Ajit R. Jadhav's blog

Can you define FEM in one line?

If yes, what would it be? And, in that case, permit me a second question: How?

...Really interested in knowing what the members of this community think (of this matter), if they do...

--Ajit

[E&OE]

1. Background:

A couple of things concerning books happened recently, in the last week or two.

(i) Dr. Biswajit Banerjee announced last week that a new book on metamaterials and waves in composites authored by him is coming out in print within a few months.

Here is an idea I submit for consideration by all iMechanicians, but esp. so by the admins and moderators. Discussion is welcome.

Idea: Why not have a Mechanics Gallery section here?

Origin: Recently, I was browsing for some OpenGL-encapsulating C++ class libraries, e.g. OpenSceneGraph, VTK, the game development libraries, etc. The Web sites of all such libraries always carry a "Gallery" page which is designed to attract the potential users. The Gallery page shows the capabilities and advantages of that library/framework.

Hi all, 

[Warning: The writing is long, as is usually the case with my posts :)]

It all began with a paper that I proposed for an upcoming conference in India. The extended abstract got accepted, of course, but my work is still in progress, and today I am not sure if I can meet the deadline. So, I may perhaps withdraw it, and then submit a longer version of it to a journal, later.

As a consultant in computational mechanics, I currently help write some FEM-related code, and while doing this job, an episode from a recent past came to my mind. Let me go right on to the technical issue, keeping aside the (not so good) particulars of that episode. (In case you are curious: it happened outside of my current job, during a job interview.)

If you are a design engineer, FE analyst, researcher, or any professional dealing with stress analysis in your work, I seek answers to a couple of questions from you:

Question 1:

A recent discussion at iMechanica following my last post here [^] leads to this post. The context of that discussion is assumed here.

I present here three sample problems, thought of almost at random, just to see how the suggestions made by Jaydeep in the above post work out.

To the best of my knowledge, the two momentum conservation principles, namely, the conservation of linear- and angular-momentum, operate completely independent of each other. For an isolated object, there is no possibility of conversion of one form of momentum to the other.

Summary:

I am thinking of informally conducting a specific case-study concerning the FEA solvers. The reference problem is a very simple but typical problem from stress analysis, leading of course to the linear systems: Ax = b and Ax = Lx.

I seek advice as to what software libraries currently available in the public domain would be best to use---the ones that would be fastest in terms of execution time for the reference problem.

I have a personal and longer-term research interest with certain issues related to the solvers technologies.

Since my research touches on the basics of QM, I have developed this habit of visiting arXiv.org every now and then. Last week or so, at arXiv.org, I found a couple of interesting articles on physics in general. I would like to share these with you.

I am pleased to inform you that I will be defending my Ph.D. thesis, formally in mechanical engineering, at COEP, University of Pune, India, on the next Sunday (i.e. 20th September, 2009).

The title of my thesis is: "A New Approach to Computer Modeling and Analysis of Certain Fundamental Field Problems from Engineering Sciences." 

Unlike other blog-posts of mine, I am not going "own" this particular thread. By that, I mean to say: I am going to only begin this thread and immediately turn it over to you completely. I am not going to watch over whether the discussion here continues to stick to its main theme or not, whether it slides into some minor side issues, whether it deserts the main theme altogether, etc., the way I usually do.

- - - - -

If someone knows of books/articles dealing with the meaning of the concept of potential in physics (or concerning the physical bases underlying the energy methods of mechanics) then I would very much appreciate getting to know about these.

0. I was idly thinking about the current H1N1 flue pandemic, and the following things occurred to me. Please note, I know very little about this subject matter. So, please consider descriptions in the following as, at best, tentative.

1. There is a basic difference between how alcohol kills viruses and how salt-water kills bacteria. [Alcohol is used in the hand-cleaners they use in hospitals. Girgling with salt-water is the first line of defense (and an unexpectedly highly effective one) which is well known for millenia.]

But the mechanisms involved are different.

(i) 3rd International Congress on Computational Mechanics and Simulation (ICCMS09) to be held this year at IIT Bombay, on December 1--5, 2009. Abstracts due by July 31, 2009:

http://www.civil.iitb.ac.in/help/114_iccms09/iccms09.html

(ii) 54th Congress of the Indian Society of Theoretical and Applied Mechanics (An International Meet), to be held this year at the Netaji Subhas Institute of Technology, New Delhi, during December 18--21, 2009. Abstracts due by September 30, 2009:

Ideally, this post of mine should carry a poll, but I guess as an ordinary user, I cannot insert one.

Currently, I am writing a small software program that is especially designed to help learn FEM. For instance, I will be providing detailed listings for every intermediate step, e.g. all those [D], [B], [k], etc. matrices for each element, as well as the final assembled global system {F} = [K]{d} and its solution separately at each Gauss point. Only linear static problems for the time being; will add transients/eigenvalue problems in near future.

The following is a (relatively minor) question which had occurred to me more than two decades ago. By now I have forgotten precisely when it was... It could have been when I was in my TE (third year engineering) at COEP. ... Or, perhaps, it was later on, when I as at IIT Madras (studying stress analysis on my own). ... I don't remember precisely when it occurred to me, only *how* it did---it was when I was poring over the first part of Dieter's book.

In the past few days at iMechanica, there have been quite a few messages dealing with different aspects of programming, libraries and so on...

It would perhaps be timely, therefore, to ask:

Do you have any opinion about using Java in numerical analysis (NA) / FEM / CFD etc.---i.e., in computational engineering and sciences (CES)?

Do you have any experience or hard data concerning performance of Java vis-a-vis C++ or FORTRAN, esp. for large systems, or for high-performance applications? Any pointers?

In the literature, FEM has sometimes been characterized as a local approach, but IMO this needs to be corrected.

The piecewise continuous trial-functions of FEM can be looked at from two different viewpoints:

It has been quite some time (more than 1.5 years) that I had touched upon the topic of the physical bases of FEM in general, and of the general weighted residual (WR) approach in particular, at iMechanica (see here).

The position I then took was that there is no known physical basis at all for the WR approach---despite its loving portrayals in mathematical terms, or its popularity.

Hello,

The 53rd Congress of the Indian Society of Theoretical and Applied Mechanics (an International Meet) is slated to be held during last week of December 2008, in Hyderabad, India. The last date for sending in both the abstracts and the full-length papers is 30th September, 2008.

People from outside India are especially encouraged to participate. Hyderabad is well connected by flights. Usually, the ISTAM conferences are low on budget but high on enthusiasm. The ISTAM conferences typically cover a broad range of topics.