Mike Ciavarella's blog
2 post doc positions in Italy --- Regulating adhesion using viscoelastic oscillating contact --- some solutions
We are hiring 2 post-docs soon in Italy at the Department of Mechanics DMMM of the Politecnico di BARI. The subject is here described.
classical rate-independent models for viscoelastic fracture do not work!
It is 50 years that people use models of viscoelastic fracture which assume the fracture energy in the process zone is independent on the crack speed. This has been assumed in the cohesive models by Knauss and Schapery and then by the dissipation theory of de gennes and Persson-Brener. Researchers like to use this model because it is simple. Unfortunately, it does not work, as we show in adhesion experiments in the recent JMPS paper attached. We obtain nice results for a broad band power law material, but these results only work at very low speeds.
The Fiorillo index -- a new index to attempt to spot citation gaming
An index has been proposed by Fiorillo (document attached).
On productivity, big multicenter grants, and paper-mills: the pursuit of an academic career leads to scientific progress?.
We are in the time where big multi-centre projects with an ever-increasing number of scientists involved seem to multiply, and single scientist projects seem to die, apart from the happy island of ERC funding in Europe (probably NSF career funding in US?). I believe that with ERC funding and the direct call of ERC winners some European universities have taken a path of excellence to follow, while on multicentre big money projects they are less effective.
can we stop cracks due to elastic modulus changes ahead of crack tips?
Dear Colleague
It is known that ahead of a crack subject to static or fatigue loading microcracking and damage makes the material soften (of smaller elastic modulus) but also its strength degrades (in composite materials, there are so called “wearout models” which associate strength reduction exactly to the reduction of modulus).
hyper and probably over-prolific scientific authors (Nature article)
dear friends
Nature reported in Dec.2023 that up to four times more researchers pump out more than 60 papers a year than less than a decade ago. Saudi Arabia and Thailand saw the sharpest uptick in the number of such scientists over the past few years, according to a preprint posted on bioRxiv on 24 November.
Cancelling the effect of sharp notches or cracks with graded elastic modulus materials
Dear colleague
Friction for a sliding adhesive viscoelastic cylinder: Effect of Maugis parameter
Prediction of friction is one of the nigthmares of tribologists! For elastomers, friction may be due to shear stresses or to dissipation and adhesion hysteresis. Here we consider the two effects in rolling/ sliding a viscoelastic cylinder. We find that at low speeds the numerical bem results confirm Persson/Brener theory for crack propagation at large Tabor parameter.