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Ciavarella-McMeeking. Crack propagation at the interface between viscoelastic and elastic materials

Crack propagation at the interface between viscoelastic and elastic materials

M.Ciavarella, R.McMeeking

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A Griffith theory for fatigue from Delft group?

I came across an interesting theory for fatigue crack propagation from collegues in Delft, I think the group of prof Benedictus, but I have mixed feelings about it, because while there seems to be something very interesting experimentally, there seems to be some confusion between concepts of energy balance like Griffith seminal theory of fracture (which do not apply in fatigue) and Paris type of law, which are only weak forms of power law scalings which depend on all dimensionless parameters of the problem, so that C and m in Paris are not material constants, and there is no energy balance

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On the Afferrante-Carbone theory of ultratough peeling

I attach a preprint of a note on the elegant and interesting and simple theory by Afferrante and Carbone on ultratough peeling of an elastic tape from a viscoelastic substrate.   Any comment is most welcome.   Regards, MC

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In the 100 000 top scientists there is decline of USA, and a jump of China and India

Not everyone has noticed, also from our previous studies including a letter to Nature,  that in the list of 100 000 most cited scientists by Ioannides et al. recently published in PLOS Biology, comparing the career database (1996-2017) with that of 2017, composed of around 2% of Italians, all the states we analysed except for Italy and China and India have suffered a decline in the number of researchers present in the 2017 data set compared to even substantial career data (Japan –20% nationally ).

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Analytical Models for Fatigue Life Prediction of Metals in the Stress-Life Approach -- phd thesis by Pietro D’Antuono

dear collegues

  I'd be very grateful if you could have a look, if not a deep reading, at the phd thesis of my last student, playing on classical results on uniaxial fatigue, but with a view of simple, unified perspective on constant and varying amplitude fatigue.  We made large use of e-fatigue.com web site and the data in there.
 Thanks in advance for any remark.  The final thesis will be submitted in few weeks time.

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electroadhesion of rough surfaces, with application to touch screen technology

Just submitted a paper on electroadhesion of rough surfaces, greatly simplifying the recent theory of the great Bo Persson , with hot application to touch screens :  see here

Comments welcome.

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The false myth of the rise in Italian self-citations, and the impressively positive effect of bibliometric evaluations on the increase of the impact of Italian research

Title: The false myth of the rise in self-citations, and the impressively positive effect of bibliometric evaluations on the increase of the impact of Italian research

Authors: Pietro D'Antuono and Michele Ciavarella

Categories: physics.soc-ph math.ST stat.TH   Comments: 20 pages, 8 figures, 10 tables, in English and inItalian  License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/

 https://arxiv.org/abs/1910.02948

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Mean stress effect on Gaßner curves interpreted as shifted Wöhler curves

A criterion for the mean stress effect correction in the shift factor approach for variable amplitude life prediction is presented for both smooth and notched specimens. The criterion is applied to the simple idea proposed by the authors in a previous note that Gaßner curves can be interpreted as shifted Wöhler curves. The mean stress correction used has been proposed by Smith, Watson and Topper and, more in general, by Walker.

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On the top 100 000 scientists in the world / the most authoritative and impressive ranking available today

See this impressive ranking of the top 100 000 scientists in the world.

 

Somebody told me about it as I appear as the best of my University, Politecnico di Bari in Italy.

https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.30...

 

 

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Nick Spencer ETH wins 2018 tribology gold medal

My sincere congatulations to prof Nick Spencer for a well deserved achievement.   A lifelong dedication to many important problems of tribology, the creation of a world class lab, and editing of an important journal (Trib Lett) are just a few of many achievements of Nick.    see here.  

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Universal features in "stickiness" criteria for soft adhesion with rough surfaces

A very interesting recent paper by Dalvi et al. has demonstrated convincingly with adhesion experiments of a soft material with a hard rough material that the simple energy idea of Persson and Tosatti works reasonably well, namely the reduction in apparent work of adhesion is equal to the energy required to achieve conformal contact. We demonstrate here that, in terms of a stickiness criterion, this is extremely close to a criterion we derive from BAM (Bearing Area Model) of Ciavarella, and not very far from that of Violano et al.

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A comment on "A dimensionless measure for adhesion and effects of the range of adhesion in contacts of nominally flat surfaces" by M. H. Muser

I attach a Letter I sent to the Editor of a tribology journal, concerning adhesion of rough surfaces. 

I contend that some "criteria" that have been proposed based on extrapolation of numerical results are due to the limitations in present numerical sophisticated rough contact simulations, which only span at most 3 orders of magnitude of wavelengths, so typically people simulate from nanometer to micrometer scale.

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review paper: The role of adhesion in contact mechanics

Journal of The Royal Society Interface 16(151), February 2019.    DOI: 10.1098/rsif.2018.0738

Michele Ciavarella Junki Joe Junki Joe Antonio Papangelo James Richard Barber

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Is Tribology Approaching Its Golden Age? Grand Challenges in Engineering Education and Tribological Research

An interesting paper by VL Popov which suggests many problems of tribology are still very far from being remotely solved.  Despite the very detailed theories for example on rough contact using fractal surfaces on which we have debated mainly academically , there is not a single theory for any quantitative prediction of friction coefficient which can vary by 1 order of magnitude and its dependence on many variables, let alone wear coefficient which can vary up to 7 orders of magnitude.  What is left to do, other than measure?   Is tribology bound to be in practice just an experimental area? 

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On stickiness criteria for multiscale random rough contacts

We have just submitted a paper which solves a problem that I have been struggling to solve for many years.

Any comments are welcome to improve, while the paper goes the standard review process in the journal we submitted it.

 

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