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Reliability
Triple Layer Structure
·There is no external moment (torque) at zn, thus:
·f is the averaged local stress of the film:
3
E t -
E t + E (t + t )
s s
b
b
s
=
s s
=
f
t -
(
2 E + E )
f
s
b
12Rt
r (t + t +
)
f
s
b
2
= 2E t (t + ) - E t t
t
s
s
s
b [
3
3
( +
- ) - ( - )
b
s
s
]

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