Please enable JavaScript.
Coggle requires JavaScript to display documents.
FRACTURE (TOUGHNESS
energy needed to break a unit volume material…
FRACTURE
- TOUGHNESS
- energy needed to break a unit volume material
Material toughness
- slow absorption of energy by the material
-
-
-
-
- FRACTURE TOUGHNESS (FT)
- ability of material containing a crack to resist fracture
METAL
- highest FT (cracks cannot propagate easily in tough materials)
- highly resistant to cracking under stress - large zone of plastic flow
ENGINEERING CERAMICS
- lower FT
- easy to crack
- exceptional improvement in stress fracture due to 1.5 orders of magnitude strength increase - relative to metal
Measured by Stress-Intensity Factor, SIF (K)
- function of loading, crack size & structural geometry
CONDITION FOR CRACK PROPAGATION
- fracture in material occurs when stress intensity factor (K) exceeds FT of material (Kc): K > Kc
Material Thickness
-
when thickness exceed critical dimension, SIF becomes constant = value of FT
-
FRACTURE MECHANICS
- crack geometry, material strength & toughness & stress system
FAST FRACTURE
- caused by growth of cracks, flaws / defects
- suddenly become unstable & propagate at speed of sound
-
imposed stress
2) CRACK PROPAGATION
- Mode of fracture highly dependent on mechanism of crack propagation
-
- FRACTURE TYPE
- depends on type & condition of material
FACTORS
-
-
-
-
-
size & nature of internal flaws
(vacancies, precipitates, cracks)
external flaws
(crack, oxides)
-
-
-