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Research Projects
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Project 3
Project 3
A Micromechanical Model for Light-interactive Molecular Crystals
A Micromechanical Model for Light-interactive Molecular Crystals
Molecular crystals respond to a light stimulus by bending, twisting, rolling, jumping, or other kinematic behaviors. These behaviors are known to be affected by, among others, the intensity of the incident light, the aspect ratios of crystal geometries, and the volume changes accompanying phase transformation. While these factors, individually, explain the increase in internal energy of the system and its subsequent minimization through macroscopic deformation, they do not fully explain the diversity of deformations observed in molecular crystals.
Objectives
Objectives
Develop a micromechanical model—rooted in the principles of the Cauchy-Born rule, the finite deformation theory, and photoreaction kinetics—to predict macroscopic photomechanical response in molecular crystals.
Results
Results
We demonstrate that the macroscopic behavior of molecular crystals in response to a light stimulus is closely linked to the structural transformation of lattices at the atomic scale. Our continuum model, based on the Cauchy-Born rule and photoreaction theory, uses lattice geometries as the primary input to predict experimentally consistent bending, twisting, and shearing deformation in the salicylideneamine molecular crystal (a representative material).
Project 2
Project 2
A Diffused Interface Non-local Crystal Plasticity Model to Capture Size Dependent Plasticity in Polycrystals
A Diffused Interface Non-local Crystal Plasticity Model to Capture Size Dependent Plasticity in Polycrystals
Grain Boundaries (GBs) disrupt the motion of dislocations and thereby affect the elasto-plastic deformation behavior of polycrystalline alloys. While non-local CPFEM through the incorporation of GND can capture grain size effect, modeling the interaction of dislocations between the grains adjacent to a GB remains elusive in this approach due to the sharp or stepped representation of the interface.
Objectives
Objectives
To develop a novel constitutive formulation for a finitely thick GB region which incorporates properties of all the adjoining grains, and to investigate the micromechanisms of dislocation interactions near grain boundaries and their impact on polycrystalline plasticity behavior.
Results
Results
Our model can capture the effect of grain size and misorientation of grains across GBs. For both bicrystal and polycrystal simulations, the size dependency is observed to follow the Hall-Petch relation.
Project 1
Project 1
Diffused Interface CPFEM: Biased Mesh Generation and Accuracy
Diffused Interface CPFEM: Biased Mesh Generation and Accuracy
The use of uniformly structured mesh in diffused interface CPFEM reduces the utility of this approach by increasing the computational cost exorbitantly. Furthermore, the inaccuracy associated with the distorted elements of unstructured conforming finite element mesh can be alleviated by using structured non-conforming meshes.
Objectives
Objectives
To develop a biased mesh generation algorithm for polycrystalline domains, perform sensitivity study to identify the critical parameters that control the mesh and evaluate accuracy the framework by comparing the global and local responses from the diffused interface CPFEM simulations with sharp and stepped interface results.
Results
Results
The results clearly show that the diffused interface representation reduces the stress concentration when compared with the stepped interface. Furthermore, the responses in the grain interior and also at the grain boundary region agrees reasonably well with that of grain boundary conforming mesh.
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