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Mike Ciavarella's blog

are there platforms similar to iMechanica? should we list them all?

Submitted by Mike Ciavarella on

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 node/2996)

a review of a paper by HD Bui found in the internet !!

Submitted by Mike Ciavarella on

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

Rail corrugation: ”one hundred years of solitude”? or a true enigma?

Submitted by Mike Ciavarella on

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.

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

Submitted by Mike Ciavarella on

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.

Does anyone know a collection of Lennard Jones potential material constants??

Submitted by Mike Ciavarella on

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.

Contact mechanics of rough surfaces: is Persson's theory better than Greenwood & Willamson?

Submitted by Mike Ciavarella on

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.