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Browsing by Author "Simonovski, Igor"

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    Intrinsic and Statistical Size Effects in Microforming
    (American Institute of Physics, 2017-10) Yalçınkaya, Tuncay; Demirci, Aytekin; Simonovski, Igor; Özdemir, İzzet; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    This paper analyzes the intrinsic (grain size dependent) and the statistical (grain number and orientation distribution dependent) size effects of micron level polycrystalline metallic specimens under plastic deformation through a strain gradient crystal plasticity framework. The macroscopic and local behavior of specimens from very limited number of grains to high number of grains are studied and the results are discussed in detail taking into account different boundary conditions.
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    Citation - WoS: 21
    Citation - Scopus: 27
    Micromechanical Modeling of Intrinsic and Specimen Size Effects in Microforming
    (Springer Verlag, 2018-09) Yalçınkaya, Tuncay; Özdemir, İzzet; Simonovski, Igor; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Size effect is a crucial phenomenon in the microforming processes of metallic alloys involving only limited amount of grains. At this scale intrinsic size effect arises due to the size of the grains and the specimen/statistical size effect occurs due to the number of grains where the properties of individual grains become decisive on the mechanical behavior of the material. This paper deals with the micromechanical modeling of the size dependent plastic response of polycrystalline metallic materials at micron scale through a strain gradient crystal plasticity framework. The model is implemented into a Finite Element software as a coupled implicit user element subroutine where the plastic slip and displacement fields are taken as global variables. Uniaxial tensile tests are conducted for microstructures having different number of grains with random orientations in plane strain setting. The influence of the grain size and number on both local and macroscopic behavior of the material is investigated. The attention is focussed on the effect of the grain boundary conditions, deformation rate and the grain size on the mechanical behavior of micron sized specimens. The model is intrinsically capable of capturing both experimentally observed phenomena thanks to the incorporated internal length scale and the crystallographic orientation definition of each grain.
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    Citation - WoS: 4
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    Micromechanical Modelling of Size Effects in Microforming
    (Elsevier Ltd., 2017) Yalçınkaya, Tuncay; Demirci, Aytekin; Simonovski, Igor; Özdemir, İzzet; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    This paper deals with the micromechanical modelling of the size dependent mechanical response of polycrystalline metallic materials at micron scale through a strain gradient crystal plasticity framework. The model is implemented into a Finite Element software as a coupled implicit user element subroutine where the plastic slip and displacement fields are taken as global variables. Uniaxial tensile tests are conducted for microstructures having different number of grains with random orientations in plane strain setting. The influence of the grain size and number on both local and macroscopic behavior of the material is investigated. The model is capable of capturing both size effect due to statistical distribution of the grains and their size taking into account the grain boundary conditions.
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    Citation - WoS: 1
    Citation - Scopus: 1
    Strain Gradient Polycrystal Plasticity for Micro-Forming
    (American Institute of Physics, 2016-10) Yalçınkaya, Tuncay; Simonovski, Igor; Özdemir, İzzet; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The developments in the micro-device industry has produced a substantial demand for the miniaturized metallic components with ultra-thin sheet materials that have thickness dimensions on the order of 50-500 μm which are produced through micro-forming processes. It is essential to have predictive tools to simulate the constitutive behavior of the materials at this length scale taking into account the physical and statistical size effect. Recent studies have shown that on the scale of several micrometers and below, crystalline materials behave differently from their bulk equivalent due to micro-structural effects (e.g. grain size, lattice defects and impurities), gradient effects (e.g. lattice curvature due to a non-uniform deformation field) and surface constraints (e.g. hard coatings or free interfaces). These effects could lead to stronger or weaker material response depending on the size and unique micro-structural features of the material. In this paper a plastic slip based strain gradient crystal plasticity model is used to address the effect of microstructural features (e.g. grain size, orientation and the number of grains) on the macroscopic constitutive response and the local behavior of polycrystalline materials.