Fracture

1
Fracture
2
Recall.
3
Fracture process
4
TYPES OF FRACTUREMacroscopic Features
Ductile
Brittle

• Slow crack propagation
• Crack velocity 10ft/s
• Stable crack growth
• Slant face fracture
• Dull fracture surface
• Rough/fibrous surface
• Cup and cone fracture
• Necking occurs

• Fast crack propagation
• Crack velocity1000 ft/s
• Unstable crack growth
• Flat face fracture
• Shiny fracture surface
• Smooth fracture surface
• Chevron marks or radial lines

5
(No Transcript)
6
CHEVRON MARKS/RADIAL LINES
7
Microscopic features

• Void formation
• Dimpled fracture surface
• Transgranular

• River pattern
• Transgranular and intergranular

8
DUCTILE
BRITTLE
9
Fatigue failure

• Fatigue is failure under repeated/dynamic loads
• Accounts for 95 of failure in moving parts
• Generally initiates on the surface
• Fracture surface shows macroscopic beach marks
  and microscopic striations

10
Fatigue beach marks
11
Fatigue striations
12
A fracture surface