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Biswajit Banerjee's blog

Fractal surface mesh generation

Saber El Arem (node/14053 ) wanted to know how a fractal surface mesh could be created.

I've had to do that in the past.  What I did was to use Arjun Viswanathan's 1999 Matlab snippet on creating a plasma fractal and write a wrapper around it to create an output file that could be read by the then available version of Abaqus.

I've attached a couple of Matlab files that should be able to do the job.   The .txt extensions are needed because iMechanica does not accept files with .m extensions.

ME/PhD Positions open: Fracture Simulation for Visual Effects

ME/PhD Positions open:   Fracture Simulation for Visual Effects

High speed simulations of the fracture of wood, glass, concrete, brick walls, and many other materials are used every day in the visual
effects industry. The project team will develop the next generation of fracture effects technology, bringing visual effects fracturing to the next level through novel computational methods in conjunction with realistic material models for deformation and fracture.

11th Global Congress on Manufacturing and Management GCMM 2012

Dear Colleagues

This is a gentle reminder that the final date for submission of abstracts to the

11th Global Congress on Manufacturing and Management GCMM 2012

has been extended to 31 March 2012.

You are cordially invited to submit a paper and be a part of this event.

Spring stiffness of a helical spring

Once in a while I have to find the stiffness of a spring that I get from the local hardware shop.  I usually use a formula that can be found in some books on mechanics of materials.

But the assumptions bother me a bit because the springs that I used usually underwent large deformations and I wasn't sure whether the numbers I was using were correct or not.  

To check the formula I compared its predicted k to numbers from Abaqus simulations and found reasonably good results for many situations - but not for soft springs.

Notes on thermoplasticity

I've recently had the opportunity to take another look at plasticity in the large deformation context.  I've avoided going into geometric and other issues involved with multiplicative deformations (points stressed in earlier blog posts by Giovanni (node/11545), Arash (node/11623)  and Xiabo (node/11599).  Attached are some old notes that I'd prepared some years ago to help me with the details.  I hope they're of use to other students of mechanics.

-- Biswajit

A comparison of Ansys Shell181 and Solsh190 elements

Please find attached a report on a comparison between ANSYS SHELL181 and SOLSH190 elements with particular emphasis on applicability to linear elastic sandwich panels.

Title: Comparison of Ansys elements Shell181 and Solsh190


New computational mechanics page

Prof. Rebecca Brannon and her team have created a wonderful page containing interesting information on aspects of plasticity, damage, and computational mechanics (particularly, the Material Point Method).

Check it out at

-- Biswajit

Nicolae Nicorovici 1944-2010



VALE Nicolae Nicorovici 1944-2010

11 February 2011

On proposals

Every year I try to get funding for things that I'm personally interested in but which may not have any immediate economic benefits.  A couple of years ago, after reading Penrose's "Road to Reality", I thought about applying Clifford algebra ideas to fracture mechanics and wrote up a proposal to that effect.  The proposal wasn't funded, but I think the idea is worth exploring.

The summary of the proposal was

From the literature

Naturally negative bulk modulus material.


Negative Linear Compressibility and Massive Anisotropic Thermal Expansion in Methanol Monohydrate

An introduction to metamaterials and waves in composites

My book on metamaterials, "An introduction to metamaterials and waves in composites" has been published on June 16, 2011 by CRC Press (Taylor and Francis).

The book is meant for students, researchers, engineers, and educators who want to get a basic grounding on the theory that is the basis of recent excitement about negative materials, cloaking, transformation optics/acoustics and other wave phenomena in composites.

Reliability and engineering mechanics

The word "failure" can mean different things to different people.  Over the past couple of years, my interactions with various groups from industry has shown me that for some people failure means catastropic fracture/buckling while for others it can mean highly localized plastic yielding.  Even for relatively simple sandwich composite structures, there is no clearly agreed upon definition of the word.

What do we do?

Yesterday, as I was waiting for the rain to stop before I could walk home from work, a stranger accosted me in the lobby of the building.  He asked me what I did, to which I replied "Mechanics".  He mulled over the answer for a bit and asked me to be more specific, at which point I said that we were trying to design materials that could guide waves around objects.  He said "Water waves?".  I replied "All types of waves."  Clearly, common words can mean quite different things to different people.

Two PhD positions available at the University of Auckland, NZ

There are a couple of funded PhD positions available at the University of Auckland, New Zealand.


The topics are, roughly, 

1) Advanced material models and variability

2) Biomimetic sensing and adhesion.


The deadline for applications is Friday, October 29, 2010.  Please send a current CV, a statement of purpose, and transcripts/grades from your undergraduate work (and master's work if you have a master's degree in a related field).


A comments wordle

I was hoping to see Abaqus or Ansys as the top words. Instead I see help, thanks, stress and incident.

Understanding continuity

Worth reading

in case you need to explain the epsilon-delta  definition of continuity to an engineering student.

-- Biswajit 

Deformation gradients and atomistic simulations

I came upon a recent paper called "Deformation gradients for continuum mechanical analysis of atomistic simulations" by Jonathan A. Zimmerman , Douglas J. Bammann,  and Huajian Gao, International Journal of Solids and Structures 46 (2009) 238–253 where the authors conclude with

A new idea and a not so new one

Two new papers grabbed my attention on my long unread list of journal tables of contents in Google Reader. 

1) The first was

Ideomechanics of transitory and dissipative systems associated with length, velocity, mass and energy
by G.C. Sih

where it is stated that

" One of the rules of the development of IDM is that the “flow of nature” takes precedent when deducting and/or constructing quantitative results. It is hoped that

USNCTAM Address 2009

Check out the talk by Dr. Arden L. Bement, Jr., Director , National Science Foundation 
on TAM 


For the proceedings of the 2008 SBE&S workshop go to


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