As different angles are investigated, various combinations of normal stress ${\mathrm{\sigma }}_{\mathrm{n}}$ and shear stress ${\mathrm{\tau }}_{\mathrm{nt}}$ are found to be acting on the plane surface. These combinations of $\mathrm{\sigma }$ and $\mathrm{\tau }$ are present internally in the material even though the bar is simply an axial member subjected to a normal force.