Fatigue of pseudoelastic NiTi within the stress-induced transformation regime: a modified Coffin–Manson approach

Abstract

Strain controlled fatigue tests of a pseudoelastic nickel–titanium (NiTi) shape memory alloy (SMA) have been carried out in this investigation. In particular, flat dog-bone shaped specimens, obtained from commercial NiTi sheets, have been analyzed, under pull–pull loading conditions, in two subsequent steps: (i) material stabilization and (ii) fatigue life estimation. The first step was carried out to obtain a stable pseudoelastic response of the SMA, i.e. with no residual deformations upon unloading, and it can be regarded as a preliminary processing condition of the alloy. Results on functional fatigue, i.e. in terms of stabilized pseudoelastic response, and on structural fatigue, in terms of cycles to failure, are reported and discussed. Furthermore, a modified Coffin–Manson approach for fatigue life estimation of SMAs is proposed, which takes into account the strain mechanisms involved during repeated stress-induced martensitic transformations.

Non-proportional multiaxial whole-life transformation ratchetting and fatigue failure of super-elastic NiTi shape memory alloy micro-tubes

“…It can be concluded from the above-mentioned experimental observations that the multiaxial fatigue life of super-elastic NiTi SMA micro-tubes depends greatly on the applied stress level and loading paths simultaneously, and is too complicated to be reasonably predicted by the existing failure models mainly based on the dissipation energy per cycle and its evolution (Moumni et al [10]; Kan et al [26]), or the modified Manson-Coffin models (Maletta et al [24,25]). Furthermore, in the stress-controlled cyclic loading test with a non-zero mean stress, the occurrence of the transformation ratchetting can degenerate the fatigue life of the NiTi SMA micro-tubes and should be reasonably considered in the construction of the corresponding fatigue failure model.…”

“…In general, the fatigue lives obtained in the multiaxial cyclic tests with the loading paths containing certain P/V stress holds (e.g., square, hourglass-typed and butterfly-typed ones) are shorter than that with the paths containing no P/V stress holds (e.g., rhombic and octagonal ones). It is very difficult to precisely predict such complicated fatigue behavior by the existing failure models as suggested by Maletta et al [24,25], Moumni et al [10] and Kan et al [26] for the uniaxial ones. As shown in Fig.…”

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

“…amount of nickel or titanium in a Nitinol alloy), treatment process, or test temperature, may affect significantly the fatigue behavior of these alloys. One of the main challenges in evaluating the fatigue resistance of Nitinol is the formation of stress-induced martensite under mechanical deformation, and therefore, classical fatigue theories may not be applicable directly to superelastic Nitinol alloys (Maletta et al, 2012).…”

Three-dimensional constitutive model for structural and functional fatigue of shape memory alloy actuators

“…Probabilistic modeling may be a useful tool in fatigue life analysis of SMA bodies, given the scattering observed in the thermomechanical response of nearly identical test samples demonstrated in experimental works (Figueiredo et al, 2009;Nemat-Nasser and Guo, 2006). Relevant experiments (Scirè Mammano and Dragoni, 2014) Maletta et al (2012Maletta et al ( , 2014 to predict the fatigue life of NiTi SMAs under the stress-controlled cyclic loading conditions. A third…”