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The theory of scattering by an inhomogeneous dielectric medium has been extended so as to account for the turbidimetric behavior of polymer solutions in solvent-precipitant mixtures. It is predicted by this theory and verified by experiment that correct values of molecular weight are obtained by the usual interpretation of turbidity measurements if and only if the solvent and precipitant have the same refractive index. The practical utility of turbidimetry in high polymer solutions is shown to be greatly increased by the proper use of solvent-precipitant mixtures. If the solvent and precipitant have different refractive indices, scattering measurements give information about the extent of selective absorption of solvent by the polymer.

The main purpose of this paper is to demonstrate that besides the stress triaxiality parameter, the Lode angle, which can be related to the third invariant of the deviatoric stress tensor, also has an important effect on ductile fracture. This is achieved by conducting a series of micromechanics analyses of void-containing unit cells and experimental-numerical studies of carefully designed specimens experiencing a wide range of stress states. As a result, a fracture criterion is expressed in terms of the equivalent failure strain as a function of the stress triaxiality and the Lode angle (or the third invariant of the stress deviator) and this function is calibrated for a DH36 steel plate.