How this calculator works
Engineering shear strain is the relative lateral displacement divided by the transverse height for small simple shear. In linear elasticity it also equals shear stress divided by shear modulus. A circular shaft in torsion has strain increasing linearly from zero at its axis to the largest magnitude at its surface. A signed twist determines the strain sign.
Formula
gamma = x/h = tau/G; shaft gamma(r) = r phi/L.
Worked example
A 1 mm displacement across a 100 mm height gives gamma = 0.01. A shaft of radius 20 mm, length 1 m and twist 0.1 rad has surface strain 0.002.
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Frequently asked questions
Is engineering strain the tensor shear component?
Engineering shear strain is twice the corresponding off-diagonal infinitesimal tensor component.
Can I use a large shear angle?
The small-angle approximation becomes inaccurate. Finite-deformation measures are needed for large shear.
Why is strain zero at a shaft centre?
The twist-induced circumferential displacement is proportional to distance from the axis.