CHAPTER 7
DISLOCATIONS AND STRENGTHENING MECHANISMS
PROBLEM SOLUTIONS
7.2
When the two edge dislocations become aligned, a planar region of vacancies will exist between the
dislocations as:
7.7
Below is shown the atomic packing for a BCC {110} type plane.
The arrows indicate two different
<111> type directions.
= (2.5 MPa)cos(65
°
)cos(
30°
)
[
] = 0.90 MPa
(130 psi)
7.13
This problem asks that we compute the critical resolved shear stress for silver.
In order to do this,
we must employ Equation (7.3), but first it is necessary to solve for the angles
λ
and
φ
from the
sketch below.
172
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View Full DocumentIf the unit cell edge length is
a
, then
λ
= tan
1
a
a
= 45
°
For the angle
φ
, we must examine the triangle
OAB
.
The length of line
OA
is just
a
, whereas, the
length of
AB
is
a
2
.
Thus,
φ
= tan
1
a
2
a
= 54.7
°
And, finally
τ
crss
=
σ
y
(cos
φ
cos
λ
)
= (1.1 MPa) cos(54.7
°
)cos(45
°
)
[
]
= 0.45 MPa (65.4 psi)
7.15
This problem asks, for a BCC metal, that we compute the applied stress(s) that are required to
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 Spring '11
 Staff
 Force, Cos, The Unit, Equals sign

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