Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

Browse

Filters

2000 - 200992010 - 2019112020 - 202516

Settings

Department: search.filters.department.İzmir Institute of Technology. Mechanical EngineeringHas files: No

Search Results

Now showing 1 - 10 of 36
  • Article
    Enhancing trajectory-tracking accuracy of high-acceleration parallel robots by predicting compliant displacements
    (Cambridge University Press, 2025) Paksoy, Erkan; Dede, Mehmet Ismet Can; Kiper, Gokhan
    For precision-required robot operations, the robot's positioning accuracy, repeatability, and stiffness characteristics should be considered. If the mechanism has the desired repeatability performance, a kinematic calibration process can enhance the positioning accuracy. However, for robot operations where high accelerations are needed, the compliance characteristics of the mechanism affect the trajectory-tracking accuracy adversely. In this paper, a novel approach is proposed to enhance the trajectory-tracking accuracy of a robot operating at high accelerations by predicting the compliant displacements when there is no physical contact of the robot with its environment. Also, this case study compares the trajectory-tracking characteristics of an over-constrained and a normal-constrained 2degrees-of-freedom (DoF) planar parallel mechanism during high-acceleration operations up to 5 g accelerations. In addition, the influence of the end-effector's center of mass (CoM) position along the normal of the plane is investigated in terms of its effects on the proposed trajectory-enhancing algorithm.
  • Conference Object
    Citation - Scopus: 3
    A Continuously Variable Transmission System Designed for Human–robot Interfaces
    (Springer, 2021) Mobedi, Emir; Dede, Mehmet İsmet Can
    Within a predefined limit, continuously variable transmission (CVT) systems can continuously vary the power transmission ratio. The transmission in CVTs is achieved via friction, belt or gear systems. If CVT designs can incorporate backdrivability, independent output position and impedance variation, shock absorbtion, and low mass and inertia, they can be employed in human–robot interfaces. Among various types of CVT designs, the two-cone drive CVT designs have a major drawback since the output torque and position cannot be changed independent of each other. The friction wheel used in this design does not have a holonomic motion capability and causes this inconvenience. In order to overcome this problem, a sphere is used in this work for the CVT design as the transmission element. In addition, it is stated in the literature that common CVT drive systems do not have the capability to be used in cyclic bidirectional motion. In the presented CVT design, a second sphere is added to the system with two springs from the lower part of the cones for pretension in order to solve the bidirectional transmission problem. In this paper, the working principle and conceptual design details of the novel two-cone CVT drive are presented. Experimental results showed that the novel CVT has the capacity to transmit bidirectional power with some accuracy. © 2021, Springer Nature Singapore Pte Ltd.
  • Conference Object
    Determination of Interfacial Heat Transfer Coefficient for a Mixed Convection Heat Transfer in a Vertical Channel Filled With Uniformly Heated Blocks
    (Begell House Inc., 2015) Çelik, Hasan; Mobedi, Moghtada; Manca,O.; Buonomo,B.
    The interfacial convective heat transfer coefficient of a periodic porous medium under mixed convection heat transfer is determined computationally by using volume averaging method. The porous medium consists of square blocks in inline arrangement. The continuity, momentum and energy equations are solved in dimensionless form for a representative elementary volume of porous medium and the velocity and temperature fields for different values of Richardson and Reynolds numbers are obtained. Based on the obtained results, the interfacial convective heat transfer coefficient is calculated by using volume average method. The temperature of the solid phase is considered uniform and different than the inlet temperature. A detailed discussion on the effect of the governing dimensionless parameters (i.e. Reynolds, Richardson numbers, and porosity) on the local and average interfacial Nusselt number is done. It is concluded that the local interfacial convective heat transfer coefficient increases with Reynolds number, however the rate of increase depends on Richardson number and porosity. The study is performed for two values of porosity of 0.51 and 0.94. © 2021, Begell House Inc. All rights reserved.
  • Conference Object
    A Numerical Study on the Determination of the Effects of Pore To Throat Size Ratio on the Thermal Dispersion in Porous Media
    (Begell House, 2014) Özgümüş, Türküler; Mobedi, Moghtada; Özkol, Ünver
    Direct pore-level numerical simulations are widely used to estimate macroscopic properties of fluid flow and heat transfer in porous media. Thermal dispersion is one of the most important macroscopic transport parameters for analyzing convective heat transfer in a porous medium. It should be known in order to predict the macroscopic temperature distribution. In the present study, a microscopic scale analysis is performed for a porous medium with periodic structure. A representative elementary volume is chosen from an infinite medium consists of rectangular rods in inline arrangement. The continuity and momentum equations are solved to obtain flow field and the energy equations for fluid and solid phases are solved to obtain microscopic temperature distributions in two phases. There are velocity and temperature deviations between macroscopic and microscopic local values. Volume averaging method is applied to the computed deviations and thermal dispersion conductivity of porous media is determined. The aim of this study is to analyze the effects of pore to throat size ratio on the longitudinal and transverse thermal dispersion in porous media. The study is performed for representative elementary volumes with different pore to throat size ratios and Reynolds numbers from 1 to 100. The study is performed for high porosity porous media (ε = 0.7 and 0.91). It is shown that the porosity and pore to throat size ratio have more influence on the transverse rather than longitudinal thermal dispersion. © 2014, Begell House Inc. All rights reserved.
  • Book Part
    Citation - WoS: 1
    Citation - Scopus: 1
    A Historical Review of Polyhedral Linkages
    (Springer, 2024) Kiper, Gökhan
    Polyhedral linkages are linkages that resemble polyhedral shapes at different configurations. This paper summarizes the necessary geometrical fundamentals of polyhedral geometry and presents a historical and critical review of the polyhedral linkage designs available in the literature. Basic definitions of polyhedral geometry and operations are needed to comprehend and design polyhedral linkages. First, early works on polyhedral linkages are presented, where flexible polyhedra with rigid faces and flexible edges are issued. The final part is reserved to conformal polyhedral linkages, which go through shape transformations while plane, dihedral and solid angles are preserved. Conformal polyhedral linkages are examined in four categories: 1) Jitterbug-like linkages with screwing polygonal links connected to each other with dihedral angle preserving links, 2) polyhedral linkages with planar kinematic chains in radial motion planes, 3) polyhedral linkages with planar kinematic chains on faces, that are connected to each other with dihedral angle preserving links, and 4) other conformal polyhedral linkages. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.
  • Conference Object
    Energy and Exergy Analysis of a Roof-Mounted Photovoltaic System in Gebze-Turkey
    (Springer, 2024) Khalejan, Seyed Hamed Pour Rahmati; Cankurt, Tolga; Dede, Mehmet İsmet Can
    This study investigates the electrical and thermal exergy, power conversion efficiency and exergy efficiency of a roof-mounted photovoltaic (PV) system considering environmental parameters such as solar irradiation, ambient temperature and wind speed over a year. The values of solar exergy and solar potential are obtained by taking into account the solar insolation. Experimental and theoretical results indicate that wind speed and surface temperature have significant effects on the thermal exergy and exergy efficiency of solar PV systems. The mean solar potential in the region was found to be 93%. In addition, the electrical exergy was varied from 9145 W to 40460 W and the thermal exergy of PV systems was varied from 1639 W to 6193 W. While the range of PV power conversion efficiency varies from 6.15% to 11.56% over a year, the range of exergy efficiency varies from 5.31% to 9.78%. © 2024, The Author(s), under exclusive license to Springer Nature Switzerland AG.
  • Article
    Citation - WoS: 8
    Citation - Scopus: 9
    Dynamic Computational Wear Model of Peek-On Bearing Couple in Total Hip Replacements
    (Elsevier, 2023) Alpkaya, Alican Tuncay; Mihçin, Şenay
    Understanding wear mechanisms is a key factor to prevent primary failures causing revision surgery in total hip replacement (THR) applications. This study introduces a wear prediction model of (Polyetheretherketone) PEEK-on-XLPE (cross-linked polyethylene) bearing couple utilized to investigate the wear mechanism under 3D-gait cycle loading over 5 million cycles (Mc). A 32-mm PEEK femoral head and 4-mm thick XLPE bearing liner with a 3-mm PEEK shell are modeled in a 3D explicit finite element modeling (FEM) program. The volumetric and linear wear rates of XLPE liner per every million cycles were predicted as 1.965 mm3/Mc, and 0.0032 mm/Mc respectively. These results are consistent with the literature. PEEK-on-XLPE bearing couple exhibits a promising wear performance used in THR application. The wear pattern evolution of the model is similar to that of conventional polyethylene liners. Therefore, PEEK could be proposed as an alternative material to the CoCr head, especially used in XLPE-bearing couples. The wear prediction model could be utilized to improve the design parameters with the aim of prolonging the life span of hip implants. © 2023
  • Conference Object
    A Parametric Numerical Analysis of Laminar Hydrogen Diffusion Flames
    (International Association for Hydrogen Energy, IAHE, 2022) Korucu, Ayşe; Benim, Ali Cemal
    Atmospheric, laminar, diffusion flames of hydrogen and air are numerically investigated. A detailed hydrogen combustion reaction scheme, in combination with the extended Zeldovich mechanism for the thermal nitrogen oxide formation are used. For comparison purposes, a global mechanism is also applied. The numerical procedure is first validated by comparisons with results of other authors. Subsequently, parametric studies are performed to find optimal solutions with respect to the related to the operation parameters of such flames to achieve minimum low nitrogen oxide emission levels. The question that are addressed include the Reynolds number effect on nitrogen emissions, and the interaction of neighbouring flames, when they are applied in an array. For ensuring an adequately fine resolution of the flame fronts, local adaptive grid refinement techniques are applied to track the flame front. For preliminary results the radiative heat loses has assumed to be insignificant however it should be taken into the account for the further analyses. The maximum temperature is predicted to be ~2040 K which is higher than the reported adiabatic stoichiometric flame temperature, 2023K for the exit velocity of 0.5 m/s. The radial mole fractions of N2 and H2 at the centerline are observed to be 0.66 and 0.41 respectively at the axial distance of 10 mm. Furthermore, the width of the high temperature region of the flame is observed to be ~6.5 mm. © 2022 Proceedings of WHEC 2022 - 23rd World Hydrogen Energy Conference: Bridging Continents by H2. All rights reserved.
  • Article
    Enabling Personalization of a Robotic Surgery Procedure Via a Surgery Training Simulator
    (Cambridge University Press, 2022) Dede, Mehmet İsmet Can; Büyüköztekin, Tarık; Hanalıoğlu, Şahin; Işıkay, İlkay; Berker, Mustafa
    Although robotic or robot-assisted surgery has been increasingly used by many surgical disciplines, its application in cranial or skull base surgery is still in its infancy. Master-slave teleoperation setting of these robotic systems enables these surgical procedures to be replicated in a virtual reality environment for surgeon training purposes. A variety of teleoperation modes were previously determined with respect to the motion capability of the surgeon's hand that wears the ring as the surgeon handles a surgical tool inside the surgical workspace. In this surgery training simulator developed for a robot-assisted endoscopic skull base surgery, a new strategy is developed to identify the preferred motion axes of the surgeon. This simulator is designed specifically for tuning the teleoperation system for each surgeon via the identification. This tuning capability brings flexibility to adjust the system operation with respect to the motion characteristics of the surgeon.
  • Conference Object
    Asymmetry in the Tension and Compression Flow Stress and the Effect of Sub-Cell Size on the Hardness of a Selective Laser Melt 316l Stainless Steel
    (Springer, 2022) Güden, Mustafa; Enser, Samed; Arslan Hamat, Burcu; Tanrıkulu, A. Alptuğ; Yavaş, Hakan
    An asymmetry between tension and compression tests was determined experimentally in the Selective Laser Melt (SLM) stainless steel 316L alloy in the building direction. The asymmetry was ascribed to the used biaxial scanning strategy which resulted in a strong alignment of 〈110〉 along the build direction (fiber texture) and a random distribution of 〈100〉, 〈110〉 and 〈111〉 directions normal to the building direction. The strong fiber texture in the building direction induced lower twinning stress in tension than in compression, while the tension and compression twining stresses were found similar in the normal to building direction. The favored twinning in the specimens tested in the building direction resulted in a higher tensile true fracture strain; hence, a higher ductility. Lastly, the hardness measurements made on the specimens having similar gain sizes, but different sub-cell sizes processed using higher and lower laser powers tended to support that the sub-cell boundaries in SLM-316L alloy acted as imperfect barriers to the dislocation motion.