Virtual Diffraction Techniques used to Study Dislocation Loop ? Grain Boundary Interactions and Assess Slip Transfer Criteria
Abstract
The objective of this proposal is to develop a multiscale simulation approach to study dislocation Ð grain boundary interactions and to employ this approach to advance criteria for slip transfer across grain boundaries to consider the grain boundary damage state. In addition, the proposed simulation approach will allow for an analysis of the role of dislocation core structures on slip transfer. The hypothesis of this proposal is that the mechanisms by which dislocations are obstructed, absorbed, and/or transmitted through grain boundaries are sensitive to the damage state of the grain boundary (defined as a departure from equilibrium atomic structure) in addition to slip geometry. Such details are critically important to understand how grain boundaries promote strengthening or act as sources/sinks for damage during high rate plastic deformation. To meet this objective, this proposal introduces a unique approach to integrate classical atomistic simulations (molecular statics and molecular dynamics) and discrete dislocation dynamics (DDD) simulations. In addition to basic dislocation properties, the elastic strain energy landscape of single dislocation loops (which can be used to compute dislocation core energy) and grain boundaries after dislocation Ð grain boundary reactions will be used as key validation metrics. To extract the elastic strain energy landscape of a dislocation loop or a damaged grain boundary, the novel idea here is to use Òvirtual diffractionÓ methods, developed by the PI and his Collaborator for both atomistic and discrete dislocation dynamics simulations. Through comparison of the atomistic and DDD diffraction patterns computed after dislocation reaction with a grain boundary, slip transfer criteria will be assessed and refined to include the role of grain boundary damage. This research will advance the field scientifically and will provide new numerical toolkits for modeling dislocations and grain boundaries at multiple length scales. (1) The role of grain boundary damage state has been mostly disregarded in the literature and this research will illustrate the importance of grain boundary damage on slip transfer. (2) The use of virtual diffraction will enable calculations of stable/metastable dislocation core energies and the influence of the dislocation core structure on dislocation mobility and grain boundary evolution during slip transfer. (3) The research in this proposal will provide an improved computational approach to study dislocation loop Ð grain boundary interactions that overcomes many of the limitations of existing approaches in the literature. (4) Simulations of slip transmission may identify non-equilibrium grain boundary states that are more resistant to damage accumulation during dislocation reactions, or reveal metastable dislocation core structures that deposit less damage on the grain boundary during slip transfer, resulting in enhanced mechanical behavior. Atomistic and DDD simulations will be performed at the University of Florida. In year 1, focus will be on the advancement of the atomistic virtual diffraction tool and the computation of dislocation properties (including core energies) from atomistic simulations to validate the DDD model. Atomistic and DDD simulations of dislocation Ð grain boundary interactions will be conducted primarily in years 2 and 3. Supporting microdiffraction experiments will be performed in year 3 via partnership with Los Alamos National Laboratory (LANL). The supported students will be provided the opportunity to intern at LANL during the summer semesters.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 16, 2018
- Source ID
- W911NF1710194
Entities
People
- Douglas E Spearot
Organizations
- Army Contracting Command
- United States Army
- University of Florida