On the role of lattice defects interactions on strain hardening: A study from discrete dislocation dynamics to crystal plasticity modelling

This thesis focuses on the effects of slip-slip, slip-twin, and slip-precipitates interactions on strain hardening, with the intent of developing comprehensive modelling capabilities enabling to investigate unit processes and their collective effects up to the macroscopic response. To this end, the modelling strategy adopted in this work relies on a two-way exchange of information between predictions obtained by discrete dislocation dynamics (DDD) simulations and crystal plasticity laws informed by DDD. At the scale of lattice defects, a DDD tool enabling simulations on any crystalline structure is developed to model dislocation-dislocation, dislocation-twin and dislocation-particles interactions. The tool is first used to quantify the collective effect and strength of dislocation-dislocation interactions on latent-hardening, especially in the case of pure Mg. With regards to slip-twin interactions, a transmission mechanism is implemented in the DDD framework so as to investigate the collective effects of dislocation transmission across a twin-boundary. With respect to slip-particles interactions, an efficient novel DDD approach based on a Fast Fourier Transform (FFT) technique is developed to include the field fluctuations related to elastic heterogeneities giving rise to image forces on dislocation lines. In addition, the DDD-FFT approach allows for the efficient treatment of anisotropic elasticity, thereby paving the way towards performing DDD simulations in low-symmetry polycrystals. The information extracted from the collective dislocation interactions are then passed to a series of constitutive models, and later used to quantify their effects at the scale of the polycrystal. For such purpose, a constitutive framework capable of receiving information from lower scales and establishing a direct connection with DDD simulations is notably developed.

Level thesis:degree_level

Doctoral

Department dc:contributor.department

Mechanical Engineering

Grantor dc:publisher

Georgia Institute of Technology

Year dc:date.issued

2015

Author dc:creator

• Bertin, Nicolas

Advisor dc:contributor.advisor

• Capolungo, Laurent

Committee members dc:contributor.committeemember

• McDowell, David L.
• Kalidindi, Surya R.
• Garmestani, Hamid
• Tomé, Carlos N.

• DDD
• Dislocation dynamics
• Anisotropic elasticity
• Heterogeneous elasticity
• Spectral method
• Crystal plasticity
• Scale transition

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/1853/54370

OAI identifier oai:identifier

oai:repository.gatech.edu:1853/54370