EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

The propagation of short cracks in FCC metals is highly influenced by the surrounding microstructure, particularly the one generated by 3D dislocation configuration. A reliable tool to model crack - dislocation microstructure interaction is Discrete Dislocation Dynamics (DDD). DDD is a numerical method to simulate the movement of dislocations under external loading and it is based on an analytical formulation of dislocation internal stress field, assuming an infinite isotropic medium. However, the presence of crack surfaces necessitates to compute the stress field numerically to handle dislocation and free surface interactions. The Discrete-Continuous Model (DCM) (1) overcomes DDD limitations, by coupling DDD with a Finite Element elastic solver (FE). 3D-modeling of a static short crack under tensile loading has been investigated during the PhD work of L. Korzeczek (PhD thesis, 2017). It has been shown that FE is a limiting factor in terms of calculation time and memory storage to model slow propagation, as observed in ductile materials and cyclic loading.

We propose here a numerical coupling, based on the DCM scheme, using a Fast Fourier Transform (FFT) elastic solver to compute the mechanical equilibrium. This solver is mathematically stable for any type of interface and massively parallel. In addition, in order to model the quasi-static propagation of a fatigue short crack, the Phase-Field Method (PFM) is used and incorporated in the coupling. Different PFM models are tested and compared. In particular, we show how these models allow to simulate in three dimensions the interaction of a short crack in FCC metals with its surrounding dislocation microstructure.

(1) O. Jamond, R. Gatti, A. Roos, B. Devincre, "Consistent formulation for the Discrete-Continuous Model: Improving complex dislocation dynamics simulations", International Journal of Plasticity, 80, 19-37, 2016.