Civil Engineering / İnşaat Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/13

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Publisher: search.filters.publisher.ElsevierSubject: search.filters.subject.Crystal plasticity

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  • Article
    Modeling Plasticity and Damage in Fiber Reinforced Composites by a Crystal Plasticity Based Approach
    (Elsevier, 2023) Dizman, E. Aybars; Özdemir, Izzet
    In very thin ply laminates, delamination failure initiation occurs at much higher stress levels as compared to conventional ply laminates. This results in significant plastic deformation in the matrix accompanied by large fiber rotations. A closer look reveals that microstructure of fiber reinforced composites at large strains do not rotate with the plastic spin induced by the total deformation gradient and therefore inelasticity of such materials requires dedicated constitutive models. This paper focuses on inelastic response of such composites by using a recently proposed crystal plasticity based modeling framework and extents it by a non-local continuum damage mechanics formulation. As opposed to existing works related to composites, adapted crystal plasticity model is formulated and implemented in an implicit manner. To address the initiation and evolution of damage observed at large strains, localizing implicit gradient damage (LIGD) framework is used to degrade the slip resistance and hardening mechanisms on longitudinal and transverse slip systems by means of two separate damage variables. A user element (UEL) subroutine encapsulating all the components of the model is developed and integrated within the commercial finite element solver Abaqus. Capabilities of the model are assessed at material point, ply, and component levels by comparisons with analytical solutions and selected experimental results from the literature.
  • Article
    Citation - WoS: 32
    Citation - Scopus: 37
    Void Growth Based Inter-Granular Ductile Fracture in Strain Gradient Polycrystalline Plasticity
    (Elsevier, 2021) Yalçınkaya, Tuncay; Tandoğan, İzzet Tarık; Özdemir, İzzet
    The precipitation hardened, high strength aerospace alloys (e.g. Al 7000 alloy series) suffer from loss of fracture toughness due to the heat treatment leading to intergranular ductile fracture. Depending on the quenching and aging processes, large precipitates at the grain boundaries with wide precipitate free zones might develop. Therefore the grain boundaries constitute a potential location for micro void formation and evolution under the effect of external loads. This is a common problem of such materials where there is considerable ductile intergranular fracture, which is normally attributed to the embrittlement effects of the environment in other type of alloys. In this context, for the modeling of such a degradation process, the current paper develops a physics based intergranular cracking model of polycrystalline materials where a strain gradient crystal plasticity model is combined with cohesive zone elements whose traction separation relation is based on the evolution of micro-voids at the grain boundaries. The framework successfully predicts the intergranular crack formation and propagation, taking into account different microstructural features, such as porosity, pore shape, grain orientation distribution, and grain boundary conditions.