Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Material Science > MAE 3324 Ch 6 > Flashcards

MAE 3324 Ch 6 Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

What factors should be considered when choosing a material?

A

Nature of the applied load (cyclic vs constant), duration, environmental conditions (sea spray–> corrosion, temp–> Thermal expansion coeficient) etc.

Ref: Pg 143

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the three principal ways that a load can be applied?

A
  1. Compression
  2. Tension
  3. Shear

Ref: Pg 144

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

True or False

A stress-strain test is destructive? (e.g. permanent deformation takes place and usually fracture)

A

True

Ref: Pg 145

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Define Engineering stress and give the SI and BG units.

A

Stress = Force/Area before deformation
Pa or psi

Ref: Pg146

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Define Engineering strain and give the units.

A

Strain = change in length/ origional length
Unitless

Ref: Pg 146

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

True or False

Sometimes strain value is shown as a percentage.

A

True

Ref: Pg 146

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

True or False

In a compression test, a compressive force is considered to be positive.

A

False, compressive forces are negative by convention.

Ref: Pg 147

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

True or False

In a compression test, a compressive strain is considered to be negative.

A

True

Ref: Pg 147

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Define “Pure shear,” and give the units.

A

Shear = Force/Area [Pa, or psi]

Note: The force acts parallel to the cross-sectional area.

Ref: Pg 147

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Define Shear strain and give the units.

A

Shear strain is the tangent of the strain angle. [rad]

Ref: Pg 147

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Define Hooks Law.

A

Hook’s law states that stress is equal to the product of strain and the modulus of elasticity E (also known as Young’s Modulus).

Ref: Pg 148

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Define “Elastic Deformation.”

A

Deformation in which stress and strain are proportional. A plot of stress vs strain should show a linear relation.

Ref: pg 148

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

True or False

On a stress-strain graph, in the elastic deformation region, the slope of the cure is the modulus of elasticity.

A

True

Ref: Pg 148

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

True or False

The greater the value for the modulus of elasticity (E) the stiffer the material (resistance to elastic deformation).

A

True

Ref: Pg 148

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

True or False

Elastic deformation is permanent.

A

False, it is non-permanent.

Ref: Pg 149

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

For materials that demonstrate non-linear behavior in the elastic region what is used to find the modulus of elasticity?

A

The tangent (secant) modulus is used.

Ref: Pg 149

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe elastic strain on an atomic scale.

A

Macroscopic elastic strain is manifested as small changes in the interatomic spacing and the stretching of interatomic bonds.

Extra Notes: As a consequence, the magnitude of the modulus of elasticity is a measure of the resistance to the separation of adjacent atoms (interatomic bonding forces)

Ref: Pg 149

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the relationship between the modulus of elasticity and the force-separation curve?

A

The modulus of elasticity is proportional to the slope of the interatomic force-separation curve at the equilibrium spacing.

Ref: Pg 149

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

For a weekly bonded material the force-separation curve will have a ____ slope and a ____ modulus of elasticity.

A

Shallow
Low

Ref: Pg 149

20
Q

For a strongly bonded material, the force-separation curve will have a ____ slope and a ____ modulus of elasticity.

A

Steep
High

Ref: Pg 149

21
Q

True or False

The values of the modulus of elasticity for ceramic material are about the same as for metals.

A

True

Ref: Pg 150

22
Q

True or False

The values for the modulus of elasticity for polymers are higher than for metals.

A

False, they are lower for polymers.

Ref: Pg 150

23
Q

As temperature increases, the modulus of elasticity ____.

A

Decreases.

Ref: Pg 150

24
Q

Shear stress and strain are related through ____. What are the units?

A

The shear modulus of elasticity (G) which also has the units of pascals.

Ref: Pg 150

25
Q

How is G found experimentally?

A

By measuring the slope of the shear stress vs shear strain curve in the elastic region.

Ref: Pg 150

26
Q

What is anelasticity?

A

The time-dependent behavior of materials under loads. For example, when a material is deformed elastically it takes a certain time period for it to return to its original state.

Ref: Pg 151

27
Q

True or False

In metals, the anelastic component can often be ignored because it is so small.

A

True

Ref: Pg 151

28
Q

What is Poisson’s ratio?

A

The ratio of the lateral and axial strains on a body.

v = -1* ex/ez

Ref: Pg 151

29
Q

What is the relationship between shear (G) and elastic modulI (E)? (give the actual equation)

A

E = 2G(1 + v)

Ref: Pg 152

30
Q

For most metallic materials, elastic deformation persists only to strain of about ____.

A

0.005

31
Q

What is plastic deformation?

A

Plastic deformation occurs when strains exceed the elastic region and permanent deformation occurs. At the start of the plastic region hooks law is no longer necessarily valid and stress is no longer directly proportional to strain.

Ref: Pg 154

32
Q

Describe plastic deformation from the perspective of atomic bonds.

A

Plastic deformation corresponds to the breaking of bonds with original atomic neighbors and then reforming of bonds with new neighbors as large numbers of atoms or molecules move relative to one another. Upon removal of this stress, they do not return to their original positions.

Ref: Pg 154

33
Q

For crystalline solids, plastic deformation is accomplished by means of a process called _____.

A

Slip; which involves the motion of dislocations discussed in Chapter 7.2

Ref: Pg 154

34
Q

Plastic deformation in non-crystalline solids is accomplished by ____.

A

A viscous flow mechanism discussed in section 12.10

Ref: Pg 154

35
Q

What is the “proportional limit” with respect to materials?

A

The point at which a material goes from elastic to plastic deformation.

Ref: Pg 154

36
Q

What does the yield strength measure?

A

In a metal, the yield strength is a measure of its resistance to plastic deformation.

Ref: Pg 155

37
Q

What is the tensile strength?

A

The maximum on the stress-strain curve.

Ref: Pg 155

38
Q

Where does fracture ultimately occur?

A

At the necking point.

Ref: Pg 156

39
Q

Define “ductility.”

A

It is a measure of the degree of plastic deformation that has been sustained at fracture.

Ref: Pg 158

40
Q

A metal that experiences very little or no plastic deformation upon fracture is termed _____.

A

Brittle.

Ref: Pg 158

41
Q

What is “resilience” with respect to materials?

A

The capacity of a material to absorb energy when it is deformed elastically and then upon unloading to have this energy recovered.

Ref: Pg 159

42
Q

What are the two main characteristics of resilient materials?

A

High yield strengths and low modulus of elasticities (used in springs).

Ref: Pg 160

43
Q

What is toughness with respect to materials?

A

The ability of a material to resist fracture when a crack or other defect is present.

Ref: Pg 160

44
Q

What is true stress?

A

The force divided by the instantaneous cross-sectional area.

Ref: Pg 161

45
Q

What is true strain? (Give the equation)

A

e_t = ln( li / lo )

Material Science (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions