A modified Nadai's method is proposed to determine the shear stress-strain curve by use of a solid circular cylinder subjected to torsional load. The modification is accomplished by taking into account the axial length change of the specimen. The method is extended to give the shear stresses in tubular specimens.

A series of experiments on annealed isotropic high purity cast aluminum material was conducted under the pure torsion condition. Torque-twist and axial elongation-twist curves were recorded. The shear stress-strain curves obtained from tubular specimens of various wall-thicknesses and solid circular cylindrical specimens are compared by using different methods of data analysis. It is found that the present method is the most appropriate one among all methods considered. It is suggested that long gage-sectioned, thick-walled tubular specimens be used to determine the shear stress-strain curve in the large strain range.