1-stress &strain-mechanics of materials.ppt

8/18/2019 1-Stress &Strain-Mechanics of Materials.ppt

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Mechanics of Materials

Mechanics of Solid

Strength of MaterialsMechanics of Deformable Bodies

Eng. Mechanics Statics

Model Rigid Bodies

Mechanics of Materials

Model Deformable Bodies

Forces, LengthForces, Length, Section,

Mechanical Properties

of Materials

Mekanika Kekatan Bahan


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Mekanika kekuatan bahan

Stress AnalysisAnalisa Tegangan

Deflection AnalysisAnalisa Lendutan

Free!Bod"!Diagram, #nternal Forces, Stress Formla,

Deflection Formla


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Ilmuwan-Ilmuwan di bidang Mekanika


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Konsep "ang dignakan dalam

mekanika kekatan bahan

$ Keseimbangan

$ %km %ooke

$ Kompatibilitas &smsi!&smsi "ang dipakai'

! Bahan homogen

! Bahan isotropis! Deformasi relatif kecil


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How Materials Carry Load

asic modes of loading a material! Tension" com#ression and shear


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Stress!

Loads applied on a material are distribted o(er a srface.

For e)ample, the point load sho*nin the follo*ing figre might actall" be a niforml" distribted load

that has been replaced b" its e+i(alent point load.


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Stress is the load applied per nit area of the srface it is applied on.

ormal stress is the stress normal to a srface

and is denoted b" the s"mbol - - sigma/.

#n the abo(e figre the normal stress is niform o(er the srface of the bar

and is gi(en b"

Shear stress is the stress tangent to a srface. #f in the follo*ing figre the shear stress

ta/ that reslts in the shear load V is niforml" distribted o(er the srface,

then the shear stress can be calclated b" di(iding the shear force b" the area it is applied on.


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0nit Stress


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earing Stress


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Strain is the way engineers re#resent the distortion of a body&

A%ial strain 'normal strain( in a bar is a measure of the e%tension of a bar #er unit length of the bar

before deformation& The following figure shows a bar of initial length l o that is e%tended by

the a##lication of a load to the length l &

Strain!

1he a)ial strain, denoted b" epsilon/


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Shear strain, denoted b" gamma/,


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1ensile 1est0nia)ial 1esting

Machine'


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Standard 1ension 2opon


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Engineering Stress!Strain 2r(e

for mild steel


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Elastic Response

Hooke)s law!

%ooke3s la* for e)tension'

%ooke3s la* for shear'

E is the elastic modls

G is the shear modls


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Elastic!Plastic Response


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*oisson)s +atio

The relation between the elastic moduli '


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4enerali5ed %ooke3s La* for Mlia)ial Loading

isotropic materials

[ ]

[ ]

[ ])(1)(

1

)(1

y x z z

z x y y

z y x x

E

E

E

σ σ ν σ ε

σ σ ν σ ε

σ σ ν σ ε

+−=

+−=

+−=


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GG

GG

GG

zx xz zx xz

zy yz

zy yz

yx xy

yx xy

τ τ γ γ

τ τ γ γ

τ τ γ γ

===

===

===

Pre shear'


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6olmetric strain dring e)tension

6olmetric Strain e/'


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,actor of safety n/


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1-stress &strain-mechanics of materials.ppt

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