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A comparison of Gent-Schultz law with cohesive models of viscoelastic subcritical crack propagation

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

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Viscoelastic cracks: a discrepancy of factor 2.42 found with respect to Wang, Lu, Barber and Thouless and Schapery classical solution

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.

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Comparison between theories on viscoelastic cracks -- a modest note finds problems in the theory of deGennes and Persson

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.  

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Improved Muller approximate solution of the pull-off of a sphere from a viscoelastic substrate

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.

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world first ONLINE webinar of Ferrari Formula 1 Head of Stress unit - Politecnico di BARI

Monday 15 February 16.30 (Rome time) 

Webinar EXPERIENCES STRUCTURAL CALCULATION IN FERRARI F1 Eng. Matteo Parliament, Head Stress Unit, Ferrari Formula 1 racing team

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online petition for basic research funding in Italy

dear Imechanica friend

  maybe you want to sign the petition I launched, together with many top scientists and president of the italian evaluation agency and former rector of University of Bari, and other former rectors, to the italian president Mattarella and prime Minister Draghi , which you find here. You can see there is also an english translation.

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on the "strange" theory of ultratough peeling by Afferrante & Carbone

dear collegue   please comment on our recent paper on the "strange" theory of Afferrante and Carbone, paper not yet accepted so your comments are welcome https://www.researchgate.net/pub

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2 Webinar of Politecnico di BARI graduates who are working in FORMULA 1 --- FERRARI and BREMBO

 

 

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

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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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