Fatigue of Shape Memory Alloys

Mahtabi, Mohammad J.; Shamsaei, Nima; Elahinia, Mohammad

doi:10.1002/9781118426913.ch5

Cited by 5 publications

(5 citation statements)

References 39 publications

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“…Despite being quite reduced, with the successive loading these plastic strains cause changes in the mechanical properties of the material due to a rearrangement of the crystalline structure [4,15,72,73]. According to [17], strain amplitudes between ∼0.7% and 2%, a range where the fatigue life constantly decreases as the strain amplitude increases, the fatigue life is in the range of approximately 10 3 -10 5 cycles, corroborating with the results found in this work. Prymak et al [20] also obtained a fatigue life of the order of 10 5 cycles in NiTi orthodontic wires under small bending strains (deflection of 240 µm) and frequency of 5 Hz using a DMA equipment.…”

Section: Mechanical Fatiguesupporting

confidence: 84%

“…In addition, under specific conditions, SMA can Fatigue in SMA can be of two types: functional fatigue, which refers to the degradation of its functional properties (SME and SE, for example), and structural fatigue, associated with the microstructural damages in the material and the number of cycles the material resists before fracture occurs [15]. Over the years, both structural and functional fatigue of NiTi SMA have been studied from different perspectives and test conditions, mainly under cyclic tensile loading [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] and also in bending-rotation tests [15,[31][32][33][34][35][36].…”

Section: Introductionmentioning

confidence: 99%

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Fatigue tests of superelastic NiTi wires: an analysis using factorial design in single cantilever bending

Araújo¹,

Grassi²,

Araújo³

2021

Smart Mater. Struct.

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This paper investigates the fatigue behavior of superelastic NiTi shape memory alloy thin wires with circular and rectangular cross-sections under single cantilever bending mode. A dynamic mechanical analyzer operating in single cantilever mode is employed as a testing machine. The fatigue life of the wires was analyzed at different strain amplitudes and loading frequencies. The simultaneous influence of these parameters was assessed through a factorial design with replication. Circular wires have higher fatigue life compared to rectangular wires. Higher strain amplitudes decrease the fatigue life of both circular and rectangular cross-section wires. On the other hand, the loading frequency strongly affected the rectangular cross-section wire, while having a significantly weaker effect on the circular wire. The NiTi wires showed fatigue lives between 103 and 105 cycles in the evaluated range of strain amplitude, which falls within the fatigue life observed for shape memory alloy (SMA) wires under similar loading conditions. Furthermore, the factorial design proved to be a valuable tool in the study of fatigue life of NiTi SMA, especially for the visualization and interpretation of the effect of the chosen variables.

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Section: Mechanical Fatiguesupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Fatigue tests of superelastic NiTi wires: an analysis using factorial design in single cantilever bending

Araújo¹,

Grassi²,

Araújo³

2021

Smart Mater. Struct.

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“…This approach can be a promising method to increase the fatigue life of elastocaloric materials and, by retransforming the residual martensite, to improve the eCE during the cycling. Comprehensive reviews on the fatigue life of SMAs can be found in [42][43][44][45].…”

Section: Overview Of Sma Fatigue Behaviour From An Elastocaloric Persmentioning

confidence: 99%

“…austenitic) region [46]. It is known from literature [44,45] that for superelastic SMAs a fatigue limit exceeding 10 7 cycles can be reached with strain amplitudes up to 0.75%, but in most cases this relates mostly with the elastic region, where no phase transformation takes place. It must be emphasized that straining the SMA in the elastic region is useless for elastocaloric applications, as it does not generate the eCE, which is only associated with the austenitic-martensitic transformation (if neglecting R-phase transformation [9,10]).…”

Section: Overview Of Sma Fatigue Behaviour From An Elastocaloric Persmentioning

confidence: 99%

“…Furthermore, it should be noted that the great majority of studies that concluded that the strain amplitude limit of Ni-Ti was up to 0.75% were performed on wire specimens with a rotary-bending test with fully reversed tension-compression loading (except where pre-strain was applied, e.g. [33,34]) or with a diamond-shaped specimen, where stresses and strains are highly inhomogeneous over the sample [44,45]. These experiments cannot be directly applied for elastocaloric cooling, where uniaxial tension-tension or compression-compression loading with a homogenous stress/strain distribution is required.…”

Section: Overview Of Sma Fatigue Behaviour From An Elastocaloric Persmentioning

confidence: 99%

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

et al. 2018

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Structural fatigue is the major obstacle that prevents practical applications of the elastocaloric effect (eCE) in cooling or heat-pumping devices. Here, the eCE and fatigue behaviour of Ni-Ti sheets are systematically investigated in order to define the material's fatigue strain limit and the associated eCE. Initially, the eCE was evaluated by measuring adiabatic temperature changes at different strain amplitudes and different mean strains along the loading and unloading transformation plateaus. By comparing the eCE with and without pre-strain conditions, the advantages of cycling an elastocaloric material at the mean strain around the middle of the transformation plateau were demonstrated. In the second part of this work, we evaluated the fatigue life at the mean strain of 2.25% within the loading plateau and at the unloading plateau after initial pre-straining up to 6% and 10%, respectively. It is shown that on polished samples, durable operation of 10 5 cycles can be reached with a strain amplitude of 0.50% at the loading plateau, which corresponds to adiabatic temperature changes of approximately 5 K. At the unloading plateau (after initial pre-strain of 10%), durable 1 operation was reached at a strain amplitude of 1.00%, corresponding to adiabatic temperature changes of approximately 8 K. The functional fatigue was analysed after the cycling and it is shown that once the sample has been stabilized there is no further degradation of the eCE, even after 10 5 cycles. These results present guidelines for the design and operation of efficient and durable elastocaloric devices in the future.

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Fatigue Modeling for Superelastic NiTi Considering Cyclic Deformation and Load Ratio Effects

Mahtabi

Shamsaei

2017

Shap. Mem. Superelasticity

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Fatigue of Shape Memory Alloys

Cited by 5 publications

References 39 publications

Fatigue tests of superelastic NiTi wires: an analysis using factorial design in single cantilever bending

Fatigue tests of superelastic NiTi wires: an analysis using factorial design in single cantilever bending

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

Fatigue Modeling for Superelastic NiTi Considering Cyclic Deformation and Load Ratio Effects

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