Browsing by Author "Demiral, Murat"

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Citation - WoS: 4
Citation - Scopus: 7
Enhanced Gradient Crystal-Plasticity Study of Size Effects in a Β-Titanium Alloy
(Iop Publishing Ltd, 2017) Nowag, Kai; Roy, Anish; Ghisleni, Rudy; Michler, Johann; Silberschmidt, Vadim V.; Demiral, Murat; 06.06. Makine Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
A calibrated model of enhanced strain-gradient crystal plasticity is proposed, which is shown to characterize adequate deformation behaviour of bcc single crystals of a beta-Ti alloy (Ti-15-3-3-3). In this model, in addition to strain gradients evolving in the course of deformation, incipient strain gradients, related to a component's surface-to-volume ratio, is accounted for. Predictive capabilities of the model in characterizing a size effect in an initial yield and a work-hardening rate in small-scale components is demonstrated. The characteristic length-scale, i.e. the component's dimensions below which the size effect is observed, was found to depend on densities of polar and statistical dislocations and interaction between them.
Modelling and simulations of nanoindentation in single crystals
(John Wiley and Sons LTD., 2017) Liu, Qiang; Demiral, Murat; Roy, Anish; Silberschmidt, Vadim V.; 06.06. Makine Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Citation - WoS: 2
Citation - Scopus: 2
Modelling and Simulations of Nanoindentation in Single Crystals
(John Wiley & Sons Ltd, 2017) Liu, Qiang; Demiral, Murat; Roy, Anish; Silberschmidt, Vadim V.; 06.06. Makine Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Modelling of micro-/nano-indentation of single crystals has been developed extensively to elucidate experimentally observed features such as the size effect, pile-up phenomenon and lattice rotations. The indentation size effect (ISE) of three types of single crystals, i.e. f.c.c. copper single crystal, b.c.c. ß phase of Ti-6Al-4V (ß-Ti-64) and b.c.c. ß phase of Ti-15V-3Cr-3Al-3Sn (ß-Ti-15-3-3-3), is investigated using finite-element analysis. In indentation modelling, an idealised conical indenter and spherical indenters were chosen to study the effects of indenter's geometry on the mechanical response of the tested material. A crystal plasticity model was used to describe the material's behaviour of these single crystals during nanoindentation. In this chapter, a conventional single-crystal plasticity (SCP) model and the mechanism-based strain-gradient crystal-plasticity (MSGCP) model were employed to compare and contrast the (de)merits of the types of crystal plasticity models. © 2017 John Wiley & Sons Ltd.
Citation - WoS: 30
Citation - Scopus: 35
Void Growth in High Strength Aluminium Alloy Single Crystals: a Cpfem Based Study
(Iop Publishing Ltd, 2017) Siddiq, M. Amir; Demiral, Murat; Asim, Umair; 06.06. Makine Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
High strength aluminium alloys that are produced through forming and joining processes are widely used in aerospace components. The ductile failure in these metals occurs due to the evolution and accumulation of microscopic defects, such as microvoids and shear bands. The present work investigates the underlying physical mechanisms during ductile failure by performing a rigorous, fully-validated, three-dimensional crystal plasticity, finite element study with aluminium alloy single crystals. Representative volume element (RVE) based simulations of single crystalline aluminium alloys (AA-5xxx) with different void geometries and orientations have been performed. Both local and nonlocal crystal plasticity constitutive models have been implemented in a finite element framework and are used to seek new insights into the interrelationships among void growth, initial porosity, initial void size, plastic anisotropy, and local/nonlocal size effects.