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Mechanisms of dislocation multiplication at crack tips

: Bitzek, E.; Gumbsch, P.

Preprint urn:nbn:de:0011-n-2364633 (1.0 MByte PDF)
MD5 Fingerprint: 38c66873f97284090bbdde3d286ee8bf
Erstellt am: 7.5.2016

Acta Materialia 61 (2013), Nr.4, S.1394-1403
ISSN: 1359-6454
Deutsche Forschungsgemeinschaft DFG
GU 367/30
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer IWM ()
fracture; dislocations; crack-dislocation interaction; brittle-to-ductile transition; atomistic simulations

Whether a stressed material fractures by brittle cleavage or ductile rupture is determined by ist ability to onvert elastic strain energy to plastic deformation through the generation and motion of dislocations. Although it is known that pre-existing dislocations play a crucial role in crack tip plasticity, the involved mechanisms are unclear. Here it is demonstrated by atomistic simulations that individual pre-existing dislocations may lead to the generation of large numbers of dislocations at the crack tip. The newly generated dislocations are usually of different types. The processes involved are fundamentally different for stationary cracks and propagating cracks. Whereas local crack front reorientation plays an important role in propagating cracks, the multiplication mechanism at stationary cracks is connected with cross-slip in the highly inhomogeneous stress field of the crack. Analysis of the forces acting on the dislocations allows to determine which dislocations multiply and the slip systems they activate. These results provide the necessary physical link between pre-existing dislocations and the generation of dislocations at crack tips.