{"id":{"repo_id":"greece","oai_identifier":"oai:10442/1696"},"canonical_url":"https://search.dev.ndltd.org/etd/greece/oai:10442/1696","repository":{"repo_id":"greece","name":"Greek National Archive of PhD Theses","base_url":"https://phdtheses.ekt.gr/eadd_oai/request"},"display":{"title":"Συμβολή της ηλεκτρονικής μικροσκοπίας σαρώσεως στη μελέτη ελαστοπλαστικών φαινομένων κατά τη θραύση των υλικών","abstract":"By means of scanning electron microscopy a systematic study of some basic elastoplastic phenomena during the fracture of edge-cracked specimens is undertaken. In this way the formation process of plastic zones, the field and \"pseudofield\" of slip- lines around a static and a propagating crack is studied qualititavely and quantitatively. It is observed that the examinated materials (copper and Lexan) exhibited very different behavior as far as the above mentioned phenomena are concerned. In the case of Lexan an intense formation of a (oblongs) damaged ligament ahead of the crack-tip is observed. This ligament is of a Dugdale general type plastic zone. On the contrary in the case of copper it is not possible to observe these phenomena. Another phenomenon which is studied is the blunting of a sharp crack tip before it has been propagated and which consist the main part of this thesis. Thus, the two materials exhibit different behaviour as far as this phenomenon is concerned. It was possible to measure precisely the two components of the blunting, i.e. the CTOD and the CTAD. By means of these two components a quantitative comparison with known models, shown for Lexan a satisfactory up to a good correlation, while for copper only satisfactory. It is still observed that this phenomenon is very complicated as far as its morphological education is concerned. The CTOD (crack tip opening displacement) may be used, under certain conditions, as a \"mechanical parameter\" of the elastic plastic fracture of a material.","abstract_html":"By means of scanning electron microscopy a systematic study of some basic elastoplastic phenomena during the fracture of edge-cracked specimens is undertaken. In this way the formation process of plastic zones, the field and "pseudofield" of slip- lines around a static and a propagating crack is studied qualititavely and quantitatively. It is observed that the examinated materials (copper and Lexan) exhibited very different behavior as far as the above mentioned phenomena are concerned. In the case of Lexan an intense formation of a (oblongs) damaged ligament ahead of the crack-tip is observed. This ligament is of a Dugdale general type plastic zone. On the contrary in the case of copper it is not possible to observe these phenomena. Another phenomenon which is studied is the blunting of a sharp crack tip before it has been propagated and which consist the main part of this thesis. Thus, the two materials exhibit different behaviour as far as this phenomenon is concerned. It was possible to measure precisely the two components of the blunting, i.e. the CTOD and the CTAD. By means of these two components a quantitative comparison with known models, shown for Lexan a satisfactory up to a good correlation, while for copper only satisfactory. It is still observed that this phenomenon is very complicated as far as its morphological education is concerned. The CTOD (crack tip opening displacement) may be used, under certain conditions, as a "mechanical parameter" of the elastic plastic fracture of a material.","abstract_has_math":false,"creators":["Kytopoulos, Victor","Κυτόπουλος, Βίκτωρ"],"institution":"National Technical University of Athens (NTUA)","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":1991,"date_issued":"1991","date_published":"1991","updated_at":"2026-07-24T02:25:05Z","subjects":["Άμβλυνση της αιχμής μιας ρωγμής","Ανάλωση της στενής ζώνης χαλαρής συνοχής","Δυναμικό μοντέλο τύπου Dugdale διάδοσης ρωγμής","Ζώνες-λωρίδες γενικού τύπου Luders","Κατάσταση επίπεδης έντασης και παραμόρφωσης","Μακρόστενη \"εφθαρμένη\" ζώνη χαλαρής συνοχής","Πεδία slip-lines τύπου Rice-Johnson κλπ","Πλαστικές ζώνες Dugdale","Ψευδοπεδία τύπου post, κύριες τροχιές τάσεων","Blunting phenomena of a crack tip","Dugdale plastic-zones, damaged ligament","Luder zones-bonds","Slip-lines fields of Rice-Johnson etc","Επιστήμες Μηχανικού και Τεχνολογία","Μηχανική Υλικών","Engineering and Technology","Materials Engineering"],"languages":["gre"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["10.12681/eadd/1696"],"render_values":[{"text":"10.12681/eadd/1696","href":"https://doi.org/10.12681/eadd/1696","code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/10442/hedi/1696","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Kytopoulos, Victor","Κυτόπουλος, Βίκτωρ"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["1991"]},{"key":"dc:publisher","label":"Institution","values":["National Technical University of Athens (NTUA)","Εθνικό Μετσόβιο Πολυτεχνείο (ΕΜΠ)"]},{"key":"dc:type","label":"Dc Type","values":["PhD Thesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Άμβλυνση της αιχμής μιας ρωγμής","Ανάλωση της στενής ζώνης χαλαρής συνοχής","Δυναμικό μοντέλο τύπου Dugdale διάδοσης ρωγμής","Ζώνες-λωρίδες γενικού τύπου Luders","Κατάσταση επίπεδης έντασης και παραμόρφωσης","Μακρόστενη \"εφθαρμένη\" ζώνη χαλαρής συνοχής","Πεδία slip-lines τύπου Rice-Johnson κλπ","Πλαστικές ζώνες Dugdale","Ψευδοπεδία τύπου post, κύριες τροχιές τάσεων","Blunting phenomena of a crack tip","Dugdale plastic-zones, damaged ligament","Luder zones-bonds","Slip-lines fields of Rice-Johnson etc","Επιστήμες Μηχανικού και Τεχνολογία","Μηχανική Υλικών","Engineering and Technology","Materials Engineering"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["gre"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["10.12681/eadd/1696","http://hdl.handle.net/10442/hedi/1696"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["By means of scanning electron microscopy a systematic study of some basic elastoplastic phenomena during the fracture of edge-cracked specimens is undertaken. In this way the formation process of plastic zones, the field and \"pseudofield\" of slip- lines around a static and a propagating crack is studied qualititavely and quantitatively. It is observed that the examinated materials (copper and Lexan) exhibited very different behavior as far as the above mentioned phenomena are concerned. In the case of Lexan an intense formation of a (oblongs) damaged ligament ahead of the crack-tip is observed. This ligament is of a Dugdale general type plastic zone. On the contrary in the case of copper it is not possible to observe these phenomena. Another phenomenon which is studied is the blunting of a sharp crack tip before it has been propagated and which consist the main part of this thesis. Thus, the two materials exhibit different behaviour as far as this phenomenon is concerned. It was possible to measure precisely the two components of the blunting, i.e. the CTOD and the CTAD. By means of these two components a quantitative comparison with known models, shown for Lexan a satisfactory up to a good correlation, while for copper only satisfactory. It is still observed that this phenomenon is very complicated as far as its morphological education is concerned. The CTOD (crack tip opening displacement) may be used, under certain conditions, as a \"mechanical parameter\" of the elastic plastic fracture of a material.","Με την βοήθεια της μεθόδου της ηλεκτρονικής μικροσκοπίας σάρωσης γίνεται μια συστηματική και σε βάθος μελέτη ορισμένων βασικών ελαστοπλαστικών φαινομένων κατά τη θραύση ρηγματωμένων υλικών. Έτσι μελετάται ποιοτικά και ποσοτικά η εξελικτική πορεία σχηματισμού πλαστικών ζωνών και πεδίων ή \"ψευδοπεδίων\" slip-lines γύρω από το άκρο μιας στατικής και μιας διαδιδομένης ρωγμής σε δοκίμια από Lexan και χαλκό. Παρατηρείται, ότι για τα δύο αυτά υλικά τα παραπάνω φαινόμενα έχουν διαφορετική νομοτέλεια. Έτσι στο Lexan υπάρχει έντονος σχηματισμός μιας μακρόστενης ζώνης χαλαρής συνοχής γενικού τύπου dugdale, αλλά ταυτόχρονα και σχηματισμός πεδίων ή \"ψευδοπεδίων\" slip-lines, πράγμα που δεν παρατηρείται στα δοκίμια από χαλκό. Ένα άλλο φαινόμενο που μελετάται είναι αυτό της άμβλυνσης μιας αιχμής ρωγμής πριν την διάδοση της, φαινόμενο το οποίο αποτελεί και τον πυρήνα της διατριβής. Έτσι σε ότι αφορά αυτό το φαινόμενο τα δύο υλικά δείχνουν μεγάλες διαφορές. Μέσω της ακριβούς μέτρησης των συνιστωσών της άμβλυνσης, δηλ. Του CTOD και του CTAD, γίνεται ποσοτική σύγκριση με γνωστά μοντέλα, όπου για το Lexan υπάρχει ικανοποιητική μέχρι καλή προσέγγιση, ενώ στο χαλκό αυτή δεν είναι ικανοποιητική. Διαπιστώνεται ακόμα, ότι το παραπάνω φαινόμενο, είναι πολυσύνθετο σε ότι αφορά την μορφολογική του εξέλιξη. Το CTOD μπορεί να χρησιμοποιηθεί υπό ορισμένες συνθήκες σαν μια \"παράμετρο\" της ελαστοπλαστικής θραύσης ενός υλικού."]},{"key":"dc:title","label":"Title","values":["Συμβολή της ηλεκτρονικής μικροσκοπίας σαρώσεως στη μελέτη ελαστοπλαστικών φαινομένων κατά τη θραύση των υλικών"]}]}],"canonical_facts":{"dc:creator":["Kytopoulos, Victor","Κυτόπουλος, Βίκτωρ"],"dc:date":["1991"],"dc:description":["By means of scanning electron microscopy a systematic study of some basic elastoplastic phenomena during the fracture of edge-cracked specimens is undertaken. In this way the formation process of plastic zones, the field and \"pseudofield\" of slip- lines around a static and a propagating crack is studied qualititavely and quantitatively. It is observed that the examinated materials (copper and Lexan) exhibited very different behavior as far as the above mentioned phenomena are concerned. In the case of Lexan an intense formation of a (oblongs) damaged ligament ahead of the crack-tip is observed. This ligament is of a Dugdale general type plastic zone. On the contrary in the case of copper it is not possible to observe these phenomena. Another phenomenon which is studied is the blunting of a sharp crack tip before it has been propagated and which consist the main part of this thesis. Thus, the two materials exhibit different behaviour as far as this phenomenon is concerned. It was possible to measure precisely the two components of the blunting, i.e. the CTOD and the CTAD. By means of these two components a quantitative comparison with known models, shown for Lexan a satisfactory up to a good correlation, while for copper only satisfactory. It is still observed that this phenomenon is very complicated as far as its morphological education is concerned. The CTOD (crack tip opening displacement) may be used, under certain conditions, as a \"mechanical parameter\" of the elastic plastic fracture of a material.","Με την βοήθεια της μεθόδου της ηλεκτρονικής μικροσκοπίας σάρωσης γίνεται μια συστηματική και σε βάθος μελέτη ορισμένων βασικών ελαστοπλαστικών φαινομένων κατά τη θραύση ρηγματωμένων υλικών. Έτσι μελετάται ποιοτικά και ποσοτικά η εξελικτική πορεία σχηματισμού πλαστικών ζωνών και πεδίων ή \"ψευδοπεδίων\" slip-lines γύρω από το άκρο μιας στατικής και μιας διαδιδομένης ρωγμής σε δοκίμια από Lexan και χαλκό. Παρατηρείται, ότι για τα δύο αυτά υλικά τα παραπάνω φαινόμενα έχουν διαφορετική νομοτέλεια. Έτσι στο Lexan υπάρχει έντονος σχηματισμός μιας μακρόστενης ζώνης χαλαρής συνοχής γενικού τύπου dugdale, αλλά ταυτόχρονα και σχηματισμός πεδίων ή \"ψευδοπεδίων\" slip-lines, πράγμα που δεν παρατηρείται στα δοκίμια από χαλκό. Ένα άλλο φαινόμενο που μελετάται είναι αυτό της άμβλυνσης μιας αιχμής ρωγμής πριν την διάδοση της, φαινόμενο το οποίο αποτελεί και τον πυρήνα της διατριβής. Έτσι σε ότι αφορά αυτό το φαινόμενο τα δύο υλικά δείχνουν μεγάλες διαφορές. Μέσω της ακριβούς μέτρησης των συνιστωσών της άμβλυνσης, δηλ. Του CTOD και του CTAD, γίνεται ποσοτική σύγκριση με γνωστά μοντέλα, όπου για το Lexan υπάρχει ικανοποιητική μέχρι καλή προσέγγιση, ενώ στο χαλκό αυτή δεν είναι ικανοποιητική. Διαπιστώνεται ακόμα, ότι το παραπάνω φαινόμενο, είναι πολυσύνθετο σε ότι αφορά την μορφολογική του εξέλιξη. Το CTOD μπορεί να χρησιμοποιηθεί υπό ορισμένες συνθήκες σαν μια \"παράμετρο\" της ελαστοπλαστικής θραύσης ενός υλικού."],"dc:identifier":["10.12681/eadd/1696","http://hdl.handle.net/10442/hedi/1696"],"dc:language":["gre"],"dc:publisher":["National Technical University of Athens (NTUA)","Εθνικό Μετσόβιο Πολυτεχνείο (ΕΜΠ)"],"dc:subject":["Άμβλυνση της αιχμής μιας ρωγμής","Ανάλωση της στενής ζώνης χαλαρής συνοχής","Δυναμικό μοντέλο τύπου Dugdale διάδοσης ρωγμής","Ζώνες-λωρίδες γενικού τύπου Luders","Κατάσταση επίπεδης έντασης και παραμόρφωσης","Μακρόστενη \"εφθαρμένη\" ζώνη χαλαρής συνοχής","Πεδία slip-lines τύπου Rice-Johnson κλπ","Πλαστικές ζώνες Dugdale","Ψευδοπεδία τύπου post, κύριες τροχιές τάσεων","Blunting phenomena of a crack tip","Dugdale plastic-zones, damaged ligament","Luder zones-bonds","Slip-lines fields of Rice-Johnson etc","Επιστήμες Μηχανικού και Τεχνολογία","Μηχανική Υλικών","Engineering and Technology","Materials Engineering"],"dc:title":["Συμβολή της ηλεκτρονικής μικροσκοπίας σαρώσεως στη μελέτη ελαστοπλαστικών φαινομένων κατά τη θραύση των υλικών"],"dc:type":["PhD Thesis"]},"updated_at":"2026-07-24T02:25:05Z"}