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.

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.

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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Assignment: Each student completes a term paper of selected topics that (a) addresses a fracture phenomenon in materials or structures, and (b) involves analyses using fracture mechanics. The project contributes 25% of the final grade, distributed as follows:

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This symposium is part of the Spring 2008 ACS National Meeting and Exposition , to be held at New Orleans, Louisiana, from Sunday, April 6 to Thursday, April 10, 2008.

Organizers: Christopher M. Stafford (NIST), Adam J. Nolte (NIST), Rui Huang (UT Austin)

Sponsors: ACS Division of Polymeric Materials: Science and Engineering (PMSE) and National Science Foundation

Technical Program:

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As part of the 2008 ASME International Mechanical Engineering Congress and Exposition (IMECE), this symposium is being organized by Technical Committee of Integrated Structures (TCIS) of the ASME Applied Mechanics Division (AMD).

When and Where: October 31 - November 6, 2008, Boston, Massachusetts.

Abstract submission deadline: March 3, 2008 

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1. Introduction

2. Elements of linear elasticity

3. Stress intensity factors

4. Energy release rate

5. Fracture toughness

6. Applications of LEFM - Practical Issues 

7. Mixed mode and interface fracture

Abstract: 

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Add Problem 5: use the method of superposition to obtain the stress field around a hole in an infinite sheet under uniaxial remote stress.

Due date extended to Monday, January 28, 2008. 

Homework Problem 1: Self introduction in iMechanica (due January 21, 2008)

Homework Problems 2-5 (due January 28, 2008) 

Homework Problems 5-8 (due February 7, 2008) 

Homework Problems 9-18 (due March 3, 2008) 

Homework Problems 19-23 (due March 24, 2008) 

Homewrok Problems 24-28 (due April 9, 2008) 

1. Post a comment to this entry to explain to your teaching staff and classmates why you are taking this class. Include the following items in your comment:

• Which department or graduate program are you currently enrolled in?

• Your prior courses in solid mechanics.

• Your undergraduate major and where you were enrolled.

• What might be your strength and weakness related to this course.

• Your research group if you already belong to one (please give a link to the web page of your group).

• Your likely research direction(s).

• How do you think fracture mechanic will help you in your research?

Time: Monday and Wednesday 3:00 - 4:30 pm

Place: WRW 312, University of Texas at Austin

Instructor: Rui Huang, WRW 117D, (512) 471-7558, ruihuang@mail.utexas.edu

Lecture notes 

Homework Sets

Term Papers (with links to abstracts, presentation slides and final reports)