Couple creep with

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Topics

• Couple creep with
• wrinkling
• cracking
• diffusion

What came first, chicken or egg?
Chicken is eggs way to make more eggs. Systems
dynamics
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SiGe island under compression
Strained SiGe island
glass
Si

Yin et al., J. Appl. Phys. 2003
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Two Relaxation Modes
Before annealing
Expansion
Wrinkling

• Small islands expand
• Large islands wrinkle and fracture

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Stress as a function time
s
Liang et al. Acta Mater. 50, 2933 (2002)
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Constraint, and its gradual loss
Free-standing film
?
a
?
h
l a
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2D Shear Lag Model
Huang, Prevost, Suo, Acta Mater. 50, 4137 (2002)
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Stationary long crack, blanket film
K(t)
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Stationary finite crack, island film
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Steady Crack Growth
viscous underlayer
Liang, Huang, Prévost, Z. Suo, Experimental
Mechanics 43, 269 (2003).
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Subcritical Cracking and Creep
Crack Velocity, V
Stress Intensity Factor, K
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Ratcheting-Induced Stable Crack (RISC)
Huang, Suo, Ma, Fujimoto, J. Mater. Res, 15,
1239 (2000). Begley, Evans, J. Appl. Mech., 68,
513 (2001).
Tensile Film
Ratcheting Layer
Cyclic temperature
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Power law creep underlayer
Delayed crack growth
Liang, Zhang, Prevost, Suo, Int. J. Fracture. In
press
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Examples of stress generation
INTEFACIAL PROCESS Deposition-induced
compression (chemical potential
excess) Solidification Oxidation-induced tension
Ni (chemical potential deficit)
Oxidation-induced compression Si
Chason et al. PRL 88, 156103 (2002)
NONRCIPROCAL DIFFUSION (Kirkendall
effect) Diffusion couple ZnCu
COMBINED EFFECTS Selective oxidation
NiAl Selective evaporation ZnCu
Suo, Kubair, Evans, Clarke, Tolpygo Acta
Materialia 51, 959 (2003)
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Coupled creep and diffusionin body of a single
atomic species
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Kinematics
Suo, Kubair, Evans, Clarke, Tolpygo Acta
Materialia 51, 959 (2003)
v
N
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Energetics
Define driving forces as energy-conjugates
power dissipation
power supply
kinematic constraint
Suo and Kubair
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Kinetics
diffusion
creep
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Summary of equations for v and s
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Example thick substratestress generation
J
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Example thin foillateral expansion/contraction
J
2H
is independent of
force balance
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Coupled creep and diffusion in a binary solution
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Coupled creep and diffusion in a binary solution

• A synthesis of
• Stokess creep
• Herrings stress-driven diffusion
• Darkens nonreciprocal diffusion