Συμβολή της ηλεκτρονικής μικροσκοπίας σαρώσεως στη μελέτη ελαστοπλαστικών φαινομένων κατά τη θραύση των υλικών

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.

Grantor dc:publisher

National Technical University of Athens (NTUA)

Year dc:date

1991

Authors dc:creator

• Kytopoulos, Victor
• Κυτόπουλος, Βίκτωρ

• 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

Language dc:language

gre

Identifier

10.12681/eadd/1696

OAI identifier oai:identifier

oai:10442/1696