Modeling of localization and necking in dual phase steels through polycrystalline plasticity

Çakmak, Serhat Onur.
In this thesis, the effect of ferrite crystallographic orientation distribution and other microstructural parameters such as martensite morphology, martensite volume fraction, and ferrite grain size on the plastic deformation, localization, and the necking behavior of dual-phase steels are investigated. Two different type of finite element models, i.e. full size micron-scale polycrystalline samples and polycrystalline Representative Volume Element (RVEs) are built through Voronoi tessellation. Local crystal plasticity and J2 plasticity with isotropic hardening frameworks are used to model ferrite and martensite phases, respectively. This work demonstrated that the martensite morphology and the ferrite orientation distribution affect highly the formation of the shear bands and the necking location in the samples. In addition, they significantly affect stress-strain partitioning, location of the plastic localization, tensile strength and hot spots for void formation in the RVEs.


A Micromechanics Based Numerical Investigation of Dual Phase Steels
Yalçınkaya, Tuncay; Çakmak, Serhat Onur (Elsevier BV; 2019-01-01)
The aim of this paper is to investigate the effects of microstructural parameters such as the volume fraction, morphology and spatial distribution of the martensite phase and the grain size of the ferrite phase on the plasticity and localized deformation of dual-phase (DP) steels. For this purpose, Voronoi based representative volume elements (RVEs) are subjected to proportional loading with constant stress triaxility. Two alternative approaches are employed in a comparative way to model the plastic respons...
Microstructural modelling of dual-phase steelsthrough polycrystalline plasticity at RVE level
Güngör, Gönül Öykü; Yalçınkaya, Tuncay; Department of Aerospace Engineering (2019)
In this work the plasticity, localization and the damage behavior of dual phase steels are investigated through both J2 and crystal plasticity frameworks. For this purpose, Voronoi based Representative Volume Elements (RVE) are created with different martensite volume fractions, which are studied at different constant triaxiality values. The micromechanical and the macroscopic constitutive responses are analyzed in detail for considering various loading conditions and microstructural parameters. The results...
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Sarıtaş, Afşin; Özel, Halil Fırat (null; 2015-07-21)
A mixed formulation frame finite element with internal semi-rigid connections is presented for the nonlinear analysis of steel structures. Proposed element provides accurate responses for spread of inelasticity along element length by monitoring the nonlinear responses of several crosssections, where spread of inelasticity over each section is captured with fiber discretization. Each material point on the section considers inelastic coupling between normal stress and shear stress. The formulation of the ele...
Numerical and Experimental Determination of the Residual Stress State in Multipass Welded API 5L X70 Plates
Garipova, Nuriya; Batıgün, Caner; Gür, Cemil Hakan (2014-01-01)
Residual stress distributions in multipass welded API 5L X70 steel plates were determined by numerical and experimental methods. SYSWELD finite element software was used for numerical simulations. Microstructure variations were also considered for calculation of residual stresses. The continuous cooling transformation diagram was obtained via JMatPro software. The results showed that residual stress distribution is sensitive to number of weld passes, and microstructure changes. The simulation results were c...
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Materializing Continuum Damage Mechanics (CDM), numerical modeling of discrete internal cracks, namely central bursts, in direct forward extrusion process is presented. Accordingly, in a thermodynamically consistent setting, a local Lemaitre variant damage model with quasi-unilateral evolution is coupled with hyperelastic-plasticity. The formulations are constructed in the principal axes where simultaneous local integration schemes are efficiently developed. To this end, the framework is implemented as ABAQ...
Citation Formats
S. O. Çakmak, “Modeling of localization and necking in dual phase steels through polycrystalline plasticity,” Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Aerospace Engineering., Middle East Technical University, 2020.