ESDU 72013 gives curves from which the principal stresses and their direction can be found from a knowledge of the direct and shear stress components applied. The formulae on which the curves are based are given@ together with formulae for the maximum shear stresses and shear strains. These formulae apply to any material and condition. For elastic isotropic materials@ formulae for the principal direct strains and maximum shear strains are also given when the material is in either plane stress or plane strain.
ESDU 72013-1972 history
1972ESDU 72013-1972 Principal stresses and strains in a two-dimensional stress field.