Materials Ch4 And 12

Front 1

Calculate the Modulus of Elasticity

Back 1

E= change in stress/change in strain

Front 2

Calculate the Percent Elongation

Back 2

% elongation = (final length-initial length) / initial length

Front 3

Calculate the Percent Reduction in Area

Back 3

% Reduction in Area = (initial area-final area) / initial area

Front 4

Calculate Poisson’s Ratio

Back 4

Calculate Poisson’s Ratio

Front 5

Calculate Resilience

Back 5

Resil.
= 1/2 * (stress at elastic limit)^2 * (strain at elastic limit)
= ((stress at elastic limit)^2) / (2*mod of elas)

Front 6

Calculate Resilience
Using Poisson’s Ratio and the Modulus of Elasticity, calculate the Shear Modulus of Elasticity.

Back 6

Calculate Resilience
Using Poisson’s Ratio and the Modulus of Elasticity, calculate the Shear Modulus of Elasticity.
Shear Modulus = G = E / (2(1+γ); gamma = Poisson’s Ratio

Front 7

What does a high percent elongation indicate?

Back 7

The material is more ductile and therefore formable.

Front 8

State the differences between the stress-strain diagram created using the data in this excel sheet and a true stress-strain diagram. Using a true stress-strain diagram can provide us with what further information about the material.

Back 8

The engineering stress-strain diagram created is not a measure of true stress and true strain. To get true values you need to measure the instantaneous gage lengths and diameters as the test proceeds using an extensometer. Once we have the true-stress and true strain we can determine the strain-hardening coefficient (n) which indicates how much a material will work harden when subjected to plastic deformation. This is important in many shaping and molding processes.

Front 9

What is resilience, how does this differ from toughness?

Back 9

Resilience is a measure of the ability of a material to absorb elastic energy
Toughness is the ability of the material to absorb all energy before fracture

Front 10

On a stress-strain graph, which area indicates resilience and which indicates toughness?

Back 10

Front 11

What materials is creep important in? What materials is creep not so important in?

Back 11

Creep is very important in materials with low melting points such as polymers.
Creep is usually not important in metals with operating conditions under 800 F.

Front 12

What can be said about graphs a-d?

Back 12

(a) Has significant work-hardening which is evident from it’s continued ability to withstand increased stress until fracture.
(b) exhibits very little work hardening but the ductility allows it to continue to elongate.
(c) Is extremely brittle with no ability to work harden
(d) Ductile plastics undergo a reorganization and “orientation strengthening” at the atomic level before fracture