Cracks 3 Flashcards
What is the similitude concept?
A test sample and actual component will behave te same if the loading situation gives the same stress intensity factor
KA = KB
What does Y equal for an infinitely large centre-cracked panel, and what does this mean?
Y=1
Geometry has NO effect on the stress intensity factor
What is a for an infinitely large centre cracked panel?
2a = full crack length
a = half crack length
What are a, b, w, and t on a crack diagram for one crack dimension?
t = thickness
w = width
b = uncracked ligament length
a = crack depth (length)
What is the crack tip?
The furthest point from the crack mouth
What are a and c on a diagram for more than one crack dimension?
a = crack depth
c = half crack length
How do you find Y for a finite sized panel in tension?
Use a plot of a/W vs Y (2a is crack length, 2W is plate width)
What is K for multiple loading?
K(P+M) = KP + KM
What is the difference between KI and KIC?
KI = applied stress intensity factor; it is a MECHANICS PARAMETER
KIC = fracture toughness; it is the MATERIAL PROPERTY
What does KI tell us?
The magnitudes of the crack tip stresses ahead of a loaded crack in the structure
What does KIC tell us?
How resistant the material is to fracture
What happens with KI and KIC at the point of fracture?
KI = KIC
(Same concept as applied stress = yield stress)
What is the relationship between yield strength and toughness?
Overall ductility reduces strength, but there is no direct relation between them
What type of fracture surfaces do plane strain and plane stress give?
Strain: flat
Stress: slant/shear fracture surfaces
What is the most conservative fracture toughness value?
Plane strain
