Finite element simulation of the influence of heat treatment temperature on tension, compression and bending behavior of nanostructured NiTi wires

The mechanical behavior of cold worked wires is strongly modified by heat treatments (HT) performed after the last cold working. For low HT temperatures, deformation during tensile tests is uniform and tension-compression behavior is asymmetric. Localized behavior is observed in tension for higher HT temperatures. Depending on the HT temperature, uniform or localized behavior is observed during pure bending tests.
To the best of the authors knowledge, there is no constitutive equations which are able to model all these experimental results. An “elastohysteresis constitutive equation” was proposed in 1990 to model superelastic bahaviour of shape memory alloys ; this equation was implemented in the finite element software “Herezh”. In this paper, the elastohysteresis equation and the Herezh software are used to simulate tensile and pure bending tests of NiTi wires taking into account the influence of the HT temperature. Uniform or localized tension and pure bending behavior is obtained during loading and unloading depending on the HT temperature.