1 Analysis , Development and Enhancement 서론 서론 서론 서론 및 기계적 기계적 기계적 기계적 물성 물성 물성 물성 측정 측정 측정 측정 현황 현황 현황 현황.( .( .( .(원리와 원리와 원리와 원리와 응용 응용 응용 응용) f{|Å \Ç V{âÄ f{|Å \Ç V{âÄ f{|Å \Ç V{âÄ f{|Å \Ç V{âÄ Analysis , Development and Enhancement 1. Organic Materials(Polymers)에 대한 관점 2. Vision은 깊게, Touch는 넓게. 유기물질은 보이는 현상과는 다른 화학적 물리적 조성에 의한 변수가 매우 다양하고, 환경(온/습도)에 의한 변화가 시간에 따라 동적으로 결정됩니다. 3. 측정 기구와 측정 변수의 한계는 분명히 다르므로 측정 기 구의 선택은 신중해야 합니다. 4. (사용효율/장비 가격) X 100 = 100% ????? To Start this Seminar
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ROUGHNESS (거칠기) 측정은 기재의 거친 정도를 측정함으로써 기재 거칠기를 측정하는 하나의 지수로써 사용된다. 기재가 심한 거칠기를 가질 경우 그로인한 CRACK/BROKEN이 예상된다.
ROUGHNESS SPEC LIMIT : MAX 0.3 um
PRINCIPLE OF MEASUREMENT : STYLUS METHOD (CONTACT)LASER METHOD (NON-CONTACT)
MEASURING RANGES : 0.25 mm
Measure LengthL
RmaxRa
Y
Xf(x)
Ra = 1/L∫ 0L
f(x) dx
용어 정리
• Rmax (최대 높이) : 한 기준 길이 안에서 단면 곡선의 최저점으로 부터 최고점까지의 높이
• Ra (중심선 평균 거칠기) : 한 기준 길이내의 산과 골의 높이를 기준선을 중심으로 평균하여 얻어지는 값
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Analysis , Development and Enhancement
3차원 형상 측정기 개발 현황
(출처 덕인/KRISS 측정클럽 발표 자료)
Analysis , Development and Enhancement
PDP 격벽 3D 레이저(CCD) 구조 분석 사례
KRISS 측정클럽 발표자료
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Analysis , Development and Enhancement
I wonder if some stress applied…As a view point of Material Viscoelasticity
And very small stress have applied…
Analysis , Development and Enhancement
Principles of Rheology (cont’d.)
Introduction to Viscoelasticity
• Most materials behave such that they have a combination of viscous and elastic
responses under stress or deformation.
• Materials behave in the linear manner, as described by Hooke and Newton, only
on a small scale in stress or deformation.
Most MaterialsIdeal Solid Ideal Liquid
Hooke Newton
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Analysis , Development and Enhancement
Dynamic Mechanical Analyser의의의의 개념개념개념개념
점탄성의 측정
Analysis , Development and Enhancement
DMA Curves for Epoxy resin
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Analysis , Development and Enhancement
Schematic Concept
56789
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Glassy Rubbery
Cross-linked
Temperature
A
B
C
DE
Deformation
MolecularMotion
UnstrainedState
StrainedState
E D C B AHookeanBehavior
SecondTransition
PrimaryTransition Highly Visco Elastic Flow
(rubbery)(gamma) (beta) (alpha)
Bend &StretchBonds
SideGroups
MainChain
GradualMain Chain Large
Scale MobilityChain
Slipping
Increasing
F
FSecondaryDispersion
LocalizedMotion
R. Seymour, 1971
(melt)
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Crystal-crystal slip
Crystalline Polymer
Analysis , Development and Enhancement
Common changes show as:
E’E’E’E’
tan tan tan tan δδδδ
MW MWD Crosslink Density Crystallinity
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Analysis , Development and Enhancement
• Stress or Strain is varied sinusoidally
Oscillation Experiments of Rheometer
Stimulus
Response
phase lag, δ
• Separates Elastic and Viscous effects
• The modulus and Viscosity of Oscillation experiments are called Complex ModulusComplex ModulusComplex ModulusComplex Modulus and Complex Complex Complex Complex ViscosityViscosityViscosityViscosity.
Analysis , Development and Enhancement
Linear and Non-Linear Stress-Strain Behavior of Solids
Viscoelasticity: Having both viscousand elastic properties
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Analysis , Development and Enhancement
Response for Classical ExtremesResponse for Classical ExtremesResponse for Classical ExtremesResponse for Classical Extremes
Purely ElasticResponse
Hookean Solidσ = Eε or τ = Gγ
Purely ViscousResponse
Newtonian Liquidσ = ηγ
In the case of the classical extremes, all that matters is the values of stress, strain, strain rate. The response isindependent of the loading.
Spring Dashpot
Analysis , Development and Enhancement
At short times (high frequencies) the response is solid-like
At long times (low frequencies) the response is liquid-like
THE HISTORY OF LOADING IS CRUCIAL
Response for a Viscoelastic MaterialResponse for a Viscoelastic MaterialResponse for a Viscoelastic MaterialResponse for a Viscoelastic Material
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Analysis , Development and Enhancement
TimeTimeTimeTime----Dependent Viscoelastic Behavior:Dependent Viscoelastic Behavior:Dependent Viscoelastic Behavior:Dependent Viscoelastic Behavior:Solid and Liquid Properties of "Silly Putty"
T is short [< 1s] T is long [24 hours]
Deborah Number [De] = τ / Τ
Analysis , Development and Enhancement
Old Testament Prophetess who said :"The Mountains Flowed before the Lord"
Everything Flows if you wait long enough!
Deborah Number, De - The ratio of a characteristic relaxation time of a material (τ) to a characteristic time of the relevant deformation process ( Τ ).
Hookean elastic solid - τ is infiniteNewtonian Viscous Liquid - τ is zeroPolymer melts processing - τ may be a few seconds
High De Solid-like behaviorLow De Liquid-like behavior
IMPLICATION: Material can appear solid-like because1) it has a very long characteristic relaxation time or2) the relevant deformation process is very fast
The Deborah NumberThe Deborah NumberThe Deborah NumberThe Deborah Number
For small deformations (strains within the linear region) the ratio of stress to strain is a function of time only.
This function is a material property known as the STRESS RELAXATION MODULUS, G(t)
G(t) = σ(t)/γ
Stress decreases with timestarting at some high value and decreasing to zero.
time
0
Analysis , Development and Enhancement
Stress is applied to sample instantaneously, t1, and held constant for a specific period of time. The strain is monitored as a function of time (γ(t) or ε(t)).The stress is reduced to zero, t2, and the strain is monitored as a function of time (γ(t) or ε(t)).
– Stain for t>t1 is constant– Strain for t >t2 is 0
time
time
time
– Stain rate for t>t1 is constant– Strain for t>t1 increase with time– Strain rate for t >t2 is 0
t2t1
t1 t2t2t1
Analysis , Development and EnhancementReference: Mark, J., et.al., Physical Properties of Polymers ,American Chemical Society, 1984, p. 102.
Creep Recovery Experiment:Creep Recovery Experiment:Creep Recovery Experiment:Creep Recovery Experiment:Response of Viscoelastic Material
Creep σ> 0
timet 1 t2
RecoverableStrain
Recovery σ = 0 (after steady state)
σ/η
Strain rate decreases with time in the creep
zone, until finally reaching a steady state.
In the recovery zone, the viscoelastic fluid recoils, eventually reaching a equilibrium at some small total strain relative to the strain at unloading.
Ω = Motor angular velocity in radians/sec.β = Cone angle in radiansH = Gap for parallel plate in mmR = Radius of plate or cone in mmR1 = Radius of concentric cylinder bob in mmR2 = Radius of concentric cylinder cup in mm
More on ViscosityMore on ViscosityMore on ViscosityMore on Viscosity
According to Isaac Newton, viscosity is constant for all times and shear-rates –Newtonian Fluids
Viscosity is dependent on Temperature and Pressure
Viscosity may not be constant – Non-Newtonian Fluids
Viscosity of Non-Newtonian fluids can depend on– Time :– Thixotropy, Rheopexy– Shear-rate :– Shear-thinning, Pseudoplasticity, Dilatency
Time-DependenceAt constant shear-rate, if viscosity
– Decreases with time - Thixotropy– Increases with time - Rheopexy
Analysis , Development and Enhancement
Non-Newtonian, Time Independent Fluids
Shear-ThinningA decrease in viscosity with increasing shear
rate. Also referred to as Pseudoplasticity.
Shear-ThickeningAn increase in viscosity with increasing shear
rate. Also referred to as Dilatancy (a special case of shear-thickening).
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Analysis , Development and Enhancement
Non-Newtonian, Time Dependent Fluids
ThixotropyA decrease in apparent viscosity with time under
constant shear rate or shear stress, followed by a gradual recovery, when the stress or shear rate is removed.
RheopexyAn increase in apparent viscosity with time under
constant shear rate or shear stress, followed by a gradual recovery when the stress or shear rate is removed. Also called Anti-thixotropy or negative thixotropy.
Reference:Barnes, H.A., Hutton, J.F., and Walters, K., An Introduction to Rheology, Elsevier Science B.V., 1989. ISBN 0-444-87469-0
TTS is based on the observation that, for a single material,the curves of the viscoelastic properties, generated at different temperatures, are similar in shape when plotted againstlog time or log frequency. The Curves generated at differenttemperatures can be exactly superimposed by shiftingalong these axes.
TTS applies to stress relaxation, creep and dynamic mechanicalmeasurements
Analysis , Development and Enhancement
Time and Temperature: Two Sides of the Same CoinTime and Temperature: Two Sides of the Same CoinTime and Temperature: Two Sides of the Same CoinTime and Temperature: Two Sides of the Same Coin