Thermal analysis of the hot torsion test taking into account radiation

A formula for the view factor for a system consisting of a shaft of non-uniform cross section and coaxial cylinder has been derived. The formula was applied to provide for inclusion of radiation in the thermomechanical analysis of the hot torsion test by a rigid viscoplastic FE code. The results of computation for simulated tests with three rates of twist, with and without radiation between the test bar and the cylindrical enclosure, were compared. Failure to consider radiative heat loss may significantly affect the torque which, with the associated twist, is commonly used to derive the constitutive equation for analysing hot working processes.