Experimental Study of the Biaxial Cyclic Behavior of Thin-Wall Tubes of NiTi Shape Memory Alloys

Experimental investigation on transformation, reorientation and plasticity of Ni47Ti44Nb9SMA under biaxial thermal–mechanical loading

“…When ε is applied after the shear deformation in the first stage, σ eq has a sharp drop and then rises gradually, which is similar to the results obtained by McNaney et al [21]. The phenomenon of the plateaus existing in tensile stress-strain curves disappearing during torsion has also been reported by some researchers for NiTi SMAs, for example, by Liu et al [42] and Wang et al [27]. Chen et al [3] also reported and discussed this phenomenon.…”

“…Grabe and Bruhns [24,25] investigated the effects of strain rate on the pseudoelastic behavior of NiTi SMAs using tension/torsion tests with or without temperature control and found that the NiTi SMAs do not show distinct rate dependence when the temperature remains constant. Wang [26] and Wang et al [27] investigated the pseudoelastic behavior, the dissipated energy densities and the evolution of the characteristic stresses of NiTi SMAs subjected to cyclic biaxially proportional and non-proportional loadings. Moreover, Wada et al [28] found that the magnitudes of the recovery strains in biaxially pre-strained FeMnSi-based SMA specimens are smaller than those in uniaxially pre-strained ones.…”

“…Suppose that during a test the torsional load had been applied initially, the martensitic transformation had already finished and distinct plastic shear deformation had occurred, after which the torsional strain was kept unchanged and a tensile load was applied; would this subsequent tensile loading be able to further induce transformation and reorientation? It is known that the equivalent stress-strain curve under pure tension is distinctly different from that under pure torsion [3,27]; are the martensite variants activated in the subsequent tensile deformation different from those in the previous torsional deformation? Little progress in the pursuit of these questions can be found in the literature.…”

Fatigue of Nitinol: The state-of-the-art and ongoing challenges

“…The functional fatigue under multiaxial cyclic loading is also a possible failure mode for components made of Nitinol (Song et al, 2014;Wang et al, 2012). Similar to uniaxial testing, the capability of the superelastic Nitinol to dissipate energy decreases for the first few cycles and then reaches a stable state under multiaxial state of deformation.…”

Modeling of torsion fatigue in shape memory alloys

“…Many efforts have been put into investigating the functional behavior and cyclic degradation of superelastic Nitinol (Eggeler et al, 2004;Frotscher et al, 2011;Gall et al, 1998;Maletta et al, 2014;Mao et al, 2006;Miyazaki et al, 1986a;Moumni et al, 2005;Nemat-Nasser and Guo, 2006;Sehitoglu et al, 2001), martensitic Nitinol (Kang et al, 2012;Melton and Mercier, 1979a), or a mixture of two phases (Nayan et al, 2008) under uniaxial loading. These studies have also been extended not only to torsional loading (Jensen, 2005;Wang et al, 2010) but also to multiaxial loading (Song et al, 2014;Wang et al, 2012). Generally, all of the existing works have reported that the hysteresis loop narrows cycle by cycle, and that the stabilized cycle will be attained after several cycles of loading for superelastic Nitinol.…”