Antonio Papangelo's blog

Just published on JMPS

AbstractHigh-frequency micrometrical vibrations have been shown to greatly influence the adhesive performance of soft interfaces, however a detailed comparison between theoretical predictions and experimental results is still missing. Here, the problem of a rigid spherical indenter, hung on a soft spring, that is unloaded from an adhesive viscoelastic vibrating substrate is considered. The experimental tests were performed by unloading a borosilicate glass lens from a soft PDMS substrate excited by high-frequency micrometrical vibrations.

Title: “Experimental characterization of micropatterned interfaces subjected to dynamic loading” (PhD research project)

Advancements in smart soft materials are enhancing the capabilities of robotic manipulators in object interactions and complex tasks. Mechanochromic materials, acting as lightweight sensors, offer easily interpretable visual feedback for localized stress detection, structural health monitoring, and energy-efficient robotic skins.

The contact between a rigid Hertzian indenter and an adhesive broad-band viscoelastic substrate is considered. The material behavior is described by a modified power law model, which is characterized by only four parameters, the glassy and rubbery elastic moduli, a characteristic exponent n and a timescale tau0.

In classical experiments, it has been found that a rigid cylinder can roll both on and under an inclined rubber plane with a friction force that depends on a power law of velocity, independent of the sign of the normal force. Further, contact area increases significantly with velocity with a related power law.

The problem of the detachment of a flat indenter from a plane adhesive viscoelastic strip of thickness “b” is studied.

Dear friends and colleagues, there is a new open position in soft contact mechanics in my group! We are looking for a motivated mechanical engineer (or alike) to contribute to cutting edge research on adhesion with biological tissue. We aim at developing soft micro-structured bio-compatible adhesive patch and scaffolds to be used for tissue re-attachment after injuries.

The problem of the detachment of a sufficiently large flat indenter from a plane adhesive viscoelastic strip of thickness “b” is studied. For any given retraction speed, three different detachment regimes are found: (i) for very small “b” the detachment stress is constant and equal to the theoretical strength of the interface, (ii) for intermediate values of “b” the detachment stress decays approximately as b−1/2, (iii) for thick layers a constant detachment stress is obtained corresponding to case the punch is detaching from a halfplane.

Location: Polytechnic University of Bari, Department of Mechanics Mathematics and Management (DMMM), Via Orabona 4 - 70125 Bari – Italy

Job Type: Full Time

Deadline: 17 July 2023

Location: Polytechnic University of Bari, Department of Mechanics Mathematics and Management (DMMM), Via Orabona 4 - 70125 Bari – Italy

Job Type: Full Time

Deadline: 17 July 2023

Location: Polytechnic University of Bari, Department of Mechanics Mathematics and Management (DMMM), Via Orabona 4 - 70125 Bari – Italy

Job Type: Full Time

Very proud to have been collaborating for long time, since my PhD, with Prof. M.

Our research Topic on Fingerpad Contact Mechanics is still open! Please follow the link below for abstract submission!

A new research topic opened in Forntiers in Mechanical Engineering.

Viscoelastic materials are receiving increasing attention in soft robots and pressure sensitive adhesives design, but also in passive damping techniques in automotive and aerospace industry. Here, by using the correspondence principle originally developed by Lee and Radok and further extended by Ting and Greenwood, we transform the elastic solutions of Persson for contact of nominally flat but randomly rough surfaces to viscoelastic indentation. As an example, the cases of step loading and of the response to a single cycle of harmonic loading are studied.

How can shear loading rate affect the soft adhesive contact area? A new blog post in tribonet.org discusses the problem following the paper "Papangelo, Antonio. (2021). On the Effect of Shear Loading Rate on Contact Area Shrinking in Adhesive Soft Contacts. Tribology Letters. 69." just published in Tribology Letters.

Mode-coupling instabilities are known to trigger self-excited vibrations in sliding contacts. Here, the conditions for mode-coupling (or "flutter") instability in the contact between a spherical oscillator and a moving viscoelastic substrate are studied. The work extends the classical 2-Degrees-Of-Freedom conveyor belt model and accounts for viscoelastic dissipation in the substrate, adhesive friction at the interface and non-linear normal contact stiffness as derived from numerical simulations based on a boundary element method capable of accounting for linear viscoelastic effects.

AbstractPatterned surfaces have proven to be a valuable design to enhance adhesion, increasing hysteresis and the detachment stress at pull-off. To obtain high adhesive performance, soft materials are commonly, used, which easily conform to the countersurface, such as soft polymers and elastomers. Such materials are viscoelastic; i.e., they show rate-dependent properties. Here, the detachment of two half spaces is studied, one being flat and the other having a dimple in the limit of short range adhesion and a power law rate-dependent work of adhesion, as observed by several authors.