Degradation of two-way shape memory effect due to the relaxation of internal oriented stress in NiTi alloy on holding at 640÷700 K

Constitutive modeling for the training process of two-way shape memory effect under thermal cyclic loading

“…Generally, the recovery due to two-way SME is less than that of one-way SME. In the literature, different types of training are proposed to induce the two-way shape memory effect: the pseudoelastic cycle (Perkins, 1981), one-way shape memory cycle (Gallardo Fuentes et al, 2002), a combination of one-way and pseudoelastic cycles (Gallardo Fuentes et al, 2002; Tokuda et al, 2001), a constant temperature cycle of transformed martensite (Gallardo Fuentes et al, 2002), secondary deformation in martensite phase (Gallardo Fuentes et al, 2002; Ponikarova et al, 2019) and constrained aging in austenite or martensite phase (Zhang et al, 2002).…”

Effects of Predefined Thermomechanical Procedure on the Microstructure and Mechanical Properties of the Two-Way Shape Memory Effect in the NiTi Alloy

“…(1) Signifcant deformation caused by cooling below the Martensite fnish temperature (2) Deforming and heating above Austenite fnish temperature while cooling below Martensite fnish temperature (3) Loading and unloading and cooling below M d (4) Cooling below Martensite fnish temperature, loading and constraint, release, and heating above Austenite fnish (5) Heat above the Austenite fnish, deforming and constraining, cooling below the Martensite fnish, and cycling between these two fnishes Ponikarova et al [9] investigated the two-way shape memory efect degradation due to stress relaxation during holding predeformed Ni-50.0 at % Ti alloy at temperatures from a range of 640-700 K for 0-60 min. Tey found that the main degradation of the two-way shape memory efect is related to holding the sample up to 60 min, while full degradation is not observed even after holding at 700 K for 6 h. A three-dimensional fnite strain constitutive model for SMAs was applied by Xu et al [10] to investigate the two-way shape memory efect through a large deformation framework.…”