The effect of specimen geometry on the accuracy of the constitutive equation derived from the hot torsion test

A rigid-viscoplastic FE code has been used to simulate the isothermal hot torsion of specimens used in tests designed for determining the relationship governing constitutive behaviour. For a given constitutive equation, the torque-rotation data were derived from the FE analysis of specimens of various geometries. Subsequently, based on these data, the constitutive equation was regenerated using an existing analytical relationship relating torque and twist in a cylindrical specimen. The effect of geometry of hot torsion specimens on the accuracy of the constitutive equation derived from the analytical relationship was investigated. Recommendations on the preferred geometry of hot torsion specimens for high deformations were made