Effects of Lüders-like bands on NiTi fatigue behaviors

Abstract

International audienc

Elastocaloric effect vs fatigue life: Exploring the durability limits of Ni-Ti plates under pre-strain conditions for elastocaloric cooling

“…It is important to distinguish between cycling in the elastic region, where the material is always austenitic, and in the plateau, where the martensitic transformation occurs. As demonstrated by Zheng et al [46,47], the failure in superelastic Ni-Ti strips always occurs in the part of the sample where the martensitic transformation with Lüders-like bands occurs.…”

A digital image correlation study of a NiTi alloy subjected to monotonic uniaxial and cyclic loading-unloading in tension

“…The literature on fatigue tests has suggested that during unloading, the formation of stable remnant B19′ variants, along with de-twinning, grain reorientation effects and the retention of lattice defects within B2 and remnant B19′ grains hinder the latter phase′s reverse transformation back to B2 [14,15,[22][23][24][25][26][27][28]. The combined effect of the above mechanisms serves to increase the magnitude of residual strains upon unloading after each cycle along with a progressive degradation in superelasticity.…”

“…Fatigue testing of NiTi alloys typically involves repeated cycles of loading up to the end of the macroscopic stress plateau region and then unloading back to zero load. Such investigations reported increases in the irreversible strain component (through highly accumulated dislocation densities and the formation of stable martensite variants with successive cycles) contributing to an increase in the residual strain upon unloading and a progressive degradation in superelasticity involving the retention of an increasing phase fraction of B19′ [14,15,[22][23][24][25][26][27][28][29].…”

Prestress state evolution during thermal activation of memory effect in concrete beams strengthened with external SMA wires

“…The simulations are based on a SMA behavior in uniaxial tension considering three internal variables: wire temperature T , strain SMA and martensite volume fraction z . Phase changes in NiTi-based SMA wires are generally associated with the propagation of transformation fronts separating austenite and martensite [37][38][39][40], which leads to complex thermomechanical couplings in the case of heterogeneous temperature distribution. For the sake of simplicity, the three variables T , SMA and z were here considered as homogeneous within the wires.…”