Fatigue cracks in additively manufactured (AMed) Inconel 718 (IN-718) in machined surface condition often initiate from persistent slip bands (PSBs) unlike other popular AM alloys such as 17-4 PH stainless steel or Ti-6Al-4V, where fatigue crack initiation is exclusively from volumetric defects; therefore, a competition between PSB- vs. defect- mediated crack initiation clearly exists. To shed light on the factors governing the competition, this study investigates the characteristics of cyclic strain localization, PSB formation, and crack initiation via crystal plasticity (CP) modeling of cyclic loading on polycrystalline aggregates which are then validated by experiments. In this work, a physics-based, free slip distance (FSD) dependent slip strength evolution law is proposed, which is shown to enable the CP model to simulate the heterogeneous strain distribution in IN-718. Implementing a crack initiation criterion based on strain contrast, the locations and lives for crack initiation can also be calculated. It is shown that both FSD and resolve shear stress influence the strain localization and crack initiation behaviors. The distribution of a localization parameter calculated based on the multiplication of FSD and Schmid factor within a grain is found to correlate well with the locations of PSBs. The maximum values of the localization parameters within a microstructure are shown to correlate well with the experimentally obtained crack initiation lives. The presence of volumetric defects in IN-718 generally do not impact strain localization behavior unless their size is large compared to the grain size.
Dodaran, Mohammad S., et al. "Synergistic effect of microstructure and defects on the initiation of fatigue cracks in additively manufactured Inconel 718." International Journal of Fatigue, vol. 162, May. 2022. https://doi.org/10.1016/j.ijfatigue.2022.107002
Dodaran, Mohammad S., Muhammad, Muztahid, Shamsaei, Nima, & Shao, Shuai (2022). Synergistic effect of microstructure and defects on the initiation of fatigue cracks in additively manufactured Inconel 718. International Journal of Fatigue, 162. https://doi.org/10.1016/j.ijfatigue.2022.107002
Dodaran, Mohammad S., Muhammad, Muztahid, Shamsaei, Nima, et al., "Synergistic effect of microstructure and defects on the initiation of fatigue cracks in additively manufactured Inconel 718," International Journal of Fatigue 162 (2022), https://doi.org/10.1016/j.ijfatigue.2022.107002
@article{osti_1867812,
author = {Dodaran, Mohammad S. and Muhammad, Muztahid and Shamsaei, Nima and Shao, Shuai},
title = {Synergistic effect of microstructure and defects on the initiation of fatigue cracks in additively manufactured Inconel 718},
annote = {Fatigue cracks in additively manufactured (AMed) Inconel 718 (IN-718) in machined surface condition often initiate from persistent slip bands (PSBs) unlike other popular AM alloys such as 17-4 PH stainless steel or Ti-6Al-4V, where fatigue crack initiation is exclusively from volumetric defects; therefore, a competition between PSB- vs. defect- mediated crack initiation clearly exists. To shed light on the factors governing the competition, this study investigates the characteristics of cyclic strain localization, PSB formation, and crack initiation via crystal plasticity (CP) modeling of cyclic loading on polycrystalline aggregates which are then validated by experiments. In this work, a physics-based, free slip distance (FSD) dependent slip strength evolution law is proposed, which is shown to enable the CP model to simulate the heterogeneous strain distribution in IN-718. Implementing a crack initiation criterion based on strain contrast, the locations and lives for crack initiation can also be calculated. It is shown that both FSD and resolve shear stress influence the strain localization and crack initiation behaviors. The distribution of a localization parameter calculated based on the multiplication of FSD and Schmid factor within a grain is found to correlate well with the locations of PSBs. The maximum values of the localization parameters within a microstructure are shown to correlate well with the experimentally obtained crack initiation lives. The presence of volumetric defects in IN-718 generally do not impact strain localization behavior unless their size is large compared to the grain size.},
doi = {10.1016/j.ijfatigue.2022.107002},
url = {https://www.osti.gov/biblio/1867812},
journal = {International Journal of Fatigue},
issn = {ISSN 0142-1123},
volume = {162},
place = {United States},
publisher = {Elsevier},
year = {2022},
month = {05}}
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol. 373, Issue 2038https://doi.org/10.1098/rsta.2014.0132