Scientific Publications

Prediction of mechanical properties of nanocrystalline materials using Voronoi FE models of representative volume element

REFERENCE
Panagiotis Bazios, Konstantinos Tserpes, & Spiros Pantelakis (2018). Prediction of mechanical properties of nanocrystalline materials using Voronoi FE models of representative volume elements. Proceedings of the 8th EASN-CEAS International Workshop on Manufacturing for Growth & Innovation. http://doi.org/10.1051/matecconf/201823300029
ABSTRACT
In the present work, a numerical model is developed to predict the mechanical properties of nanocrystalline materials using a Finite Element Analysis. The model is based on Representative Volume Elements (RVE) in which the microstructure of the material is described using the Voronoi tessellation algorithm. The use of the Voronoi particles was based on the observation of the morphology of nanocrystalline materials by Scanning Electron and Transmission Electron Microscopy. In each RVE, three-dimensional modelling of the grain and grain boundaries as randomlyshaped sub-volumes is performed. The developed model has been applied to pure nanocrystallline copper taking into account the parameters of grain size and grain boundary thickness. The mechanical properties of nanocrystalline copper have been computed by loading the RVE in tension. The numerical results gave a clear evidence of grain size effect and the Hall-Petch relationship, which is a consequence of macroscopic strain being preferentially accumulated at grain boundaries. On the other hand, for a given grain volume fraction, the results for elastic moduli showed no effect of the grain size. The model predictions have been validated successfully against numerical results from the literature and predictions of the Rule of Mixtures and the Mori-Tanaka analytical model.
LINKS
View this paper in the ICARUS community in Zenodo.

 

Computation of elastic moduli of nanocrystalline materials using Voronoi models of representative volume element

REFERENCE
Panagiotis Bazios, Konstantinos Tserpes, & Spiros Pantelakis. (2018). Computation of elastic moduli of nanocrystalline materials using Voronoi models of representative volume elements. Proceedings of the 5th International Conference of Engineering Against Failure (ICEAF-V 2018). http://doi.org/10.1051/matecconf/201818802006
ABSTRACT
In the present work, a numerical model is developed to predict the Young’s modulus and shear modulus of nanocrystalline materials using a Finite Element Analysis. The model is based on Representative Volume Elements (RVE) in which the microstructure of the material is described using the Voronoi tessellation algorithm. The use of the Voronoi particles was based on the observation of the morphology of nanocrystalline materials by Scanning Electron and Transmission Electron Microscopy. In each RVE, three-dimensional modelling of the grain and grain boundaries as randomlyshaped sub-volumes is performed. The developed model has been applied to pure nanocrystallline copper at grain volume fractions of 80%, 90% and 95% taking also into account the parameters of grain size and grain boundary thickness. The elastic moduli of nanocrystalline copper have been computed by loading the RVE in tension. The numerical results reveal that the elastic moduli of nanocrystalline copper increase with increasing the grain volume fraction. On the other hand, for a given grain volume fraction, the results showed no effect of the grain size. The model predictions have been validated successfully against numerical results from the literature and predictions of the Rule of Mixtures and the Mori-Tanaka analytical model.
LINKS
View this paper in the ICARUS community in Zenodo.

 

In situ TEM observations on the structural evolution of a nanocrystalline W-Ti alloy at elevated temperature

REFERENCE
M. Callisti , F. D. Tichelaar , T. Polcar (2018). In situ TEM observations on the structural evolution of a nanocrystalline W-Ti alloy at elevated temperatures. Journal of Alloys and Compounds, Volume 749, 15 June 2018, Pages 1000-1008. https://doi.org/10.1016/j.jallcom.2018.03.335
ABSTRACT
The thermal stability and nanoscale structural evolution at elevated temperatures of a sputter deposited W-Ti alloy thin film were studied by a combination of ex situ and in situtechniques. XRD, FIB, SEM-EDX and STEM-EDX were used to characterise the film annealed ex situ in vacuum at 1373 K for 48 h. In situ TEM heating experiments were conducted at various temperatures up to 923 K to capture transitional phenomena occurring in the alloy upon heating and cooling. At a microscopic level, the alloy annealed at 1373 K for 48 h transformed from a single-phase β-(WTi) solid solution into a two-phase alloy consisting of Ti-rich grains in equilibrium with Ti-depleted β-(WTi) solid solution grains. In situTEM observations revealed initial Ti segregations along columnar grain boundaries at T ∼423–573 K, followed by Ti-rich clusters formation in the grains interior at T ∼ 573–773 K. The microstructure observed at 923 K remained stable upon cooling to room temperature and consisted of Ti-rich segregations along the columnar grain boundaries and of alternate Ti-rich and Ti-depleted nanoscale domains in the grains interior, which formed a stable dual-phase nanocrystalline structure.

 

 

 

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This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 713514.

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