Lattice Boltzmann modeling of dendritic growth

Lattice Boltzmann modeling of dendritic growth in a forced melt convection

D Sun et al

A two-dimensional (2D) lattice Boltzmann-based model is developed to simulate solutal dendritic growth of binary alloys in the presence of forced flow. The model adopts the lattice Boltzmann method (LBM) that describes transport phenomena by the evolution of distribution functions of moving pseudoparticles to numerically solve fluid flow and solute transport governed by both convection and diffusion. Based on the LBM-calculated solutal field, the dynamics of dendritic growth is determined according to a previously proposed local solutal equilibrium approach. After detailed model analysis and validation, the model is applied to simulate single and equiaxed multidendritic growth of Al–Cu alloys with forced convection. The results demonstrate the quantitative, numerically stable and computationally efficient capabilities of the proposed model. It is found that the solute distribution and dendritic growth are strongly influenced by convection, producing asymmetrical dendrites that grow faster in the upstream direction, but mostly slower in the downstream direction.

Crystal plasticity using DFT

Crystal plasticity simulations using discrete Fourier transforms

M Knezevic, H F Al-Harbi, and S R Kalidindi

In this paper, we explore efficient representation of all of the functions central to crystal plasticity simulations in their complete respective domains using discrete Fourier transforms (DFTs). This new DFT approach allows for compact representation and fast retrieval of crystal plasticity solutions for a crystal of any orientation subjected to any deformation mode. The approach has been successfully applied to a rigid–viscoplastic Taylor-type model for face-centered cubic polycrystals. It is observed that the novel approach described herein is able to speed up the conventional crystal plasticity computations by two orders of magnitude. Details of this approach are described and validated in this paper through a few example case studies.

Internal strain around crack-tip

In situ neutron-diffraction study of internal strain evolution around a crack tip under variable-amplitude fatigue-loading conditions

S Y Lee et al

In situ neutron-diffraction measurements were performed to investigate the lattice-strain evolution around a fatigue crack under five different loading conditions (i.e., fatigued, tensile overloaded, compressive underloaded, tensile overloaded-compressive underloaded, and compressive underloaded-tensile overloaded) during fatigue crack growth. The results show that different crack-growth behaviors are closely related to the distinct strain distributions developed near the crack tip under the various loading conditions.