1. Look inside yourself and you can see the universe
-Zensunni aphorism

2. Example problem -
hardness ––> tensile strength
Estimate tensile strength of 4340 steel connecting rod - RC = 50
Rule of thumb -
TS (psi) = 500 x HBrinell

3. Example problem -
hardness ––> tensile strength
But 4340 in what condition?
Properties vary w/ structure
structure varies w/ ht treatment

4. Fracture toughness - KIc = Yc a
resistance to brittle fracture in presence of
a crack - resistance to crack propagation
under load
Common specimen configurations
pre-cracked here before testing - usually 1000 cycles, 0.03 in/in strain

5. Fracture toughness
Hypothetical example - surface crack in a semi-infinite sheet loaded in tension
Find critical crack size

6. Some fracture surfaces
ductile fracture
transgranular
fracture
intergranular
fracture

7. Crack origins

8. Creep
deformation under small loads at
elevated temps.

9. Fatigue
deformation under small cyclic loads

10. Fatigue
S-N curves & endurance limit

11. Get your paper clip for experiment on the way into class!!

12. Fatigue failure
fatigue crack w/ beachmarks

13. Assignments for next class:
1. Review today's classnotes; know:
a. tensile strength/hardness conversion
b. fracture toughness test
c. fracture surface appearance
d. finding crack origin
e. 3 stages of creep; S-N curves
f. beachmarks
2. Read text: pp , , ,