Uniqueness and stability of activated dislocation shapes in crystals

0545719 - ÚFM 2022 RIV GB eng J - Journal Article
Gröger, Roman - Šremr, J. - Vydrová, J.
Uniqueness and stability of activated dislocation shapes in crystals.
Modelling and Simulation in Materials Science and Engineering. Roč. 29, č. 2 (2021), č. článku 025006. ISSN 0965-0393. E-ISSN 1361-651X
R&D Projects: GA ČR(CZ) GA19-23411S; GA MŠMT(CZ) LQ1601
Institutional support: RVO:68081723
Keywords : dislocations * slip * activation enthalpy * boundary value problem * uniqueness * stability
OECD category: Applied mathematics
Impact factor: 2.421, year: 2021
Method of publishing: Limited access
https://iopscience.iop.org/article/10.1088/1361-651X/abd041

Simplified models of thermally activated dislocation glide constitute an important link between atomic-level studies of isolated dislocations and macroscopic thermodynamic properties of materials. These models rest upon the activation enthalpy, which is the energy to transform an initially straight dislocation into its activated state at finite applied stresses. Minimizing this activation enthalpy leads to a boundary value problem for the shape of the dislocation line. Besides two constant solutions corresponding to a straight dislocation in its stable and unstable states at the applied stress, there exist an infinite number of non-constant solutions. We investigate the characters of these solutions for dislocations anchored at their ends. Using the second variation of the activation enthalpy, we derive a set of conditions that define a unique activated state of the dislocation. The corresponding analysis demonstrates that the shape of the dislocation in this activated state must change with the applied stress to maintain the state of minimum activation enthalpy.
Permanent Link: http://hdl.handle.net/11104/0322626