Mike Ciavarella's blog

dear colleagues     I have written some general comments about viscoelastic models which may you find useful, mixing results from Wang Thouless Barber vs Schapery vs de Gennes Persson, etc. I conclude that Gent-Schultz is the most practical and solid approach, despite it seems empirical and too simple.  It corresponds very closely to work with Schapery model, and the finite size effects in Persson's theory are quite suspicious if not completely wrong (besides, there are two Persson's theory, one in contradiction to the other), as demonstrated by theory and actual Finite Element simulations

Wang, Lu, Barber, & Thouless (WLBT, 2016) have written recently an interesting paper on the crack growth in visco-elastic and creeping materials, using a simple Maxwell "liquid" material, and the Double Cantilever Beam (DCB) model under pure moment. Using correspondence principle, they obtained an analytical solution for a viscoelastic beam on an elastic foundation, corresponding to a simple linear force-separation law for the cohesive law.

dear Colleagues

  Please find enclosed a short and modest note on comparisons between the precise cohesive model of Schapery for viscoelastic cracks, with the rather crude model of de Gennes and then Persson and Brener, which is found to lead to errors possibly of an order of magnitude of propagation speed for a given applied load.   Since this is a preprint, any comment is welcome.  

dear colleague 

Hello The next Beard Tribology Webinar is Tuesday, March 2nd at 1pm US Central Time. Dr. Ali Erdemir will present about “Vanishing Friction: How Close are We?”

M. Ciavarella (2021) Improved Muller approximate solution of the pull-off of a sphere from a viscoelastic substrate, Journal of Adhesion Science and Technology, DOI: 10.1080/01694243.2021.1882766

See also in attach the PDF.

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.