scholarly journals A Direct Method for Predicting the High-Cycle Fatigue Regime of Shape-Memory Alloys Structures

2017 ◽  
pp. 13-28
Author(s):  
Michaël Peigney
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
High Cycle Fatigue ◽  
Direct Method ◽  
Cycle Fatigue ◽  
A Direct Method

scholarly journals A shakedown analysis of high cycle fatigue of shape memory alloys

2016 ◽  
Vol 87 ◽  
pp. 112-123 ◽  
Author(s):  
F. Auricchio ◽  
A. Constantinescu ◽  
C. Menna ◽  
G. Scalet
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
High Cycle Fatigue ◽  
Cycle Fatigue ◽  
Shakedown Analysis

scholarly journals Hysteretic Behavior and Ultimate Energy Dissipation Capacity of Large Diameter Bars Made of Shape Memory Alloys under Seismic Loadings

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1099
Author(s):  
González-Sanz ◽  
Galé-Lamuela ◽  
Escolano-Margarit ◽  
Benavent-Climent
Keyword(s):  
Energy Dissipation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
High Cycle Fatigue ◽  
Large Diameter ◽  
Hysteretic Behavior ◽  
Cycle Fatigue ◽  
Seismic Loadings ◽  
Energy Dissipation Capacity ◽  
Energy Dissipation Devices

Shape memory alloys in the form of bars are increasingly used to control structures under seismic loadings. This study investigates the hysteretic behavior and the ultimate energy dissipation capacity of large-diameter NiTi bars subjected to low- and high-cycle fatigue. Several specimens are subjected to quasi-static and to dynamic cyclic loading at different frequencies. The influence of the rate of loading on the shape of the hysteresis loops is analysed in terms of the amount of dissipated energy, equivalent viscous damping, variations of the loading/unloading stresses, and residual deformations. It is found that the log-log scale shows a linear relationship between the number of cycles to failure and the normalized amount of energy dissipated in one cycle, both for low- and for high-cycle fatigue. Based on the experimental results, a numerical model is proposed that consists of two springs with different restoring force characteristics (flag-shape and elastic-perfectly plastic) connected in series. The model can be used to characterize the hysteretic behavior of NiTi bars used as energy dissipation devices in advanced earthquake resistant structures. The model is validated with shake table tests conducted on a reinforced concrete structure equipped with 12.7 mm diameter NiTi bars as energy dissipation devices.

Shakedown based model for high-cycle fatigue of shape memory alloys

2016 ◽  
Vol 25 (11) ◽  
pp. 115012 ◽  
Author(s):  
Xiaojun Gu ◽  
Ziad Moumni ◽  
Wael Zaki ◽  
Weihong Zhang
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
High Cycle Fatigue ◽  
Cycle Fatigue

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

2016 ◽  
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.

Modeling of Internal Damage Evolution During Actuation Fatigue in Shape Memory Alloys

2018 ◽  
Author(s):  
Francis R. Phillips ◽  
Daniel Martin ◽  
Dimitris C. Lagoudas ◽  
Robert W. Wheeler
Keyword(s):  
Phase Transformation ◽  
Constitutive Model ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Damage Evolution ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Internal Damage ◽  
Functional Fatigue ◽  
Non Linear

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.

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

2020 ◽  
Vol 178 ◽  
pp. 442-446 ◽  
Author(s):  
Harshad M. Paranjape ◽  
Bill Ng ◽  
Ich Ong ◽  
Lot Vien ◽  
Christopher Huntley
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Low Cycle Fatigue ◽  
Nickel Titanium ◽  
Cycle Fatigue
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