Mike Ciavarella's blog

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 PREPRINT of a paper on the Menga, Carbone & Dini paradox (published in JMPS last year, available at https://arxiv.org/pdf/1710.06506.pdf), that is on the application of thermodynamics to mixed mode fracture mechanics models of contacts with friction and adhesion, and an apparent paradox which emerges from this treatment.  Comments welcome.   

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.

For infos about projects in contact mechanics, friction, wear, thermoelastic instabilities (for some ideas https://www.researchgate.net/profile/Michele_Ciavarella2), please contact me at mciava@poliba.it

Deadline for application Sept.6, 2019.

Details on admission at:

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.

In 2007 I wrote a question in Imechanica, IS THERE NO PULL-OFF FOR ADHESIVE FRACTAL SURFACES?

Clearly, in 2007 this question was too hard to answer.  I pointed there that Fuller and Tabor 1975 asperity theory predicted a weird limit for a true fractal surface, that of no stickiness for any fractal dimension or amplitude, in the limit.

I am pleased to suggest a very interesting new book from prof JR Barber of UMich, a leading scientist in the field of contact mechanics.

Knowing the strength of adhesion

26.02.2018 tribonet Computational Tribology 80 Views

See a national broadcast on Politecnico di BARI and the region Puglia, with its successes, including the worldwide success of Diesel common rail technology, the GE centre on Addittive Manufacturing and Cold Spray, and others.

Tribology International

Available online 12 February 2018

In Press, Accepted Manuscript — Note to users

See online App for rough contact adhesion based on the BAM model of Ciavarella

http://www.tribonet.org/adhesion-calculator-for-rough-surfaces-bearing-a...

On the distribution and scatter of fatigue lives obtained by integration of crack growth curves: does initial crack size distribution matter?