BIREFRINGENCE IN ROTATING STRESS FIELDS 1 by

The transformations of the components of a two-dimensional vibration caused by axis rotation and by a relative phase retardation are used to derive three methods for expressing the changes suffered by polarized light travelling through an inhomogeneous stress field, namely the Poincar4 sphere; Neumann's differential equations; and 2x2 complex transformation matrices, and shows their relation with the explicit solution of Drucker and Mindlin. The complex matrix method is applied to the calculation of strain birefringence by alignment and of polarization changes in a stress field with a continuous variation direction and magnitude of principal stress-difference. A comparison with experimental observations shows ex-cellent agreement and indicates some of the difficulties inherent in the problems of birefringence in rotating stress fields. It is hoped that the unified derivation of these methods will facilitate their wider use in photoelasticity. TE0FlnRIOAL LIBRARYBLDG 313 13AZRDEE pBOyNG 10 OU11D)W.STEAP-T