Thermal activation and ductile vs. brittle behavior of microcracks in 3D BCC iron crystals under biaxial loading by atomistic simulations

0536302 - ÚT 2021 RIV CH eng J - Článek v odborném periodiku
Uhnáková, Alena - Machová, Anna - Hora, Petr
Thermal activation and ductile vs. brittle behavior of microcracks in 3D BCC iron crystals under biaxial loading by atomistic simulations.
Metals. Roč. 10, č. 11 (2020), č. článku 1525. E-ISSN 2075-4701
Grant CEP: GA ČR(CZ) GA17-12925S; GA MŠk(CZ) EF15_003/0000493; GA TA ČR(CZ) TK01030108
Institucionální podpora: RVO:61388998
Klíčová slova: thermal activation * ductile-brittle transition * T-stress * bcc iron * molecular dynamics
Obor OECD: Materials engineering
Impakt faktor: 2.351, rok: 2020
Způsob publikování: Open access
https://www.mdpi.com/2075-4701/10/11/1525

We present the results of free 3D molecular dynamics (MD) simulations, focused on the influence of temperature on the ductile-brittle behavior of a pre-existing central Gri_th through
microcrack (110)[110] (crack plane/crack front) under biaxial loading _A and _B in tension mode I. At temperatures of 300 K and 600 K, the MD results provide new information on the threshold
values of the stress intensity factor K and the energy release rate G, needed for the emission of 111{112} blunting dislocations that support crack stability. A simple procedure for the evaluation of thermal activation from MD results is proposed in the paper. 3D atomistic results are compared with continuum predictions on thermal activation of the crack induced dislocation generation. At elevated
temperature T and biaxiality ratios _B/_A _ 0.8 dislocation emission in MD is observed, supported by thermal activation energy of about ~30 kBT.With increasing temperature, the ductile-brittle transition moves to a higher biaxiality ratios in comparison with the situation at temperature of ~0 K. Near the transition, dislocation emission occurs at lower loadings than expected by continuum predictions. For the ratios _B/_A _ 1, the elevated temperature facilitates (surprisingly) the microcrack growth below Gri_th level.
Trvalý link: http://hdl.handle.net/11104/0314650