seoul national university smart structure & design lab...

Seoul National UniversitySmart Structure & Design Lab

ASME Workshop on Multibody and Nonlinear Dynamics

Smart Structure & Design Lab ( ssnd.snu.ac.kr )

Introduction

• Multiscale modeling & simulations

• Photo-Responsive Polymers

• Lithium ion Battery

• System Reduction Method

• Laminated Composites

• Smart Actuators

Smart Structure & Design Lab ( ssnd.snu.ac.kr )

Introduction

- 18 Ph.D students, 7 M.S. students, 8 Post. Doc.

- 1 Professor

Photo-responsive Self-deforming Structures

Introduction

Piezoelectric Material

Shape Memory Alloy (SMA)

PiezomagneticMaterial

PVMS(poly-vinylmethylsiloxane)

Thermal Electricity Magnet Chemical

Force Thermal Electricity ChemicalMagnet Light

v Various kind of Energy Sources for deformation

Introduction

Photo Responsive Polymer

§ Different reactions to Light Wavelength (

UV/Visible/IR )

Visible lightUltraviolet Infrared

IRVisVisUVUV

Main target

• Investigation of Material Behavior

with multiscale simulation

• Synthesize & Fabrication of PRP

• Design a controllable device with PRP

v Liquid Crystal based PRP (Photo-Responsive Polymer)

- Contract & Expand due to the trans-cis photoisomerization

Yanlei.Yu, Soft Matter, 2012

L0L

Trans Cis

- Light irradiation in upper surface inducesbending deformation

Introduction

Stiffner Pattern

Ø Various Bending Behavior with Alignment of Molecules & Stiffner

Simple Bending & Complex Bending

Mesogen Alignment

UV

Lam

p

Complex Bending Behavior

mesogen

Pattern

mesogen

Pattern

mesogen

Pattern

Patterned

None

Patterned

강화재패턴구상


ü 강화재와 아조벤젠 배향 및 패턴 설계안

아조벤젠배향

UV

Lam

p

복합거동관측

Patterned

None

Patterned

Patterned

Nonemesogen Pattern

mesogen

Pattern

mesogen

Pattern

mesogen

Pattern


Patterned

Patterned

None

Patterned

mesogen

Pattern

mesogen

Pattern

mesogen

Patternmesogen Pattern


Patterned

None

Patterned

mesogen

Pattern

mesogen

Pattern

mesogen

Patternmesogen Pattern

PRP Multiscale Analysisv Coupling of Light-Mechanical Behavior

Polymer AlignmentQuantum Mechanics PRP Structure

10-10 10-7 10-4 10-1 102(m)10-9

Phase Transition

Quantum Molecular Mechanics Continuum Mechanics & Multiscale Design

Deformation of PRP

광변형 거동 관측

ü Quantum Mechanics – Molecular Dynamics – Continuum Mechanics

QM FEM

Sub-Atomic Level Macromolecular Structure Nonlinear Continuum Analysis

Energy Level Change with Light Illumination in Single Molecule

cis trans

MD

Multiscale Analysis Methodology

trans-PRP cis-PRP

Macroscopic Deformation

( ),cis cisN N nw q= : Isomerization ratio : Light intensity : Light incident angle

( ),photo photo cisr r N T= : microstructure : temperature

( )( )

( )

photo

photo photo photo

photo

r

r

u u

e e

e

=

=

=

C C : Displacement

C : Stiffnessε : Photo-strain

10-10 10-7 10-4 10-1 102(m)10-9

Quantum Molecular Mechanics Continuum Mechanics & Multiscale Design

Molecular Arrangement & Material Property


cis trans

<Alignment change w.r.t photo-isomerization>

Azobenzene

<Photo-isomerization distribution>

10-10 10-7 10-4 10-1 102(m)10-9

Quantum Mechanics & Molecular Design


L h

• Simulation with different geometry

• Simulation of buckling behavior

• Optimization of light pattern

Flat → Sphere

ü FE Simulation with the data from QM & MD simulation

10-10 10-7 10-4 10-1 102(m)10-9

Continuum Mechanics & Multiscale Design

Y. Yu et al., Nature, 2003

• Ambient air temperature change

• Light penetration increase

HPC Clusters : 301 1353-1 (132m2)

Computing resources

Computing resourcesHCP Clusters : 301 1353-1 (132m2)

ü Design of photo gripper ü Demonstration of gripping mechanism

Ø Photo-responsive gripping mechanism

Design & production of PRP Application

[Gripping] [Releasing]

VISIBLE INFRARED Transp

arency d

ecrease

Frequency (Hz)Time (s)

Tem

pera

ture

(℃)

Ø Pattern design of light illumination

Hexahedron

Icosahedron

• Optical property


Lotus flower

Robot

• Hexahedron • Lotus flower

Hexahedron

Icosahedron

Lotus flower

Robot



à 받침대

접착제

Hexahedron

Icosahedron

Lotus flower

Robot



Multiscale based design framework of irradiation pattern on the photo-responsive polymer; a topology

optimization

Contents

1. Introduction & Motivation

2. Research Background

3. Results & Discussion

4. Conclusion

Introduction

v Large-scale bending mechanismUV light

PRP specimen) penetration

depth

photostrainResultant Force & Moment

N ph M ph

NematicIsotropic

( )

{ } ( ) ( ){ }

/2 /2

/2 /2

1 1 ,

0

ph h hph phph h h

T Tph ph ph ph ph phx y xy

Ndz C z dz

z zM

z z

s e

e e e g e ne

- -

é ù é ù é ù= =ê ú ê ú ê ú

ë û ë ûë û

= = -

ò ò

Induced force & bending moment

00 0

( ) ( )ln 1I z I z zII I d

té ù æ ö

+ G - = -ç ÷ê úë û è ø

( )( / )0

0

( ) 1 ,z dL

I z W e II

aa a ta

-= = G

( )3

NI NI

NI

1 ( ) for

1 for

T T T Tr

T T

zaì + - £ï= í³ïî

Motivation

v Localized irradiation pattern design for complex structure

• Long-range controllability

• Various mechanical behavior

by light irradiation patternOptimization based pattern searchtechnique is required

Y .Nakabo, Biomimetic soft robots using IPMC

J .Mamiya, Polymer Journal (2013) 45

Contents

1. Introduction & Motivation



4. Conclusion

Research Background

v Corotational FE Formulation & Topology optimization

Global totaldisplacement & spins

CR deformationaldisplacement & rotations

§ Illustration of Corotational FEM Concept

§ OPT & DKT plate elementOPTimal Membrane

TriangleDiscrete Kirchhoff

Triangular elementx, y translation

z rotationx, y axis rotation

z translation

Rigid body rotation

0C

RC

DC

0e

Re

Elastic deformation

du

di di i i

di di i i

d d d dd d d dé ù é ù é ù é ùê ú ê ú ê ú ê úë û ë û ë û ë û

u u u u= H = HP = HPT

θ ω ω ωM. Bendsoe, O. Sigmund,

Archive of applied Mechanics, 1999 (635-654)

1

0

min : ( )

( )s.t. ; ; 0 1

NT p T

e e e ee

x

V x f Ku F xV

r=

=

= = £ £

åu Ku u k u

§ Topology optimization

0.5 0.518

phM 18

phM

1

phM

0Penalized( p = 3 )

Efficient Inefficient

- Simulating mechanical behavior : Bending of cantilever, Left edge clamped

Simulation Procedure

v Topology optimization

§ Optimization Analysis Settings

Light IrradiationClamped B.C

8010

2

E = 71.5 kPa

v = 0.49 (incompressible)

v_ph = 0.3

Penetration depth : 0.5

contact point

( )

( ) ( )curv vol

1

min ( )

s.t. ( ) 0 and 0

obj

m

N

ii

f

g g S

S

rr

r k r

r=

- £ - £

=å

u

u

2obj tip target( )= -f u u 1

1Tc

Tobjobj obj

Ti i i

curv curT

i i

urv

i

v

df fd

dg ggd

fr r r

r r r

-

-

¶ ¶= -

¶¶

¶ ¶

¶ ¶= -

¶ ¶

¶

¶RK

RK

u

u

§ Objective function & Constraints § Sensitivity analysis

analyticallyobtained

numericallycomputed

Methodology

v Matching of photostrain with light intensity

PRP specimen) penetration

depth

photostrain

( )

{ } ( ) ( ){ }

/2 /2

/2 /2

1 1 ,

0

ph h hph phph h h

T Tph ph ph ph ph phx y xy

Ndz C z dz

z zM

z z

s e

e e e g e ne

- -

é ù é ù é ù= =ê ú ê ú ê ú

ë û ë ûë û

= = -

ò ò

In-plane force & bending moment

Photostrain model Light intensity model

ü Consider light-thermal-order coupling

ü Light decay profile (Lambert-W fcn.)

ü Constant strain through thickness

ü Photostrain as design variablemax max, 0.5ph p

e ee e r e= × =

( )3

NI NI

NI

1 ( )

1 ( )

T T T Tr

T T

zaìé ù+ - £ïë û= íï ³î

Light incident intensity (by element)

Light profile (Lambert-W)

Steady state cis population

Orientation order

cis 1 1eff

eff

IInI I

tt

¥ G= =

+ G +

Material property, A,B,D matrixIn-plane force & bending moment

Photo-induced strain1

ph

ph

NM

ek

- ì üì ü é ù ï ï=í ý í ýê úï ïî þ ë û î þ

A BB D

( )( / )0

0

( ) 1 ,x dL

I x W e II

aa a ta

-= = G

Methodology

v Matching of photostrain with light intensity

Photostrain model Light intensity model

ü Consider light-thermal-order coupling

ü Light decay profile (Lambert-W fcn.)

ü Constant strain through thickness

ü Photostrain as design variable

Light incident intensity I0& Characteristic depth d

1ph

ph

NM

ek

- ì üì ü é ù ï ï=í ý í ýê úï ïî þ ë û î þ

A BB D

( )11 113

22 222

12 12

1 01 0

12 1 0 0 1

ME tM

M

n kn k

n n k

ì ü é ù ì üï ï ï ïê ú=í ý í ýê ú-ï ï ï ïê ú-î þ ë û î þ

( )

13

11 112

22 22

1112 1

ME tM

k nk nn

-æ öì ü ì üé ùç ÷=í ý í ýê úç ÷- ë ûî þ î þè ø

0I

kd

11k22k

Input :

Initial assumption of design variables

Deformed shape (FEM analysis)

Sensitivity analysis forobjective & constraint

Update design variable

Eigenstrain – light matchingvia photomechanics

Tolerance check for objective & constraint

Obtain photostrain pattern

Methodology

: Control target point & constraint parameters

: Multiscale effect is applied

Obtain light intensity pattern

: FMINCON(Matlab in-built function)

1. Introduction



4. Conclusion

Contents

Results & Discussion

Ø Strain distribution profile with constraint difference

Ø Deformation comparison for different flatness constraint location

S = 0.5

S = 0.8


Ø Strain pattern change with different target point

S = 0.5

Target

0.6D

0.8D

1.0D

S = 0.8

D = L/(pi/2) ~ 50


Ø Path tracing - Programmable bending behavior

Conclusion

Ø Topology-optimization based design method for photo-responsive self-deformingstructure is proposed

Ø By modifying objective function and curvature constraint, versatile mechanical bendingare effectively controlled.

Ø More comprehensive case of simulation should be done for overall understanding ofpattern shape change with design conditions such as geometric properties of specimenor deformation target shape.

• Research Plan

Ø Consider the angel of incident light

Ø Time-dependent dynamic simulation should be considered

Ø Implementing to optical techniques (photomask, light filter, etc…)

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