Mechanical Engineering / Makina Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/4129

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Start date: 2000Publisher: search.filters.publisher.Springer Verlag

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Now showing 1 - 10 of 52
  • Conference Object
    Citation - WoS: 2
    Citation - Scopus: 2
    Function Generation Synthesis of Planar Slider-Crank Linkages for Given 3 Positions and a Dead-Center Position
    (Springer Verlag, 2020) Kiper, Gokhan; Gorgulu, Ibrahimcan; Kucukoglu, Sefa Furkan
    Function generation for finitely many positions and dead-center design problems are generally separately handled in the literature. This paper presents a mixed formulation for planar slider-crank linkages where three precision points and a folded or extended dead-center position are to be satisfied. The formulation results in an 8th degree univariate. Examples show that generally there are four real solutions, only two of which result in distinct solutions.
  • Article
    Citation - WoS: 47
    Citation - Scopus: 46
    Surface Charge-Dependent Transport of Water in Graphene Nano-Channels
    (Springer Verlag, 2018) Çelebi, Alper Tunga; Barışık, Murat; Beşkök, Ali
    Deionized water flow through positively charged graphene nano-channels is investigated using molecular dynamics simulations as a function of the surface charge density. Due to the net electric charge, Ewald summation algorithm cannot be used for modeling long-range Coulomb interactions. Instead, the cutoff distance used for Coulomb forces is systematically increased until the density distribution and orientation of water atoms converged to a unified profile. Liquid density near the walls increases with increased surface charge density, and the water molecules reorient their dipoles with oxygen atoms facing the positively charged surfaces. This effect weakens away from the charged surfaces. Force-driven water flows in graphene nano-channels exhibit slip lengths over 60 nm, which result in plug-like velocity profiles in sufficiently small nano-channels. With increased surface charge density, the slip length decreases and the apparent viscosity of water increases, leading to parabolic velocity profiles and decreased flow rates. Results of this study are relevant for water desalination applications, where optimization of the surface charge for ion removal with maximum flow rate is desired.
  • Article
    Citation - WoS: 35
    Citation - Scopus: 39
    Development of Graphene Nanoplatelet-Reinforced Az91 Magnesium Alloy by Solidification Processing
    (Springer Verlag, 2018) Kandemir, Sinan
    It is a challenging task to effectively incorporate graphene nanoplatelets (GNPs) which have recently emerged as potential reinforcement for strengthening metals into magnesium-based matrices by conventional solidification processes due to their large surface areas and poor wettability. A solidification processing which combines mechanical stirring and ultrasonic dispersion of reinforcements in liquid matrix was employed to develop AZ91 magnesium alloy matrix composites reinforced with 0.25 and 0.5 wt.% GNPs. The microstructural studies conducted with scanning and transmission electron microscopes revealed that fairly uniform distribution and dispersion of GNPs through the matrix were achieved due to effective combination of mechanical and ultrasonic stirring. The GNPs embedded into the magnesium matrix led to significant enhancement in the hardness, tensile strength and ductility of the composites compared to those of unreinforced AZ91 alloy. The strength enhancement was predominantly attributed to the grain refinement by the GNP addition and dislocation generation strengthening due to the coefficient of thermal expansion mismatch between the matrix and reinforcement. The improved ductility was attributed to the refinement of β eutectics by transforming from lamellar to the divorced eutectics due to the GNP additions. In addition, the strengthening efficiency of the composite with 0.25 wt.% GNP was found to be higher than those of the composite with 0.5 wt.% GNP as the agglomeration tendency of GNPs is increased with increasing GNP content. These results were compared with those of the GNP-reinforced magnesium composites reported in the literature, indicating the potential of the process introduced in this study in terms of fabricating light and high-performance metal matrix composites.
  • Conference Object
    Citation - Scopus: 2
    Function Generation Synthesis With Planar 4-Bar Linkage as a Mixed Problem of Correlation of Crank Angles and Dead-Center Design
    (Springer Verlag, 2019) Kiper, Gökhan; Erez, Melih
    The function generation synthesis of planar four-bar linkage is formulated as a mixed problem of correlation or crank angles and dead-center design. The syn-thesis is based on three desired configurations of the linkage, where the input and output joint angles are specified for two of the configurations and the coupler link is folded upon the output link for the third configuration. The formulation results in a set of nonlinear equations which can be solved analytically. The formulations are tested with numerical examples and similar mixed function generation problems are briefly discussed.
  • Conference Object
    Citation - Scopus: 1
    Structural Compliance Effects on the Accuracy and Safety of a R-Cube Haptic Device
    (Springer Verlag, 2019) Carbone, Giuseppe; Acinapura, Antonio; Mundo, Domenico; Görgülü, İbrahimcan; Dede, Mehmet İsmet Can
    This paper addresses the contribution of structural compliance on stiffness and safety of a R-CUBE Haptic Device. Structural compliance is determined in several poses via FEM analysis and addressed by referring to local and global indices of performance. Results are also compared with evidences from experimental tests. Comparison of numerical and experimental data allows to identify and separate the contributions to the overall compliance that are due to the structural stiffness, and other contributions such as joint clearance, pose and loading conditions.
  • Book Part
    Control Methods for a Teleoperated Endoscope Robot
    (Springer Verlag, 2019) Işıtman, Oğulcan; Dede, Mehmet İsmet Can
    In this study, control of a endoscope robot for the pituitary gland surgery is presented. This co-worker robot has non-backdrivable actuation system with external brakes on the actuators. Since it is required to move in a constrained environment, which is the inside the nostrils in this case, modifications are required for the motion controller. In order to provide safe procedure, the maximum force and torque limits are defined for the real surgical case by using human cadaver head. By considering these limits and application specific requirements, a compliance controller is proposed and experimentally tested.
  • Conference Object
    Kinematic Synthesis of Planar 4-Bar Path Generators for Finite Line Positions
    (Springer Verlag, 2019) Kiper, Gökhan; Söylemez, Eres
    Although the kinematic synthesis of planar function, point-path and motion gen-erators are vastly studied in the literature, surprisingly synthesis of line-path gen-erators is not formulized in detail. This study presents the formulization of the planar 4-bar line-path generator synthesis problem for up to 5 homologous posi-tions. Numerical examples for 3 and 4 line positions are presented for the illustra-tion of the formulations.
  • Conference Object
    Citation - Scopus: 4
    Static Force Balancing of a 2r1t Parallel Manipulator With Remote Center of Motion
    (Springer Verlag, 2019) Yaşır, Abdullah; Kiper, Gökhan; Dede, Mehmet İsmet Can; Van der Wijk, Volkert
    Assistive robots in surgical applications should be gravity balanced due to safety considerations. This study presents a gravity balancing solution for a 3-degree-of-freedom parallel manipulator to be used as an endoscope navigation robot for transnasal minimal invasive surgery applications. The manipulator has a rather simple structure that allows individual balancing of the three legs in their respec-tive planes of motion. First, sole counter-mass balancing is investigated, but it is seen that the extra mass amount is too much. Sole spring balancing is not consid-ered as an option due to constructional complexity. A hybrid solution as a combi-nation of counter-mass and spring balancing is devised. In the proposed solution, the masses on the distal links of a leg are balanced with counter-masses so that all masses are lumped to the link connected to the base of the manipulator. Hence the problem is simplified into the balancing of a pendulum. The necessary formula-tions are derived and numerical calculations demonstrate that the hybrid balancing yields a feasible solution.
  • Conference Object
    Low-Power and Low-Cost Stiffness-Variable Oesophageal Tissue Phantom
    (Springer Verlag, 2017) Thorn, Alexander; Afacan, Dorukhan; Ingham, Emily; Kavak, Can; Miyashita, Shuhei; Damian, Dana D.
    Biological tissues are complex structures with changing mechanical properties depending on physiological or pathological factors. Thus they are extendible under normal conditions or stiff if they are subject to an inflammatory reaction. We design and fabricate a low-power and low-cost stiffness-variable tissue phantom (SVTP) that can extend up to 250% and contract up to 5.4% at 5 V (1.4 W), mimicking properties of biological tissues. We investigated the mechanical characteristics of SVTP in simulation and experiment. We also demonstrate its potential by building an oesophagus phantom for testing appropriate force controls in a robotic implant that is meant to manipulate biological oesophageal tissues with changing stiffness in vivo. The entire platform permits efficient testing of robotic implants in the context of anomalies such as long gap esophageal atresia, and could potentially serve as a replacement for live animal tissues.
  • Conference Object
    Citation - Scopus: 2
    Fault-Tolerance Experiments With a Kinematically Redundant Holonomic Mobile Robot
    (Springer Verlag, 2018) Şahin, Osman Nuri; Çelik, Onur; Dede, Mehmet İsmet Can
    Indoor locomotion with mobile robots has found applications in industrial part moving, factory floor investigation and cleaning tasks. Holonomic mobile robots have the advantage of moving in tight and winding passages without the need of steering. In this study, a four omni-directional wheeled mobile robot is considered. The mobile robot is kinematically redundant having four of these wheels and this is used in providing fault-tolerance due to a malfunction in one of the wheels. In this paper, the redundancy resolution for this mobile robot is explained providing a solution to a fault in one of the wheels during operation. A top level controller to compensate for the orientation errors is introduced. Finally experimental set-up is presented along with the result of the fault-tolerance experiments.