User login

You are here

blogs

Zhigang Suo's picture

Books, essays and websites that have influenced the development of iMechanica

In this blog entry, I'll maintain a list of books, essays and websites that have influenced me in developing iMechanica. I'll also list my notes on them whenever available. Because iMechanica shares many common problems with other online communities, it is natural that we find solutions discovered by other online communities helpful. At the same time, iMechanica is unique in some respects, and has its own unique problems, so that we cannot adopt any methods or viewpoints without adjustment.

atmaca's picture

Crack Propagation

Hi

I have an investigation on Crack Propagation.

How can i predict the path of a crack.

Please help me!

Mike Ciavarella's picture

Some notes on Luan and Robbin's papers on contact and adhesion at atomic scale

As I promised, I start with some brief notes on themes loved by Ken Johnson to hopefully raise some interest for discussion on iMechanica. Regards, Mike

L. Roy Xu's picture

Tensile strength and fracture toughness of nanocomposite materials

Are not as high as we expected although very stiff and strong nanotubes or nanofibers (Young’s modulus E~1000GPa) are added into soft polymer matrices like epoxy (E~4GPa).  In our early investigation on the  systematic mechanical property characterizations of nanocomposites (Xu et al., Journal of Composite Materials, 2004--among top 5 in 2005;and top 10 in 2006 of the Most-Frequently-Read Articles in Journal of Composite Materials.) have shown that there was a very small increase (sometimes even decrease) of critical ultimate tensile/bending strengths, and mode-I fracture toughnesses in spite of complete chemical treatments of the interfacial bonding area, and uniform dispersions of nanofibers (click to view a TEM image). Similar experimental results were often reported in recent years. Therefore, mechanics analysis is extremely valuable before we make these “expensive” nanocomposite materials. Our goal is to provide in-depth mechanics insight, and future directions for nanocomposite development. Till now, nanocomposite materials are promising as multi-functional materials, rather than structural materials. Here we mainly focus on two critical parameters for structural materials: tensile strength and fracture toughness. We notice that other mechanical parameters such as compressive strengths and Young’s moduli of nanocomposite materials have slight increase over their matrices.

Dean Eastbury's picture

2nd International Conference on Mechanics of Biomaterials & Tissues

In December 2007 Elsevier will organise the 2nd International Conference on Mechanics of Biomaterials & Tissues (www.icmobt.elsevier.com). The aim of the conference is to provide a forum for the discussion of the modeling and measurement of deformation and fracture behavior in biological materials and in those materials which are used to replace them in the human body.

Ashkan Vaziri's picture

"Persistence of a pinch in a pipe" by L. Mahadevan, Ashkan Vaziri and Moumita Das

The response of low-dimensional solid objects combines geometry and physics in unusual ways, exemplified in structures of great utility such as a thin-walled tube that is ubiquitous in nature and technology.

Interfacial toughness and mode mixity

When I was a graduate student, I spent several months to measure interfacial toughness between metalic (Cu and Au) films and thick substrates(Si and Polycarbonate). My methods were bulge test (blistering test) and 4-point bending test. I had many problems such as making an initial crack(pre-cracking), changing load phase angle applied to specimens, preparing/patterning thin films, constructing my own test apparatus, etc. The biggest problem was to measure the interfacial toughness over a wide range of loading phase angle. For a bimaterial with a non-zero oscillatory index(epsilon), we don't know the phase angle for a minimum interfacial toughness beforehand. Therefore, we need to measure the interfacial toughness over a wide range of phage angle. For engineering purpose, we need a minimum interfacial toughness value for reliability design because this value will lead to a conservative design of systems.

arindam.chakraborty's picture

A paper on developing stochastic micromechanical model for elastic properties of functionally graded material (FGM)

Given link is for a stochastic micromechanical model developed for predicting probabilistic characteristics of elastic mechanical properties of an isotropic functionally graded material (FGM) subject to statistical uncertainties in material properties of constituents and their respective volume fractions.

Robert Gracie's picture

2007 NSF Summer Institute on Nano Mechanics and Materials

Please find below the announcement for the NSF Summer Institute on Nano Mechanics and Materials:

Mogadalai Gururajan's picture

Some write-ups in mechanics

My googling today brought me to this treasure trove of write-ups in mechanics:

This site contains informal (usually rough draft) technical notes and tutorials on topics in mechanics. The sophistication is at the first or second year graduate level. These write-ups include:

Francisco T S Aragao's picture

Homework 1, problem 1 - Self description

        I'm Francisco Thiago S. Aragao. Please call me Thiago. I'm currently enrolled at the University of Nebraska at Lincoln Civil Enginering Master's Program under the advisory of Dr. Yong-Rak Kim. I have also a minor course in Engineering Mechanics. Below I'm answering the questions from the Problem 1 of Fracture Mechanics' Assignment 1.

Prior courses in solid mechanics:

Zhigang Suo's picture

Journal publishers are pioneers of Web 2.0

Eric Mockensturm has just posted a publication agreement proposed by provosts of several universities. In structuring iMechanica, we have tried to avoid the question of open access, and simply asked the question what if all papers are already openly accessible. Many mechanicians have discovered iMechanica, and the registered users have recently passed 1000. Recent discussions of copyright on iMechanica have prompted Eric to post his entry, which has just led to this one.

Is there a shear instability in metal foams?

Last year I spent three months modeling the compressive behavior of aluminum alloy foams. I had hoped to find some evidence of the banding instability that is often observed in elastomeric foams [1]. Lakes writes that this sort of banding instability provides indirect experimental evidence for negative shear modulus [2].

Deformation of Top-Down and Bottom-Up Silver Nanowires

I wanted to share some our work on the deformation behavior of metal nanowires that was recently published in Advanced Functional Materials. In this work, we considered the tensile deformation of three experimentally observed silver nanowire geometries, including five-fold twinned, pentagonal nanowires. The manuscript abstract and urls to videos of the tensile deformation of the three nanowire geometries are below. A copy of the manuscript is attached.

Mark Tschopp's picture

Tension-Compression Asymmetry in Homogeneous Dislocation Nucleation

Abstract. This letter addresses the dependence of homogeneous dislocation nucleation on the crystallographic orientation of pure copper under uniaxial tension and compression.  Molecular dynamics simulation results with an embedded-atom method potential show that the stress required for homogeneous dislocation nucleation is highly dependent on the crystallographic orientation and the uniaxial loading conditions; certain orientations require a higher stress in compression (e.g., <110> and <111>) and other orientations require a higher stress in tension (<100>).  Furthermore, the resolved shear stress in the slip direction is unable to completely capture the dependence of homogeneous dislocation nucleation on crystal orientation and uniaxial loading conditions.

Honghui Yu's picture

Integral Formulations for 2D Elasticity: 1. Anisotropic Materials

Might also be useful for simulating dislocation motion in a finite body.

Several sets of boundary integral equations for two dimensional elasticity are derived from Cauchy integral theorem.These equations reveal the relations between displacements and resultant forces, between displacements and tractions, and between the tangential derivatives of displacements and tractions on solid boundary.Special attention is given to the formulation that is based on tractions and the tangential derivatives of displacements on boundary, because its integral kernels have the weakest singularities.The formulation is further extended to include singular points, such as dislocations and line forces, in a finite body, so that the singular stress field can be directly obtained from solving the integral equations on the external boundary without involving the linear superposition technique often used in the literature. Body forces and thermal effect are subsequently included. The general framework of setting up a boundary value problem is discussed and continuity conditions at a non-singular corner are derived.  The general procedure in obtaining the elastic field around a circular hole is described, and the stress fields with first and second order singularities are obtained. Some other analytical solutions are also derived by using the formulation. 

rbatra's picture

Elastic Modulus of a Carbon Nanotube/Yacobson's Paradox

Myfeeling is that what we're trying to find are elastic constants of a continuum structure whose response in several (ideally all) deformations is the same as that of the carbon nanotube subjected to the same boundary conditions as the continuum structure.  We (A. Sears and R. C. Batra, Macroscopic Properties of Carbon Nanotubes from Molecular-Mechanics Simulations, Physical Reviews B, 69, 235406, 2004) have simulated simple tension and torsional deformations of a SWNT and its equivalent continuum structure defined as the one whose strain energy density is the same as that of the SWNT.  For an isotropic structure, the thickness of the equivalent structure was found to be~0.21 and it depends upon the MM potential used.  This has been validated by performing bending, buckling and combined loading tests on the SWNT and the equivalent continuum structure.

C.H. Wang, "Introduction to Fracture Mechanics"

Here is a link to a 1996 book by C.H. Wang on Fracture Mechanics from the DSTO Aeronautical and Maritime Research Laboratory in Melbourne.

http://www.dsto.defence.gov.au/publications/1880/DSTO-GD-0103.pdf

fengliu's picture

Modeling and Simulation of Strain-mediated Nanostructure Formation on Surface

In this chapter of "Hankbook of Theoretical and Computational Nanotechnology", I will provide an overview of the progress made in the last decade on theoretical modeling and computer simulation of strain-mediated formation of nanostructures on surface, focusing on strain-induced self-assembly and self-organization of two-dimensional (2D) patterns and structures. As part of a handbook, the main objective of the chapter is not to provide an extensive literature review on the topic. Instead, I will try to provide a general introduction and overview of the basic concepts and physical models along with some relatively detailed discussion of mathematical derivations and technical treatments so that readers (especially graduate students) who are interested in this topic can use this chapter as a guide and reference to start their own modeling and simulation.

6th International Conference on Mechanics of Time-Dependent Materials 2008, Monterey, CA, short/tentative abstracts due March 20

We invite you to submit an abstract for the 6th international conference on Mechanics of Time-Dependent Materials, to be held at the Portola Plaza Hotel, Monterey CA, March 30 - April 1, 2008. The conference is held in coordination with the journal of the same name. (Profs. Igor Emri and Wolfgang Knauss, editors-in-chief.)  The hotel overlooks beautiful Monterey Bay. The program will feature: several distinguished plenary speakers addressing a selection of the described topics; a day highlighting US and international governmental support with keynote by Dr.

Pages

Subscribe to RSS - blogs

Recent comments

More comments

Syndicate

Subscribe to Syndicate