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Key collaborations

Papers have been written in collaboration with collegues from Michigan U (Jim Barber), Oxford U (David Hills), Harvard U (Jim Rice, Joost Vlassak), Ecole Polytechnique (H.Maitournam), Politecnico di Torino (Dino Chiaia, Nicola Pugno, Marco Paggi, and Alberto Carpinteri), Leicester U in UK (Alan Ponter), Università di Padova (Paolo Lazzarin), Università di Modena (Antonio Strozzi), Univ Hamburg (N. Hoffmann).

Key research results

Few comments follow with cross-reference to publication list.

1) General contact mechanics:

In papers [2,3,9] the procedure devised independently by Cattaneo & Mindlin for Hertzian contact problem with sequential normal and tangential loading has been extended for a general geometry (in 2D and, with some restrictions, also in 3D), permitting the solution of a number of fretting contact problems, and paper [5] introducing the flat and rounded geometry has given rise to a number of recent models for fretting fatigue (notch, crack and more general asymptotic “analogies”). The indentation modulus has been computed for arbitrarily anisotropic materials, indented by tips of any shape [40]. An invited review paper has been written [18] on contact mechanics. More recently, extensions of the celebrated Dundurs’ theorems for “receding” contact have been obtained for “regressive” and “progressive” contact [69], showing in particular a normalising loading parameter useful in summarizing the mechanical response of “almost conforming” contacts of any shape, with potential application in design of many components, ranging from multiple fasteners to artificial joints. In particular, application to compliant layered artificial hip joints and in metal-on-metal hip replacements are presented and assessed versus several literature results in [77].

2) Fretting Fatigue and frictional shakedown

Various classical methodologies have been reviewed, see paper [31], and extensions to crack and notch analogues have been proposed [34, 37, 44] resulting more recently on a general “crack-like notch analogue” model [42] which is an improvement of Subra Suresh’s MIT group “crack analogue” model. Recently [76], some theorems have been derived to show that, despite non-associative, Coulomb’s law can still lead to Melan’s statical theorem on shakedown, provided the structure has uncoupled normal and tangential DOFs. In general, however, coupling gives rise to a richer behavior. Potential applications could be for example in the design of joints, from bolted to turbine blade attachments, or shakedown of frictional geomaterials in pavement design.

3) Rolling Contact Fatigue

This has involved the completion of shakedown maps for a general sliding elliptical contact [41], but also seen the limitations of the plasticity approach in studying what is essentially a fatigue problem, with a re-examination of classical ratchetting experiments by Merwin and K.L. Johnson [49], and those of Su and Clayton [50].

4) Thermo-Elastic Instabilities (TEI)

Various results have been obtained for the thermo-elastic contact of sliding systems namely critical speed and transient behaviour of multidisk clutches and brakes [27, 35, 36], complete assessment of simple rod models [46, 48] or half-plane geometries [52, 53], general existence and uniqueness theorems [51]. More recently, a coupling mechanism between TEI and natural elastodynamics modes (i.e. Dynamic Instabilities) has been found, and denominated TEDI [66, 74, 75].

5) Fatigue and fracture from notches and cracks

Classical and more recent methodologies for estimating the effect of notches in fatigue have been compared [43], the general elasto-plastic asymptotic solution for a sharp notch has been derived [39]. Recently, a generalized Paris law has been proposed [72] using an “asymptotic matching” procedure to use material properties taken from Wohler’s curve of the material to correct the SIF of small cracks. A different but analogous procedure has been proposed in [65] to generalize the use of Kitagawa-Takahashi diagram and of the El Haddad equation for finite life of a specimen.

6) Effect of roughness in mechanical and electrical contacts

The long-disputed problem of scale-dependence of roughness parameters and their role into contact mechanics has been approached with a rigorous investigation using a Weierstrass series profile [19], showing that the contact area predicted within the limits of elasticity theory is a fractal itself, with lower dimension, the higher is the fractal dimension of the profile. This paradoxical result was shown to be true also for the original Archard profile [54], but other macroscopic quantities such as the elastic contact stiffness and the contact resistance where shown to be bounded and dependent on few largest scales rather than the finest one as other [55]. Recently, we have found that classical models can be re-interpreted to fit most results [63,73].

7) Corrugations in railways as a wear-induced instability.

In [81], we have considered the so-called short pitch corrugation “enigma”, which consists in unexplained corrugations of 20-80mm in length in railways particularly strong in BR’s Weast Coast Main Line in England after its electrification in the 1970’s. We showed that classical simple models of used by Prof Johnson and his co-workers in the 1980’s studying corrugations were making a strong and unjustified assumption about constant creepage. The results of a simple model like [81] may not explain all possible short-pitch corrugation evidence, but are not incompatible with the possibility of corrugation existence. Further in [84] we have developed more refined models to study the transient dynamical effect in the contact area, and in [86] we have considered the “enigma” more at large introducing also lateral creepage, and the different receptances corresponding to the change of sleepers after the electrification of the West Main Coast Line in UK, showing some quantitative aspects of short-pitch corrugation are still very difficult to include in the models. Indeed, one of the most tricky aspects is parametric resonance, for which a much simplified model was considered in [85] in collaboration with Hamburg University.

H-index

H/index Scholar = 13 (total number of papers 78)

H/index Web of Science (ISI) = 11 (total number of papers 81).


Ultime 15 pubblicazioni

15 most recent journal articles

  1. L. Afferrante and M. Ciavarella A note on thermoelastodynamic instability (TEDI) for a 1D elastic layer: Force control International Journal of Solids and Structures, Volume 44, Issue 5, 1 March 2007, Pages 1380-1390. ISSN: 0020-7683

  2. L. Afferante, M.Ciavarella and J.R.Barber, Sliding thermoelastodynamic instability, Proc.Roy.Soc. (London), Vol.A462 (2006), pp.2161—2176. Print: ISSN 01364-5021 Online: ISSN 1471-2946

  3. A. Klarbring, M.Ciavarella and J.R.Barber, Shakedown in elastic contact problems with Coulomb friction, International Journal of Solids and Structures. 44 (25-26), 8355-8365, 2007. ISSN: 0020-7683.

  4. Ciavarella, M., Strozzi, A., Baldini, A., Giacopini, M., Normalization of load and clearance effects in ball in socket-like replacements, Proc Inst. Mech Eng H Journal of Engineering in Medicine, Volume 221, Number 6, 2007 , pp. 601-611(11). Publisher: Professional Engineering Publishing ISSN 0954-4119.

  5. J.R.Barber, A. Klarbring, M.Ciavarella Shakedown in elastic contact problems for the continuum, Comptes Rendue Mechanique. (8 Janvier 2008) "Duality, Inverse Problems and Non linear Problems" ed J.B.Leblond et X. Markenscoff, Comptes Rendus Mécanique, Volume 336, Issues 1-2, January-February 2008, Pages 34-41, ISSN: 1631-0721.

  6. M.Ciavarella, M.Paggi, J. A. Greenwood, Inclusion of “interaction” in the Greenwood & Williamson contact theory, Wear. Volume 265, Issues 5-6, 25 August 2008, Pages 729-734, ISSN: 0043-1648

  7. Y.Gao, M. Ciavarella, H. Gao, Adhesion maps corrected for strength limit, J Colloids Interf Sci. Volume 315, Issue 2, 15 November 2007, Pages 786-790, ISSN 0021-9797 Publisher: Academic Press

  8. Barber JR Ciavarella, M. On the influence of longitudinal creepage and wheel inertia on short pitch corrugation — a resonance-free mechanism to explain the roaring rail phenomenon, Proceedings of the Institution of Mechanical Engineers, Part J, Journal of Engineering Tribology, Vol. 222 Number 3 / 2008 LEEDS–LYON SYMPOSIUM SPECIAL ISSUE: (2008), pp. 1-11.

  9. Ciavarella, M. , Strozzi, A., Baldini, A., Giacopini, M., Rivasi S. and Rosi, R. On the Applicability of the Loading Parameter F in Pinned Connections with Relevant Initial Clearance, Applied Mechanics and Materials ISSN: 1660-9336 pN Worksheets Worksheets Studyofmath F Trigonometry En Dl Samsung Remote Client Study Of Math CEMeCz d Study Of Math lN Worksheets Worksheets Studyofmath F Trigonometry En Dl Samsung Remote Client Study Of Math CEMeCa z Study Of Math Study Of Math