Shear strain

Shear strain is a strain that acts parallel to the face of a material that it is acting on. Normal strain acts perpendicular to the face of that it is acting on. There are two ways to interpret shear strain: the average shear strain and the engineering shear strain. The variable used to denote average shear strain is ε while γ denotes engineering shear strain.

Additional recommended knowledge

Daily Sensitivity Test

Essential Laboratory Skills Guide

Safe Weighing Range Ensures Accurate Results

Consider an infinitesimal rectangle in the xy plane subject to shear strain. The rectangle becomes a parallelogram where α is the displacement from the y axis in the x direction and δ is the displacement from the x axis in the y direction. The average shear strain is

ε_xy = 0.5(α+δ) = ε_yx

Definition of engineering shear strain:

γ = ε_xy+ε_yx = 2ε_xy

γ = α+δ = θ-β

θ is the angle before deformation and β is the angle at that same point after deformation. Therefore γ describes the total deformation. Although, strain is dimensionless, it is usually stated as in./in. or some similar sign convention.

See also

• Shear modulus
• Moiré pattern (the Moiré effect can be used to measure strain)