing,China.) Department of Engineering Mechanics Tsinghua University Beijing China

A micromechanics constitutive theory which takes into account both the dilatation and shear ef- fects of the transformation is proposed to describe the macroscopic plastic behavior of structure ceramics during forward transformation under different *** some basic assumptions,the analytic expressions of the Helmholtz and complementary free energy of the constitutive element are derived in a self-consistent manner by using the Mori-Tanaka's method which takes into account the interaction between the transformed *** the framework of Hill-Rice's internal variable constitutive theory,the forward transformation yield function and incremental stress strain relations,in analogy to the theory of metal plasticity,for non-proportional loading histories are obtained.

关键词： shear effect internal variables constitutive element

A MICROMECHANICS CONSTITUTIVE MODEL FOR PURE DILATANT MARTENSITIC TRANSFORMATION OF ZrO2 CONTAINING CERAMICS

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Acta Mechanica Sinica 1990年第2期6卷 141-150页

作者： Sun Qingping Yu Shouwen hwang kehchih (Dept.of Engng.Mech.,Tsinghua University,Beijing,China) Dept. of Engng. Mech. Tsinghua University Beijing China

A new micromechanics constitutive model for pure dilatant transformation plasticity of structure ceramics is proposed in this *** on the thermodynamics,micromechanics and microscale t→ m trans- formation mechanism analysis of the TZP and PSZ ZrO2-containing ceramics,an analytic expressions of the Helmholtz and complementary free energy of the constitutive element for the case of pure dilatant transforma- tion is derived for the first time in a self-consistent *** the analysis of energy dissipation in the for- ward and reverse transformations,the mieromechanics constitutive law is derived in the framework of Hill-Rice’s internal variable constitutive theory.

关键词： constitutive element microscopic and macroscopic quantities internal variables free energy thermodynamic force pure dilatant transformation inclusions and matrix

Coarse-grained Molecular Dynamics Simulations of Ligands Binding in to HIV-1Protease

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Coarse-grained Molecular Dynamics Simulations of Ligands Bin...

CONTACT ANGLE HYSTERESIS AND WET ADHESION AT SMALL SCALE

中国力学学会学术大会'2009

作者： hwang kehchih Department of Engineering Mechanics School of AerospaceTsinghua University

Single-molecule mechanics of DNA/RNA, polypeptide and protein has become a new frontier in life *** is an increasing need in participant of researcher in applied mechanics to perform a systematic study on methodologie... 详细信息

关键词： ligands binding HIV-1 protease coarse-grained dynamics inhibition binding free energy association rate

来源： cnki会议评论

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CONTACT ANGLE HYSTERESIS AND WET ADHESION AT SMALL SCALE

SOME POSSIBLE ALTERNATIVE SOLUTIONS OF NEAR TIP FIELDS FOR STEADY CRACK GROWTH IN ELASTIC PERFECTLY-PLASTIC MEDIA

庆祝中国力学学会成立50周年暨中国力学学会学术大会’2007

作者： hwang kehchih Department of Engineering Mechanics Tsinghua University

Wet adhesion is widely adopted by biological adhesion systems in nature for the activity and survival of *** the first part of the talk,we analyze the mechanics of the wet adhesive systems with different contact shapes at small scale:flat,concave,convex and ring-like,to study the effect of the contact shape on the adhesion

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Acta Mechanica Sinica 1991年第2期7卷 140-146页

作者： Luo Xuefu hwang kehchih (Dept.of Eng.Mechanics,Tsinghua University)Han Bin(Dept.of Appl.Mech.,Beijing Institute of Technology) Dept. of Eng. Mechanics Tsinghua University Beijing China Dept. of Appl. Mech. Beijing Institute of Technology Beijing China

Some possible alternative solutions of near-tip fields are studied for plane-strain Mode-I qua- si-static steady crack growth in incompressible(v=1/2)elastic perfectly-plastic media.A group of four-sector so- lutions and a three-sector solution in which the elastic-unloading region vanishes are *** functions,plas- tic flow factors and plastic strains in each region are also given.

关键词： growing crack near-tip fields elastic perfectly-plastic medium

ANTIPLANE SHEAR FIELDS NEAR A CRACK-TIP IN A BRITTLE DAMAGED MATERIAL

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Acta Mechanica Sinica 1989年第3期5卷 227-236页

作者： Jin Zhihe Yu Shouwen hwang kehchih(Department of Engineering Mechanics,Tsinghua University) The current address:Institute of Engineering Mechanics,Northern Jiaotong University,Beijng. Department of Engineering Mechanics Tsinghua University Tsinghua China

In this paper,a simplified brittle damage model is proposed according to the Mazars-Lemaitre damage model for concrete.A closed-form solution for a mode Ⅲ crack is obtained based on the simplified model under small scale damage conditions,which allows for discontinuities of displacement-gradient and tangential stress on the damage *** is pointed out that the discontinuities of field variables near the tip region exist for the brittle damaged material induced by the softening effect of the material.

关键词： brittle damage crack-tip field antiplane shear small scale damage