In this paper, the grain microstructure and strain partitioning in a polycrystalline NiTi wire subjected to tensile loading was reconstructed from an experimental 3D-XRD dataset. The reconstruction of a volume containing more than 8000 stressed grains involved optimization with respect to both the geometrical features and material elastic properties. The geometrical features of the microstructure were reconstructed using Laguerre tessellations based on the experimental 3D-XRD dataset. Two different algorithms fitting Laguerre tessellations were applied in order to assess the sensitivity of the reconstruction to the choice of the algorithm. The material properties in terms of elastic anisotropy were refined from an initial published value to minimize the mismatch between experiment and simulation using an optimization algorithm based on linear elasticity simulations. As a result of this, we constructed a numerical microstructure model that statistically matches the experimentally probed material in terms of positions and sizes of grains as well as partitioning of elastic strain and stress in the microstructure (average elastic properties and standard deviations of piecewise constant components of elastic strain and stress tensors in grains).
In spite of the fact that the US Food and Drug Administration (FDA) has approved Intracoil and s.m.a.r.t Nitinol stents for superficial femoral artery (SFA), some alternative designs of Nitinol stents are being implanted today, representing the off-label use of the devices. Among the currently stents used for the SFA, s.m.a.r.t and Intracoil stents show the most desirable long-term results but it is not understood why. In the present work, delivery of the s.m.a.r.t and Intracoil Nitinol stents and their release inside a stenotic point of the artery was simulated by FE implemented SMA model using a creative manual controlled method. The influence of the stent design on the stent–vessel interactions and stress state within the stent material after completion of the deployment was revealed. It was found that the Intracoil stent shall be more successful in eliminating the stenosis and less prone to fatigue failure, even though it had less thickness and less mean coil diameter.
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