Plane stress
= Plane stress
{title2=$\tau_{zz}=\tau_{xz}=\tau_{yz}=0$}
A <stress tensor> state with all traction components involving one normal direction zero. In an isotropic solid, its two remaining normal stresses obey $\tau_x=E(e_x+\nu e_y)/(1-\nu^2)$ and $\tau_y=E(e_y+\nu e_x)/(1-\nu^2)$. The out-of-plane <strain> need not vanish: $e_z=-\nu(\tau_x+\tau_y)/E$. Constraining the out-of-plane deformation instead would be a different boundary condition.