Phase transformation volume amplitude as a low-cycle fatigue indicator in nickel–titanium shape memory alloys

Shape memory alloys (SMAs) are unique materials capable of undergoing a thermo-mechanically induced, reversible, crystallographic phase transformation. As SMAs are utilized across a variety of applications, it is necessary to understand the internal changes that occur throughout the lifetime of SMA components. One of the key limitations to the lifetime of a SMA component is the response of SMAs to fatigue. SMAs are subject to two kinds of fatigue, namely structural fatigue due to cyclic mechanical loading which is similar to high cycle fatigue, and functional fatigue due to cyclic phase transformation which typical is limited to the low cycle fatigue regime. In cases where functional fatigue is due to thermally induced phase transformation in contrast to being mechanically induced, this form of fatigue can be further defined as actuation fatigue. Utilizing X-ray computed microtomography, it is shown that during actuation fatigue, internal damage such as cracks or voids, evolves in a non-linear manner. A function is generated to capture this non-linear internal damage evolution and introduced into a SMA constitutive model. Finally, it is shown how the modified SMA constitutive model responds and the ability of the model to predict actuation fatigue lifetime is demonstrated.

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Characterization Techniques of a Shape Memory Nickel Titanium Alloy

Proceedings ◽

10.3390/proceedings2019038015 ◽

2020 ◽

Vol 38 (1) ◽

pp. 15

Author(s):

Andrade ◽

Soares ◽

Nobrega ◽

Hilário ◽

Santos

Keyword(s):

Differential Scanning Calorimetry ◽

Titanium Alloy ◽

Phase Transformation ◽

Shape Memory Alloys ◽

Shape Memory ◽

Tensile Tests ◽

Metallic Alloys ◽

Nickel Titanium ◽

Metallographic Analysis ◽

Scanning Calorimetry

This paper presents a characterization processes study of metallic alloys, more specifically the shape memory alloys (SMA) composed by Nickel and Titanium (NiTinol). Two different wire suppliers were studied, starting with metallographic analysis until observe the contours of the grain wires. Differential scanning calorimetry (DSC) test was also performed to obtain phase transformation temperatures of the NiTinol alloys. Finally, after several tensile tests, some results were obtained for stresses, strains, elasticity modules and maximum rupture deformation.

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Influence of the Post-Deformation Annealing Heat Treatment on the Low-Cycle Fatigue of NiTi Shape Memory Alloys

CrossRef Listing of Deleted DOIs ◽

10.1361/105994902770343593 ◽

2002 ◽

Vol 11 (6) ◽

pp. 614-621 ◽

Cited By ~ 8

Author(s):

Vladimir Brailovski ◽

Patrick Terriault ◽

Sergei Prokoshkin

Keyword(s):

Heat Treatment ◽

Shape Memory Alloys ◽

Shape Memory ◽

Low Cycle Fatigue ◽

Cycle Fatigue ◽

Annealing Heat Treatment ◽

Niti Shape Memory Alloys ◽

Annealing Heat

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Metallurgical Characterization of M-Wire Nickel-Titanium Shape Memory Alloy Used for Endodontic Rotary Instruments during Low-cycle Fatigue

Journal of Endodontics ◽

10.1016/j.joen.2011.09.028 ◽

2012 ◽

Vol 38 (1) ◽

pp. 105-107 ◽

Cited By ~ 78

Author(s):

Jia Ye ◽

Yong Gao

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

Low Cycle Fatigue ◽

Nickel Titanium ◽

Cycle Fatigue ◽

Rotary Instruments ◽

Metallurgical Characterization

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High-Cycle Fatigue Criterion for Shape Memory Alloys Based on Shakedown Theory

Volume 2: Modeling, Simulation and Control; Bio-Inspired Smart Materials and Systems; Energy Harvesting ◽

10.1115/smasis2016-9165 ◽

2016 ◽

Cited By ~ 1

Author(s):

Wael Zaki ◽

Xiaojun Gu ◽

Ziad Moumni ◽

Weihong Zhang

Keyword(s):

Phase Transformation ◽

Shape Memory Alloys ◽

Shape Memory ◽

High Cycle Fatigue ◽

Cycle Fatigue ◽

Mesoscopic Scale ◽

Shakedown Theory ◽

Elastoplastic Materials ◽

Elastic Shakedown ◽

Fatigue Criterion

Based on a recently developed shakedown theory for non-smooth nonlinear materials, we derive a criterion for high-cycle fatigue in shape memory alloys (SMAs). The fatigue criterion takes into account phase transformation as well as reorientation of martensite variants as the source of fatigue damage. The mathematical derivation of the criterion is based on the requirement of elastic shakedown for a given structure to achieve unlimited fatigue endurance. Elastic shakedown is defined as an asymptotic state in which damage due to time-varying load becomes confined at the mesoscopic scale, or the scale of the grain, with no discernable inelasticity at the macroscopic scale. From an energy standpoint, elastic shakedown corresponds to a situation where energy dissipation becomes bounded and the response elastic after a certain number of loading cycles. A sufficient condition to achieve this state was established by Melan (1936) [1] and Koiter (1960) [2] for elastoplastic materials and later generalized to hardening plasticity by Nguyen (2003) and to non-smooth non-linear materials by Peigney (2014). The latter formulation is applicable to SMAs obeying the ZM constitutive model (Zaki & Moumni, 2007) and is shown here to allow the derivation of a high-cycle fatigue criterion analogous to the one proposed by Dang Van (1973) for elastoplastic materials. The criterion allows establishing a safe domain in stress deviator space at the mesoscopic scale consisting of a hypercylinder with axis parallel to the direction of martensite orientation. The hypercylinder is delimited along its axis by two transverse hyperplanes representing bounds on admissible stress states consistent with the loading conditions for phase transformation. Safety with regard to high-cycle fatigue, upon elastic shakedown, is conditioned by the persistence of the macroscopic stress path, as the load varies and at every material point, strictly within the hypercylinder. The size of the hypercylinder is shown to strongly depend on the relative amount of martensite present in the SMA.

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