Computer-Simulation Assessment of the Stress–Strain and Kinematic States of a Titanium Nickelide Billet during Screw Rolling

Computer simulation of three- and four-high screw rolling of titanium nickelide billets was carried out using QForm finite-element software. Based on the results of the computer simulation, the parameters of the stress–strain and kinematic states are compared. The paths of several points located on the billet radius during rolling were plotted. The normalized Lode angle at these points was calculated. The spread of values of the normalized Lode angle in three-high rolling is wider by a factor of 5 than in four-high rolling. The spread of values of the normalized mean stress is almost the same for both types of rolling. The increment of strain per 1 mm of the path in the deformation zone during four-high screw rolling is less by 43% than during three-high rolling. This suggests that the strain state is softer during four-high rolling and more preferable for rolling low-ductility and difficult-to-form materials. It was found out that the qualitative change in the total velocity of the tracked points in the deformation zone is the same for both types of rolling: the total velocity of the central layers of the billet increases, while the total velocity of the surface layers decreases.