3D coupled dislocation dynamics in nano- and micro-scales

During the last decades, as usages of Nano- and Micro-Electro-Mechanical Systems (MEMS and NEMS) increase significantly, it becomes necessary to understand performances (e.g. strength and ductility) of small-scaled materials. In such small scales, dislocation dynamics involving interactions with microstructures influence strongly on material strengths [1]. Several computational methods (DDD and MD) exist to simulate individual dislocation behaviors and interactions. However, each of these methods is limited to fully characterizing dislocation dynamics due to its length-scale. The Coupled Atomistic and Discrete Dislocations Dynamics (CADD) [2, 3] is the only multiscale method permitting dislocations traveling between atomistic to continuum scales. However, it operates within a limit of a plane strain approximation (2d). In this presentation, a new framework for 3d coupled dislocation dynamics in atomistic and continuum scales (CADD3d) is shown. In the CADD3d domain, MD is used, where atomistic representations are required (e.g. nucleation and intimate interactions of dislocations), and DDD is employed in the remaining region. The main challenge of CADD3d is a moment that a dislocation exists in the MD and DDD domains at the same time. This dislocation, the so-called hybrid dislocation, can travel as one single dislocation structure by periodically synchronizing the MD and DDD boundary conditions. This scheme requires the two building blocks: core templates [4] and mobility law [5]. With the well-constructed building constituents, the CADD3d method is validated with the two problems: a hybrid straight dislocation and a hybrid dislocation loop. As an application of CADD3d, a Frank-Read source in aluminum alloy is studied. The results show that dislocation-related mechanisms involving short and long range interactions with microstructures (e.g. grain sizes and densities of alloying atoms).

Presented at:
Seminar Talk at KAIST, Daejeon, South Korea, January, 9, 2017

 Record created 2017-03-17, last modified 2018-01-28

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