Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 11Citation - Scopus: 12A Novel Transformable Structural Mechanism for Doubly Ruled Hypar Surfaces(The American Society of Mechanical Engineers(ASME), 2015) Maden, Feray; Aktaş, Engin; Aktaş, Engin; Korkmaz, Koray; Korkmaz, Koray; 02.02. Department of Architecture; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology; 02. Faculty of ArchitectureA novel structural mechanism (SM) that is capable of transforming itself into various hyperbolic paraboloid (hypar) geometries is introduced in this paper. Composed of straight bars and novel joint types, the SM is designed based on the ruled surface generation method. Thus, the paper first investigates the geometrical properties and morphology of the hypar surface. Second, it constructs the SM and discusses its transformation capability with respect to its kinematic properties. Then, it presents a parametric model not only to analyze the geometry and possible configurations of the SM but also to prepare a model for the structural analysis. Finally, a transformable shelter structure is proposed as an architectural application of the SM and its feasibility is tested based on the structural analysis conducted in different configurations of the structure. According to the results of the structural analysis, the strength, and the stiffness of the structure are discussed in detail.Conference Object Citation - WoS: 1Citation - Scopus: 1Development of a New Universal Inverse Through-Flow Program and Method for Fully Coupled Split-Flow Turbomachinery Systems(The American Society of Mechanical Engineers(ASME), 2015) Acarer, Sercan; Özkol, Ünver; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyStreamline curvature technique for inverse through-flow modeling of turbomachinery is still one of the most prevalent alternatives in design. Even though the subject has been studied in numerous aspects over many years, open literature on fully coupled split-flow turbomachinery system design which is encountered in turbofan engines, is still limited. The principal method, viable for analysis mode, may easily give rise to undesired streamline distortion near the splitter leading edge whilst operating in design mode. Besides, spanwise discontinuity of flow properties along the stagnation streamline prior to final solution convergence may be another outcome. The present study is geared towards eliminating these potential drawbacks by developing an alternative generally applicable split-flow scheme incorporated in a recently developed streamline curvature software. This new scheme disposes the need to define a stagnation streamline, while preserving full coupling between the main and split ducts. This is achieved through removal of by-pass ratio restriction, which makes local velocity vector always perfectly aligned with the splitter leading edge without any limit on fan-splitter axial distance. A two-step validation strategy is followed: Firstly, 2D split-flow solutions of the developed method for representative duct geometries having design by-pass ratios ranging between 0.25 and 6.5, but without turbomachinery, are compared with a commercial CFD software; Secondly, the method is compared with 3D viscous CFD solution of NASA Rotor 37 geometry, whose flowpath is modified to include a downstream flowpath splitter. It is shown that the proposed scheme can be used as a practical alternative to the conventional treatment that promises minimal effort to implement to an existing compressor streamline curvature methodology.Article Citation - WoS: 5Citation - Scopus: 6An Extended Jacobian-Based Formulation for Operational Space Control of Kinematically Redundant Robot Manipulators With Multiple Subtask Objectives: An Adaptive Control Approach(The American Society of Mechanical Engineers(ASME), 2019) Çetin, Kamil; Tatlıcıoğlu, Enver; Tatlıcıoğlu, Enver; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn this study, an extended Jacobian matrix formulation is proposed for the operational space tracking control of kinematically redundant robot manipulators with multiple subtask objectives. Furthermore, to compensate the structured uncertainties related to the robot dynamics, an adaptive operational space controller is designed, and then, the corresponding stability analysis is presented for kinematically redundant robot manipulators. Specifically, the proposed method is concerned with not only the stability of operational space objective but also the stability of multiple subtask objectives. The combined stability analysis of the operational space objective and the subtask objectives are obtained via Lyapunov based arguments. Experimental and simulation studies are presented to illustrate the performance of the proposed method.Article Citation - WoS: 4Citation - Scopus: 3A Model-Free Continuous Velocity Observer Formulation With Self-Tuning for Mechatronic Systems(The American Society of Mechanical Engineers(ASME), 2018) Deniz, Meryem; Bayrak, Alper; Tatlıcıoğlu, Enver; Bayrak, Alper; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn this study, the design of a smooth robust velocity observer for a class of uncertain nonlinear mechatronic systems is presented. The proposed velocity observer does not require a priori knowledge of the upper bounds of the uncertain system dynamics and introduces time-varying observer gains for uncertainty compensation. Practical stability of the velocity observation error is ensured via Lyapunov-type stability analysis. Experimental results obtained from Phantom Omni haptic device are presented to illustrate the performance of the proposed velocity observer.Article Citation - WoS: 12Citation - Scopus: 13A General Expression for the Stagnant Thermal Conductivity of Stochastic and Periodic Structures(The American Society of Mechanical Engineers(ASME), 2018) Bai, X.; Mobedi, Moghtada; Çelik, Hasan; Mobedi, Moghtada; Nakayama, Akira; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyA general expression has been obtained to estimate thermal conductivities of both stochastic and periodic structures with high-solid thermal conductivity. An air layer partially occupied by slanted circular rods of high-thermal conductivity was considered to derive the general expression. The thermal conductivity based on this general expression was compared against that obtained from detailed three-dimensional numerical calculations. A good agreement between two sets of results substantiates the validity of the general expression for evaluating the stagnant thermal conductivity of the periodic structures. Subsequently, this expression was averaged over a hemispherical solid angle to estimate the stagnant thermal conductivity for stochastic structures such as a metal foam. The resulting expression was found identical to the one obtained by Hsu et al., Krishnan et al., and Yang and Nakayama. Thus, the general expression can be used for both stochastic and periodic structures.Conference Object Citation - WoS: 1Citation - Scopus: 1Numerical and Experimental Studies of High Strain Rate Mechanical Behavior of E-glass/Polyester Composite Laminates(The American Society of Mechanical Engineers(ASME), 2010) Tunusoğlu, Gözde; Taşdemirci, Alper; Güden, Mustafa; Hall, Ian W.; Taşdemirci, Alper; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyQuasi-static ∼10-3 s-1) and high strain rate (∼850 s-1) compression behavior of an E-glass/polyester composite was determined in the through-thickness and in-plane directions. In both directions, modulus and failure strength increased with increasing strain rate. Higher strain rate sensitivity for both elastic modulus and failure strength was observed in the in-plane direction. A numerical model was developed to investigate the compressive deformation and fracture of an E-glass/polyester composite. Excellent agreement was demonstrated for the case of high strain rate loading. Also, the fracture geometries were successfully predicted with the numerical model.Article Citation - WoS: 10Citation - Scopus: 10Constructal Microdevice Manifold Design With Uniform Flow Rate Distribution by Consideration of the Tree-Branching Rule of Leonardo Da Vinci and Hess-Murray Rule(The American Society of Mechanical Engineers(ASME), 2017) Çetkin, Erdal; Çetkin, Erdal; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn this paper, we show how the design of a microdevice manifold should be tapered for uniform flow rate distribution. The designs based on the tree-branching rule of Leonardo da Vinci and the Hess-Murray rule were considered in addition to the constructal design. Both da Vinci and Hess-Murray designs are insensitive to the inlet velocity, and they provide better flow uniformity than the base (not tapered) design. However, the results of this paper uncover that not only pressure drop but also velocity distribution in the microdevice play an integral role in the flow uniformity. Therefore, an iterative approach was adopted with five degrees-of-freedom (inclined wall positions) and one constraint (constant distribution channel thickness) in order to uncover the constructal design which conforms the uniform flow rate distribution. In addition, the effect of slenderness of the microchannels (Svelteness) and inlet velocity on the flow rate distribution to the microchannels has been documented. This paper also uncovers that the design of a manifold should be designed with not only the consideration of pressure distribution but also dynamic pressure distribution especially for non-Svelte microdevices.Article Citation - WoS: 8Citation - Scopus: 7A New Approach To the Generation of Retractable Plate Structures Based on One-Uniform Tessellations(The American Society of Mechanical Engineers(ASME), 2017) Gazi Gezgin, Aylin; Korkmaz, Koray; Korkmaz, Koray; 02.02. Department of Architecture; 02. Faculty of Architecture; 01. Izmir Institute of TechnologyRetractable plate structure (RPS) is a family of structures that is a set of cover plates connected by revolute joints. There exists wide range of possibilities related with these structures in architecture. Configuring the suitable shape of rigid plates that are able to be enclosed without any gaps or overlaps in both closed and open configurations and eliminating the possibility of contact between the plates during the deployment have been the most important issues in RPS design process. Many researchers have tried to find the most suitable shape by using kinematical or empirical analysis so far. This study presents a novel approach to find the suitable shape of the plates and their assembly order without any kinematical or empirical analysis. This approach is benefited from the one-uniform mathematical tessellation technique that gives the possibilities of tiling a plate using regular polygons without any gaps or overlaps. In the light of this technique, the shape of the plates is determined as regular polygons and two conditions are introduced to form RPS in which regular polygonal plates are connected by only revolute joints. It should be noted that these plates are not allowed to become overlapped during deployment and form gaps in closed configuration. Additionally, this study aims to reach a single degreeof- freedom (DoF) RPS. It presents a systematic method to convert multi-DoF RPS into single DoF RPS by using the similarity between graph theory and the duality of tessellation.Article Citation - WoS: 4Citation - Scopus: 4Predicting and Measuring Surface Enlargement in Forward Rod Extrusion(The American Society of Mechanical Engineers(ASME), 2016) Duran, Deniz; Özdemir, İzzet; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologySurface enlargement during bulk metal forming processes is one of the key parameters controlling the tribology at the tool-workpiece interface. Not only the surface roughness evolution but also the integrity of the lubricant layer critically reposes on surface enlargement. As an attempt to address this issue, in the first part of this work, a general, deformation gradient based surface enlargement description is implemented in a commercial finite element program. In the second part, forward rod extrusion tests with different area reductions are conducted using customized steel workpieces in which cylindrical copper rods are embedded through the depth. By sectioning the extruded parts and by identifying the position of the copper rods on the lateral surface, average surface enlargement values could be measured locally at different positions along the extrudate. Comparison of experiments and numerical predictions reveal that the deformation gradient based description performs reasonably well in capturing surface enlargement profiles both qualitatively and quantitatively.Article Citation - WoS: 13Citation - Scopus: 15Constructal Vascular Structures With High-Conductivity Inserts for Self-Cooling(The American Society of Mechanical Engineers(ASME), 2015) Çetkin, Erdal; Çetkin, Erdal; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn this paper, we show how a heat-generating domain can be cooled with embedded cooling channels and high-conductivity inserts. The volume of cooling channels and high-conductivity inserts is fixed, so is the volume of the heat-generating domain. The maximum temperature in the domain decreases with high-conductivity inserts even though the coolant volume decreases. The locations and the shapes of high-conductivity inserts corresponding to the smallest peak temperatures for different number of inserts are documented,