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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