Engr 54

Hardness is a measure of a material's

Ability to absorb energy up to fracture

Ability to absorb energy upon elastic deformation

Resistance to localized plastic deformation

Fracture point

Max sustainable load prior to failure

A material with a high elastic modulus has all of the following characteristics except

Strong bonding

A high melting temperature

A high toughness

A limited amount of ductility

Toughness is a measure of a material's

Fracture point

Maximum sustainable load prior to failure

Resistance to localized plastic deformation

Ability to absorb energy up to fracture

Ability to absorb energy upon elastic deformation

Along which directions do planes of atoms slip most easily

Directions with the lowest atom density

Directions with the highest atom density

[111] in FCC metals

Directions with the largest atom spacing

All of the above

Elastic deformation in a tensile test is due to

Dislocation movement

Bonds stretching under an applied stress

Planes of atoms slipping past one another

Bonds breaking under the applied stress

Microscopic cracks forming

The term 'force' is another name for 'stress'

True

False

Solid solution hardening and precipitation hardening strengthen materials by enhancing dislocation motion

True

False

Alloying with impurity atoms that go into solid solution impose lattice strains on surrounding host atoms, and restrict dislocation motion

True

False

A material with a large grain size will have a higher yield strength relative to a material with a smaller grain size

True

False

The driving force for grain growth is the reduction in total grain boundary energy

True

False

The hardness of a material scales with the tensile strength

True

False

With increasing temperature, values of elastic modulus as well as tensile and yield strengths decrease, whereas the ductility increases.

True

False

Resilience is the capacity of a material to absorbed energy when it is deformed plastically up to the ultimate tensile strength

True

False

The elastic modulus of a metal is roughly proportional to the melting temperature

True

False

A crystalline material has a melting temperature of 1000C. Which is the lowest temperature of the choices below where creep is significant

370 C

500 C

509 C

637 C

1040 steel has the following wt% carbon

40%

0.4%

10.4%

Creep is

Not when dislocations are removed by climb and added by work hardening

Not when strain increases under a constant load or stress

Not important at low temperatures relative to the melting T

All of the above are true

None of the above are true

Which of the following phenomena occurs when a cold-worked metal is annealed at high temperatures

Which is a refractory metal with a high melting T

Which of the following is (are) NOT true

Steels are expected to have fatigue (endurance) limit

Fatigue failure occurs only when the stress is higher than the yield stress

All of the above

None of the above

Which of the following ways will NOT increase the yield stress of Ag

Cold work then anneal at high T for a long time

Precipitation hardening

Solid solution hardening

All of the above will increase the yield stress

None of the above will increase the yield stress

Engr 54

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