Physics Study ProgramFaculty of Mathematics and Natural SciencesInstitut Teknologi Bandung
FI-1101Fisika Dasar IA
Kuliah 18
ELASTISITAS
Physics Study Program - FMIPA | Institut Teknologi Bandung
PHYSI S
Materi Hari Ini
Tegangan (stress) Regangan (strain) Modulus Elastisitas
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PHYSI S
ElastisitasAdalah cabang dari Fisika yang menjelaskan tentang bagaimana suatu benda berubah bentuk ketika diberikan suatu gaya
Real rigid bodies are elastic we can slightly change their dimensions by pulling, pushing, twisting or compressing them.
Stress: Deforming force per unit areaStrain: Unit deformation
Tensile stress: associated with stretching
Shearing stress Hydraulic stress
Stress = Elasticity Modulus x Strain
Elastic modulus: describes the elastic behavior (deformations) of objects
as they respond to forces that act on them
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PHYSI S
(1) Stress = cte x Strain Recovers original dimensions when stress removed.
(2) Stress > yield strength Sy specimen becomes permanently deformed.
(3) Stress > ultimate strength Su specimen breaks.
Tension and compression:
A
FStress
L
LStrain
( F= force applied perpendicular to the area A of the object)
( fractional change in length of the specimen)
Stress = (Young’s modulus) x StrainL
LE
A
F
Shearing:
A
FStress ( F= force in the plane of the area A)
L
xStrain
( fractional change in length of the specimen)
Units of Young modulus: F/m2
L
xG
A
F
Stress = (Shear modulus) x Strain
Hydraulic stress:
A
FppressureFluidStress
V
VStrain
Hydraulic Stress = (Bulk modulus) x Hydraulic compression
V
VBp
Physics Study Program - FMIPA | Institut Teknologi Bandung
PHYSI S
Young’s Modulus Everything is a
spring…
LF Y A
L
…until it breaks!
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PHYSI S
Shear Modulus0
XF S A
L
Shear moduli and Young moduli are comparable in magnitude for most materials
(Liquids have zero shear modulus)
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PHYSI S
Pressure and Bulk Modulus Pressure is defined as force per
unit area Unit of pressure is N/m2 = Pascal (Pa) Atmospheric pressure ~ 105 Pa=
15psi 1 psi = 1 pound per square inch Bulk modulus B relates
fractional volume change to pressure change
0
VP B
V
FP
A
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PHYSI S
Stress, Strain and Hooke’s law
F/A or pressure are known as “stress”
Fractional changes in length or volume are known as “strain”
Above relations between stress and strain account for “elastic” behavior and Hooke’s law
0
VP B
V
0
/X
F A SL
/
LF A Y
L
Physics Study Program - FMIPA | Institut Teknologi Bandung
PHYSI S
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