Material Properties

Question 1

Draw and annotate Stress Strain diagram ?

Answer 1

No pictures just Google it

Question 2

What is the elastic region?

Answer 2

When stress and strain are proportional and E (Youngs Modulus) is the constant of proportionality

Question 3

What is the Youngs modulus equation and what does it define?

Answer 3

Hooke’s Law
(sigma) = (E)(epsilon)

The stiffness of the material

Question 4

What is the Poisson’s ratio equation and what does it describe?

Answer 4

v = - (Lateral Strain) / (Longitudinal Strain)

v = - (epsilon L) / (epsilon)

The ratio by which a material contracts (or expands) in lateral or tranverse directions, when the material is stretched (or compressed)

Question 5

What are the equations of Shear and Bulk modulus equations?

Answer 5

Shear Modulus
(tau) = (G) (gamma)
tau = shear stress
gamma = shear strain

Bulk Modulus
(P) = - (K) ((delta V) / (Vo))
V = volume
P = pressure

Question 6

What are the special relations of isotropic materials?

Answer 6

G = (E) / (2(1+v))

K = (E) / (3(1-2v))

Question 7

Define Toughness

Answer 7

Energy to break a unit volume of material.

Approximated by the area under the stress-strain curve

Question 8

What type of energy is contained in a brittle fracture vs a ductile fracture?

Answer 8

Brittle fracture : elastic energy

Ductile fracture : elastic + plastic energy

Question 9

Define the relationships between both the Brinell and Vickers hardness and Tensile strength and why would you use it?

Answer 9

Tensile Strength = 3.55 HB (HB < 175)
Tensile Strength = 3.38 HB (HB>175)

Tensile Strength = (HV) / 3

Tensile tests are a form of destructive testing whereas Hardness tests are non-destructive.

Question 10

How does engineering stress differ from true stress?

Answer 10

Engineering considers Ao

True considers Ai

Question 11

Define Hardness

Answer 11

Describes the resistance of a material to deformation by indentation.
Also related to wear and scratch resistance.