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

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

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

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