Makine Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/263
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Article Citation - WoS: 7Citation - Scopus: 9A Novel Zero-Dead Sample Loading Interface for Microfluidic Devices: Flexible Hydraulic Reservoir (Fhr)(Iop Publishing Ltd, 2018) Cetin, Barbaros; Yildirim, Ender; Hatipoglu, UtkuInfusing minute amounts of valuable liquids such as samples to microfluidic chips by using common pumping schemes such as syringe pumps often result in an excessive dead-volume. We present a simple yet effective sample loading interface, which helps by pumping the sample to the chip by using the hydraulic pressure generated by the syringe pump. Results show that sample volumes as low as 25 mu l can be delivered at flow rates ranging between 10-30 mu l min(-1). Maximum dead volume ratio was observed to be 3% when infusing 200 mu l of sample at 10 mu l min(-1).Article Citation - WoS: 4Citation - Scopus: 7Enhanced 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, MuratA 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.Article Citation - WoS: 33Citation - Scopus: 38Void Growth in High Strength Aluminium Alloy Single Crystals: a Cpfem Based Study(Iop Publishing Ltd, 2017) Siddiq, M. Amir; Demiral, Murat; Asim, UmairHigh 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.Conference Object Citation - WoS: 12Analysis and Characterization of an Electrostatically Actuated In-Plane Parylene Microvalve(Iop Publishing Ltd, 2011) Kulah, H.; Yildirim, E.This paper presents analysis and implementation of a simple electrostatic microvalve designed for use in parylene-based lab-on-a-chip devices. The microvalve utilizes an in-plane collapsing diaphragm. To investigate the pull-in behavior of the diaphragm and flow characteristics, a thorough analysis is carried out using the finite element method. Microvalves with different diaphragm radii are fabricated using surface micromachining techniques. Pull-in tests are carried out under the no-flow condition with air, oil and water as the working fluid. Test results show that the pull-in occurs around 20 V for 450 mu m radius diaphragms with oil and air. However, it is not possible to observe pull-in up to 100 V (both ac and dc) for the case of water as the working fluid, due to its relatively high dielectric constant and conductivity. The flow tests show that no leakage flow was observed up to 4 kPa inlet pressure under 85 V actuation potential. The leakage ratio becomes 17% at 10 kPa inlet pressure. It is observed that the leakage can be reduced controllably by increasing the actuation potential, enabling the precise control of the flow rate.