Antonio Papangelo's blog

Usually, roughness destroys adhesion and this is one of the reasons why the "adhesion paradox", i.e. a "sticky Universe", is not real. However, at least with some special type of roughness, there is even the case of adhesion enhancement, as it was shown clearly by Guduru, who considered the contact between a sphere and a wavy axisymmetric single scale roughness, in the limit of short-range adhesion (JKR limit).

The interaction between contact area and frictional forces in adhesive soft contacts is receiving much attention in the scientific community due to its implications in many areas of engineering such as surface haptics and bioin-spired adhesives. In this work, we consider a soft adhesive sphere that is pressed against a rigid substrate and is sheared by a tangential force where the loads are transferred to the sphere through a normal and a tangential spring, representing the loading apparatus stiffness.

Dear Colleagues,

In the last twenty years, tribology and nonlinear dynamics have included several major contributions related to key topics such as rough contact, friction, damping mechanisms, and dynamical behaviour of nonlinear systems, which are paving the way for future engineering challenges. The two fields are largely intertwined as, among the others, contact nonlinearities are almost omnipresent in any technical application ranging from the development of NEMS/MEMS to bioengineering, automotive, civil/mechanical industry, and aerospace.

Self-excited vibrations represent a big concern in engineering, particularly in automotive, railway and aeronautic industry. Many lumped models have been proposed over the years to analyze the stability of such systems. Among the instability mechanisms a falling characteristic of the friction law and mode coupling have been shown to give friction-excited oscillations. The mass-on-moving-belt system has been studied extensively in Literature, very often adopting a prescribed form of the friction law and linearizing the contact stiffness.

The eigenfunction method pioneered by Galin (J Appl Math Mech 40: 981–986, 1976) is extended to provide a general solution to the transient evolution of contact pressure and wear of two sliding elastic half-planes, under the assumption that there is full contact and that the Archard–Reye wear law applies. The governing equations are first developed for sinusoidal profiles with exponential growth rates. The contact condition and the wear law lead to a characteristic equation for the growth rate and more general solutions are developed by superposition.