# 23.2: Hookean Elasticity

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For many materials loaded in uniaxial tension, the tensile stress on the material, σ, is directly proportional to the tensile strain , ε.

A sample loaded in uniaxial tension

The linear relationship between stress and strain is known as Hooke's Law,

σ ∝ ε

The constant of proportionality in this equation for simple tension is the Young Modulus of the material, E:

$E=\frac{\sigma}{\varepsilon}$

The Young Modulus of a material has values ranging from approx. 0.01 GPa for rubbers to approx. 1000 GPa for diamond.

Hooke's Law further states that the stress response of a material is independent of time and that the strain of a material disappears completely on removal of the applied stress (i.e. a Hookean material shows elastic deformation ).