Προχωρημένες υπολογιστικές μέθοδοι υψηλών επιδόσεων για την επίλυση προβλημάτων διάδοσης ρωγμών με τη μέθοδο των εξελιγμένων πεπερασμένων στοιχείων

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dc.contributor.author Μπακαλάκος, Σεραφείμ
dc.contributor.author Bakalakos, Serafeim
dc.date.accessioned 2022-10-12T10:01:07Z
dc.date.available 2022-10-12T10:01:07Z
dc.identifier.uri https://dspace.lib.ntua.gr/xmlui/handle/123456789/55896
dc.identifier.uri http://dx.doi.org/10.26240/heal.ntua.23594
dc.rights Αναφορά Δημιουργού-Μη Εμπορική Χρήση-Όχι Παράγωγα Έργα 3.0 Ελλάδα *
dc.rights.uri http://creativecommons.org/licenses/by-nc-nd/3.0/gr/ *
dc.subject Πεπερασμένα στοιχεία el
dc.subject Υποφορείς el
dc.subject Μετάδοση θερμότητας el
dc.subject Διάδοση ρωγμών el
dc.subject Υπολογιστικά συστήματα υψηλών επιδόσεων el
dc.subject XFEM en
dc.subject Domain decomposition en
dc.subject Heat transfer en
dc.subject Crack propagation en
dc.subject High performance computing en
dc.title Προχωρημένες υπολογιστικές μέθοδοι υψηλών επιδόσεων για την επίλυση προβλημάτων διάδοσης ρωγμών με τη μέθοδο των εξελιγμένων πεπερασμένων στοιχείων el
dc.contributor.department Laboratory of Structural Analysis & Antiseismic Research el
heal.type doctoralThesis
heal.secondaryTitle Advanced high performance computing methods for the solution of crack propagation and material design problems using the extended Finite Element method (XFEM) el
heal.classification Υπολογιστική Μηχανική el
heal.classification Computational Mechanics en
heal.language en
heal.access free
heal.recordProvider ntua el
heal.publicationDate 2022-06-16
heal.abstract The need for advanced high-performance materials in the industry led to the development of various innovative solutions over the years, designed to possess application-specific properties, such as improved thermal conductivity. To model heat transfer in composite materials, their complex micro-structure, as well as the thermal resistance at the interfaces between materials must be taken into account. The standard finite element treatment requires very fine meshes to conform to the complex geometry of these interfaces. This thesis proposes an eXtended Finite Element Method (XFEM) formulation that captures the temperature jump by enriching the polynomial approximation around the material interfaces with appropriate discontinuous functions. Specifically, a new XFEM enrichment scheme is developed to address the issue of multiple-phase junctions, namely areas where multiple interfaces with different resistance properties intersect. In addition, a double-mesh LSM technique is developed for describing the geometry of material interfaces. A very fine mesh is employed by a Level Set Method (LSM) to represent complex interface geometries with high accuracy, whereas XFEM uses a mesh that does not conform to the material interfaces, but is instead a coarser version of the LSM mesh, to reduce the computational cost of the analysis. The combined numerical model is first validated against existing results from the literature on polycrystalline materials. Then, it is applied for heat conduction analysis of polymers reinforced with carbon-nanotubes. The unknown thermal resistance between these materials is inferred by calibrating the numerically predicted effective conductivity to corresponding experimental measurements. The proposed XFEM model can be straightforwardly extended to other similar problem types, such us elasticity or electrical conduction. XFEM is also an attractive choice for modeling crack propagation, by enriching the polynomial displacement field of FEM with specialized non-smooth functions, without the need of remeshing in the vicinity of the crack at each propagation step. However, this enrichment causes the stiffness matrix to become strongly ill-conditioned, rendering the convergence of iterative solvers very slow. On the other hand, direct solvers are inefficient in 3D problems, due to the increased bandwidth of the system matrix. In this thesis, two domain decomposition solvers, namely FETI-DP and P-FETI-DP, are proposed for solving the linear systems resulting from XFEM crack propagation analysis in large-scale 3D problems. By modifying the coarse problem of both solvers, any singularities caused by the crack propagation are avoided and the XFEM-related ill-conditioning is completely eliminated, ensuring the scalability of FETI-DP and P-FETI-DP as the number of subdomains is increased. Finally, an efficient implementation in high performance computing systems, specifically computer clusters is developed, by altering the original FETI-DP and P-FETI-DP equations to minimize communication and computation bottlenecks in distributed memory environments. en
heal.sponsor I gratefully acknowledge the funding received towards my Ph.D from the Special Account for Research Funding (E.L.K.E.) of National Technical University of Athens (N.T.U.A.) scholarship. Funding was also provided by participation in the project ``Optimal multiscale design of innovative materials for heat exchange applications, (HEAT-68/1286)'', from the European Regional Development Fund and Greek National Funds through the operational program Competitiveness, Entrepreneurship and Innovation, under the call Research-Create-Innovate. el
heal.advisorName Παπαδόπουλος, Βησσαρίων
heal.advisorName Παπαδρακάκης, Μανόλης
heal.advisorName Papadopoulos, Vissarion
heal.advisorName Papadrakakis, Manolis
heal.committeeMemberName Παπαδόπουλος, Βησσαρίων
heal.committeeMemberName Σπηλιόπουλος, Κωνσταντίνος
heal.committeeMemberName Λαγαρός, Νικόλαος
heal.committeeMemberName Σαπουντζάκης, Ευάγγελος
heal.committeeMemberName Νεραντζάκη, Μαρία
heal.committeeMemberName Στεφάνου, Γεώργιος
heal.committeeMemberName Τριανταφύλλου, Σάββας
heal.committeeMemberName Papadopoulos, Vissarion
heal.committeeMemberName Spiliopoulos, Konstantinos
heal.committeeMemberName Lagaros, Nikolaos
heal.committeeMemberName Sapountzakis, Euaggelos
heal.committeeMemberName Nerantzaki, Maria
heal.committeeMemberName Stefanou, Georgios
heal.committeeMemberName Triantafullou, Savvas
heal.academicPublisher Σχολή Πολιτικών Μηχανικών el
heal.academicPublisherID ntua
heal.numberOfPages 277
heal.fullTextAvailability false

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Αναφορά Δημιουργού-Μη Εμπορική Χρήση-Όχι Παράγωγα Έργα 3.0 Ελλάδα Except where otherwise noted, this item's license is described as Αναφορά Δημιουργού-Μη Εμπορική Χρήση-Όχι Παράγωγα Έργα 3.0 Ελλάδα