Dear Yavari

I have promised more replies on Mandelbrot, fractals, strongly emotive discussions in journals, and here is a coincise statement, which I take from a Nobel prize, prematurely passed away last year.  I think it has a lot to teach (including the kind of attitude that leads to Nobel prize, i.e. close to no human weakness), you will recognize the real name of the "Caesar" in this book is somebody with a 58 pages CV on his web site, most likely.

For a better idea of fractals, read please the other attachment.

Regards

Mike

Arash, I am quite shocked by your reply http://imechanica.org/node/3045#comment-7151.  First you say "with all the due respect", then you say "trivial history".  But you prudently say "maybe I miss the point".  Maybe useful to clarify, also because probably iMechanica should start a discussion about history of mechanics starting a little earlier than this century. How can we judge Leonardo da Vinci? He has no published papers, no citation, no index, no Nobel prize... Not even a Timoshenko medal!  Maybe we should give him one post-mortem?    Please see the attachment.  Watch also the videos:

I think it would be useful to collect a list of most useful sites, to start with iMechanica-look-alike.  Not exactly similar but a good site for CFD is http://www.cfd-online.com/.  This incidentally suggests us some "ways" to improve iMechanica.  (see my other blog PROPOSAL for iMechanica http://imechanica.org/node/2996)

dear iMechanica friends

I came across a review of a paper by HD Bui who was somewhere in the internet, and I find it is very interesting. I could even have written this review myself !!  I don't think the reviewer exaggerates....

michele

You may remember that I promised some time ago to discuss each of the topics mentioned by Ken Johnson in his Timoshenko Medal speach. Here I take rail corrugation. Rail corrugation has been noticed at least for 100 years, but (particularly short pitch one in the range 20÷80 mm) has been considered an enigma because measured corrugation wavelength did not relate well with wear instabilitymodels.

Hello imechanica users: I launch a few ideas. Can we improve imechanica stealing ideas from successful web systems like google, amazon, wikipedia, myspace, youtube? Taking the best of the various worlds to improve our imechanica?

Recent experiments in sliding friction are a major embarassment for all present understanding of friction using Coulomb or Rice-Ruina-Dieterich-Prakash rate-state dependent theories, which are the subject of large research programs. In particular, Rubinstein et al; (Detachment fronts and the onset of dynamic friction. Nature 430, 1005—1009. 2004) suggest that the contact area is not significantly altered by the fast fronts which perhaps are only precursors to the most important "slow fronts" travelling at speeds about 1/10 of the Rayleigh speed.

dear Imechanica users,

a wonderful location for our annual italian conference in stress analysis -- see www.aias2007.it. 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.

I am trying to find out the theoretical adhesive strength limit of a few materials, or more precisely the ratio adhesive strength limit to elastic modulus. I think this is after all part of the Lennard-Jones constants potential - theoretical adhesive strength limit is simply the maximum of the curve.

A recent string of papers originated from Persson's paper in the physics literature contain a number of interesting new ideas, but compare, of the many theories for randomly rough surfaces, only Persson's and Bush et al, BGT. These papers often assume the original Greenwood and Williamson (GW) theory [1] to be inaccurate, but unfortunately do not test it, assuming BGT to be its better version. The original GW however is, I will show below, still the best paper and method today (not surprisingly, as not many papers have the level of 1300 citations), containing generally less assumptions than any other model, including the constitutive equation which does not need to be elastic! I just submitted this Letter to the Editor: On "Contact mechanics of real vs. randomly rough surfaces: A Green's function molecular dynamics study" by C. Campaña and M. H. Müser, EPL, 77 (2007) 38005. C. Campaña and M. H. Müser also make several questionable statements, including a dubious interpretation of their own results, and do not even cite the original GW paper; hence, we find useful to make some comments.

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

Anders Klarbring, Jim Barber and I are preparing a paper on the subject of shakedown in elastic contact problems with Coulomb friction. In particular, we establish the (rather limited) conditions under which a frictional equivalent of Melan's theorem can be applied, and we counterprove the theorem in all other cases.There is no plasticity here - the contacting bodies are linear elastic - but the analogies between the Coulomb friction law and elastic plastic deformation make us think the plasticity community might be interested in the results.