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Alexander A. Spector's picture


Recently I received a message from the Cambridge University Press regarding a coming text on biomechanics entitled Introductory Biomechanics, From Cells to Organisms. by C. Ross Ethier and Craig A. Simmonds. I ordered an exam copy, went through, and found it very interesting. It covers cellular biomechanics, hemodynamics, circulatory system, ocular biomechanics, muscles and movement, and skeletal biomechanics. Each section has a significant number of problems. I examined closely the part on cellular biomechanics which is one of the main areas of my research and teaching interests, and enjoyed reading it. The cellular mechanics is presented in its interrelation to cell structure and biology (there are nice images of cells and their components to use for teaching). The main techniques of probing the cell, such as micropipette aspiration, AFM, optical tweezers, and magnetic cytometry, are considered. Models of the cytoskeleton (tensergity, foams) are also introduced. The math is limited to linear equations, one-dimensional or axisymmetric problems, but it seems appropriate for the introductory level. In addition, some results of computational (finite element) modeling are also included. I certainly expect that this textbook will be quite useful in my teaching. The web site has more details on the book.

Nanshu Lu's picture

Delamination of stiff islands patterned on stretchable substrates

As another celebration of March Journal Club of Mechanics of Flexible Electronics, this paper has just been submitted.


In one design of flexible electronics, thin-film islands of a stiff material are fabricated on a polymeric substrate, and functional materials are grown on these islands. When the substrate is stretched, the deformation is mainly accommodated by the substrate, and the islands and functional materials experience relatively small strains. Experiments have shown that, however, for a given amount of stretch, the islands exceeding a certain size may delaminate from the substrate. We calculate the energy release rate using a combination of finite element method and complex variable method. Our results show that the energy release rate diminishes as the island size or substrate stiffness decreases. Consequently, the critical island size is large when the substrate is compliant. We also obtain an analytical expression for the energy release rate of debonding islands from a very compliant substrate.

Mogadalai Gururajan's picture

Elastic stress driven phase inversion

A typical two phase microstructure consists of a topologically continuous `matrix' phase in which islands of `precipitate' phase are embedded. Usually, the matrix phase is also the majority phase in terms of volume fraction. However, sometimes this relationship between the volume fraction and topology is reversed, and this reversal is known as phase inversion. Such a phase inversion can be driven by an elastic moduli mismatch in two-phase solid systems. In this paper (submitted to Philosophical magazine), we show phase inversion, and the effect of the elastic moduli mismatch and elastic anisotropy on such inversion.

Mogadalai Gururajan's picture

Elastic stress driven rafting

During solid-solid phase transformations elastic stresses arise due to a difference in lattice parameters between the constituent phases. These stresses have a strong influence on the resultant microstructure and its evolution; more specifically, if there be externally applied stresses, the interaction between the applied and the transformation stresses can lead to rafting.

A spectral decomposition problem

Choose a channel featured in the header of iMechanica: 

This post is both a question and a test how well Latex2HTML performs. The algebra might be useful for students who are starting off in the field. Please go through the details and comment on the question at the end of the post.

verron's picture

Definition of a new predictor for multiaxial fatigue crack nucleation in rubber

From an engineering point of view, prediction of fatigue crack nucleation in automotive rubber parts is an essential prerequisite for the design of new components. We have derived a new predictor for fatigue crack nucleation in rubber. It is motivated by microscopic mechanisms induced by fatigue and developed in the framework of Configurational Mechanics. As the occurrence of macroscopic fatigue cracks is the consequence of the growth of pre-existing microscopic defects, the energy release rate of these flaws need to be quantified. It is shown that this microstructural evolution is governed by the smallest eigenvalue of the configurational (Eshelby) stress tensor. Indeed, this quantity appears to be a relevant multiaxial fatigue predictor under proportional loading conditions. Then, its generalization to non-proportional multiaxial fatigue problems is derived. Results show that the present predictor, which covers the previously published predictors, is capable to unify multiaxial fatigue data.

On the crack growth resistance of shape memory alloys

With the increasing use of shape memory alloys in recent years, it is important to investigate the effect of cracks. Theoretically, the stress field near the crack tip is unbounded. Hence, a stress-induced transformation occurs, and the martensite phase is expected to appear in the neighborhood of the crack tip, from the very first loading step. In that case, the crack tip region is not governed by the far field stress, but rather by the crack tip stress field. This behavior implies transformation toughening or softening.

Arash_Yavari's picture

On the geometric character of stress in continuum mechanics

This paper shows that the stress field in the classical theory of continuum mechanics
may be taken to be a covector-valued differential two-form. The balance laws and other funda-
mental laws of continuum mechanics may be neatly rewritten in terms of this geometric stress. A

Andrew Norris's picture

Free access to Computational Mechanics back to Vol 1 - but only 'til end of month.

Springer - in an attempt to get customers I suppose - are offering free access to the journal Computational Mechanics, but only for March 2007.

You can access all articles in Computational Mechanics back to vol 1/1, e.g. the first article

E. Reissner
Some aspects of the variational principles problem in elasticity
Volume 1, Issue - 1, First Page - 3, Last Page - 9
DOI - 10.1007/BF00298634
Link -

To get the free access (for the rest of March) go to

Rashid K. Abu Al-Rub's picture

Dr. Stelios Kyriakides’ election to the United States National Academy of Engineering

Dr. Stelios KyriakidesPlease joint me in congratulating Dr. Stelios Kyriakides’ (Editor of International Journal of Solids and Structures) for his election to the United States National Academy of Engineering.

zishun liu's picture

Computational Cancer Mechanics

Since Dec. 2006, Institute of High Performance Computing (IHPC) has set up a biophysics research team that comprises research scientists in the fields of biophysics, solid mechanics and fluid mechanics, and has kicked off the "Computational Cancer Mechanics" project.

What's wrong with the way we learn Applied Mechanics?

I was reading professor Zhigang Suo's post titled "What's Wrong with Applied Mechanics", thinking about the large amount of knowledge available. There are so many applications of mechanics that they seem endless in any subfield that one can think of. It made me recall some homework problems that wanted to include real life applications. However, real life applications tend to turn out much more complicated than what can be covered in one homework problem.

Zhigang Suo's picture

How to read new comments at a glance?

As the number of comments increases rapidly, how can anyone keep up? One answer is to use a RSS reader. The service is free, and takes 5 minutes to set up. It allows you to see all new comments at a glance, without clicking on individual ones. Once you have set up your Google Reader, paste the URL for the feed of comments crss

Ravi-Chandar's picture

Movie of an expanding ring experiment

I have posted a movie showing a ring expansion experiment. A thin aluminum ring is made to expand through electromagnetic interaction at strain rates of about 10^4 per second. As the strain increases, numerous necks and fragments appear.

Mahdi Kazemzadeh's picture

"iMechanica",Promotes the "Education"??

Choose a channel featured in the header of iMechanica: 

Let's contribute in a bit more educational topic!! If I want to mention two unique properties of the iMechanica, I can say iMechanica is a place where an alive discussion about popular topics of the mechanics going on every day and non stop. So this improves new ideas and as a consequence build some platforms for future research topics in the mechanics world. For me as an student, there is another beneficial and that is some courseworks or lecture notes which I download regularly. These handouts prepared by very expert scientists and are so useful. I appreciate this activities and I am very grateful to all people who also update the educational part of the webpage. Here is a new topic which with your help and comments can improve this part more and give it serious role to play here. Would you write about the summer schools which you are going to have in your universities and institutes located all over the world this summer? The summer schools is a point of interest among all students, specially if the topic will be about mechanics, modelling and simulation, nanomechanics and specially biomechanical issues. Also I will be very pleased if you will recommend the conferences you are going to hold or you like to introduce to student's section. That is another point which will be very useful. I am sure that it will be interesting for other members also. I am waiting for all your helps and news about "summer schools" and other "educational activities" running by you or your universities. I wish you all the best. Thank you.   

Chwee Teck Lim's picture

GEM4 Summer School on Cell & Molecular Mechanics in Biomedicine 2007, Singapore - 25 June to 6 July 2007

Dear friends and colleagues,

We will be organizing a GEM4 Summer School on Cell & Molecular Mechanics in Biomedicine (with a focus on Cancer) at the National University of Singapore from 25 June to 6 July 2007. It will also be held in conjunction with the GEM4 Conference on Cancer to be held from 1 to 6 July 2007.

Mike Ciavarella's picture

Italian stress analysis AIAS conference in Ischia --- call for papers Sept.

dear Imechanica users,

a wonderful location for our annual italian conference in stress analysis -- see It is organized by our collegues in Università di Napoli, Prof. Renato Esposito. Attached the call for papers in PDF, and more info are below.

Floating ships of ice and increasing the toughness of glass

I was surprised several years ago when delving into the literature to not find any references about addition of nanoparticles to ice, to study their impact on the mechanics of ice.  In short, to make nanocomposites where the matrix is ice.  So, with 2 high school students from IMSA, the Illinois Math and Science Academy, we set about (with their limited time for a bit of research) to try adding some nanoparticles to water and to freeze it.  The students simply used their home freezers to do this, and their mechanics measurements were with a hammer and chisel...

Simpleware signs up reseller in China

Simpleware Ltd., the world leader in image-based meshing software, has signed an agreement with Gaitech International Ltd. to resell the Simpleware suite of software products in China, Hong Kong, Taiwan and Macao.

Simpleware software offers an advanced solution to problems that were previously intractable due to the complexity in geometry reconstruction. Simpleware's technology has opened up numerical analysis (CFD and FEA) to a variety of applications, including biomedical engineering, material characterisation and industrial reverse engineering.

jfmolinari's picture

A new methodology for ranking scientific institutions


We extend the pioneering work of J.E. Hirsch, the inventor of the h-index, by proposing a simple and seemingly robust approach for comparing the scientific productivity and visibility of institutions. Our main findings are that i) while the h-index is a sensible criterion for comparing scientists within a given field, it does not directly extend to rank institutions of disparate sizes and journals, ii) however, the h-index, which always increases with paper population, has an universal growth rate for large numbers of papers; iii) thus the h-index of a large population of papers can be decomposed into the product of an impact index and a factor depending on the population size, iv) as a complement to the h-index, this new impact index provides an interesting way to compare the scientific production of institutions (universities, laboratories or journals).

Zhigang Wei's picture

Any suggestion for a fast sparse solver

It seems that a customized FEM code is always necessary for special research purposes. In our group we use a home-made FEM code to simulate arbitrary crack growth in 3D domain with nodal release or re-meshing.


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