Polycrystalline plasticity modeling of anisotropic grain structures and statistical size effect in metallic alloys

Orhun, Bulut
In this thesis, two important microstructural phenomena affecting the plastic behavior of metallic materials are addressed through a local crystal plasticity modeling framework. Initially the influence of anisotropic grain structure developing during various forming procedures and additive manufacturing processes is studied following a multiscale modeling strategy, where Representative Volume Elements (RVEs) are analyzed under axial loading conditions. Macroscopic response of different degrees of anisotropic microstructures and related lattice alignment effects are discussed in detail. Then, the influence of specimen thickness to grain size ratio affecting the forming behavior of micron sized specimens is studied. The statistical size effect that can be captured through a local crystal plasticity model is discussed in comparison to the existing literature. The thesis is concluded with an outlook for possible future studies.


Crystal plasticity modeling of additively manufactured metallic microstructures
Acar, Sadik Sefa; Bulut, Orhun; Yalçınkaya, Tuncay (2021-01-01)
Different manufacturing processes such as flow forming, rolling, wire drawing and additive manufacturing induce anisotropic grain structure and texture evolution at the micro scale, which results in macroscopic anisotropic plastic behavior. Among these microstructures, development of columnar grain structure is quite common especially in additively manufactured metallic materials. A systematic micromechanical analysis is necessary to evaluate the influence of both grain morphology and texture (orientation a...
Plastic slip patterns through rate-independent and rate-dependent plasticity
Lancioni, Giovanni; Yalçınkaya, Tuncay (2014-05-09)
Plastic deformation induces various types of dislocation microstructures at different length scales, which eventually results in a heterogeneous deformation field in metallic materials. Development of such structures manifests themselves as macroscopic hardening/softening response and plastic anisotropy during strain path changes, which is often observed during forming processes. In this paper we present two different non-local plasticity models based on non-convex potentials to simulate the intrinsic rate-...
Non-convex rate dependent strain gradient crystal plasticity and deformation patterning
Yalçınkaya, Tuncay; Geers, M.G.D. (2012-09-15)
A rate dependent strain gradient crystal plasticity framework is presented where the displacement and the plastic slip fields are considered as primary variables. These coupled fields are determined on a global level by solving simultaneously the linear momentum balance and the slip evolution equation, which is derived in a thermodynamically consistent manner. The formulation is based on the 1D theory presented in Yalcinkaya et al. (2011), where the patterning of plastic slip is obtained in a system with no...
Multi Scale Modeling of Microstructure Evolution Induced Anisotropy in Metals
Yalçınkaya, Tuncay (2013-06-01)
This paper presents two crystal plasticity based computational constitutive models for the intrinsic formation of plastic microstructure during monotonic loading and its altered evolution under strain path changes in metal forming operations. The formation step is modeled via a non-convex strain gradient crystal plasticity framework which could simulate the intrinsic development of the plastic microstructures. The evolution under strain path changes is modeled via phenomenologically based constitutive equat...
Covalent and noncovalent functionalization of pristine and defective graphene by cyclohexane and dehydrogenated derivatives
Sayin, Ceren Sibel; Toffoli, Daniele; Toffoli, Hande (2015-10-01)
The interaction of cyclohexane (C6H12), cyclohexyl (C6H11*) and cyclohexene (C6H10) with both pristine and defective graphene (single vacancy and a carbon adatom), is systematically investigated within the density functional theory framework. C6H12 physisorbs on both pristine and defective graphene while C6H10 chemisorbs on graphene in the presence of an adatom. The C6H11* radical binds covalently with the graphene substrate in all adsorption geometries considered.
Citation Formats
B. Orhun, “Polycrystalline plasticity modeling of anisotropic grain structures and statistical size effect in metallic alloys,” M.S. - Master of Science, Middle East Technical University, 2022.