Mike Ciavarella's blog

Webinar 1) Working experience in Bosch & Ferrari Formula 1 of a POLIBA graduate.   

Dear friends

Dear friends,        we have created the list  of Italian researchers in the top 2% of the Stanford ranking.http://tis-apulia.di.uniba.it/index.php/2020/12/26/ranking-stanford-ital...http://tis-apulia.di.uniba.it/index.php/2020/12/26/ranking-stanford-sing...regardsMC

Crack propagation at the interface between viscoelastic and elastic materials

M.Ciavarella, R.McMeeking

dear Colleagues

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

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

dear Collegues

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.

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.

A nice seminar, here.

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.  

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.

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.

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

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.