Micromechanical methodology for fatigue in cardiovascular stents |
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| Affiliation: | 1. Department of Mechanical Engineering and Materials Science and Engineering, Cyprus University of Technology, Limassol 3036, Cyprus;2. Department of Materials Science, Transilvania University of Brasov, Brasov 500036, Romania;3. Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294-0111, USA;4. Department of Pathology, University of Alabama at Birmingham, Birmingham, AL 35294-0111, USA;5. Department of Prosthodontics, University of Alabama at Birmingham, Birmingham, AL 35294-0111, USA;1. Biomedical Engineering, Department of Human Biology, University of Cape Town (UCT), South Africa;2. Centre for Research in Computational and Applied Mechanics (CERECAM), UCT, South Africa;1. Division of Solid Mechanics, Lund University, P.O. Box 118, SE-221 00 Lund, Sweden;2. Norwegian University of Science and Technology, Department of Marine Technology, 7491 Trondheim, Norway;3. Norwegian University of Science and Technology, Department of Structural Engineering, 7491 Trondheim, Norway;1. Department of Materials, Imperial College, London SW7 2AZ, UK;2. Rolls-Royce plc, PO Box 31, Derby DE24 8BJ, UK |
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| Abstract: | A finite element based micromechanical methodology for cyclic plasticity and fatigue crack initiation in cardiovascular stents is presented. The methodology is based on the combined use of a (global) three-dimensional continuum stent-artery model, a local micromechanical stent model, the development of a combined kinematic–isotropic hardening crystal plasticity constitutive formulation, and the application of microstructure sensitive crack initiation parameters. The methodology is applied to 316L stainless steel stents with random polycrystalline microstructures, based on scanning electron microscopy images of the grain morphology, under realistic elastic–plastic loading histories, including crimp, deployment and in vivo systolic–diastolic cyclic pressurisation. Identification of the micromechanical cyclic plasticity and failure constants is achieved via application of an objective function and a unit cell representative volume element for 316L stainless steel. Cyclic stent deformations are compared with the J2-predicted response and conventional fatigue life prediction techniques. It is shown that micromechanical fatigue analysis of stents is necessary due to the significant predicted effects of material inhomogeneity on micro-plasticity and micro-crack initiation. |
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