lecture 6 creep failure
DESCRIPTION
Creep FailureTRANSCRIPT
Creep failure
Diffusion creep
•
bulk crystaldiffusion
d
grain boundarydiffusion
d
Dislocation creep
glide
glide
climb
Diffusion assisted climb important:
climb
1. Annihilation:
poof !
2. By passing obstacles:
Dislocation Climb:
Stress Relaxation
total = el + pl = 0 so el = - pl
el = / E and pl = c = A n (@ cont. T)
-n d = - A E dt
1-n | =- A E t |0
. .
. .
. .
time
time
p
el
o
t
Tertiary creep :
c
time
tertiary creep
Creep damage starts
Creep Failure
Design against creep (metals)
• Minimize T / Tmelting
to slow diffusion, climb, and creep.
• Arrange for large grain sizes to slowdiffusion.
• Use precipitates (oxide particles) and solid solutions to slow dislocations.
