Rui Huang's blog

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Minisymposium on Mechanics and Physics of Soft Matter Materials

As part of USNCTAM2014 (17th U.S. National Congress on Theoretical & Applied Mechanics) to be held at Michigan State University, East Lansing, Michigan from June 15-20, 2014, we are organizing a Minisymposium entitled

Mechanics and Physics of Soft Matter Materials 

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Journal Club Theme of March 2013: Interfacial Adhesion of Graphene - Measurements and Analysis

Several recent papers have reported measurements of adhesion energy between graphene and other materials (e.g., Si/SiOx and copper) [1-3]. Like thin films, many experimental methods may be adopted to measure the interfacial properties of graphene, such as the pressurized blister test [2] and the double-cantilever beam test [3]. The challenges lie in the handling of atomically thin membranes and analysis/interpretation of the data.

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Symposium on Mechanics and Physics of Soft Matter

On behalf of the organizing committee, I cordially invite your participation in Symposium on Mechanics and
Physics of Soft Matter
, as part of the 13th Pan-American Congress of Applied Mechanics (PACAM XIII), to be held in Houston, Texas, May 22-24, 2013.

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A kinetics approach to surface wrinkling of elastic films

This chapter summarizes our works on surface wrinkling of elastic thin films, taking a kinetics approach as a physical pathway to both ordered and disordered wrinkle patterns.

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Fraud, h-index, etc.

This is an interesting article: Fraud, the h-index and Pasternak. How do we evaluate ourselves and others, especially those not in our own fields? We may not have to find an answer as an individual researcher, but the univeristy adminstrators have to.

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Effect of surface tension on swell-induced surface instability of substrate-confined hydrogel layers

This paper has been accepted for publication in Soft Matter. DOI: 10.1039/c0sm00335b.

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Effects of mismatch strain and substrate surface corrugation on morphology of supported monolayer graphene

In a previous work, substrate-modulated morphology of graphene was analyzed using a numerical Monte Carlo method. Here we present an analytical approach that explicitly relates the van der Waals interaction energy to the surface corrugation and the interfacial properties. Moreover, the effect of mismatch strain is considered, which predicts a strain-induced instability under a compressive strain and reduced corrugation under a tensile strain.

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Swell induced surface instability of confined hydrogel layers

A previous work suggested a critical condition to form surface creases in elastomers and gels. For elastomers, the critical condition seems to have closed a gap between experimental observations (e.g., by bending a rubber block) and the classical instability analysis by Biot. For gels, however, experiments have observed a wide range of critical swelling ratios, from around 2 to 3.7. Here we present a linear perturbation analysis for swollen hydrogels confined on a rigid substrate, which predicts critical swelling ratios in a similar range.

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11th International Workshop on Stress-Induced Phenomena in Metallization

11th International Workshop on Stress-Induced Phenomena in Metallization
April 12 - 14, 2010 in Dresden, Germany

The workshop will provide a forum for presenting current research and
for discussions on issues related to stress-induced phenomena in
on-chip metal interconnects and solder joints. Stresses arising in
metal structures and surrounding dielectric materials due to novel
process steps, thermal mismatch of thin film materials,
electromigration or microstructure changes can lead to degradation and
failure of microelectronic products.

Please see attachment for Call-for-Papers.

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Excess energy and deformation along free edges of graphene nanoribbons

Q. Lu and R. Huang, Excess energy and deformation along free edges of graphene nanoribbons. Posted online at arXiv:0910.0912, October 2009.

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Viscoelastic properties of confined polymer films measured via thermal wrinkling

We present a new wrinkling-based measurement technique for quantifying the viscoelastic properties of confined polymer thin films. This approach utilizes real-time laser-light scattering to observe the kinetics of thermally-induced surface wrinkling, which evolves isothermally as a function of annealing time. Specifically, wrinkling is induced by applying a thermal stress to a polystyrene film that is sandwiched between a silicon substrate and an aluminium thin film superstrate. By following the time evolution of the wrinkle wavelength and amplitude, we can infer the rubbery modulus and shear viscosity of the polystyrene film with the aid of a theoretical model.

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von Karman plate equations

Many of us (including myself) have used the nonlinear equations for elastic plates, originally proposed by von Karman (1910). I recently came across a book with some interesting comments about the plate equations, which may be of interest to share with others on imechanica. The book's title is "Plates and Junctions in Elastic Multi-Structures", authored by Philippe G. Ciarlet and published by Springer-Verlag in 1990.

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Effect of constraint on swelling of hydrogels and formation of surface creases

Inspired by recent works by Wei Hong , Xuanhe Zhao, Zhigang Suo, and their coworkers, we started a project on hydrogels, with particular interest in various instability patterns observed in experiments. The attachment is our first manuscript on this subject. Through this work we hope to achieve the following:

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comments on second page

I just noticed a new problem with imechanica: when a blog entry has received too many comments, additional comments will be placed on a second page but not linked properly. For example, the comment, "Work-free isochoric deformation", has a link , which leads to the original blog entry rather than the comment. One can find the comment either by scrolling all the way down to the bottom of the page and then clicking "Next" or by a direct link, This seems to be a rare situation that the software does not handle properly.

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a point and a particle

A few of us have been discussing/debating over the existence or non-existence of Cauchy stress questioned in a theory proposed by Mr. Falk H. Koenemann. While such discussions may appear funny or irrelevant to many mechanicians, I take it as a challenge from an educational point of view to clearly understand what continuum mechanics is about and if any what are its limitations. Unfortunately, the discussions have not been fruitful and probably have become annoying to many who read imechanica. For that I apologize from my part. However, I remain hopeful that some consensus may be reached, if we can clear out or admit the misconceptions that have been brought up in the discussions from both sides. To begin with, I summarize below in a list of possible misconceptions about a point in a continuum and a particle in a discrete system. It is my understanding that the two are fundamentally different but have been mixed up in Mr. Koenemann's theory as well as in the discussions. As many mechanicians are doing research in both continuum mechanics and discrete modeling (e.g., atomistic, molecular dynamics), such a list may not be totally irrelevant. Of course I would welcome comments and discussions to make the list more accurate and more complete.

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Engineering Mechanics 397: Thin Film Mechanics

Time: Tuesday and Thursday 2:00 - 3:30 pm

Place: ECJ 1.214, University of Texas at Austin

Instructor: Rui Huang, WRW 117D, (512) 471-7558,

Lecture notes (coming soon)

Homewrok sets (coming soon)

Brief Outline of Topics

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Wrinkle Patterns of Anisotropic Crystal Films on Viscoelastic Substrates

In this paper we analyze evolution of wrinkle patterns of anisotropic crystal films on viscoelastic substrates. The effects of the residual stress state in the film and the anisotropic elastic property are emphasized. Analytical solutions for the initial growth kinetics and the equilibrium states are presented along with numerical simulations based on nonlinear evolution equations. Compared to wrinkling of isotropic elastic films, more ordered wrinkle patterns are predicted, including orthogonal, zigzag, parallel, and checkerboard patterns. Tranistion of the wrinkle patterns under various stress states is elucidated. Some related experimental works are referred to, but quantitative comparisons between the model the experiments await further studies.

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Effect of Elastic Anisotropy on Surface Pattern Evolution of Epitaxial Thin Films

This paper aims to illustrate how anisotropic elastic properties of the crystal substrate affect epitaxial surface evolution and pattern formation. Specifically, for Ge and SiGe films on silicon substrates of various surface orietations, it is shown that the elastic anisotropy plays an important role. However, it must be pointed out that the evolution dynamics of epitaxial surfaces can be much more complicated, due to the combination/competition of various anisotropic properties (e.g., surface energy, surface diffusivity, etc.). Furthermore, for some surface orietations. e.g., Si(111) and Si(113), discrete surface steps play critical roles in the nucleation and growth of epitaxial islands and other surface structures.

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2008 Summer Research Seminars on Mechanics of Materials

Place: University of Texas at Austin, WRW 312

Time: Friday 3:00 - 4:30 pm, May 23 - August 22, 2008

Faculty advisors: Chad Landis and Rui Huang

Speakers: postdocs and graduate students, including guest speakers from other groups

Tentative schedule:

(Date, Seminar title, Speaker name, Group affiliation)

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EM 388F Lecture Notes 9: Nonlinear Fracture Mechanics II

one file is attached

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EM 388F Lecture Notes 8: Nonlinear Fracture Mechanics I

one file is attached

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EM 388F Homework Problems 29-30

One file is attached.

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