Research Topics

Broadly speaking, our research themes are:

  • Enhancing our understanding of multifunctional materials by making use of numerical analysis, specifically nonlinear finite element method
  • Designing optimum, adaptive structures that conforms to their environment

Here are examples of these endeavors:

Design Optimization

Multiscale and multiphysics topology optimization has a great potential in conceiving materials and structures that have intricate material layouts (multi-scale), and experiences coupled stimulus (multi-physics). To fully exploit such potential, we derive and incorporate the consistent sensitivity to topology optimization. We also discuss the fidelity of the complex model with regards to the widely used simplified model so to identify whether such an effort is actually of worth.

Related works:

  • Chung, et al., Development of topology optimization considering nonlinear multiphysics, CMAME, 2020
  • Level-set based topology optimization of periodic cellular structures under thermoelastic coupled load (work in progress)
  • Robust topology optimization considering thermoelasticity (work in progress: Mr. Byeonghyon Go)

Under construction

Related works:

  • Development of efficient moment-fitting method to consider weakly discontinuous material (work in progress: Mr. Tae Hun Kang)

We thrust topology optimization methods to incorporate high-fidelity structural models and solve large-scale design problems. In-depth use of parallel computing, HPC, as well as usage of interoperable optimization tools, are under investigation for this aim.

Related works:

  • Chung et al., Topology optimization in OpenMDAO, SMO, 2019
  • Chung et al., Topology Optimization of 3D Nonlinear Thermoelastic Structure using a Level-set method”, USNCCM 15, 2019.
  • Discrete adjoint method for shape sensitivity calculation

Multiscale analysis of multifunctional materials

Simulation of the mechanical behaviors of multifunctional structures requires a thorough understanding of the materials and their interaction with the surrounding environment, not to mention the numerical method that solves the partial differential equations.

For example, when irradiated by UV light, smectic liquid crystal polymer exhibits nontrivial deformation, namely alternating bending direction with a single stimulus. To simulate the behavior, phase transition modeling based on Landau-de Gennes energy has cooperated with the constitutive model of smectic LCP.

Related works:

  • Chung et al., Numerical study of light-induced phase behavior of smectic solids, PRE, 2017
  • Chung et al., Finite element analysis of the optical-texture-mediated photoresponse in a nematic strip, Comp. Mech., 2017

  • Chung et al., Light and thermal responses of liquid crystal network films: A finite element study, PRE, 2015.

Particles and granular matters are widely observed in many engineering disciplines, e.g., nano-scaled structures and additive manufacturing. They have more differences than commonalities in terms of engineering, although their behaviors are largely governed by the same rule of physics. In this subject, we use large-scale particle simulations, including molecular dynamics simulations and discrete element methods, to investigate and facilitate their underlying physics.

By simulating uniaxial tensile simulation of a copper bicrystal of [100] rotation axis, nano-scaled inter/transgranular fracture has been investigated. It also revealed the directional anisotropy, presumably affecting nano-polycrystalline material strength.

Related works:

  • Chung and Cho, A molecular dynamics study on the biased propagation of intergranular fracture found in copper STGB, JMST, 2018
  •  Choi, Chung, Yun, and Cho, Molecular Dynamics Study on the Photothermal Actuation of a Glassy Photoresponsive Polymer Reinforced with Gold Nanoparticles with Size Effect. ACS Applied Materials & Interfaces, 2016.
  • Kim, Chung, and Cho, Anisotropic Hyperelastic Modeling for Face-Centered Cubic and Diamond Cubic Structures, CMAME, 2015

Under construction

To understand nonconventional bending phenomena exhibited by PRPN (Photo-Responsive Polymer Network), a phase-behavior simulation done by molecular dynamics simulation was incorporated within nonlinear shell finite element model.

Related works:

  • Chung et al., Nonlinear photomechanics of nematic networks: upscaling microscopic behaviour to macroscopic deformation, Scientific Report, 2016

More to come...

  • The multiphysics level set topology optimization
  • Simulation of self-orginizing behavior of liquid crystals
  • The level-set topology optimization of structure experiencing large-scale thermoelastic loading
  • 3D large-scale topology optimization considering finite elasticity
  • etc …