Week 2 Flashcards
What are material properties?
Attribute of a material that is independent of size or shape; e.g., hardness, color
What is engineering stress?
s=F/A0
What is engineering strain?
e = (L-L0)/L0)
stress strain plot has 2 phases:
elastic region, plastic region
Plastic region exists of:
uniform plastic extension (till top called tensile strength), followed by neck(ing)
what is Y and how can it be calculated?
Y (yield strength) is where the material changes from the elastic region to plastic region, can usually be calculated by 0.2% offset of elastic region line till it hits graph in plastic region
What is Hookse Law, and where does it take place?
elastic region, s = E*e
What is resilience?
It is the opposite of stiffness
What is the 2nd phase of a stress-strain plot, and what formula is used?
Tensile Strength -> TS = Fmax/A0
What is ductility
the amount of strain that a material can endure before failure.
Ductility allows forming processes
What is the opposite of ductility
brittle
How to measure ductility?
EL = (Lf-L0)/L0 (elongation)
What kinds of fractures are there?
cup-cone fracture (aluminum)
Brittle fracture (mild steel)
What is true stress and true strain and why is it needed
in the plastic region the diameter changes thus needing a new measure of these variables.
true stress: is the ratio of load, F, to the actual (instantaneous) cross-section area, A, of the specimen
true strain: provides a more realistic assessment of “instantaneous” elongation per unit length
What is toughness
the area under the true stress-strain curve up to fracture. the amount of energy the material must absorb
What is stain hardening
true stress increases continuously in the plastic region until necking, metal becomes stronger as strain increases.
also known as work hardening
What is shear?
application of stresses in opposite directions on either side of a thin element to deflect it
shear stress -> t(greek) = F/A
shear strain -> y(greek) = 8 (greek)/b
Hardness
resistance to permanent indentation
HB = (2F)/ piDb(Db-root(Db^2-Di^2))
What is hot hardness
the ability of a material to retain hardness at elevated temperatures. (good hot hardness is desirable in tooling materials)
