Την Τρίτη 14 Μαρτίου 2023 και ώρα 19.00 θα μεταδοθεί ζωντανά η συνεδρία υποδοχής του κ. Alberto Carpinteri, Καθηγητή Δομικής Μηχανικής του Τμήματος Πολιτικών Μηχανικών του Πολυτεχνείου του Τορίνο, ως αντεπιστέλλοντος μέλους της Ακαδημίας Αθηνών. Κατά τη διάρκεια της τελετής υποδοχής, ο Ακαδημαϊκός κ. Εμμανουήλ Γδούτος θα παρουσιάσει τον Καθηγητή Carpinteri, ο οποίος ακολούθως θα εκφωνήσει ομιλία με θέμα “Fracture and Complexity”.
Τη συνεδρία μπορείτε να την παρακολουθήσετε ζωντανά από τον παρακάτω σύνδεσμο:
FRACTURE & COMPLEXITY
Politecnico di Torino, Department of Structural, Geotechnical and Building Engineering, Torino, Italy
The lecture deals with the opposite natural trends in composite systems: catastrophe and chaos arising from simple nonlinear rules, as well as order and structure emerging from heterogeneity and randomness.
Part I deals with Nonlinear Fracture Mechanics models (in particular, the Cohesive Crack Model to describe strain-localization both in tension and in compression) and their peculiar consequences: fold catastrophes (post-peak strain-softening and snap-through instabilities) or cusp catastrophes (snap-back instabilities) in plain or reinforced structural elements. How can a relatively simple nonlinear constitutive law, which is scale-independent, generate a size-scale dependent ductile-to-brittle transition? Constant reference is made to Dimensional Analysis and to the definition of suitable nondimensional brittleness numbers that govern the transition. These numbers can be defined in different ways, according to the selected theoretical model. The simplest way is that of directly comparing critical LEFM conditions and plastic limit analysis results. This is an equivalent way --although more effective for finite-sized cracked plates-- to describe the ductile-to-brittle size-scale transition, if compared to the traditional evaluation of the crack tip plastic-zone extension in an infinite plate. In extremely brittle cases, the plastic zone or process zone tends to disappear and the cusp catastrophe conditions prevail over the strain-softening ones and tend to coincide with the LEFM critical conditions in the case of initially cracked plates.
Part II deals with the occurrence of self-similar and fractal patterns in the deformation, damage, fracture, and fragmentation of heterogeneous disordered materials, and with the consequent apparent scaling in the nominal mechanical properties of the same materials. Such a scaling is negative (lacunar fractality) for tensile strength and fatigue limit, whereas it is positive (invasive fractality) for fracture energy, fracture toughness, and fatigue threshold. At the same time, corresponding fractal (or renormalized) quantities emerge, which are the true scale-invariant properties of the material. They appear to be the constant factor (the universal property) in the power-law relating the nominal canonical quantity to the size-scale of observation. When the reference sets from self-similar become self-affine, we obtain Multi-fractal Scaling Laws, which are asymptotic and present a decreasing fractality for increasing structural sizes. They reproduce the experimental data very consistently. On the other hand, Critical Phenomena are always associated to the emergence of self-similar or self-affine patterns, to fractal (renormalized) or multi-fractal quantities, and to spontaneous self-organization. Typical examples are represented by: phase transformations, laminar-to-turbulent fluid flow transitions, avalanches in granular media, earthquakes, micro-cracking and fracture in structural materials. In a fractal framework, it is then possible to define a scale-invariant constitutive law: the so-called Fractal Cohesive Crack Model, in which stress and strain are defined over lacunar fractal sets and the fracture energy in an invasive fractal set, which is the Cartesian product of the two previous sets.
A. Carpinteri, Fracture and Complexity, Springer-Nature, Heidelberg, 2021.
Curriculum Vitae (Short)
Alberto Carpinteri received his Doctoral Degrees in Nuclear Engineering cum Laude (1976) and in Mathematics cum Laude (1981) from the University of Bologna (Italy). After two years at the Consiglio Nazionale delle Ricerche, he was appointed Assistant Professor at the University of Bologna in 1980.
He moved to the Politecnico di Torino in 1986 as a full professor, and became the Chair Professor of Solid and Structural Mechanics, as well as the Director of the Fracture Mechanics Laboratory. During this period, he has held different positions of responsibility, among which: Head of the Department of Structural Engineering (1989-1995), and Founding Director of the Post-graduate School of Structural Engineering (1990-2014).
Prof. Carpinteri was a Visiting Scientist at Lehigh University, Pennsylvania, USA (1982-1983), and was appointed as a Fellow of several Academies and Professional Institutions, among which: the European Academy of Sciences (2009-), the International Academy of Engineering (2010-), the Turin Academy of Sciences (2005-), the American Society of Civil Engineers (1995-). He is presently the Head of the Engineering Division in the European Academy of Sciences (2016-).
Prof. Carpinteri was the President of several Scientific Associations and Research Institutions: the International Congress on Fracture, ICF (2009-2013), the European Structural Integrity Society, ESIS (2002-2006), the International Association of Fracture Mechanics for Concrete and Concrete Structures, lA-FraMCoS (2004-2007), the Italian Group of Fracture, IGF (1998-2005), the National Research Institute of Metrology, INRIM (2011-2013).
Prof. Carpinteri was appointed as a Member of the Congress Committee of the International Union of Theoretical and Applied Mechanics, IUTAM (2004-2012), a Member of the Executive Board of the Society for Experimental Mechanics, SEM (2012-2014), a Member of the Editorial Board of eleven international journals, the Editor-in-Chief of the journal “Meccanica” (Springer, IF=1.949). He is the author or editor of over 1,000 publications, of which more than 490 are papers in refereed international journals (G-Scholar H-Index=86, more than 30,000 Citations; Scopus H-Index=64, more than 14,000 Citations) and 58 are books or journal special issues.
Prof. Carpinteri received numerous international Honours and Awards: the Robert L'Hermite Medal from RILEM (1982), the Griffith Medal from ESIS (2008), the Swedlow Memorial Lecture Award from ASTM (2011), the Inaugural Paul Paris Gold Medal from ICF (2013), the Doctorate Honoris Causa in Engineering from the Russian Academy of Sciences (2016), the Frocht Award from SEM (2017), the Honorary Professorship from Tianjin University (2017), the Founding Fellowship from the Indian Structural Integrity Society (2018), the “Pearl River” Professorship from Guangdong Province, Shantou University (2019), and the Giuliano Preparata Medal from the International Society for Condensed Matter Nuclear Science (2022).