Pages in this set

Page 1

Preview of page 1
Hooke's Law &
Elasticity
Definitions Material property terms
Characteristic graphs

Page 2

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Hooke's Law
The extension of an object is
directly proportional to the applied
force up to the limit of
proportionality F x F = k x k is
the Force Constant for that object
(units: Nm-1)
The same equation can also be used for
compression springs

Page 3

Preview of page 3
Hooke's Law
F
p
e
Gradient = k Area = elastic strain energy
d
x p = limit
of proportionality e = elastic limit
dotted line = unloading d =
permanent extension

Page 4

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Elastic Energy
F
Area = elastic strain energy
x For the straight line region only:
E = 1/2 F x
E = 1/2 k x2

Page 5

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Elastic deformation
The term "Elastic" in the context of
materials means "Elastic behaviour"
i.e. up to the Elastic Limit. A
material which returns to its original
dimensions when the deforming
force is removed has deformed
Elastically.
So metals can behave elastically over
small extensions.

Page 6

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Plastic deformation
A material which does not return to
its original dimensions when
unloaded has deformed plastically.
Metals also exhibit plastic behaviour for
extensions beyond their Elastic Limit. A
useful property for, say, pressing kitchen
sinks with draining boards from a single
sheet of stainless steel.

Page 7

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Brittle
Materials which do NOT deform
plastically before breaking are
described as Brittle.

Page 8

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Ductile / Malleable
Materials which deform plastically
(and can be stretched into wires)
before breaking are described as
Ductile.
Materials which can be pressed or
hammered into different shapes are
Malleable.

Page 9

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Test
Define the following: Hooke's Law
Limit of Proportionality Elastic
Limit Ductile Brittle

Page 10

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Test
If you were asked to conduct a
Hooke's Law experiment, what
measurements would you record
AND repeat? What graph would
you plot and how would the
gradient of this graph relate to
Hooke's Law (be careful!)

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Hooke's Law & Elasticity

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Pages in this set

Page 1

Preview of page 1
Hooke's Law &
Elasticity
Definitions Material property terms
Characteristic graphs

Page 2

Preview of page 2
Hooke's Law
The extension of an object is
directly proportional to the applied
force up to the limit of
proportionality F x F = k x k is
the Force Constant for that object
(units: Nm-1)
The same equation can also be used for
compression springs

Page 3

Preview of page 3
Hooke's Law
F
p
e
Gradient = k Area = elastic strain energy
d
x p = limit
of proportionality e = elastic limit
dotted line = unloading d =
permanent extension

Page 4

Preview of page 4
Elastic Energy
F
Area = elastic strain energy
x For the straight line region only:
E = 1/2 F x
E = 1/2 k x2

Page 5

Preview of page 5
Elastic deformation
The term "Elastic" in the context of
materials means "Elastic behaviour"
i.e. up to the Elastic Limit. A
material which returns to its original
dimensions when the deforming
force is removed has deformed
Elastically.
So metals can behave elastically over
small extensions.

Page 6

Preview of page 6
Plastic deformation
A material which does not return to
its original dimensions when
unloaded has deformed plastically.
Metals also exhibit plastic behaviour for
extensions beyond their Elastic Limit. A
useful property for, say, pressing kitchen
sinks with draining boards from a single
sheet of stainless steel.

Page 7

Preview of page 7
Brittle
Materials which do NOT deform
plastically before breaking are
described as Brittle.

Page 8

Preview of page 8
Ductile / Malleable
Materials which deform plastically
(and can be stretched into wires)
before breaking are described as
Ductile.
Materials which can be pressed or
hammered into different shapes are
Malleable.

Page 9

Preview of page 9
Test
Define the following: Hooke's Law
Limit of Proportionality Elastic
Limit Ductile Brittle

Page 10

Preview of page 10
Test
If you were asked to conduct a
Hooke's Law experiment, what
measurements would you record
AND repeat? What graph would
you plot and how would the
gradient of this graph relate to
Hooke's Law (be careful!)

Comments

No comments have yet been made