Normalizing Load-Elongation to Engineering Stress-Strain
Raw Data Normalized Data
L (Elongation, m)
F(L
oad
or F
orce
,N)
(Str
ess,
MP
a)
(Strain, unitless, m/m)
= F Ao
Lo
F
FAo
L
= L Lo
Engineering stress Engineering StrainNecking – A geometric Instability
NeckNeck
Tensile Test & Mechanical Properties Visual Glossary 1
12
Engineering Stress and Engineering Strain
6
How Do Metals Behave at Low Strains?
• Modulus of Elasticity, E(Young's modulus)E = / /
E !Linear ElasticDeformation
Hooke’s Law F = k x
Thomas Young(1773-1829)
English genius – a physicist who created Young’s Modulus, a physician who discovered eye focusing mechanism, and a linguist who translated part ofthe Rosetta Stone F
Fsimple tension test
!
Tensile Test & Mechanical Properties Visual Glossary 1
126
How Do Metals Behave at Low Strains?
• Modulus of Elasticity, E(Young's modulus)E = / /
E !Linear ElasticDeformation
Hooke’s Law F = k x
Thomas Young(1773-1829)
English genius – a physicist who created Young’s Modulus, a physician who discovered eye focusing mechanism, and a linguist who translated part ofthe Rosetta Stone F
Fsimple tension test
!
Hooke’s Law and Young’s Modulus
Tensile Test & Mechanical Properties Visual Glossary 1
12
Tensile Test & Mechanical Properties Visual Glossary 2
13
Tensile Test & Mechanical Properties Visual Glossary 2
13
Tensile Test & Mechanical Properties Visual Glossary 1
12
17
• Plastic tensile strain at failure:
Ductility: % Elongation (%el) or % Reduction of Area (%RA)
• Another ductility measure: 100xA
AARA%
o
fo -=
x 100L
LLel%
o
of
LfAo Af
Lo
Adapted from Fig. 6.13, Callister & Rethwisch 8e.
Engineering tensile strain,
Engineeringtensile stress,
smaller %el
larger %el
% Reduction of Area (%RA)
E%el = x 100
Same Slope
Can %RA be measured from stress-strain curve?_________
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