Novel insight into the strain-life fatigue properties of pseudoelastic NiTi shape memory alloys

Abstract

The whole low-to-high cycle fatigue behavior of a pseudoelastic NiTi SMA was analyzed. Global and local strains measurements were carried out by an extensometer and digital image correlation. Significant differences were observed at the two scales, due to the localized nature of stress-induced transformations. Local mechanisms play a crucial role on fatigue damage and have a direct effect on the Z-shaped strain-life curves observed in previous works. The effective nature of this unusual behavior was revealed by systematic analysis of local strain. Finally, strain decomposition was made and data were analyzed by a recent modified Coffin-Manson approach.

Advances in enhancing structural and functional fatigue resistance of superelastic NiTi shape memory alloy: A Review

“…Pull-pull fatigue tests were conducted by Sgambitterra et al (2019aSgambitterra et al ( , 2019b at room temperature (A f = 14°C) on dog bone specimens made of 1.5 mm thick Ni 50.8 Ti 49.2 (at.%) sheet. The test conditions include frequency f = 0.5 Hz and runout cycles of 10 6 .…”

“…The stent is expected to maintain its integrity for more than 10 years, with an average pulse of 70 per min. It needs to withstand high-cycle (Sgambitterra et al, 2019b), T1, T2 and T4 (Pelton et al, 2013), T5 (Miyazaki et al, 1999) and (b) Phases for superelastic NiTi; (I) fully deformed martensite region, (II) stress plateau region, (III) transformation from linear-elastic to stress plateau region, (IV) austenite linearelastic region. e AM S and e AM F are martensite start and finish strain respectively, e pr is proportional stain, s AM S and s AM F are martensite start and finish stress respectively (Mahtabi et al, 2015a).…”

Analysis of the Local Functional Evolution in NiTi Shape Memory Alloys by Multicycle Nanoindentations

“…To this aim, Finite Element (FE) codes, proper constitutive models for SMAs [12,13], and analytical approaches [14][15][16] were developed to investigate the fracture properties of SMAs. In addition, special and ad hoc investigation techniques were also developed and exploited to study the crack formation and propagation mechanisms under static [17][18][19][20][21] and cyclic loadings [22][23][24][25] by both local and global analyses [26,27]. An example is represented by synchrotron X-ray micro-diffraction (XRD) [18,19], infrared thermography (IR) [20,25], and Digital Image Correlation (DIC) [21,22,[28][29][30][31][32] that allow to demonstrate that phase transition phenomena significantly affect the fatigue properties of the material as well as the functional response, [26,27].…”

Fatigue Crack Growth in Austenitic and Martensitic NiTi: Modeling and Experiments

“…Within this context, several studies were carried out in recent years with the aim of analyzing the effects of SIM and TIM on fatigue and fracture properties of SMAs, as discussed in recent review papers [4][5][6][7]. Both low-and high-cycle fatigue properties of NiTi SMAs were analyzed within the framework of modified approaches for common engineering metals [8][9][10][11][12][13][14][15]. Fracture-mechanics-based approaches were also used to analyze fatigue crack growth in SMAs [16][17][18][19].…”