Reduction of Strain Rosettes in the Plastic Range

In reducing strain-rosette data, it is not always possible to tell by inspection whether permanent strains are present. If permanent strains are present, the reduction of the principal strains to principle stresses, assuming perfectly elastic conditions, can be much in error. This paper gives equations for the principal stresses which can be used when purely elastic or elastic-plus-plastic strains are present. Comparisons of theoretical and experimental results are given in order to check the validity of the theory.