arXiv subjects

Giuseppe Carbone

Publications and source records attributed to Giuseppe Carbone.

18 recordsLinked to original sources

arXiv2026

Facade Inspection: Design, Prototyping, and Testing of a Hybrid Cable-Driven Parallel Robot

In the field of architecture, early detection of damage or degradation of building facades has become increasingly vital due to the need for continuous monitoring of structural integrity. Traditional methods, such as visual inspections, are being supplemented by technological advancements, especially in robotics, which offer innovative solutions for more efficient and precise inspections. This work focuses on the development of a five degree of freedom hybrid cable-driven parallel robot designed for vertical facade inspections. A detailed robot's design and CAD modeling, with a particular focus on a torque transmission mechanism that simplifies the motion of two cables using a single motor is presented. Two degrees of freedom are driven by cables, while the remaining three are driven by a Sarrus-type mechanism and a pan-tilt mechanism. The inverse kinematics models are also developed. A prototype is presented, involving additive manufacturing. A control system for tracking a zig-zag trajectory, commonly used in inspection tasks, was experimentally validated.

physics.class-ph↗

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

Viscoelastic peeling of thin tapes with frictional sliding

Peeling is one of the most common detachment mechanisms adopted in industrial applications. However, although several experimental investigations have proven the possible occurrence of relative sliding at the interface close to the peeling front, a comprehensive model considering the effect of both the tape viscoelasticity and frictional interfacial dissipation on the peeling behavior is lacking. The present study aims at providing a theoretical framework to investigate the peeling process of a thin viscoelastic tape from a rigid substrate in the presence of frictional sliding at the interface. It shows that, under certain conditions, significantly tougher adhesive performance can be achieved compared to stuck elastic conditions with no interfacial sliding, and that the delamination resistance of the system strongly depends on the propagation velocity.

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↗

arXiv2023

Significance of Elastic Coupling for Stresses and Leakage in Frictional Contacts

We study how the commonly neglected coupling of normal and in-plane elastic response affects tribological properties when Hertzian or randomly rough indenters slide past an elastic body. Compressibility-induced coupling is found to substantially increase maximum tensile stresses, which cause materials to fail, and to decrease friction such that Amontons law is violated macroscopically even when it holds microscopically. Confinement-induced coupling increases friction and enlarges domains of high tension. Moreover, both types of coupling affect the gap topography and thereby leakage. Thus, coupling can be much more than a minor perturbation of a mechanical contact.

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↗

arXiv2021

The role of interfacial friction on the peeling of thin viscoelastic tapes

We study the peeling process of a thin viscoelastic tape from a rigid substrate. Two different boundary conditions are considered at the interface between the tape and the substrate: stuck adhesion, and relative sliding in the presence of frictional shear stress. In the case of perfectly sticking interfaces, we found that the viscoelastic peeling behavior resembles the classical Kendall behavior of elastic tapes, with the elastic modulus given by the tape high-frequency viscoelastic modulus. Including the effect of frictional sliding, which occurs at the interface adjacent to the peeling front, makes the peeling behavior strongly dependent on the peeling velocity. Also, at sufficiently small peeling angles, we predict a tougher peeling behavior than the classical stuck cases. This phenomenon is in agreement with recent experimental evidences indicating that several biological systems (e.g. geckos, spiders) exploit low-angle peeling to control attachment force and locomotion.

cond-mat.soft↗

arXiv2021

A new technique for the characterization of viscoelastic materials: theory, experiments and comparison with DMA

In this paper we present a theoretical and experimental study aimed at characterizing the hysteretic properties of viscoelastic materials. In the last decades viscoelastic materials have become a reference for new technological applications, which require lightweight, deformable but ultratough structures. The need to have a complete and precise knowledge of their mechanical properties, hence, is of utmost importance. The presented study is focused on the dynamics of a viscoelastic beam, which is both experimentally investigated and theoretically characterized by means of an accurate analytical model. In this way it is possible to fit the experimental curves to determine the complex modulus. Our proposed approach enables the optimal fitting of the viscoelastic modulus of the material by using the appropriate number of relaxation times, on the basis of the frequency range considered. Moreover, by varying the length of the beams, the frequency range of interest can be changed/enlarged. Our results are tested against those obtained with a well established and reliable technique as compared with experimental results from the Dynamic Mechanical Analysis (DMA), thus definitively establishing the feasibility, accuracy and reliability of the presented technique.

physics.ins-det↗

arXiv2020

Do uniform tangential interfacial stresses affect adhesion?

We present theoretical arguments, based on linear elasticity and thermodynamics, to show that interfacial tangential stresses in sliding adhesive contacts does not affet at all the adhesive behavior of the system, which then follows the classical JKR solution. Our finding explains the experimental observation of Vorvolakos and Chaudhury in 2003, who found that the contact area of a PDMS sphere remains constant during sliding and is in agreement with the JKR solution, at least up to velocity of 1mm/s, and of Carpick et al. Carpick, who observed that the friction force between a platinum-coated atomic force microscope (AFM) tip and the surface of mica in ultrahigh vacuum (UHV) varies with load in proportion to the contact area predicted by the Johnson-Kendall-Roberts (JKR). We show that a reduction of the contact area, experimentlly observed at higher sliding speeds, can be caused by a reduction of the density of adhesive bonds as the velocity is increased, or caused by the repulsive energy term associated with the stress spatial fluctuation at the interface. This may explain why adhesion is completely masked at relatively large sliding velocities. This version of the paper follows the publication of the Corrigendum: Nicola Menga, Giuseppe Carbone, Daniele Dini: Corrigendum to "Do uniform tangential interfacial stresses enhance adhesion?" [Journal of the Mechanics and Physics of Solids 112 (2018) 145--156], Journal of the Mechanics and Physics of Solids, 133, 103744, https://doi.org/10.1016/j.jmps.2019.103744, available on line since 8 October 2019.

cond-mat.mtrl-sci↗

arXiv2019

Tuning the periodic V-peeling behavior of elastic tapes applied to thin compliant substrates

In this paper, we investigate the periodic peeling behavior of opposing symmetric peeling fronts involving an elastic tape peeled off from a deformable substrate of finite thickness, backed onto a rigid foundation. We treat the problem by means of an energetic formulation, and we found that, depending on the values of the initial detached length $l$, substrate thickness $h$, and peeling periodicity $λ$, the translational invariance of the peeling process is lost and restored, as the elastic interaction between the peeling fronts is limited by the substrate thickness. Indeed, given $h$ and $λ$, a critical value of the detached length can be found, which is able to prevent unstable peeling of the tape under a fixed applied load, thus resulting in enhanced adhesion strength, with respect to the classical Kendall's solution for peeling from a rigid substrate. On the other hand, given the geometrical system configuration (i.e. the detached length $l$) the load necessary to trigger the peeling can be minimized by conveniently tuning the ratio $h/λ$. This feature might be of interest for the development of innovative designs for future biomedical devices, such as Transdermal Drug Delivery Systems or wound dressing, requiring low peel adhesion for safe successive removals.

cond-mat.soft↗

arXiv2018

Thermal fuctuations and dynamic modelling of a dAFM cantilever

We discuss the Brownian thermal noise which affects the cantilever dynamics of a dAFM (dynamic atomic force microscope), both when it works in air and in presence of water. Our scope is to accurately describe the cantilever dynamics, and to get this result we deeply investigate the relationship between the cantilever thermal fluctuations and its interactions with the surrounding liquid. We present a relatively simple and very easy-to-use analytical model to describe the interaction forces between the liquid and the cantilever. The novelty of this approach is that, under the assumption of small cantilever oscillations, by using the superposition principle we found a very simple integral expression to describe fluid-cantilever interactions. More specifically we note that, beside including fluid inertia and viscosity (which is common to many existing models in the literature) an additional diffisivity term needs to be considered, whose crucial influence for the correct evaluation of the cantilever response to the thermal excitation is shown in the present paper. The coefficients of our model are obtained by using numerical results for a 2D fluid flow around a vibrating rectangular cross-section, and depend on the distance from the wall. This allowed us to completely characterize the dynamics of a dAFM cantilever also when it operates in tilted conditions. We validate the analytical model by comparing our results with numerical and experimental dAFM data previously presented in literature, and with experiments carried out by ourselves. We show that we can provide extremely accurate prediction of the beam response up and beyond the second resonant peak.

physics.ins-det↗

arXiv2016

The Human Group Optimizer (HGO): Mimicking the collective intelligence of human groups as an optimization tool for combinatorial problems

A large number of optimization algorithms have been developed by researchers to solve a variety of complex problems in operations management area. We present a novel optimization algorithm belonging to the class of swarm intelligence optimization methods. The algorithm mimics the decision making process of human groups and exploits the dynamics of this process as an optimization tool for combinatorial problems. In order to achieve this aim, a continuous-time Markov process is proposed to describe the behavior of a population of socially interacting agents, modelling how humans in a group modify their opinions driven by self-interest and consensus seeking. As in the case of a collection of spins, the dynamics of such a system is characterized by a phase transition from low to high values of the overall consenus (magnetization). We recognize this phase transition as being associated with the emergence of a collective superior intelligence of the population. While this state being active, a cooling schedule is applied to make agents closer and closer to the optimal solution, while performing their random walk on the fitness landscape. A comparison with simulated annealing as well as with a multi-agent version of the simulated annealing is presented in terms of efficacy in finding good solution on a NK - Kauffman landscape. In all cases our method outperforms the others, particularly in presence of limited knowledge of the agent.

nlin.AO↗

arXiv2016

Loading-unloading hysteresis loop of randomly rough adhesive contacts

In this paper we investigate the loading and unloading behavior of soft solids in adhesive contact with randomly rough profiles. The roughness is assumed to be described by a self-affine fractal on a limited range of wave-vectors. A spectral method is exploited to generate such randomly rough surfaces. The results are statistically averaged, and the calculated contact area and applied load are shown as a function of the penetration, for loading and unloading conditions. We found that the combination of adhesion forces and roughness leads to a hysteresis loading-unloading loop. This shows that energy can be lost simply as a consequence of roughness and van der Waals forces, as in this case a large number of local energy minima exist and the system may be trapped in metastable states. We numerically quantify the hysteretic loss and assess the influence of the surface statistical properties and the energy of adhesion on the hysteresis process.

cond-mat.soft↗

arXiv2016

Theory of Reciprocating Contact for Viscoelastic Solids

A theory of reciprocating contacts for linear viscoelastic materials is presented. Results are discussed for the case of a rigid sphere sinusoidally driven in sliding contact with a viscoelastic half-space. Depending on the size of the contact, the frequency and amplitude of the reciprocating motion, and on the relaxation time of the viscoelastic body, we establish that the contact behavior may range from the steady-state viscoelastic solution, in which traction forces always oppose the direction of the sliding rigid punch, to a more elaborate trend, never observed before, which is due to the strong interaction between different regions of the path covered during the reciprocating motion. Practical implications span a number of applications, ranging from seismic engineering to biotechnology.

cond-mat.mtrl-sci↗

arXiv2015

Model of human collective decision-making in complex environments

A continuous-time Markov process is proposed to analyze how a group of humans solves a complex task, consisting in the search of the optimal set of decisions on a fitness landscape. Individuals change their opinions driven by two different forces: (i) the self-interest, which pushes them to increase their own fitness values, and (ii) the social interactions, which push individuals to reduce the diversity of their opinions in order to reach consensus. Results show that the performance of the group is strongly affected by the strength of social interactions and by the level of knowledge of the individuals. Increasing the strength of social interactions improves the performance of the team. However, too strong social interactions slow down the search of the optimal solution and worsen the performance of the group. In particular, we find that the threshold value of the social interaction strength, which leads to the emergence of a superior intelligence of the group, is just the critical threshold at which the consensus among the members sets in. We also prove that a moderate level of knowledge is already enough to guarantee high performance of the group in making decisions.

cs.MA↗

arXiv2015

Fluid contact angle on solid surfaces: role of multiscale surface roughness

We present a simple analytical model and an exact numerical study which explain the role of roughness on different length scales for the fluid contact angle on rough solid surfaces. We show that there is no simple relation between the distribution of surface slopes and the fluid contact angle. In particular, surfaces with the same distribution of slopes may exhibit very different contact angles depending on the range of length-scales over which the surfaces have roughness.

cond-mat.soft↗

arXiv2010

Adhesive contact of rough surfaces: comparison between numerical calculations and analytical theories

We have employed a numerical procedure to analyze the adhesive contact between a soft elastic layer and a rough rigid substrate. The solution of the problem is obtained by calculating the Green's function which links the pressure distribution to the normal displacements at the interface. The problem is then formulated in the form of a Fredholm integral equation of the first kind with a logarithmic kernel, and the boundaries of the contact area are calculated by requiring that the energy of the system is stationary. The methodology has been employed to study the adhesive contact between an elastic semi-infinite solid and a randomly rough rigid profile with a self-affine fractal geometry. We show that, even in presence of adhesion, the true contact area still linearly depends on the applied load. The numerical results are then critically compared with the prediction of an extended version of the Persson's contact mechanics theory, able to handle anisotropic surfaces, as 1D interfaces. It is shown that, for any given load, Persson's theory underestimates the contact area of about 50% in comparison with our numerical calculations. We find that this discrepancy is larger than what is found for 2D rough surfaces in case of adhesionless contact. We argue that this increased difference might be explained, at least partially, by considering that Persson's theory is a mean field theory in spirit, so it should work better for 2D rough surfaces rather than for 1D rough surfaces. We also observe, that the predicted value of separation is in very good agreement with our numerical results as well as the exponent of the power spectral density of the contact pressure distribution and of the elastic displacement of the solid. Therefore, we conclude that Persson's theory captures almost exactly the main qualitative behavior of the rough contact phenomena.

physics.comp-ph↗