11
MSE 2090: Introduction to Materials Science
Chapter 7, Strengthening
Slip in single crystals - critical resolved shear stress
When the resolved shear stress becomes sufficiently large,
the crystal will start to yield (dislocations start to move
along the most favorably oriented slip system).
The onset
of yielding corresponds to the yield stress,
σ
y
(Chapter 6).
The minimum shear stress required to initiate slip is termed
the critical resolved shear stress
:
(
)
MAX
y
CRSS
cos
cos
λ
φ
σ
=
τ
Maximum value of (cos
φ
cos
λ
) corresponds to
φ
=
λ
= 45
o
⇒
cos
φ
cos
λ
= 0.5
⇒ σ
y
= 2
τ
CRSS
(
)
MAX
CRSS
y
cos
cos
λ
φ
τ
=
σ
Slip will occur first in slip systems oriented close to these
angles (
φ
=
λ
= 45
o
) with respect to the applied stress

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