Rate dependence of transformation pattern in superelastic NiTi tube

The rate dependence of transformation pattern in superelastic NiTi tube (diameter-wall thickness ratio is 10) under uniaxial tension is investigated numerically. Simulations and experiments show that mechanical instability upon martensitic transformation is manifested as inhomogeneous deformation and stress plateau. As strain rate increases, the stress plateau converts from the horizontal type to the hardening one and the transformation band transits from cylinder to helix. The rate dependence of transformation pattern originates from the contest between the mechanically favorable cylindrical band and the thermomechanically favorable helical band. The results are inspiring to unveil the rate effect of mechanical instability in phase transformable material. (C) 2020 Elsevier Ltd. All rights reserved.