Mechanical Engineering / Makina Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4129
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Conference Object Citation - Scopus: 3A Continuously Variable Transmission System Designed for Human–robot Interfaces(Springer, 2021) Mobedi, Emir; Dede, Mehmet İsmet CanWithin 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.Book Part Citation - WoS: 1Citation - Scopus: 1A Historical Review of Polyhedral Linkages(Springer, 2024) Kiper, GökhanPolyhedral 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 CanThis 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.Conference Object Citation - Scopus: 3Four-bar function generation using excel solver(Springer, 2023) Söylemez, Eres; Kiper, GökhanThe Chapter presents a simple and efficient way of approximating a function with a four-bar mechanism using four or five design parameters including one or both of the initial crank angles. The method only involves solution of linear set of equations and evaluating determinants, whereas nonlinear equations are numerically solved using a simple program such as Excel. So, the method is easy to explain and can be taught in an undergraduate course along with the wellknown linear three precision point synthesis problem. Precision point synthesis, order synthesis, mixed order synthesis, least squares approximation and extreme point synthesis can all be treated using the same method. The proposed method is illustrated with numerical examples for all mentioned synthesis problems and shown to be quite efficient with very low amount of structural error values.Conference Object Citation - Scopus: 3Design and Balancing of a Novel 2r1t Manipulator With Remote Center of Motion(Springer, 2023) Yılmaz, Tuğrul; Kiper, GökhanThe paper presents a novel manipulator design to be used as an endoscope holder for endonasal skull base surgeries. The manipulator should provide two rotational and one translational motions for the endoscope, where it should be able to be oriented about and slide along the tip of the nostril of a patient as a pivot point. First, suitable manipulators with remote center motion are investigated. Manipulators with serial and hybrid kinematic structure and redundant manipulators with a passive joint are examined. A serial manipulator with a circular arc as the second rotation axis is chosen for the detailed design. The novelty of the kinematic structure of the manipulator is that the end-effector heave motion is achieved in a tangential direction to the circular arc. The constructional design and counter-mass balancing solution for the manipulator are presented. The total assembly mass is 11.6 kg for navigating an endoscope of 0.44 kg mass.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, HakanAn 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.Conference Object A sustainable association case study: IFToMM member organization Turkey(Springer, 2022) Kiper, Gökhan; Söylemez, EresAs a member of IFToMM founded in 2011, Turkish Machine Theory Association’s (MakTeD) structure has put special emphasis on sustainability of the association and initiated several activities for improving the quality of education and research in mechanism and machine science area, hence supporting the SDG4 Quality Education of the UN. This paper presents the activities and methodologies of MakTeD. The paper starts with a brief history of mechanism and machine science in Turkey. In 10 years MakTeD organized 4 symposiums, 1 conference, 4 summer/winter schools, 8 workshops and hosted an IFToMM Executive Council meeting. Each chapter of the biyearly held National Symposium on Theory of Machines is held by a different university and especially newly established and the universities in relatively smaller cities are prioritized in order to promote those universities and to contribute to development of these universities. Especially the summer/winter schools and workshops have a widespread impact on mechanism and machine science education and research at the universities and institutions. MakTeD also contributes to the community with published books and support programs for young researchers.Conference Object Digital Twin of a Servo Driver of a Servo Motor as a First Step Towards a Digital Twin of a Robot Mechanism(Springer, 2022) Küçükoğlu, Sefa Furkan; Carbone, Giuseppe; Dede, Mehmet İsmet CanDigital Twin (DT) offers us to acquire actual system’s critical information and hence, it may be possible to develop and produce more suitable systems in terms of low energy consumption and effectiveness. In this way, responsible consumption and production systems can be designed and the system’s parameters can be tuned via DT. In this study, the model of a servomotor system that is used for industrial purposes is experimentally obtained. This study consists of two steps. In the first step, within the embedded control of the system, position and velocity control loops are deactivated. Then through the servo driver, currents with sinusoidal waveforms at various frequencies are applied to the servomotor. The resultant angular velocity of the motor is monitored and recorded. The amplitude of the current is kept constant during this study. The frequency of the current, however, is increased logarithmically. By using these data, a first-order transfer function (TF) is identified for the motor model. In the second step, all control loops are activated. Consequently, the total servomotor system could be represented in a digital environment. Furthermore, the static friction issue is overcome by using a Coulomb friction model with stiction effect. Finally, several experiments are conducted and then results are compared with the digital model of the servomotor system. The results clearly show that digital model can fairly represent the physical system.Conference Object Citation - Scopus: 26Optimization of Hip Implant Designs Based on Its Mechanical Behaviour(Springer, 2022) Göktaş, Hasan; Subaşı, Eda; Uzkut, Metin; Kara, Mustafa; Biçici, Hamit; Shirazi, Hadi; Mihçin, ŞenayTotal Hip Arthroplasty (THA) is one of the best advancements in healthcare. THA is required when the hip joint causes immobility and pain. The designed hip implants vary in geometry with different geometrical parameters. The geometry plays an important role in the mechanical behavior of the hip implant. In this study, the optimum selection of hip implant under static loading was evaluated using Finite Element Modeling (FEM). Hip implants with three different stem cross-sections including. (a) elliptic, (b) oval, and (c) trapezoidal were designed using a commercial Computer-Aided Design (CAD) software package. The FEM analysis was carried out via ANSYS R2019 to assess the key mechanical parameters of the implants such as stress distribution and deformation. The results were evaluated for the best stress and strain values. The optimum design had equivalent stress (von Misses) of 258,1 MPa, equivalent strain of 0.004, with total deformation of 0.24 mm and frictional stress of 0.362 MPa producing best values for trapezoidal cross-sectioned design. The findings of this study provided an insight into the selection of appropriate hip implant design with certain geometric design parameters to produce optimum results in clinical applications. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.Conference Object Citation - Scopus: 14Mechanical Investigation for the Use of Polylactic Acid in Total Hip Arthroplasty Using Fem Analysis(Springer, 2022) Çelik, Emre; Alemdar, Furkan; Batı, Murat; Daşdemir, Muhammed Furkan; Büyükbayraktar, Onur Alp; Chethan, K.N.; Mihçin, ŞenayPolylactic acid (PLA) is a biodegradable non-toxic, biocompatible polymer used as a popular filament material in biomedical applications with the advance of 3D printing technologies. PLA is considered a suitable implant material due to its contribution to bone regeneration. In this study, the use of PLA in Total Hip Arthroplasty (THA) as a liner material was assessed. In this regard, the PLA liner with different material combinations in THA was examined to provide evidence for its potential. The hip implant prototypewas drawn using a computer-aided design tool then transferred into a commercial finite element analysis (FEA) software. The prototypesconsisted of assemblies of PLA with titanium, chrome cobalt, stainless steels, dense NiTi shape-alloys, and Alumina-Zirconia. Simulations were run under static loading conditions. To evaluate and compare the results for the optimum design; factor of safety, total deformation and von Mises stress analysis were used. The results show that Co-Cr implemented implants produce the highest factor of safety. When Al-Zi combined with PLA, it produced least deformation and reasonable von- Mises stress values. PLA might perform best when used with Al-Zi. As a next step, experimental pre-clinical tests are planned to assess the clinical potential. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.