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Final Report: Multi-Scale Analysis of Deformation and Failure in Polycrystalline Titanium Alloys Under High Strain-Rates

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Technical Report,15 Aug 2012,14 Aug 2015

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Johns Hopkins University Baltimore United States

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The research has developed a powerful crystal plasticity based computational modeling tool for predicting mechanical response and localization, eventually leading to failure in polycrystalline titanium alloys, e.g. Ti-6Al-4V and Ti-7AL under extreme loading conditions. Ti alloys possess complex heterogeneous microstructures due to non-uniform grain size distribution and strong anisotropy arising from dislocation glide on different slip systems. The computational model aims at enhancing the predictive capabilities, accounting for the effects of morphological and crystallographic features of 3D microstructures and loading characteristics on the deformation and failure mechanisms. Collaboration has been pursued with ARL researchers on material data and experiments. Various modules pursued are Microstructural Characterization and Image-Based Virtual Model Generation We have developed robust 3D models virtual polycrystalline microstructures of Ti-7Al that represent both morphological and crystallographic statistics observed in OIM scans. Physics-Based Micromechanical Modeling This work has developed a unified dislocation density-based crystal plasticity model for hcp metals by combining the thermally-activated and drag-dominated stages of dislocation slip. The model is suitable for modeling deformation under a wide range of strain rates. The effects of temperature are considered. The proposed constitutive model is incorporated into a stabilized locking-free large deformation finite element FE framework.

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