Strain gradient crystal plasticity: thermodynamics and implementation

This chapter studies the thermodynamical consistency and the finite element implementation aspects of a rate-dependent nonlocal (strain gradient) crystal plasticity model, which is used to address the modeling of the size-dependent behavior of polycrystalline metallic materials. The possibilities and required updates for the simulation of dislocation microstructure evolution, grain boundary-dislocation interaction mechanisms, and localization leading to necking and fracture phenomena are shortly discussed as well. The development of the model is conducted in terms of the displacement and the plastic slip, where the coupled fields are updated incrementally through finite element method. Numerical examples illustrate the size effect predictions in polycrystalline materials through Voronoi tessellation.


Strain gradient crystal plasticity: Intergranular microstructure formation
Özdemir, İzzet; Yalçınkaya, Tuncay (Springer International Publishing, 2016-01-01)
This chapter addresses the formation and evolution of inhomogeneous plastic deformation field between grains in polycrystalline metals by focusing on continuum scale modeling of dislocation-grain boundary interactions within a strain gradient crystal plasticity (SGCP) framework. Thermodynamically consistent extension of a particular strain gradient plasticity model, addressed previously (see also, e.g., Yalcinkaya et al, J Mech Phys Solids 59:1-17, 2011), is presented which incorporates the effect of grain ...
Plastic deformation induced microstructure evolution through gradient enhanced crystal plasticity based on a non-convex Helmholtz energy
Klusemann, Benjamin; Yalçınkaya, Tuncay (Elsevier BV, 2013-09-01)
A gradient crystal plasticity model in the framework of continuum thermodynamics and rate variational formulation is presented for the description of plastic deformation patterning in a system with non-convex energetic hardening. The paper focuses on the extension of the 1D deformation patterning analysis of Yalcinkaya et al. (2011) to 2D for monotonic loading histories. Solution algorithm is based on the simultaneous solution of displacement and plastic slip fields, which have been considered as primary va...
Strain Path Change Effects in a BCC Crystal Plasticity Framework
Yalçınkaya, Tuncay (2006-10-26)
The presentation outlines a temperature dependent, strain rate sensitive crystal plasticity model at finite strains which is aimed to be used in the modeling of strain path change effects for BCC structured materials. Plastic anisotropy in BCC crystals originates from different sources at different length scales. Slip asymmetry and intrinsic anisotropic effects caused by screw dislocation cores are the ones at the micro level, the development of dislocation sub-structures is relevant at meso lev...
Micromechanical Modelling of Size Effects in Microforming
Yalçınkaya, Tuncay; SIMONOVSKI, IGOR; ÖZDEMİR, İZZET (2017-09-01)
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 str...
Density Functional Theory Calculations on Polyacene Molecules
Pekoz, Rengin; Erkoç, Şakir (2010-03-01)
The structural and electronic properties of isolated linear and zigzag type polyacene molecules have been investigated by density functional theory calculations using B3LYP exchange-correlation functional with 6-31G(d) basis set. The zigzag polyacene molecules found to be energetically more stable than the linear structures and the optimized molecules of both types have planar geometries. In the present study, more attention has been given to the picene molecule which is a rival to pentacene molecule and ha...
Citation Formats
T. Yalçınkaya, Strain gradient crystal plasticity: thermodynamics and implementation. 2016.