Stress Strain Behavior of DuctileBrittle Materials

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Stress Strain Behavior of Ductile/Brittle
Materials
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Why Use Stress Instead of Force?
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Stress-Strain Test
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100 kN (22,500 lb) UTM
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Typical Aluminum
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Typical Aluminum
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Typical Brittle Material
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Typical Brittle Material
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Typical Mild Steel
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Typical Mild Steel
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Typical Mild Steel
Typical Brittle Material
Typical Aluminum
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Stress-Strain Diagram Ductile Materials
P
P
Force P and extension d are measured stress s
and strain e are calculated
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True Stress vs True Strain for a Ductile Material
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Stress-Strain Diagram for Concrete
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Hookes Law Modulus of Elasticity

• Below the yield stress

• Strength is affected by alloying, heat treating,
  and manufacturing process but stiffness (Modulus
  of Elasticity) is not.

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Elastic vs. Plastic Behavior

• If the strain disappears when the stress is
  removed, the material is said to behave
  elastically.

• The largest stress for which this occurs is
  called the elastic limit.

• When the strain does not return to zero after the
  stress is removed, the material is said to behave
  plastically.

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Yield Strength by the Offset Method

e 0.002
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Strain Energy Density/Modulus of Resilience
At the proportional limit, u ? ur
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End
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Stress-Strain Diagram Brittle Materials