Ch 9 - Failure Flashcards
the separation of a body into 2 or more pieces in response to an applied stress that is static (constant) and at temperatures that are low relative to the Tm of the material
Simple Fracture
Accompanied by significant plastic deformation
ductile fracture
Little to no plastic deformation
Brittle Fracture
How do cracks propagate?
The sharpness of the crack tip
Moderately ductile failure stages
necking, void nucleation, coalescence of cavities, crack propagation, and fracture
crack propagation that results from the repeated breaking of atomic bonds along specific planes
Cleavage - crack splits thru the grains
due to elemental depletion at the grain boundaries or some type of weakening of the grain boundary due to chemical attack, oxidation, embrittlement
Intergranular failure
Causes transgranular failure
cleavage
(T or F) Larger samples contain more/longer flaws
True
T or F tensile strength in engineering materials is greater than tensile strength in ideal materials
False
Studying brittle failures of structures with preexisting flaws consists of
- ) material properties
- ) Stress level
- ) Crack producing flaws
- ) Crack propagation mechanisms
measures a materials resistance to brittle fracture when a crack is present
fracture toughness
What does fracture toughness indicate?
the amount of stress required to propagate a preexisting flaw
Types of flaws
cracks, voids, metallurgical inclusions, weld defects, design discontinuities
approach to design critical components
use the linear elastic fracture mechanism and assume flaws are present
