Discrete simulations

3D Discrete Dislocation Dynamics simulations have been developed in SIMaP since 1990's. Following the pioneering work of Y. Brechet, G. Canova and L. Kubin, the edge-screw code TRIDIS has been developed and widely distributed so that it is currently used in many groups in the world. More recently, the project NUMODIS realized in collaboration with L. Dupuy (CEA Saclay) and M. Blétry (ICMPE Paris XIII) has led to the modern nodal dislocation code aNUMODIS (a Numerical Model of Dislocations)  ​where the physics has been improved.

Examples of TRIDIS simulations of the creep behavior of Ni superalloys studied in collaboration with Bochum University (Ph.D. S. Gao 2016). For these simulations the grain shape is determined by phase field computations and the lattice mismatch is calculated using a FFT procedure.

Crack/Dislocation interactions (ERC project MicroK1c)

Within the framework of the ERC Consolidator Grant MicroK1c led by Erik BITZEK (FAU Erlangen-Nürmberg), TRIDIS code is used to model the propagation of cracks. The modeling uses the X-FEM approach already implemented in CAST3M2018 (www.cast3M.cea.fr) which has been coupled to TRIDIS via esope operators. The objective is to understand the interaction between dislocations and cracks and to compare DDD simulation results to experiments performed at FAU on a notched cantilever (Ph.D. E. Jover-Carrasco 2020).

Ultra High Cycle Fatigue Simulations (ERC project FastMat)

Both TRIDIS and NUMODIS are involved in the ERC Consolidator Grant project FastMat (Fast determination of fatigue properties of materials beyond one billion cycles) led by Nicolas RANC (PIMM, ENSAM ParisTech). The goal of FastMat is to develop a new method that reduces considerably the duration of fatigue characterization. This method involves the use of only short interrupted tests coupled with a self-heating measurement to characterize the fatigue behavior for very low stress amplitudes. The scientific objective is to develop simultaneously experimental and numerical tools for the fast determination of fatigue behavior. The experimental approach estimates simultaneously the dissipation and the stored energy, which directly reflect fatigue damage. For the numerical approach, discrete dislocation dynamics simulations are developed to establish links between the fatigue damage associated with the evolution of dislocation structures, the stored energy and the dissipated energy. Regarding DDD simulations, the irreversibility in the case of High Cycle fatigue (low stress amplitude) is strongly related to the probability of cross-slip events. The challenge is then to introduce a physically based rule for cross-slip in the DD model (Ph.D. M. Longsworth 2021).