Seminars at the Faculty of Informatics

The Faculty of Informatics is pleased to announce a seminar given by Marco Paggi

DATE: Wednesday, December 7th, 2011
PLACE: USI Università della Svizzera italiana, room A34, Red building (Via G. Buffi 13)
TIME: 14.30

ABSTRACT:
The assumption of flat surfaces within the context of contact problems is very often an oversimplification of reality. In fact, when real surfaces are examined more in details using profilometers, roughness can be found over different length scales. This multiscale feature poses enormous difficulties on the mathematical modelling of contact problems. Nevertheless, the understanding of the effect of multiscale roughness on the tribological properties of materials in contact is essential from the engineering point of view.
In this seminar, mathematical aspects and numerical treatment of normal and tangential contact problems between rough surfaces are presented. Modelling rough surfaces as invasive fractals, a first part of the talk focuses on the computation of the normal contact stiffness of the joint. This information is of paramount importance, since it can be profitably included in contact mechanics formulations based on the finite element method for the analysis of industrial problems. Moreover, the normal contact stiffness can be related to the thermal and electric contact conductances, important properties to be ascertain in thermo-electro-mechanics applications. In the second part of the talk, the tangential contact response of rough surfaces is analyzed. Special attention is given to the micro-slip range, using the recent generalization of the Cattaneo-Mindlin's theorem relating the normal contact problem to the tangential one.

Selected references

  • M. Paggi, J.R. Barber: Contact conductance of rough surfaces composed of modified RMD patches, Int. J. Heat and Mass Transfer, 4:4664-4672, 2011.
  • M. Paggi, G. Zavarise: Contact mechanics of microscopically rough surfaces with graded elasticity, Eur. J. Mech. / A Solids, 30:696-704, 2011.
  • M. Paggi, M. Ciavarella: The coefficient of proportionality κ between real contact area and load, with new asperity models, Wear, 268:1020-1029, 2010.
  • M. Ciavarella, J.A. Greenwood, M. Paggi: Inclusion of "interaction" in the Greenwood & Williamson contact theory, Wear, 265:729-734, 2008.
  • M. Paggi, A. Carpinteri, G. Zavarise: A unified interface constitutive law for the study of fracture and contact problems in heterogeneous materials, In: P. Wriggers, U. Nackenhorst (Eds.), Analysis and Simulation of Contact Problems, Lecture Notes in Appl. and Comp. Mech., 27:297-304, 2006.
  • Carpinteri, M. Paggi: Size-scale effects on the friction coefficient, Int. J. Solids and Struct., 42:2901-2910, 2005.

BIO:
Marco Paggi was born in Novara, Italy, in December 1977. He earned a Master in Civil Engineering at Politecnico di Torino in December 2001, summa cum laude. Appointed Ph.D. in Structural Engineering on May 6, 2005. Assistant Professor of Structural Mechanics in the Department of Structural and Geotechnical Engineering of Politecnico di Torino since August 2007. Appointed Alexander von Humboldt Research Fellow at the Gottfried Wilhelm Leibniz University Hannover, Germany, Institute of Continuum Mechanics, in the period February 2010-January 2011.
He has been recipient of several prizes and awards at the national and international levels, among which the "Young Scientist Award" in 2010 conferred by the European Structural Integrity Society and the "Prize for Outstanding Collaboration of a Visiting Researcher" in 2011 by the Freundeskreis der Leibniz Universitńt Hannover, Section Mechanics.
He is elected member of the Executive Board of the Italian Group of Fracture (2009-2011 & 2011-2013) and member of the Editorial Board of The Journal of Strain Analysis for Engineering Design.
He is author of more than 110 publications in the fields of fracture mechanics and contact mechanics, among which 53 in international ISI journals. He is actually the principal investigator of the "FIRB Future in Research" Project "Structural mechanics models for renewable energy applications", granted by Italian Ministry of Education, University and Research (954.800 Euro).

HOST: Prof. Rolf Krause

URL 1: http://www.inf.usi.ch