arXiv subjects

Cosimo Mandriota

Publications and source records attributed to Cosimo Mandriota.

4 recordsLinked to original sources

arXiv2025

Anisotropic shrinkage and finite strains in confined frictional contacts

We report on an experimental investigation of the interplay between friction, contact geometry and finite strains for smooth frictional contacts between rigid spherical glass probes and flat silicone substrates. Using both bulk and layered substrates under various loading conditions (normal force, radius of the probe), we show that shear-induced anisotropic shrinkage of the adhesive contact area under steady-state sliding is an effect of finite-elasticity conditions and is drastically affected by the level of geometric confinement. The resulting non-linear coupling between the normal and lateral directions is also investigated by measuring the changes in the indentation depth (conv. normal load) during the stiction of the adhesive contacts under imposed normal load (conv. indentation depth) conditions, with strong effects of contact confinement. From a comparison with adhesiveless linear contact mechanics calculations, we show that the experimental observations can only be accounted for by the occurrence of finite strains/displacements conditions. Accordingly, measurements of the in-plane surface displacements at the surface of the rubber substrates confirm that strain levels well in the neo-Hookean range are experienced during steady-state frictional sliding.

cond-mat.soft↗

arXiv2024

Modelling viscoelastic adhesion and friction in sliding contact mechanics

We present our recent study on rough adhesive contacts of viscoelastic materials in steady-state sliding, focusing on the interplay between adhesion and viscoelasticity by means of a novel energy approach. We investigate tribological features over a wide range of velocity values, exploring the effect of small- and large- scale viscoelasticity on the overall contact behavior. The former is associated with viscoelastic dissipation close to the adhesive neck at the contact edges; the latter refers to material hysteresis involving the entire bulk of the solid. Depending on the sliding velocity, we predict highly enhanced adhesive strength compared to the purely elastic conditions, increased friction compared to the adhesiveless case, and non-monotonic trend of the energy release rates at the contact leading and trailing edges. Most of our results are supported by existing experiments.

cond-mat.soft↗

arXiv2024

Enhancement of adhesion strength in viscoelastic unsteady contacts

We present a general energy approach to study the unsteady adhesive contact of viscoelastic materials. Under the assumption of infinitely short-range adhesive interactions, we exploit the principle of virtual work to generalize Griffith local energy balance at contact edges to the case of a non conservative (viscoelastic) material, subjected to a generic contact time history. We apply the proposed energy balance criterion to study the approach retraction motion of a rigid sphere in contact with a viscoelastic halfspace. A strong interplay between adhesion and viscoelastic hysteretic losses is reported which can lead to strongly increased adhesion strength, depending on the loading history. Specifically, two different mechanisms are found to govern the increase of pulloff force during either approach retraction cycles and approach, full relaxation, retraction tests. In the former case, hysteretic losses occurring close to the circular perimeter of the contact play a major role, significantly enhancing the energy release rate. In the latter case, instead, the pulloff enhancement mostly depends on the glassy response of the whole (bulk) material which, triggered by the fast retraction after relaxation, leads to a sort of frozen state and results in a flat punch like detachment mechanism (i.e., constant contact area). In this case, the JKR theory of adhesive contact cannot be invoked to relate the observed pulloff force to the effective adhesion energy, i.e. the energy release rate G, and strongly overestimates it. Therefore, a rigorous mathematical procedure is also proposed to correctly calculate the energy release rate in viscoelastic dissipative contacts.

cond-mat.soft↗

arXiv2022

Theory of viscoelastic adhesion and friction

We present a novel theory of the adhesive contact of linear viscoelastic materials against rigid substrates moving at constant velocity. Despite the non-conservative behavior of the system, the closure equation of the contact problem can be rigorously formulated in the form of a local energy balance. In the case of adhesiveless contacts, this is equivalent to enforce the stationarity of the total energy stored into the viscoelastic material. However, in the presence of interfacial adhesion, the appearance of non-conservative terms leads to different values of the energy release rates G1 and G2 at the contact trailing and leading edges, respectively. Specifically, the present theory predicts a non-monotonic trend of G1 and G2 as function of the indenter velocity, as well as a very significant enhancement of hysteretic friction due to the coupling between adhesion and viscoelasticity, compared to the adhesiveless case. Both predictions are in very good agreement with existing experimental data.

cond-mat.soft↗