Impact of thermomechanical texture on the superelastic response of Nitinol implants

Barney, Monica; Xu, David; Robertson, Scott W.; Schroeder, V.; Ritchie, Robert O.; Pelton, Alan R.; Mehta, Apurva

doi:10.1016/j.jmbbm.2011.05.013

Cited by 31 publications

(20 citation statements)

References 23 publications

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“…Based on results from a follow-up investigation of pseudoelastic Nitinol (A. Stebner, S. Clausen, A. R. Pelton, in process 2014), the amount of plastic strain contribution from the bending pre-strain in the present study is comparable to that observed in thermal martensite (Barney et al, 2011;Stebner et al, 2013). Therefore, approximately 17% of the tensile strain and 34% of the compressive strain can be attributed to Δε slip in the outer fibers for the 8% pre-strain conditions.…”

Section: Effects Of Bending Pre-strain -Plasticitysupporting

confidence: 76%

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High compressive pre-strains reduce the bending fatigue life of nitinol wire

Gupta

Pelton²,

Weaver

et al. 2015

Journal of the Mechanical Behavior of Biomedical Materials

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Prior to implantation, Nitinol-based transcatheter endovascular devices are subject to a complex thermo-mechanical pre-strain associated with constraint onto a delivery catheter, device sterilization, and final deployment. Though such large thermo-mechanical excursions are known to impact the microstructural and mechanical properties of Nitinol, their effect on fatigue properties is still not well understood. The present study investigated the effects of large thermo-mechanical pre-strains on the fatigue of pseudoelastic Nitinol wire using fully reversed rotary bend fatigue (RBF) experiments. Electropolished Nitinol wires were subjected to a 0%, 8% or 10% bending pre-strain and RBF testing at 0.3-1.5% strain amplitudes for up to 10(8) cycles. The imposition of 8% or 10% bending pre-strain resulted in residual set in the wire. Large pre-strains also significantly reduced the fatigue life of Nitinol wires below 0.8% strain amplitude. While 0% and 8% pre-strain wires exhibited distinct low-cycle and high-cycle fatigue regions, reaching run out at 10(8) cycles at 0.6% and 0.4% strain amplitude, respectively, 10% pre-strain wires continued to fracture at less than 10(5) cycles, even at 0.3% strain amplitude. Furthermore, over 70% fatigue cracks were found to initiate on the compressive pre-strain surface in pre-strained wires. In light of the texture-dependent tension-compression asymmetry in Nitinol, this reduction in fatigue life and preferential crack initiation in pre-strained wires is thought to be attributed to compressive pre-strain-induced plasticity and tensile residual stresses as well as the formation of martensite variants. Despite differences in fatigue life, SEM revealed that the size, shape and morphology of the fatigue fracture surfaces were comparable across the pre-strain levels. Further, the mechanisms underlying fatigue were found to be similar; despite large differences in cycles to failure across strain amplitudes and pre-strain levels, cracks initiated from surface inclusions in nearly all wires. Compressive pre-strain-induced damage may accelerate such crack initiation, thereby reducing fatigue life. The results of the present study indicate that large compressive pre-strains are detrimental to the fatigue properties of Nitinol, and, taken together, the findings underscore the importance of accounting for thermo-mechanical history in the design and testing of wire-based percutaneous implants.

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Section: Effects Of Bending Pre-strain -Plasticitysupporting

confidence: 76%

“…10b. For the present case of wire deformation above the A f temperature, it is expected the that strain partitions as follows: (Barney, Xu et al 2011) 4.2.…”

Section: Effects Of Bending Pre-strain -Plasticitymentioning

confidence: 83%

High compressive pre-strains reduce the bending fatigue life of nitinol wire

Gupta

Pelton²,

Weaver

et al. 2015

Journal of the Mechanical Behavior of Biomedical Materials

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“…The few {100} A grains are likely shedding some load to their neighbors as they transform, but their neighbors continue to elastically load. This finding is analogous to observations previously made by Barney et al of Ni 50.8 Ti 49.2 with synchrotron X-ray microdiffraction under tensile loading conditions [37]. Aside from this one exception, all other grains predominantly exhibit behaviors consistent with linear elasticity, including the expected trend in E hkl given in Fig.…”

Section: Regime I: Elastic Loading and Initial Transformationsupporting

confidence: 91%

In Situ Neutron Diffraction Studies of Large Monotonic Deformations of Superelastic Nitinol

Stebner

Paranjape

Clausen

et al. 2015

Shap. Mem. Superelasticity

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Superelastic Nitinol micromechanics are studied well into plastic deformation regimes using neutron diffraction. Insights are made into the nature of initial transformation, bulk transformation, plastic deformation, and unloading. Schmid factor predictions based on habit plane variants are found to best describe the very first grains that transform, prior to the transformation plateaus. However, the bulk transformation behavior that gives rise to transformation plateaus violates single crystal Schmid factor analyses, indicating that in bulk polycrystals, it is the effect of grain neighborhoods, not the orientations of individual grains, that drives transformation behaviors. Beyond the plateaus, a sudden shift in micromechanical deformation mechanisms is observed at *8.50 %/4.75 % tension/compression engineering strain. This mechanism results in reverse-phase transformation in both cases, indicating a strong relaxation in internal stresses of the samples. It is inferred that this mechanism is most likely initial bulk plastic flow, and postulated that it is the reason for a transition from fatigue life enhancement to detriment when pre-straining superelastic Nitinol. The data presented in this work provide critical datasets for development and verification of both phenomenological internal variable-driven and micromechanical theories of transformationplasticity coupling in shape memory alloys.

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“…10b In stress-induced phase transformation the hysteresis observed is caused mostly by dissipative processes which are associated mainly to the frictional work due to interfacial motion [44]. Indeed, Barney et al [14] showed that In order to suppress the effect of the R-phase, it would be better to calculate the slopes for temperatures higher than 60 • C, i.e. using only the results at 60 • C and 70 • C. However the accuracy of the slope calculated using only two temperatures would be very low, of the order of ±2MPa/K.…”

Section: Anisotropy Of Forward and Reverse Transformation Stressesmentioning

confidence: 99%

“…Barney et al [14] performed X-ray microdiffractions on micrometric tensile sam- nal tube was obtained after the last cold mandrel drawing [15,16,17]. A section of this original tube was first cut longitudinally using a pulsed optical fibre laser.…”

mentioning

confidence: 99%

Anisotropy and Clausius-Clapeyron relation for forward and reverse stress-induced martensitic transformations in polycrystalline NiTi thin walled tubes

Grassi

Chagnon

Oliveira

et al. 2020

Mechanics of Materials

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Inside the Clausius-Clapeyron regime, transformation stresses during superelastic tensile tests of polycrystalline shape memory alloys are linearly dependent on temperature, with coefficients being the slopes of the forward and reverse transformation lines. In this work, experiments are performed to investigate the anisotropy of the slopes of the forward and reverse transformation stress-temperature lines in a NiTi superelastic thin walled tube. The classical Clausius-Clapeyron relation is widely used to model these slopes, although, in a strict sense, this relation is defined at thermodynamic equilibrium. Experimen

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Impact of thermomechanical texture on the superelastic response of Nitinol implants

Cited by 31 publications

References 23 publications

High compressive pre-strains reduce the bending fatigue life of nitinol wire

High compressive pre-strains reduce the bending fatigue life of nitinol wire

In Situ Neutron Diffraction Studies of Large Monotonic Deformations of Superelastic Nitinol

Anisotropy and Clausius-Clapeyron relation for forward and reverse stress-induced martensitic transformations in polycrystalline NiTi thin walled tubes

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