Strain Gradient Crystal Plasticity Approach to Modelling Micro-Plastic Flow and Localisation in Polycrystalline Materials

Simonovski, Igor
Yalçınkaya, Tuncay
Structural materials in the reactor pressure vessels are exposed to a harsh environment, resulting in a number of material degradation processes. Irradiation generates a number of point defects in the atomic structure of a material. In addition, plastic slip localization occurs on the grain level size where highly-deformed narrow bands of material appear already at the moderate strain levels. These bands are called channels or clear bands, because they are almost empty of irradiation defects, whereas the surrounding matrix is still full of them. Clear bands are very thin with a thickness of a few tens of nm. It is thought that these clear bands contribute significantly to yield-stress increase and loss of work-hardening and ductility under irradiation. Additionally, high stress concentrations are generated at points where clear bands impinge on the grain boundaries, resulting in grain boundary damage and increasing the possibility of intergranular cracking. Continuum-based structural-mechanics models are not able to predict the initiation or the evolution of grain-level plastic slip localization. New approaches like strain-gradient crystal plasticity are being developed to tackle these issues. In the present work a numerical approach is presented where the application of strain-gradient crystal plasticity is extended to aggregates containing up to tens of grains. Plastic slip localization is demonstrated within the corresponding finite-element model.
24th International Conference on Nuclear Energy for New Europe (NENE)


Material characterization at high strain rates using modified taylor impact test and velocity interferometry
Kesemen, Latif; Kayran, Altan; Department of Aerospace Engineering (2016)
Metallic materials in aerospace structures are exposed to impact type loads depending on their usage area. High strain rate material characterization of metallic materials is very crucial to properly prepare finite element models to be used in impact loading situations. Johnson-Cook material model is a suitable material model to represent the behaviour of metallic materials at high strain rates. In the present thesis study, parameters of the Johnson-Cook material model for Al 7075-T651 are determined utiliz...
Crack propagation in a commercial steel
Bilir , Oğuz Gürkan (Springer Science and Business Media LLC, 1988-5)
In this work, the fatigue crack propagation behaviour of commercial steel sheet specimens containing a circular hole, under uniaxial loading conditions at room temperature was investigated. The experimental data have been analysed in terms of variability of material constants. The results were presented in the form of power relationship between the crack growth rate and the stress intensity factor range.
Combinatorial study of hydrogen storage alloys
Ölmez, Rabia; Öztürk, Tayfur; Department of Metallurgical and Materials Engineering (2009)
A combinatorial study was carried out for hydrogen storage alloys which involve processes similar to those normally used in their fabrication. The study utilized a single sample of combined elemental (or compound) powders which were milled and consolidated into a bulk form and subsequently deformed to heavy strains. Material library was obtained in a post annealing treatment carried out at elevated temperatures which brings about solid state reactions between the powders yielding equilibrium phases in the r...
Plane strain analytical solutions for a functionally graded elastic-plastic pressurized tube
Eraslan, Ahmet Nedim (Elsevier BV, 2006-09-01)
Plane strain analytical solutions to functionally graded elastic and elastic-plastic pressurized tube problems are obtained in the framework of small deformation theory. The modulus of elasticity and the uniaxial yield limit of the tube material are assumed to vary radially according to two parametric parabolic forms. The analytical plastic model is based on Tresca's yield criterion, its associated flow rule and ideally plastic material behaviour. Elastic, partially plastic and fully plastic stress states a...
Lateral heating effects on the PVT growth process of Hg2Cl2 crystals
Coskun, AU; Arinc, F; Yener, Y (IOP Publishing, 2003-03-01)
Effects of lateral heating on flow profiles and growth rates during the growth of mercurous chloride crystals by the physical-vapour-transport process in vertical ampoules are investigated by a two-dimensional model. The growth conditions of an experimental study available in the open literature are simulated. Lateral thermal boundary condition is modelled by a spatially sinusoidal heat flux. The results of the present computations are in agreement with the earlier experimental results and indicate that an ...
Citation Formats
I. Simonovski and T. Yalçınkaya, “Strain Gradient Crystal Plasticity Approach to Modelling Micro-Plastic Flow and Localisation in Polycrystalline Materials,” presented at the 24th International Conference on Nuclear Energy for New Europe (NENE), Portoroz, Slovenia, 2015, Accessed: 00, 2020. [Online]. Available: