Angle α_- Between Local Axis x (or y) and Principal Axis 1 (or 2) for Strains on Negative Surface Side

α_{-} = \frac{1}{2} [\arctan (\frac{γ_{x y, -}}{ε_{x, -} - ε_{y, -}}))]

Do you have any questions?

Angle α- Between Local Axis x (or y) and Principal Axis 1 (or 2) for Strains on Negative Surface Side