Evaluation of the stress-strain and thermal states of Ni–Ti-alloy billets subjected to screw piercing

We performed computer simulations of the screw piercing of titanium-nickelide shells in two- and four-high mills. On the basis of the accumulated numerical results, we compute the parameters of the stress-strain and thermal states of the shells. The distributions of levels of the accumulated strain and the normalized mean stress show that a more homogeneous stress-strain state and a lower hazard of fracture of the shells are detected in the case of four-high piercing. The analysis of the temperature distribution shows that, in the case of four-high piercing, the obtained temperature state is more favorable for guaranteeing higher levels of plasticity of the materials of pierced shells.