Ricercatore Universitario


Dipartimento di Ingegneria dell'Innovazione Università del Salento Centro Ecotekne Pal. O - S.P. 6, 73047 Monteroni (Lecce) - Italy. Tel. +39 0832 29 7815 mob.: +39 320 149 7255 fax: +39 0832 29 7815 (Room 215)

Area di competenza:

- Friction, adhesion, lubrication, soft contacts, rough contacts

- Mechanical transmissions

Curriculum Vitae

[full CV link]

Michele was born in Bari (Italy) on October 1982 (with the happyness of the relatives, despite of the initial jaundice..).

Last update for summary below: June 2012.

He gained the Bachelor Degree in Mechanical Engineering on October 2004 (summa cum laude), and the Engineering Master Degree in Mechanical Construction and Experimentation on November 2006 (summa cum laude) at the Politecnico di Bari, Italy. In the same year, he got the Qualification as a Professional Engineer of the Italian Association of Engineers. In March 2010 he took the Ph.D. in "Mechanical and Bio-Mechanical Design" at the Politecnico di Bari. He has attended a number of schools in Nano-tribology and Surface Science topics. From Feb. 2012, he is Tenure Assistant Professor of Applied Mechanics at the Faculty of Engineering, Università del Salento, Lecce - Italy.

Scientific interests and skill.
His main areas of scientific interest involve the micro- and nano-tribology, the contact mechanics of randomly rough surfaces, the friction, adhesion and lubrication of soft and hard contacts (elasto-hydrodynamics, mixed lubrication), the homogenization aspects of dry and wet contacts (e.g. texture hydrodynamics), the theory of static and dynamic sealings, continuously variable transmissions and toroidal traction drives, energy harvesting from environment mechanical motion. His expertise is on both computational mechanics (Green function-based, FFT and multigrid-multilevel based approach for large scale dry/wet contact mechanics, multiscale approaches, large scale molecular dynamics) and theoretical continuum mechanics (e.g., homogenization theories for sliding rough contacts). He also has expertise on conventional and unconventional experimental mechanics (tribology and surface measurement equipments, AFM certified user, soft lithography, light interferometry).

Research record.
He has authored more than 30 publications, the half of which is on international peer-reviewed journals. He is reviewer for some major international journals, such as Tribology Letters, Tribology International and Soft Matter. In June 2008 – Feb. 2009 he has been visiting graduate and research fellow at the Forschungszentrum-Juelich, Institute of Solid State Research, working on homogenization and numerical techniques for mixed lubrication contacts. In June-Sept 2010 he was visiting scientist at the Tribology Group of the London Imperial College, working on the friction manipulation by micro-EHL contacts. In Mar. 2010 – Feb. 2012 he was research fellow at the TriboLab (Politecnico di Bari, IT), TRASFORMA Network of Research Labs. In Apr-Jun 2013 he was invited as visiting scientist at the Peter Grunberg Institute-1 of the Juelich Research Center, DE. He has different regular international (e.g. with London Imperial College UK, Forschungszentrum-Juelich DE, RWTH Aachen University DE) and national collaborations (e.g. with the Department of Mechanical Engineering of the Politecnico di Bari, Physics Department CNR-IFN at University of Bari).

In the years 2007-2009, he has been co-worker in an important CVT transmissions scientific research project, funded by the Gear Chain Industrial b.v. (Neunen - The Netherlands). In 2007-2010 he has been involved in the research activity within the EUROCORES project named FANAS ("Friction and Adhesion in Nanomechanical Systems"), funded by the European Science Foundation. In 2009 he has been involved in a research project with the IFAS Institute at RWTH Aachen University and Forschungszentrum-Juelich for dynamic sealings mixed lubrication modeling. In 2010-2011 he has been coordinator of the computational research project “Analysis of fluid flow percolation channels at the contact interface of randomly rough surfaces” funded by CASPUR for 70khours parallel computation. During 2010-2012 he has been working on the TriboLab (Politecnico di Bari) core numerical and experimental research activities, under the financial support of EFS with the Avviso n. 16/2009 - “Reti di Laboratori Pubblici di Ricerca".



[full publication list]

Last update for summary below: June. 2012.

On peer-reviewed journals

[1]M. Scaraggi. Textured surface hydrodynamic lubrication: Discussion. Tribology Letters, pages 1-17, 2012. Article in Press. [ bib | http ]

[2]Michele Scaraggi. Lubrication of textured surfaces: A general theory for flow and shear stress factors. Phys. Rev. E, 86:026314, Aug 2012. [ bib | DOI | http ]

[3]SCARAGGI M. and B.N.J. Persson. Time-dependent fluid squeeze-out between soft elastic solids with randomly rough surfaces. TRIBOLOGY LETTERS, 47(3):409-416, 2012. [ bib | DOI | http ]

[4]SCARAGGI M., G. CARBONE, and D. DINI. Experimental evidence of micro-ehl lubrication in rough soft contacts. TRIBOLOGY LETTERS, 2011. [ bib | DOI | http ]

[5]SCARAGGI M., CARBONE G, B.N.J. PERSSON, and DINI D. Lubrication in soft rough contacts: A novel homogenized approach. part i - theory. SOFT MATTER, 2011. [ bib | DOI | http ]

[6]SCARAGGI M., CARBONE G, and DINI D. Lubrication in soft rough contacts: A novel homogenized approach. part ii - discussion. SOFT MATTER, 2011. [ bib | DOI | http ]

[7]PERSSON B.N.J and SCARAGGI M. Lubricated sliding dynamics: flow factors and stribeck curve. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER, 2011. [ bib ]

[8]SCARAGGI M., DE NOVELLIS L, and CABONE G. Ehl-squeeze in high loaded contacts: The case of chain cvt transmissions. STROJNISKI VESTNIK, 56 (4):253-260, 2010. IDS Number: 617FD. [ bib ]

[9]SCARAGGI M. and CARBONE G. Transition from elastohydrodynamic to mixed lubrication in highly loaded squeeze contacts. JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS, 58 (9):1361-1373, 2010. [ bib | DOI | http ]

[10]CARBONE G, SCARAGGI M., and SORIA L. The lubrication regime at pin-pulley interface in chain cvts. JOURNAL OF MECHANICAL DESIGN, 131 (1):011003-1--9, 2009. [ bib | DOI | http ]

[11]CARBONE G, SCARAGGI M., and MANGIALARDI L. Ehl-squeeze at pin-pulley interface in cvts: Influence of lubricant rheology. TRIBOLOGY INTERNATIONAL, 42 (6):862-868, 2009. [ bib | DOI | http ]

[12]PERSSON B.N.J and SCARAGGI M. On the transition from boundary lubrication to hydrodynamic lubrication in soft contacts. JOURNAL OF PHYSICS. CONDENSED MATTER, 21 (18):185002-1--22, 2009. [ bib | DOI | http ]

[13]CARBONE G, SCARAGGI M., and TARTAGLINO U. Adhesive contact of rough surfaces: Comparison between numerical calculations and analytical theories. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER, 30:65-74, 2009. [ bib | DOI | http ]

[14]WOHLERS A, HEIPL O, PERSSON B.N.J, SCARAGGI M., and MURRENHOFF H. Numerical and experimental investigation on o-ring-seals in dynamic applications. INTERNATIONAL JOURNAL OF FLUID POWER, 10 (3):51-59, 2009. [ bib ]

On proceedings

[1]SCARAGGI M., DINI D, and CARBONE G. Friction measurements of micro-ehl in rough contacts. In Atti del Congresso AIMETA 2011, pages -, 2011. [ bib ]

[2]SCARAGGI M. and G. CARBONE. A two scale approach for mixed lubrication modelling: The case of lip sealings. In Proceedings of ECOTRIB 2011, 2011. [ bib ]

[3]SCARAGGI M., DE NOVELLIS L, and CARBONE G. Ehl-mixed lubrication transition at pin-pulley interface in chain cvt. In Prooceeding CVT2010, 2010. [ bib ]

[4]SCARAGGI M. and CARBONE G. Mixed lubrication in high loaded squeeze contacts. In Proc. 17th International Colloquium Tribology 2010: Solving Friction and Wear Problems, pages -, 2010. [ bib ]

[5]SCARAGGI M. and CARBONE G. The role of surface roughness in mixed lubricated contacts. In Proc. FANAS Workshop 2010: Understanding Adhesion: from Nature to man-made devices, 2010. [ bib ]

[6]SCARAGGI M. and CARBONE G. A novel approach to assess lip sealing performance. In Proc. AIT Workshop 2010: Tribologia e Industria, 2010. [ bib ]

[7]SCARAGGI M. and CARBONE G. Ehl-squeeze in highly loaded contacts: The influence of fluid rheology on pin-pulley interaction in cvt transmission. In Proc. Aimeta 2009: 19° Congresso dell'Associazione italiana di meccanica teorica e applicata, pages -, 2009. [ bib ]

[8]CARBONE G and SCARAGGI M. Ehl-squeeze in high loaded contacts: The case of chain cvt transmissions. In Proc. Ecotrib 2009: 2nd European Conference on Tribology, pages -, 2009. [ bib ]

[9]CARBONE G, SCARAGGI M., and TARTAGLINO U. Contact mechanics of 1d rough surface: Comparison between numerical results and theoretical models. In Proc. Seeccm 2009: 2nd South-East European Conference on Computational Mechanics, pages -, 2009. [ bib ]

[10]SCARAGGI M. and PERSSON B.N.J. The transition from boundary to hydrodynamic lubrication regime. In Proc. Seeccm 2009: 2nd South-East European Conference on Computational Mechanics, pages -, 2009. [ bib ]

Books and other contributions

[1]SCARAGGI M., O. HEIPL, A. WOHLERS, BO N.J. PERSSON, M. FOGLIA, and G. CARBONE. La lubrificazione nelle tenute dinamiche: nuovi approcci numerici e recenti sviluppi. TRASMISSIONI DI POTENZA OLEODINAMICA PNEUMATICA LUBRIFICAZIONE, 52(1):22-27, 2011. [ bib ]

[2]HEIPL O, WOHLERS A, PERSSON B.N.J, SCARAGGI M., and MURRENHOFF H. Modellbildung dynamischer dichtungen - ein ansatz zur berechnung der reibkraft unter mischreibung. O + P . OLHYDRAULIK UND PNEUMATIK, 54 (3):76-80, 2010. [ bib ]

[1]SCARAGGI M. The role of roughness in dry and lubricated contacts: Theory and numerics. LAP LAMBERT Academic Publishing, 2011. [ bib ]

This file was generated by bibtex2html 1.95.

Temi di ricerca


















Some past research activities:



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Role of lubricant rheology in hard-EHL squeeze

We analyze the influence of di fferent fluid rheologies on the high loaded normal approach of elastic balls, which is of utmost importance in gears, bearings and continuously variable transmissions. The analyzed lubricant rheologies are 1)Newtonian (linearly viscous), 2)Maxwell (linear viscous - linear elastic) and 3)Rabinowitsch (non-linear viscous, shear thinning) constitutive laws. For the Newtonian fluid, we show that the spatial pressure distribution is characterized by an annular (sharp) pressure peak, which first appears in the external region of the contact domain and after moves toward the center of the pin with rapidly decreasing speed. This high pressure fi eld determines the formation of a high viscosity oil dimple in the center of contact. The lifetime of this pressurized oil dimple, which corresponds to the time required by the lubricant to be expelled from the conjunction, actively determines the friction and wear characteristics at the interface. In the case of Maxwell rheology we show that the pressure field is exactly the same as in the Newtonian case but with a deep reduction in the annular pressure peak value, which explains the non-failure behavior of such contacts; thus we find that the Maxwell rheology enables a more realistic prediction of high loaded lubricated contacts (for lubricants not exhibiting limiting shear stress or shear thinning). The latter case is investigated with a Rabinowitsch constitutive law. We show that if the shear stress threshold, which characterizes the transition from the linear viscous to the non-linear viscous lubricant behavior, is sufficiently small the annular pressure peak may even disappear. In this case the squeeze process occurs faster (shorter lifetime), the fi lm thickness distribution is reduced and the lubricant may not be able to avoid direct asperity-asperity contact between the two approaching surfaces. The lubrication models is applied to the investigation of the pure squeeze motion at the pin-pulley interface in continuously variable transmissions (CVTs).



The oil pressure field for Newtonian and Maxwell fluid film. The oil viscoelasticity intervenes locally to smooth the annular pressure spike.



The fi lm thickness as a function of the radial coordinate for diff erent time instants in the case on non-constant load condition. The radial displacement of the position of the minimum film thickness during time is due to the corresponding variation of normal load.



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The transition from boundary to hydrodynamic lubrication in soft contact

We consider the contact between elastically soft solids with randomly rough surfaces in sliding contact in a fluid, which is assumed to be Newtonian with constant (pressure-independent) viscosity. We discuss the nature of the transition from boundary lubrication at low sliding velocity, where direct solid-solid contact occurs, to hydrodynamic lubrication at high sliding velocity, where the solids are separated by a thin fluid film. We consider both hydrophilic and hydrophobic systems, and cylinder-on-flat and sphere-on-flat sliding configurations. We show that for elastically soft solids such as rubber, including cavitation or not result in nearly the same friction.



An asperity contact region observed at a given magnifi cation.



Fluid and asperity contact pressure surfaces.



Friction coefficient for PDMS-PDMS interaction. The green line corresponds to the predicted Couette friction, while the other curves have been obtained by Bongaerts et al., 2007.



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Mixed lubrication theory in soft contacts: The case of lip sealings.

We consider the contact between a soft rough sealing lip and a smooth rigid rotating shaft. We model the asperity-asperity and asperity-fluid interactions with a deterministic or a statistical approach depending on length scale at which the contact region is observed. Indeed, the roughness at large length scales, which mainly determines the fluid flow at the interface, is deterministically included in the model while the roughness at short-wavelengths, which strongly contributes only to the friction, is included by means of a homogenization process. This contact scheme allows to correctly capture the shear-induced deformation of the roughness asperities occurring in soft mixed lubrication contacts.



A schematic of a typical lip seal construction.



Flux lines at the contact interface (red curves are). The velocity fi eld is shown in the vector form (black arrows) and in module (white-blue color gradient, where blue color is used for the higher values).



Average interfacial separation, average fluid and solid pressure.



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The transition from hydrodynamic to mixed lubrication in high loaded squeeze contacts.

We analyze the high loaded strongly non-stationary squeeze process of an oil fi lm sandwiched between an elastic spherical ball and a rigid rough substrate. We show that the coupling between the elastic properties of the contacting solids, the oil rheology, the surface roughness and the applied load determines a wide range of lubrication conditions from fully elasto-hydrodynamic to mixed and even boundary lubrication. In particular we fi nd that increasing (decreasing) the surface roughness (the applied normal load) speeds up the squeeze process, anticipates and shrinks the time interval during which the transition to mixed lubricated conditions occurs. On the contrary, the initial separation between the approaching bodies only marginally aff ects the transition time. We also observe that, in mixed-lubricated conditions, the highest asperity-asperity contact pressure occurs in the annular region where the separation between solids takes its minimum value. One then conclude that surface damage and wear should nucleate in the outer region of the contact



A film of lubricant squeezed between a smooth elastic sphere and a rough rigid substrate.



The typical spatial distribution of fluid pressure, solid-solid contact pressure and interfacial separation for mixed lubrication squeeze contacts. Observe that in the gray area across the minimum value of separation, where the solid-solid pressure takes its maximum value, the solid-solid contact spots may coalesce and obstruct the fluid passage. The oil then may not be squeezed out and remain entrapped between the two solids.



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Adhesive contact of rough surfaces.

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, which belongs to the class of the free boundary problems, 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-infi nite solid and a randomly rough rigid profi le 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.



The logarithm of the probability as function of pressure and contact magnification. Points are numerical predictions whereas dashed lines are Persson's results. We observe that the tail of the probability distribution at large values of pressure follows exactly a Gaussian distribution.