If a normal stress ${\sigma }_x$ is applied in the $x$ direction, the element undergoes a tensile strain of:

${\epsilon }_x=\frac{ {\sigma }_x}{E}$

In the $y$ and $z$ directions, the element contracts due to the Poisson effect. The contraction strain in the $y$ direction is:

${\epsilon }_y=-\nu \frac{{\sigma }_x}{E}$