mechanical properties: review l0l0 a0a0 f (stress) (strain) y nominal (engineering)true plastic...
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Mechanical Properties: Review
l0
A0
F0
FA
0
0
l l
l
(str
ess
)
(strain)
Y
nominal (engineering)
00 0 0
lnl
totall
dl dl ld
l l l
true
i
FA
plastic – rearrange chemical bonds
elastic – stretch chemical bonds
stress
strain
true (, )
nominal (s, e)
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(s
tre
ss)
(strain)
Y
plastic
elastic
y
load
Definitions
unload
0.2 %
y = yield strength 0.2% offset yield strength
y = elastic limit
strength – some value of stress
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Definitions & Comparisons
P. L. Mangonon “Principles of Materials Selection for Engineering Design” Prentice Hall, Upper Saddle River, NJ 1999.
necking
necking
UTS = (ultimate) tensile strength
upper yield strength
lower yield strength
X
fracture without yield (ionic/colavent bonding)
Xfracture strength
ductility = strain at failure
y
= F/Ai
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Definitions
(str
ess
)
(strain)y = elastic limit ductility
X
resilience = energy to plastic deformation0
y
RU d energy/vol
PdV energy
/ F A pressure
recall:
Elastic region: Y
0
y
RU Y d 2½ yY
½
2
½
y
Y
toughness = energy to failure
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Shear stress from uniaxial tension
AF
FA force is normal to the planenormal stress
A′
n̂
consider what happens on some other plane, A′
need to know area of A′
A′ = A/cos()
consider shear force parallel to A′ along an arbitrary directionF′
need to know magnitude of F′
F′ = Fcos()
F′ can be along any direction parallel to A′ (each corresponds to a different )
Given and :
F
A cos sin
F
A cos sin res
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Solute Hardening
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Precipitate Hardening
coherent incoherent