Fracture toughness of Fe-Si single crystals in mode I: Effect of loading rate on an edge crack (-110)[110] at macroscopic and atomistic level

0560649 - ÚT 2023 RIV US eng J - Journal Article
Uhnáková, Alena - Machová, Anna - Janovská, Michaela - Ševčík, Martin - Štefan, Jan - Hora, Petr - Čapek, Jaroslav - Lejček, Pavel
Fracture toughness of Fe-Si single crystals in mode I: Effect of loading rate on an edge crack (-110)[110] at macroscopic and atomistic level.
Journal of Applied Physics. Roč. 132, č. 6 (2022), č. článku 065107. ISSN 0021-8979. E-ISSN 1089-7550
R&D Projects: GA TA ČR(CZ) TK01030108; GA ČR(CZ) GA22-20181S; GA MŠMT(CZ) EF16_019/0000760; GA MŠMT(CZ) EF15_003/0000493
Institutional support: RVO:61388998 ; RVO:68378271
Keywords : fracture * Fe-Si single crystals * dislocation emission * loading (strain) rate * molecular dynamics * bcc iron
OECD category: Materials engineering; Condensed matter physics (including formerly solid state physics, supercond.) (FZU-D)
Impact factor: 3.2, year: 2022
Method of publishing: Limited access
https://aip.scitation.org/doi/full/10.1063/5.0101626

This paper is devoted to an experimental and 3D atomistic study of the influence of loading rate on fracture toughness in dilute Fe-Si alloys and in bcc iron. We analyze new and previous experimental results from fracture tests performed at room temperature on bcc ironsilicon single crystals with edge cracks (110) [110] (crack plane/crack front). The specimens of SEN (single edge notch) type were loaded in tension mode I under different loading rates. The ductile-brittle behavior at the crack front was monitored on-line via optical microscopy together with external force and prolongation of the specimens. About 30% decrease in fracture toughness was monitored in the new experiment under the highest loading rate. The nanoscopic processes produced by the crack itself were studied at room temperature via 3D molecular dynamic (MD) simulations in bcc iron under equivalent boundary conditions as in experiments to reveal (explain) the sensitivity of the crack to loading rate. For this purpose, this MD study utilizes the self-similar character of linear fracture mechanics. The results show that the emission of blunting dislocations from the crack is the most difficult under the highest loading rate, which leads to the reduced fracture toughness of the atomistic sample. This is in a qualitative agreement with the experimental (macro) results. Moreover, MD indicates that there may be some synenergetic (resonant) effect between the loading rate and thermal activation that promotes dislocation emission.
Permanent Link: https://hdl.handle.net/11104/0334790