Optimzation of dislocation dynamics code – OPTIDIS

Plastic deformation is mainly accommodated by dislocations glide in the case of crystalline materials. The behaviour of a single dislocation segment is perfectly understood since 1960 and analytical formulations are available in the literature. However, to understand the behaviour of a large population of dislocations (inducing complex dislocations interactions) and its effect on plastic deformation, massive numerical simulations are necessary. Since 1990, simulation codes have been developed by French researchers. Among these codes, the code TRIDIS developed in the laboratory SIMAP in Grenoble is the very first dynamic dislocation code.
In 2007, the project called NUMODIS had been set up as team collaboration between the SIMaP and the SRMA CEA Saclay in order to develop a new dynamics dislocation code using modern computer architecture and numerical methods and that should be able overcome the numerical and physical limits of the previous code TRIDIS. The version NUMODIS 1.0 came out in December 2009, which confirms the feasibility of the project.

The project OPTIDIS is introduced when the code NUMODIS is mature enough to implement parallel routines. The objective of the project in to develop and validate the algorithms in order to optimise the numerical efficiency and performance of the code NUMODIS. We are aiming at developing a code able to tackle realistic materials problems such as the case of interaction between dislocations and irradiation defects in a grain plastically deformation after irradiation.

These kinds of studies where “local mechanisms” are correlated to macroscopic behaviour is a key issue for nuclear industry in order to understand materials ageing under irradiation, and hence predict power plant service life.

To carry out such studies, massive numerical optimisations of NUMODIS that involve complex algorithms, as well competences in applied mathematics and parallel computing methods are critically needed.

The project OPTIDIS involves a team collaboration between researchers specialized on one hand in dynamics dislocations and on the other hand in numerical methods.

This project is divided in 8 tasks over 4 years. Two PhD thesis will be directly financed by the project. One will be dedicated to numerical development, validation of complex algorithms and confrontation with the performance of existing dynamics dislocation codes. The objective of the second is to carry out large scale simulations to validate the performance of the numerical development made in OPTIDIS. In both cases, these simulations will be compared with experimental data obtained by experimentalists.