Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Materials 4 > Plasticity > Flashcards

Plasticity Flashcards

(62 cards)

Start Studying
1
Q

What is material failure defined as

A

The inability for a material to perform its intended function or to meet the performance criteria

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

What is the difference between plastic and elastic deformation

A

Plastic deformation cannot be recovered after loading

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

What is Youngs modulus dependant on

A

Forces of attraction/repulsion between atoms which are dependant on their interatomic separation

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

Are all solids linear elastic

A

Yes, for small strains

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

What is the ideal strength of a material

A

The stress at which atomic bond rupture takes place assuming homogenous shear

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

What is the ideal strength approximately equal to

A

E/15

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

What is greater ideal stress or shear stress

A

ideal stress

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

How does plastic deformation occur

A

Slip, motion of dislocations

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

What is a dislocation

A

a lattice distortion centred around a distortion line

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

What are the 3 types of dislocation

A

Edge
Screw
Mixed

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

What is an edge dislocation

A

A dislocation created by the interstation of an extra half plane of atoms

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

What does Bergers vector represent

A

The magnitude and direction of the lattice distortion around a dislocation, determined by comparing the atom to atom path in a perfect crystal and the path in a dislocated crystal

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

For an edge dislocation what direction is the burgers vector in

A

Perpendicular to dislocation line

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

What allows edge dislocations to move

A

Breaking and reformation of atomic bonds

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

For one atomic break what is the distance travelled by a dislocation equal to

A

Bergers vector

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

What causes screw dislocations

A

Shear stress applied to regions of a perfect crystal separated by a cutting plane

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

What direction is the Bergers vector for a screw dislocation

A

Parallel to dislocation line

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

What stresses are present in a screw dislocation

A

Shear

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

What stresses are present in edge dislocation

A

Shear, compression, tension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the dislocation density

A

The amount of dislocation lines in a crystal, can be either total length of dislocation per volume or number of lines crossing unit area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is strain energy per unit volume proportional to for a dislocation

A

Gb^2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

When does dislocation annihilation occur

A

When 2 dislocations of opposite sign on the same slip plane under the same stress move in opposite directions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

When does dislocation pile up occur

A

Dislocations of the same sign are blocked by the same hard particles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What happens if 2 dislocations moving on different planes combine

A

They will combine to produce an immovable dislocation who’s burgers vector does not lie in a slip plane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What happens when dislocations intersect
They create a relatively immovable portions of dislocations called jogs
26
What happens to the number of dislocations during plastic flow
It increases
27
Where does slip tend to occur
The most densely packed planes in the directions which atoms are packed closest together
28
What is a slip system
A combination of a slip plane and a slip system
29
What are slip bands
Step markings on a materials surface associated with plastic deformation within a single crystal. Atoms on specific crystallographic planes (slip planes) slip to cause slip bands
30
What does Schmid's law describe
The relationship between uniaxial stress on a single crystal and the resolved shear stress produced on a slip system
31
What is a twin
A twin is a region in which mirror plane symmetry of lattices exists across a twin boundary
32
When is a twin formed
During plastic deformation, recrystallisation and phase transformation to reduce lattice strain
33
Which method of deformation is preferable, slip or twinning
Twinning
34
In terms of movement of atoms what is the difference between twining and slip
In slip atoms on one side of a slip plane are all moved an equal distance whereas in twinning they move a distance proportional to the their distance from the twinning plane
35
In terms of crystallographic deformation describe the differences between slip and twinning
Slip will leave a series of steps but twinning will leave a small region of well defined deformation
36
What crystallographic structures does slip and twinning usually occur in the
Slip- BCC & FCC | Twinning- HCP
37
In terms of forces when does yielding occur
When the force per unit length exceeds the resistance force per unit length opposing the motion of a dislocation
38
How can the resistance to dislocation motion be increased
By restricting the motion of the dislocation usually by obstacles
39
What are the most common types of obstacles used to restrict motion of dislocation
Strained crystal lattices, other dislocations, solute atoms and 2nd phase particles
40
What are some methods to increase the strength against yielding
Use of precipitates Solid solution hardening strain hardening
41
What is a polycrystal yield strength effected by
The interactions individual crystals have with each other
42
How do grain boundaries effect the motion of dislocations
They act as obstacles to dislocation motion
43
How does grain size refinement effect the yield stress
It will increase the yield stress as it more grains means more grain boundaries which act as obstacles to dislocation motion
44
What is precipitation hardening
In precipitation hardening tiny hard particles are introduced into a matrix of a different phase, these act as obstacles
45
What are the 2 types of precipitates
Non-coherent and Coherent
46
What are Non-Coherent precipitates
These are when the precipitate has no relation with the crystal structure surrounding the matrix
47
What are Coherent precipitates
Ones in which there is a definite relationship between the precipitates and the matrix's crystal structures
48
What spacing yields the greatest increase in strength by precipitation
Closely spaced precipitates.
49
What are the 2 types of solid solution hardening
Interstitial and substitutional
50
What is interstitial solid solution hardening
When the solute atoms fit in between the voids of solvent atoms
51
When does interstitial solid solution hardening usually occur
When the solvent atoms are much larger then the solute atoms
52
Is there more lattice distortion during interstitial or substitutional solid solution hardening
More during interstitial
53
What is substitutional solid solution strengthening
When the solute atoms substitute the parent solvent atoms
54
What effects the strength of solid solution strengthening
Increasing atomic size difference and amount of alloying element
55
Why does strain hardening increase the materials strength
Introduces more dislocations (immovable) which act as obstacles to the motion of dislocations
56
What effect does the density of dislocations have on material properties
Increased yield strength Increased tensile strength Reduced ductility
57
How do grain boundaries act as obstacles to dislocation motion
The dislocations pile up against the grain boundaries
58
How do we increase the ductility of a cold worked metal
By reheating
59
What stages does a piece of cold worked material go through as it is heated
Recovery, Recrystallisation, grain growth
60
What happens during recovery
Some of the stored internal strain energy is relieved and the materials strength is slightly reduced but its ductility is greatly increased
61
What happens during recrystallisation
Grains nucleate in recovered metal and eventually the metal structure is completely replaced by a new grain structure. Ductility increased, tensile strength reduced
62
What factors affect recrystallisation
``` Prior deformation temperature Holding time Composition Initial grain size. ```

Materials 4 (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions