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Antonio Papangelo's blog

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The effect of wear on ThermoElastic Instabilities (TEI) in bimaterial interfaces

There is ample evidence of ThermoElastic Instabilities (TEI) occurring in sliding contacts. The very first experiments of JR Barber in 1969 suggested wear interacts in the process of localization of contact into ”hot spots”. However, studies on the interaction of TEI with wear are scarce. We consider the case of two sliding halfspaces and make a perturbation analysis permitting the formation of waves migrating over the two bodies, in presence of wear. We find that for exactly identical bodies wear does not affect the stability boundary.

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A Discussion on Present Theories of Rubber Friction, with Particular Reference to Different Possible Choices of Arbitrary Roughness Cutoff Parameters

      Since the early study by Grosch in 1963 it has been known that rubber friction shows generally two maxima with respect to speed-the first one attributed to adhesion, and another at higher velocities attributed to viscoelastic losses.
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Citation metrics author database for many scientific fields

Citation metrics are widely used and misused.  Ioannidis and co-authors have created a publicly available database of 100,000 top scientists that provides standardized information on citations, h-index, coauthorship-adjusted hm-index, citations to papers in different authorship positions, and a composite indicator.

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Reconstruction of Governing Equations from Vibration Measurements for Geometrically Nonlinear Systems

Data-driven system identification procedures have recently enabled the reconstruction of governing differential equations from vibration signal recordings. In this contribution, the sparse identification of nonlinear dynamics is applied to structural dynamics of a geometrically nonlinear system. First, the methodology is validated against the forced Duffing oscillator to evaluate its robustness against noise and limited data.

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Axisymmetric JKR-type adhesive contact under equibiaxial stretching

 Our research has just been published in Journal of Adhesion. It deals with axisymmetric frictionless adhesive contact problem for a spherical indenter pressed against an isotropic elastic incompressible half-space under equibiaxial stretching is studied in the framework of the generalized Johnson{Kendall{Roberts (JKR) theory, which accounts for the effect of weak coupling between fracture modes I and II by means of a phenomenological mode-mixity function. The model predicts that contact area can withstand a larger level of the substrate stretch under moderate pre-pulling force.

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Shear-Induced Anisotropy in Rough Elastomer Contact

R. Sahli, G. Pallares, A. Papangelo, M. Ciavarella, C. Ducottet, N. Ponthus, and J. Scheibert
Phys. Rev. Lett. 122, 214301 – https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.214301

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Adhesion of multilayered materials

Adhesion is a key factor in many tribological processes, especially wear. We generalize a recent formulation for the indentation of a multilayered material using an efficient integral transform method, to the case of adhesion, using a simple energetic transformation in the JKR regime. Then, we specialize the study for the geometry of the Surface Force Apparatus, which consists of two thin layers on a substrate, where the intermediate layer is softer than the other two. We find the pull-off force under "force control" (i.e.

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The role of adhesion in contact mechanics

Just published in Journal of the Royal Society Interface

Ciavarella M, Joe J, Papangelo A, Barber JR. 2019 The role of adhesion in contact mechanics. J. R. Soc. Interface 16: 20180738. http://dx.doi.org/10.1098/rsif.2018.0738

Abstract

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On unified crack propagation laws

The anomalous propagation of short cracks shows generally exponential fatigue crack growth but the dependence on stress range at high stress levels is not compatible with Paris’ law with exponent m=2. Indeed, some authors have shown that the standard uncracked SN curve is obtained mostly from short crack propagation, assuming that the crack size a increases with the number of cycles N as da/dN=H\Delta\sigma^h where h is close to the exponent of the Basquin’s power law SN curve.

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Bio-inspired solution for optimal adhesive performance

In recent years there has been a growing interest into high performance bioinspired adhesives. This communication focuses on the adhesive behavior of a rigid cylinder that indents an elastic layer coated on a rigid substrate. With the assumption of short range adhesive interactions (JKR type) the adhesive solution is obtained very easily starting from the adhesiveless one.

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Multistability and localization in forced cyclic symmetric structures modelled by weakly-coupled Duffing oscillators

Many engineering structures are composed of weakly coupled sectors assembled in a cyclic and ideally symmetric configuration, which can be simplified as forced Duffing oscillators. In this paper, we study the emergence of localized states in the weakly nonlinear regime. We show that multiple spatially localized solutions may exist, and the resulting bifurcation diagram strongly resembles the snaking pattern observed in a variety of fields in physics, such as optics and fluid dynamics.

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On mixed-mode fracture mechanics models for contact area reduction under shear load in soft materials

The fundamental problem of friction in the presence of macroscopic adhesion, as in soft bodies, is receiving interest from many experimentalists. Since the first fracture mechanics 'purely brittle' model of Savkoor and Briggs, models have been proposed where the mixed mode toughness is interpreted with phenomenological fitting coefficients introducing weaker coupling between modes than expected by the "purely brittle" model.

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Congratulations to Prof. M. Ciavarella, new member of IJMS editorial board!

Congratulations to Prof. M. Ciavarella for having been nominated a new member of the International Journal of Mechanical Sciences (IJMS) Editorial Board! IJMS is a well-established Journal published by Elsevier. With its Impact Factor being 2.884 in 2016, IJMS ranks No. 15 among 133 journals in the field of Mechanics! 

https://www.journals.elsevier.com/international-journal-of-mechanical-sc...

Congratulations!

Antonio

 

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Adhesion between a power-law indenter and a thin layer coated on a rigid substrate

Abstract: In the present paper we investigate indentation of a power-law axisymmetric rigid probe in adhesive contact with a "thin layer" laying on a rigid foundation for both frictionless unbounded and bounded compressible cases. The investigation relies on the "thin layer" assumption proposed by Johnson, i.e. the layer thickness being much smaller than the radius of the contact area, and it makes use of the previous solutions proposed by Jaffar and Barber for the adhesiveless case.

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Multiple spatially localized dynamical states in friction-excited oscillator chains

  • Journal of Sound and Vibration

 

A. Papangelo (a,*), N. Hoffmann (a,b), A. Grolet (c), M. Stender (a), M. Ciavarella (d)

a) Hamburg University of Technology, Department of Mechanical Engineering, Am Schwarzenberg-Campus 1, 21073, Hamburg, Germany

b) Imperial College London, Exhibition Road, London, SW7 2AZ, UK

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Discussion of “Measuring and Understanding Contact Area at the Nanoscale: A Review” by Tevis D. B. Jacobs and Ashlie Martini

M. Ciavarella(1) and A. Papangelo(2)

(1) Politecnico di BARI, Center of Excellence in Computational Mechanics, Deparment of Mechanics, Mathematics and Management. Viale Gentile 182. 70125 Bari (Italy)

(2) Hamburg University of Technology, Department of Mechanical Engineering, Am Schwarzenberg-Campus 1, 21073 Hamburg, Germany

michele.ciavarella@poliba.it, antonio.papangelo@poliba.it

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