Stress
When a material is subjected to an external force, a resisting force induced. The internal resistance force per unit area is called stress.
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| Stress Formula |
Type of stress
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| Normal Stress |
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| Normal Stress Formula |
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| Shear Stress |
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| Shear Stress Formula |
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| Bulk Stress |
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| Bulk Stress Formula |
Strain
Deformation per unit length in the direction of deformation is known as strain. It is a dimensionless quantity.
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| Strain Formula |
Types of Strain
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| Normal Strain |
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| Normal Strain Formula |
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| Shear Strain |
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| Shear Strain Formula |
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| Bulk Strain |
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| Bulk Strain Formula |
True Stress and True Strain
True stress is defined as the ratio of load to the instantaneous area.
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| True Stress |
Where σ and ε are the engineering stress and engineering strain respectively.
The true strain is defined as
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| True Strain |
Stress-Strain Curve
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| Stress-Strain Curve |
NOTE:
- Limit of Proportionality: It is the stress at which the stress-strain curve is a straight line(OA).
- Hook's law is valid up to the proportionality limit.
- Elastic limit: point in the stress-strain curve up to which the material remains elastic. There is no permanent deformation up to this point.
- Plastic Range: Region between elastic limit and point of fracture.
- Yield Point: The point just beyond the elastic limit, at which material goes increase in length without further increase in the load.
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