Chapter 8 Flashcards
failure
a material will lose its strength and fully/partially separate into several pieces
ductile fracture
material experiences plastic deformation in the form of necking - at necking voids begin to form in the material
cup and cone fracture
a type of ductile fracture that occurs at the necking
DBTT effect
ductile to brittle transition temperature - s-shaped graph - even a very ductile material can become brittle at low enough temps
brittle failure
very little stretching - fractures happen without much warning - cracks form perpendicular to the applied load
intergranular fracture
type of brittle failure - cracks propagate along grain boundary
transgranular fracture
type of brittle failure - cracks propagate through grains
what determines a material’s tendency to fail
- geometry of a part
- voids
- inclusions/imperfections in the material
max stress
stress(m) = 2*stress(o) * sqrt(a/rho(t))
stress(o) = applied stress
a = crack length
rho(t) = radius of curvature
how to determine crack length(a) for a material
surface crack = a=length of crack
interior void 2a = length of crack
the ______ the crack tip, the higher the stress
sharper
stress concentration factor
K = stress(m)/stress(o)
use for voids/crack lengths
fracture toughness
a measure of how easy it is to propagate a crack of length a - K(c)
critical stress
stress(c)
plane strain condition
when the thickness of a material is much larger than the crack length - K(IC)
