An Integrated Micromechanics Approach to Physics-Based Modeling of Deformation and Failure of Superelastic Materials

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An Integrated Micromechanics Approach to Physics-basedModeling of Deformation and Failure of Superelastic MaterialsP. Papadopoulos and R.O. RitchieThe objective of the proposed work is to develop an integrated experimental,theoretical and computational description of the deformation, fracture and cyclic fatigue behavior of polycrystalline superelastic/shape-memory alloys. Intellectual Merit: The proposed work seeks to characterize the mechanical behavior of a complextextured material that undergoes a series of solid-solid phase transitions, which crucially affect its multiaxial stress-strain response and its fatigue characteristics. The intellectual merit of the research stems from the challenging questions that it addresses and from the integrated nature(experiments, theory, computing) of the proposed methodologies. Broader Impact: Superelastic alloys are experiencing an explosive growth in use, mostly inbiomedical devices, but also in a number of other civilian and militaryapplications. As an example, the cardiovascular stent industry in 2003 is estimated at 5 billion dollars per year in the US alone and superelasticNi-Ti alloys are fast becoming the principal material for these stents. At the same time, there exist significant uncertainties regarding the mechanical response of such alloys, especially under multiaxial loading and cyclic fatigue. The proposed research intends to address these uncertainties, thus contributing to the safer and more rational use of these materials in engineering practice.