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Strain
Beginner
Fractional deformation.
Key relation
ε = ΔL/LStrain is the relative deformation: tensile ε = ΔL/L, volume strain ΔV/V, shear angle. It's dimensionless.
Worked example
A 2 m wire stretching 1 mm: ε = 5×10⁻⁴.
Common mistake
Use the original length.
In more detail
Strain is the fractional change in a dimension of a solid under stress, ε = ΔL/L. It is dimensionless, since it compares a change in length with the original length.
Real-world uses
- Strain gauges measure how much a structure deforms under load.
- Geologists measure strain in rocks to study earthquakes.
- A rubber band stretched by 10 percent has a strain of 0.1, which measures how much it has deformed relative to its length.
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Frequently asked questions
What units does strain have?
None, since it is a ratio of lengths.
Can strain be expressed as a percentage?
Yes, as strain times 100 percent.
Does strain have units?
No. It is a ratio of lengths, so the units cancel and strain is a pure number.
Related topics in Fluids & Elasticity
Cohesion and adhesion · Elasticity · Stress · Hooke's law for solids · Young's modulus · Bulk modulus