Dr. Gunjin Yun
Aerospace Structures and Materials Laboratory
3D Digital Image Correlation System
MTS Tester MachineClustered Super Computer
• KAIST BS (1994) / MS (1996)• University of Illinois
Urbana-Champaign PhD (2006)• Washington University in St. Louis
Post-Doc (2007)
• 1996-2002 Samsung Corporation Institute of Technology
Researcher• 2008-2013 The University of Akron, Assistant Professor•
2013-2016 The University of Akron, Associate Professor•
2016-Present Seoul National University, Professor
• Air Force Summer Faculty Fellowship (2012, 2013)• NASA GRC
Research Grants (2009-2012, 2014)
IN ASML
Aerospace Structural and Materials Laboratory has been
conducting cutting-edge research on m u l t i s c a l e a n
d
multiphysics problems including thermal structural behavior,
life prediction, nonlinear deformation and damage models of
aircraft structures and composite materials used in extreme
loads, including complex loads and high temperature / high
pressures. We are working on both experimental and
simulation research on composite materials.
서울대학교 창의선도
신진 연구자 지원사업
ASML(Aerospace Structure & Material Lab.)Location : Building
300 Room 503
Tel : +82-2-880-7389
Homepage : asml.snu.ac.kr
3D Printer
Molecular Dynamics Simulation of Ablation
Thermal Protection System (TPS)
• Flight Vehicles with high speed are exposed to harsh
environment in
earth’s atmosphere.
• Thermal Protection Systems are used to protect people and
vehicles
from hot temperature.
Multiscale Approach with MD (Molecular Dynamics ) Simulation
• Using MD simulation, we can understand fundamental
chemical
reactions and improve an accuracy of computational modeling
3C-SiC crystal structure
Deep Learning-based Joint Model for Hybrid FEA
A
Bolts
Bearings
X
Y
Z
Reference result Forwarding result @12500 epoch
Data acquisition Verification of the ANN-based FEA
Reference result UEL + ANN result (@20000 epoch)
Verification of the ANN-based FEA
x
y0.3 [mm]
2 beams
Data acquisition
ANN-based FEA : Forwarding result @ 25000 epoch
Reference result
Front-axle simulation
(scaled stress)
(scaled stress)
Molecular Dynamics Simulation of Nanocomposites
Nonlinear Micromechanics Analysis
Damage Plasticity Constitutive Model for CNT Nanocomposites
• Mori-Tanaka is one of the analytical homogenization scheme for
predicting effective properties of composite materials• In order to
express physical comprehensive material behaviors, nonlinear
behaviors from plasticity & damage are considered
Ellipsoidal inclusion Cylinder fiber
Aspect ratio
Straight fiber with interfacial damage Wavy fiber with
interfacial damage
Rotational
Transformation
Overall Scheme for Modified Mori-Tanaka Approach with Matrix
Ductile Damage
• Taking account of interfacial/Matrix damage & effect of
CNT waviness
+
Matrix ductile damage
Modified Mori-Tanaka Approach Results & Verifications with
FE
Flowchart for modified Mori-tanaka Approach
• Describe the effective behaviors by changing the variables •
Verification with FE model
Coarse grained MD with multi-objective optimization
Objective functions
2
,
1
1n
k k ref
k
fn MSD MSD
2 reffn
Deb, K., et al. (2002). IEEE transactions on evolutionary
computation 6(2): 182-197.
NSGA-II (Non-dominated Sorting Genetic Algorithm)
VARTM(Vacuum Assisted Resin Transfer Molding) (Microscope
Mechanical Test System)
FE Multiscale Analysis for Composites
FE2 Multiscale Anaylsis for Composite Materials• FE2 Multiscale
Anaylsis is one of the numerical homogenization scheme for
predicting
effective properties of composite materials by solving each
scale problems
FE2 Multiscale Anaylsis Results• Profile of Macro- & Micro-
FE model and results
• Identifing the plastic deformation distribution of RVE at
point A from the anaylsis
Microstructure Topology Optimization by Targeting
PrescribedNonlinear Stress-Strain Relationships
