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Mechanical Properties of Thin Films (class notes for a graduate class at Stanford University)

The attached file is a set of class notes developed by W.D. Nix of Stanford University and used in a graduate course on Mechanical Properties of Thin Films. These notes have been used in the graduate course MSE 353 since the late 1980's. That course has been taught every year or so since that time. The notes were last updated in January of 2005. The reader will see a note to the effect that many of the figures and illustrations in the file have been taken from the work of students and colleagues at Stanford without proper attribution.

Hanqing Jiang's picture

Symposium: Multiscale Multiphysics Modeling and Simulation of Nanomaterials and Nanostructures

McMat 2007, June 3-7, 2007, University of Texas at Austin

 

Call for paper

Symposium: Multiscale Multiphysics Modeling and Simulation of Nanomaterials and Nanostructures

Zhigang Suo's picture

What Is Mechanics?

So, What is Mechanics? It seems that useful answers ought to depend on who you are talking to. If you are persuading your dean to hire a new faculty member in Mechanics, perhaps you’d like to point out promising research in one area or another, and how foundational mechanics is to the education of future scientists and technologists in (almost) all fields.

How to Make a Free Web Site

In the present time the internet craze has swept the nation and these days everything and everyone is online. Everyone having fun on internet and get knowledge from the web site.

If you want to know how to make a free web site, the good news is that you've set an easy goal for yourself. Learning how to make a free web site is about more than just getting your web domain for free - you need to know how to put information on that site as well. Many domains offering free web sites also feature free online tutorials that will help you write your web pages. Some sites are so user-friendly; you don't have to write any of your own web code at all! You can select colors and font sizes from the domain's own page editing service. When the domain is willing to write your pages for you, it's very easy to learn how to make a free web site.

Michael H. Suo's picture

Who Owns Your Content? [draft]

Who owns your content? Is it you or the copyright holder? If it isn't you, then why did you pay for it? All these questions are at the heart of the current war for the rights to music, movies, and everything in between.

The first shots of this war were fired with the start of the digital age. Before, the best you could was make physical copies of media. Technically possible, yes, but the equipment and manpower needed to run an operation on a scale large enough to threaten publishers was nearly impossible to obtain without being noticed.

Mogadalai Gururajan's picture

Some numerical mechanics software

Recently, during one of my net searches, I came across this page of RPI, where I learnt about a couple of numerical mechanics software which might be of interest to some of you.

FMDB:

As for the effort toward the scalable engineering simulations on distributed environements, we addressed this challenge by developing a distributed mesh data management infrastructure that satisfies the needs of distributed domain of applications.

A structure-based sliding-rebinding mechanism for catch bonds

This is a paper by Jizhong Lou and myself, which is in press in Biophysical Journal.

Abstract.  Catch bonds, whose lifetimes are prolonged by force, have been observed in selectin-ligand interactions and other systems. Several biophysical models have been proposed to explain this counter-intuitive phenomenon, but none was based on the structure of the interacting molecules and the noncovalent interactions at the binding interface. Here we used molecular dynamics simulations to study changes in structure and atomic-level interactions during forced unbinding of P-selectin from P-selectin glycoprotein ligand-1. A mechanistic model for catch bonds was developed based on these observations. In the model, "catch" results from forced opening of an interdomain hinge that tilts the binding interface to allow two sides of the contact to slide against each other. Sliding promotes formation of new interactions and even rebinding to the original state, thereby slowing dissociation and prolonging bond lifetimes. Properties of this sliding-rebinding mechanism were explored using a pseudo-atom representation and Monte Carlo simulations. The model has been supported by its ability to fit experimental data and can be related to previously proposed two-pathway models.

How can we obtain more information from protein structure?

We know - or believe - protein function is determined by structure. Crystallographic and NMR studies can provide protein structures with atomic-level details at equilibrium. MD simulations can follow protein conformational changes in time with fs temporal resolution in the absence or presence of a bias mechanism, e.g., applied force, used to induce such changes.

Dhirendra Kubair's picture

Mode-3 spontaneous crack propagation along functionally graded bimaterial interfaces

This is a paper that has been accepted for publication in the Journal of the Mechanics and Physics of Solids from our group. The paper describes the combined effect of material inertia and inhomogeneous material property variation on spontaneous cohesive-crack propagation in functionally graded materials. The preprint is attached as a PDF.

Abstract- The effects of combining functionally graded materials of different inhomogeneous property gradients on the mode-3 propagation characteristics of an interfacial crack are numerically investigated. Spontaneous interfacial crack propagation simulations were performed using the newly developed spectral scheme. The numerical scheme derived and implemented in the present work can efficiently simulate planar crack propagation along functionally graded bimaterial interfaces. The material property inhomogeneity was assumed to be in the direction normal to the interface. Various bimaterial combinations were simulated by varying the material property inhomogeneity length scale. Our parametric study showed that the inclusion of a softening type functionally graded material in the bimaterial system leads to a reduction in the fracture resistance indicated by the increase in crack propagation velocity and power absorbed. An opposite trend of increased fracture resistance was predicted when a hardening material was included in the bimaterial system. The cohesive tractions and crack opening displacements were altered due to the material property inhomogeneity, but the stresses ahead of the cohesive zone remained unaffected.

ES 246 Project: Saint-Venant Torsion Problem

I plan to explore the Saint-Venant torsion problem applied to prismatic bars with elastic-plastic behavior. Wagner and Gruttmann have developed a finite element method to obtain the elastic/plastic stresses of a bar using a single load step. In particular, I will present the constitutive model that they have developed, and then use ABAQUS to apply Wagner and Gruttmann’s model to various cross-sections.

EM 397 Term Paper: Dislocations in Epitaxial Thin Films

Dislocations are common in epitaxial systems. For a thin film epitaxially grown on a substrate with coherent interface, it may have spontaneously-formed dislocations when its thickness is larger than certain value, i.e. critical thickness. The presence of dislocations can have an adverse effect on electrical performance of semiconductor materials, providing easy diffusion paths for dopants to lead to short circuits, or recombination centers to reduce carrier density. And, formation of dislocations is one of the most observed mechanisms of relaxation of mismatch strain. However, in optoelectric applications, strain alters the electronic bandgap and band edge alignment, and should be maintained. So, controlling formation of dislocations is very important in the manufacture of microelectronic and optoelectronic devices.

This term paper will review some basic concepts and try to produce some understanding about the control dislocation formation.

EM 397 Term Paper: Channeling crack of low-k dielectric films

Today low-k dielectric materials are integrated into computer chips to improve the operation speed and reduce the cross-talk noise. Due to weak mechanical properties of low-k dielectric materials, cohesive failure is subjected to occur. Channel cracking is one common mode of cohesive failure. In this term paper, several potential issues relevant to channel cracking of low-k dielectric thin films are reviewed.

Xuanhe Zhao's picture

ES 246 project: Planar Composite under Plastic Deformation

The mechanical performance of a homogeneous material can be varied by the addition of second-phase particles. In this project, we will model a planar composite under plastic deformation. As shown on the following figure, the composite consists of matrix material and randomly-distributed inclusion particles. The matrix is assumed to be an elastic-plastic material with isotropic or kinematic hardenings, and the inclusion particle pure elastic with a higher Young’s modulus. The stress/strain field throughout the composite will be calculated numerically with finite element method.

Semiflexible polymer chain under sustained tension as a model of cytoskeletal rheology

This is a model of a single semiflexible polymer chain under sustained tension. The model captures two key features of the cytoskeletal rheology: a) the power-law behavior; and b) the dependence of the power-law on mechanical prestress. The model also reveals the underlying mechanisms.

Haixia Mei's picture

EM 397 Term Paper: Effects of Substrate Compliance on Buckling Delamination of Thin Films under Compression

For films or coatings deposited on substrate at high temperature, residual compressive stresses are often induced in the surface layers because of the mismatch in the thermal expansion coefficients. Under such compressive residual stresses, the surface thin film is susceptible to buckling-driven delamination. Various shapes of buckled region are observed, including long straight-sided blisters, circular and the ‘telephone cord’ blister.

Nanshu Lu's picture

ES 246 project: Plane Strain Extrusion - Slip-line Field Solution vs. FEM Solution

Due to maturity of FEM package, slip-line field theory is not widely used these days. However, we shall keep in mind that slip-line field analysis can provide analytical solutions to a number of very difficult problem which may involve huge deformations or velocity discontinuities, e.g. many metal forming processes. To evaluate these two analytical and numerical methods for plasticity I will try a simple example, compare these two solutions and finally get into a conclusion of my own.

Alexander A. Spector's picture

Mechanics vs. Biochemistry in Adhesions-Cytoskeleton-Nucleus Signal Transduction in Cells

The essence of mechanobiology is, probably, the interrelation between mechanical and biochemical factors.  An exciting example of such phenomenon is signaling associated with the interaction between the cell and extracellular matrix (EM).  While some purely biochemical pathways initiated in the area of contact of the cell and EM are known, there are interesting ideas how the mechanical forces, stresses and strains can be involved too. This view goes back to works of Donald Ingber's group in the 90s that showed how perturbations of the adhesion area as a whole and of an individual integrin result in deformation of the cell nucleus. Interestingly, a distinguished oncologist at Johns Hopkins, Donald Coffey, published similar experimental results about the same time, and he also demonstrated that the observed cytoskeleton/nucleus interaction is different in tumor cells. There are several separate pieces of the puzzle that have been resolved: mechanical forces are generated at focal adhesions, the cytoskeleton is involved, nucleus deforms, gene expression changes as a result of perturbation of the adhesions, however, the whole picture of the interrelated mechanical and biochemical factors has yet to be understood. We recently published some results on this topic in the Journal of Biomechanical Engineering (Jean et al., 2004 and 2005). I was glad to find an interest in the same problem from some participants of this website (e.g., N. Wang, Z. Suo,   Long-distance propagation of forces in a cell, 2005 and P.R. LeDuc and R.M. Bellin, Nanoscale Intracellular Organization and Functional Architecture Mediating Cellular Behavior, 2006). This aspect of mechanotransduction is important for many areas beyond mechanics such as cancer, wound healing, cell adhesion and motility, effect of surface micro- and nanopatterning, etc.

In Quest of Virtual Tests for Structural Composites

Listed below is a recent publication of mine in Science for your possible interest and critics. This is a review article focusing on the multiscale simulation issues in strucutral composites. I will be more than happy to discuss with those of you who are interested. The following is the abstract.

The difficult challenge of simulating diffuse and complex fracture patterns in tough structural composites is at last beginning to yield to conceptual and computational advances in fracture modeling. Contributing successes include the refinement of cohesive models of fracture and the formulation of hybrid stress-strain and traction-displacement models that combine continuum (spatially averaged) and discrete damage representations in a single calculation. Emerging hierarchical formulations add the potential of tracing the damage mechanisms down through all scales to the atomic. As the models near the fidelity required for their use as virtual experiments, opportunities arise for reducing the number of costly tests needed to certify safety and extending the design space to include material configurations that are too complex to certify by purely empirical methods.

ssh -Y option with X11 on Macs

I've been a Mac person ever since they started basing their operating systems on what is essentially a Linux kernel.

One of the frustrating things, however, concerned the lack of OpenGL support. With the recent update to X11 by Apple, this is fixed. However, in order to use it remotely, from the X11 terminal, one has to use the option

%ssh -Y login_name@remotehost

as opposed to the previously used

%ssh -X login_name@remotehost

Teng Li's picture

Gecko, Spiderman and Climbing Robot (Video)

I am at Boston for MRS 2006 Fall meeting this week, where I met a real "spiderman" at the poster session tonight. I'd like to share with you the following videos which were posted at YouTube by the "spiderman" himself, Mr. Jose Berengueres at Tokyo Instititute of Technology.

Mr. "Spiderman" also has posted a video on fasting climbing robot.

Madhav Mani's picture

citation

I guess it's time that I cite some papers that are relevant to what I am looking at. A paper byL.Mahadevan et al.: Elements of draping
and another one
Confined elastic developable surfaces: cylinders, cones and the elastica,

Kristin M. Myers's picture

ES 246 Project: Large Deformation Plasticity of Amorphous Solids, with Application and Implementation into Abaqus

node/add/imageI propose to investigate an elastic-viscoplastic constitutive model proposed by Anand and Gurtin [1] for the large deformation of amorphous solids.  Specifically, I will present the constitutive framework proposed for elastic-plastic amorphous materials, I will implement the constitutive equations into Abaqus/Explicit, and I will compare numerical results with experimental results for polycarbonate [2]. 

 

Vlado A. Lubarda's picture

A Variable Core Model and the Peierls Stress for the Mixed Dislocation

A variable core model of a moving crystal dislocation is proposed and used to derive an expression for the Peierls stress. The dislocation width varies periodically as a dislocation moves through the lattice, which leads to an expression for the Peierls stress in terms of the difference of the total energies in the crystal corresponding to stable and unstable equilibrium configurations of the dislocation, rather than the difference in the misfit energies alone. Results for both edge and mixed dislocations are given and proposed to be used in conjunction with ab initio calculations.

Zhigang Suo's picture

Solid Mechanics Homework 43-46

43. Energy loss
44. Zener model and relaxation test
45. Zener model and cyclic-load test
46. Vibration of a viscoelastic rod

Return to the outline of the course.

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