Makine Mühendisliği Bölümü

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Neck Protection in Autonomous Car Crashes
(Kauno Technologijos Universitetas, 2020) Yavuz, Samet; Yavuz, S.; Himmetoglu, S.; Makine Mühendisliği
Autonomous cars which are expected to be on the market in the upcoming years, present new challenges to restraint system design since unconventional seating plans can put the occupants at more risk. For instance, an occupant sitting on a rear facing seat can experience higher risk of whiplash in a frontal impact considering the fact that statistically frontal impacts do happen at higher severities than rear impacts as seen in the crash test conditions of US NCAP. In this study, an improvement to car seat design is presented in which the seatback is automatically rotated into a more upright position prior to impact in order to increase the energy absorbing potential of the seatback. The study involves computer simulation of a seat-occupant system to demonstrate the benefits of the proposed system. © 2020 Kaunas University of Technology. All rights reserved.
Santrifüj Pompada Spiral Gövdenin Akışa Dik Kesit Alanının Pompa Performansına Etkisinin Sayısal Olarak İncelenmesi
(2017) Özbilgin, Onur; Türkoğlu, Haşmet
Citation - Scopus: 2
A Simple Way for Estimating Mechanical Properties From Stress-Strain Diagram Using Matlab and Mathematica
(Institute of Electrical and Electronics Engineers Inc., 2019) Yilmaz, E.; Yavuz, S.
In this paper, mechanical properties of materials, e.g. ultimate tensile strength, yield stress, elastic modulus, ductility, resilience, toughness, etc., are calculated using MATLAB and Mathematica programming language and stress-strain data of any alloy. © 2019 IEEE.
Citation - WoS: 30
Citation - Scopus: 34
Performance and Surface Alloying Characteristics of Cu-Cr and Cu-Mo Powder Metal Tool Electrodes in Electrical Discharge Machining
(Taylor & Francis inc, 2016) Uslan, Ibrahim; Usta, Yusuf; Cogun, Can; Gulcan, Orhan
The main objective of this study is to investigate the effect of Cu-Cr and Cu-Mo powder metal (PM) tool electrodes on electrical discharge machining (EDM) performance outputs. The EDM performance measures used in the study are material removal rate (MRR), tool electrode wear rate (EWR), average workpiece surface roughness (R-a), machined workpiece surface hardness, abrasive wear resistance, corrosion resistance, and workpiece alloyed layer depth and composition. The EDM performance of Cu-Cr and Cu-Mo PM electrodes produced at three different mixing ratios (15, 25, and 35wt% Cr or Mo), compacting pressures (P-c = 600, 700, and 800MPa), and sintering temperatures (T-s = 800, 850, and 900 degrees C) are compared with those machined with electrolytic Cu and Cu PM electrodes when machining SAE 1040 steel workpiece. Analyses revealed that tool materials were deposited as a layer over the work surface yielding high surface hardness, strong abrasion, and corrosion resistance. Moreover, the mixing ratio, P-c, and T-s affect the MRR, EWR, and R-a values.
Citation - Scopus: 2
Effects of Earthquake Motion on Mechanism Operation: an Experimental Approach
(Levrotto and Bella, 2015) Selvi, Ö.; Selvi, Özgün; Ceccarelli, M.; Aytar, E.B.; Makine Mühendisliği
This paper presents an experimental characterization of the effects of earthquakes on the operation of mechanical systems with the help of CaPaMan (Cassino Parallel Manipulator), which is a 3 DOF robot that can fairly well simulate 3D earthquake motion. The sensitivity of operation characteristics of machinery to earthquake disturbance is identified and characterized through experimental tests. Experimental tests have been carried out by using a slider-crank linkage, a small car model, and LARM Hand as test-bed mechanisms that have been sensored with proper acceleration or force sensors. Results are reported and discussed to describe the effects of earthquake motion on the characteristics of mechanism operation as a service application of the robotic CaPaMan system.
Citation - WoS: 16
Citation - Scopus: 18
Electrostatic Energy Harvesting by Droplet-Based Multi-Phase Microfluidics
(Springer Heidelberg, 2012) Kulah, Haluk; Yildirim, Ender
This paper presents an energy scavenging technique, merging microfluidics with electrostatic energy harvesting. The method employs droplet-based microflow of two phases with different electrical permittivities, resulting in a capacitance change across the microchannel, to harvest electrical energy. The technique is implemented on 3 mm wide, 1 mm deep minichannels. It is shown that 0.4 nW can be harvested using a single electrode pair, with air and water as the two phases flowing at 1 ml/min. The generated power can be increased significantly by microscale implementation, where the number of electrodes can also be increased for further improvement.
Citation - WoS: 1
Citation - Scopus: 3
C3: Configurable Can Fd Controller: Architecture, Design and Hardware Implementation
(Ieee, 2017) Afsin, Mehmet Ertug; Schmidt, Klaus Werner; Schmidt, Ece Guran
CAN FD (Controller Area Network with Flexible Data Rate) is a new standard which provides a fast data rate while preserving the compatibility with CAN. In this paper, we propose the C-3 (Configurable CAN FD Controller) IP core architecture, which is compatible with the non-ISO CAN FD standard. C-3 supports up to 96 transmit and receive buffers. The transmit buffers are organized as mailboxes with CAN ID prioritization in frame transmission. A separate filter mask that can be configured by the user exists for each receive buffer. Different from existing CAN/CAN FD controllers, the numbers and sizes of transmit and receive buffers of C-3 can be configured at run time. To this end, C-3 enables the best use of a single controller hardware for different applications and enables improving the real-time communication performance. C-3 communicates with the host device over SPI without any specific interface requirements using the protocol that is developed in the scope of this paper. C-3 is implemented on an FPGA Evaluation Board and its functionality is verified at a data rate of 2 Mbps.
Yüksek Sıcaklık Pem Yakıt Hücresi Mikro-Kojenerasyon Sistemi Tasarımı
(2016) Devrim, Yılser; Üregen, Nurhan; Özgirgin Yapıcı, Ekin
Citation - Scopus: 4
Small-Scale Mechanical Properties of Additively Manufactured Ti-6al
(The University of Texas at Austin, 2020) Totuk, Onat Halis; Haghshenas, M.; Totuk, O.; Masoomi, M.; Thompson, S.M.; Shamsaei, N.; Mekatronik Mühendisliği
This article aims at studying microstructure and nano/micro-scale mechanical responses of Ti-6Al4V fabricated using a Laser-based Powder Bed Fusion (L-PBF) method. To this end, an instrumented depth-sensing nanoindentation system has been used to assess hardness, Young's modulus, strain rate sensitivity and rate dependent plastic deformation of the alloy at different build Orientations (in the Z-plane and X-plane) at ambient temperature. Indentation tests were conducted at constant proportional loading rate of 15 mN/s in a depth-controlled (hind=2000 nm) testing regime. The Microstructure characterizations were performed using optical and scanning electron microscopy to assess the correlations to the mechanical properties achieved by the nanoindentation testing to better establish structure-property relationships for L-PBF Ti-6Al-4V. It is expected that the fine microstructure, developed by fast solidification during the L-PBF process, to directly contribute to the nanoindentation measurements at different strain rates. Copyright © SFF 2017.All rights reserved.
Citation - WoS: 2
Citation - Scopus: 2
Parametric Analysis of an Anti-Whiplash System Composed of a Seat Suspension Arrangement
(Springer Heidelberg, 2015) Ider, Sitki Kemal; Gokler, Mustafa Ilhan; Ozdemir, Mustafa
Neck injuries frequently seen in low-speed rear-end collisions are referred to as whiplash injuries. Most of the proposed anti-whiplash systems in the literature rely on reducing the backset. A relatively new and promising alternative concept is a slideable seat. This study aimed to parametrically analyze an anti-whiplash vehicle seat that can slide backward against a horizontal suspension arrangement composed of a spring and a damper in response to a rear-end collision, and to investigate the effects of the suspension parameters on the injury risk. A simplified model of a slideable vehicle seat is developed, and simulations are conducted in LS-DYNA (R) environment using this slideable seat model and the commercially available finite element model of the BioRID II dummy. The maximum value of the Neck Injury Criterion (NICmax) is used as the measure of the injury risk. As a result, a strong linear inverse correlation is observed between NICmax and the maximum seat sliding distance, while the stiffness and damping coefficients of the suspension are varied. This result is also verified by obtaining the same NICmax value for the same maximum seat sliding distance (although the stiffness and damping coefficients are different). It is also shown that, for a given backset value as large as 60 mm, a slideable seat with the suspension parameters selected to yield a reasonable maximum seat sliding distance such as 100 mm significantly improves NICmax compared to a standard seat. As the maximum seat sliding distance is increased, the injury risk becomes smaller.
EXPERIMENTAL AND NUMERICAL ANALYSIS OF FLOW OVER A PICKUP TRUCK
(2021) İnce, İbrahim Timuçin; Mercan, Hatice; Onur, Nevzat
The drag forces and the overall drag coefficient of a typical pickup truck are investigated experimentally and the 3D numerical analysis is performed. A detailed 1/4-scale model is constructed and experiments are performed at Reynolds numbers around 2 × 106in the Ankara Wind Tunnel (ART). The experimental study is divided into two stages: in the first stage the pressure distribution along the symmetry axis is measured and in the second stage the drag forces and overall drag coefficient are measured at five different wind speeds. The measured data are compared with the 3D numerical simulation performed in FLUENT. The turbulence standard, realizable, and RNG k-∈ models, the standard and SST k-ω models, and finally the RSM are compared for three near-wall treatments: standard wall function, nonequilibrium wall function, and enhanced wall function. The comparison revealed that for lower velocities the best turbulence model-wall treatment couple is the realizable k-∈ model with Reynolds stress model with standard wall function, whereas for higher velocities the standard k-∈ turbulence model is observed to be more compatible with experimental data. The highest pressure value is measured in front of the pickup truck and the lowest pressure value is evaluated at the rim where the windshield and the roof meet. © 2021 Begell House Inc.. All rights reserved.
Simultaneous Detection of Two Different Bacteria Using QDs and MNPs
(2016) Doğan, Üzeyir; Kasap, Esin Nagihan; Çoğun, Ferah; Yıldırım, Ender; Çetin, Demet; Suludere, Zekiye; Boyacı, İsmail Hakkı; Ertaş, Nusret; Tamer, Uğur
A fast and optimal static segment scheduling method for FlexRay v3.0
(IEEE, 2017) Çakmak, Cumhur; Schmidt, Ece Güran; Schmidt, Klaus Werner
We propose a novel and fast frame scheduling method for the Static Segment (SS) of the new in-vehicle network standard FlexRay v3.0 in this paper. The proposed methods assigns frames to the SS using the minimum number of time slots based on an Integer Linear Programming formulation. Different. from the existing method in the literature, the proposed method computes optimal frame schedules within miliseconds.
Citation - WoS: 2
Citation - Scopus: 1
Exploring the Potential of Artificial Intelligence Tools in Enhancing the Performance of an Inline Pipe Turbine
(Sage Publications Ltd, 2024) Celebioglu, Kutay; Ayli, Ece; Cetinturk, Huseyin; Tascioglu, Yigit; Aradag, Selin
In this study, investigations were conducted using computational fluid dynamics (CFD) to assess the applicability of a Francis-type water turbine within a pipe. The objective of the study is to determine the feasibility of implementing a turbine within a pipe and enhance its performance values within the operating range. The turbine within the pipe occupies significantly less space in hydroelectric power plants since a spiral casing is not used to distribute the flow to stationary vanes. Consequently, production and assembly costs can be reduced. Hence, there is a broad scope for application, particularly in small and medium-scale hydroelectric power plants. According to the results, the efficiency value increases on average by approximately 1.5% compared to conventional design, and it operates with higher efficiencies over a wider flow rate range. In the second part of the study, machine learning was employed for the efficiency prediction of an inline-type turbine. An appropriate Artificial Neural Network (ANN) architecture was initially obtained, with the Bayesian Regularization training algorithm proving to be the best approach for this type of problem. When the suitable ANN architecture was utilized, the prediction was found to be in good agreement with CFD, with an root mean squared error value of 0.194. An R2 value of 0.99631 was achieved with the appropriate ANN architecture.
Citation - WoS: 7
Citation - Scopus: 7
Development and Experimental Investigation of Electrochemical Drilling Method Using Rotary Tube Tool
(Gazi Univ, Fac Engineering Architecture, 2013) Ozerkan, H. Bekir; Çoğun, Can; Cogun, Can; Mekatronik Mühendisliği
In this study, a new hybrid electrochemical drilling (ECD) method, based on electrochemical machining in nonconventional machining processes, was developed. In the developed method, tube tool makes rotary motion together with inner through hole flushing. A small scale prototype ECD machine has been designed and manufactured to test the developed method. One of the important features of the new system is the regulation of tool feed rate using current feedback control. The Hadfield (manganese) steel, whose strain hardening behavior makes it very difficult to machine with conventional methods, and AISI 1040 steel, whose machinability is fairly good, were drilled using the prototype machine and results were compared. Workpiece material removal rate increased with the increasing machining voltage, tool rotational speed, electrolyte concentration and flushing pressure in both types of steels. Average radial overcut values increased with the rotational speed of the tool. The AISI 1040 steel hole geometries were regular than that of Hadfield steel. Experimental results showed that deep holes can be drilled successfully with the proposed hybrid ECD method.
Citation - WoS: 2
Citation - Scopus: 3
On the Stability of Inverse Dynamics Control of Flexible-Joint Parallel Manipulators in the Presence of Modeling Error and Disturbances
(Tubitak Scientific & Technological Research Council Turkey, 2019) Korkmaz, Ozan; Denizli, Mustafa Semih; Ider, Sitki Kemal
Inverse dynamics control is considered for flexible-joint parallel manipulators in order to obtain a good trajectory tracking performance in the case of modeling error and disturbances. It is known that, in the absence of modeling error and disturbance, inverse dynamics control leads to linear fourth-order error dynamics, which is asymptotically stable if the feedback gains are chosen to make the real part of the eigenvalues of the system negative. However, when there are modeling errors and disturbances, a linear time-varying error dynamics is obtained whose stability is not assured only by keeping the real parts of the frozen-time eigenvalues of the system negative. In this paper, the stability of such systems is investigated and it is proved that the linear time-varying system can be rendered stable by selecting the feedback gains such that the variation of the system becomes sufficiently slow. To illustrate the performance of the control method, deployment motion of a 3-(R) under bar PR planar parallel manipulator subject to impact is simulated. For the impact model, the impulse-momentum and the coefficient of restitution equations for the system are derived.
Citation - WoS: 3
Citation - Scopus: 5
Optimization of Vortex Promoter Parameters To Enhance Heat Transfer Rate in Electronic Equipment
(Asme, 2020) Ayli, Ece; Bayer, Ozgur
In this paper, optimization of the location and the geometry of a vortex promoter located above in a finned surface in a channel with eight heat sources is investigated for a Reynolds number of 12,500 < Re < 27,700. Heat transfer rates and the corresponding Nusselt number distributions are studied both experimentally and numerically using different vortex promoter geometries (square, circular, and triangular) in different locations to illustrate the effect of vortex promoter on the fluid flow. Optimization study considered a range of following parameters: blockage ratio of 0.30<(y/C) < 0.45 and interpromoter distance ratio of 0.2277 <(x/L) < 0.3416. Results show that fins over which rectangular and circular promoters are integrated perform better in enhancing the heat transfer. According to the numerical and experimental results, higher blockage ratios cause significantly higher heat transfer coefficients. According to the observations, as the interpromoter distances increase, shedding gains strength, and more turbulence is created. All vortex promoters enhance heat transfer resulting in lower temperature values on the finned surface for different (y/C) and (x/L) values and Reynolds numbers. The use of promoters enhances the heat transfer, and the decrease in the maximum temperature values is recorded on the finned surface changing between 15% and 27%. The biggest decrease in maximum surface temperature value is 500 K-364 K and observed in circular promoter case with (y/C) = 0.43, (x/L) = 0.3416, and Reynolds numbers of 22,200.
Citation - WoS: 5
Citation - Scopus: 6
Prediction of the Heat Transfer Performance of Twisted Tape Inserts by Using Artificial Neural Networks
(Korean Soc Mechanical Engineers, 2022) Kocak, Eyup; Ayli, Ece
A numerical study is undertaken to investigate the effect of twisted tape inserts on heat transfer. Twisted tapes with various aspect ratios and single, double, and triple inserts are placed inside a tube for Reynolds numbers ranging from 8000 to 12000. Numerical results show that the tube with a twisted tape and different numbers of tape is more effective than the smooth tube in terms of thermo-hydraulic performance. The highest heat transfer is achieved with the triple insert, with the highest turning number and an increment of 15 %. Then, an artificial neural network (ANN) model with a three-layer feedforward neural network is adopted to obtain the Nusselt number on the basis of four inputs for a heated tube with a twisted insert. Several configurations of the neural network are examined to optimize the number of neurons and to identify the most appropriate training algorithm. Finally, the best model is determined with one hidden layer and thirteen neurons in the layer. Bayesian regulation is chosen as the training algorithm. With the optimized algorithm, excellent precision for measuring the output is provided, with R2 = 0.97043. In addition, the optimized ANN architecture is applied to similar studies in the literature to predict the heat transfer performance of twisted tapes. The developed ANN architecture can predict the heat transfer enhancement performance of similar problems with R2 values higher than 0.93.
Design, Production, Theoretical And Experimental Analysis Of Parabolic Trough Solar Collector With Sun Tracking Mechanism
(2017) Özgirgin Yapıcı, Ekin; Ünver, Eymen; Çelik, Damla; Tercan, Furkan; Ünalan, Emre; Taşkan, Gökhan
Citation - WoS: 12
Citation - Scopus: 11
Effect of Constitutive Material Model on the Finite Element Simulation of Shear Localization Onset
(Elsevier, 2020) Yilmaz, Okan Deniz; Oliaei, Samad Nadimi Bavil
One of the most challenging problems in the field of machining is to determine the onset of shear localization. The consequences of the emergence of shear localized chips are fluctuations in the machining forces, tool wear, deterioration of the surface quality and out-of-tolerance machined components. Several constitutive material models are developed for the simulation of shear localization during machining, especially for Ti6Al4V. However, the accuracy and capability of the proposed models for the prediction of shear localization onset have not been investigated yet. In this study, the effect of different constitutive material models in the prediction of shear localization onset has been investigated. Different material models are studied including the Johnson-Cook (J-C) material model with Cockcroft-Latham damage model, J-C material model with a J-C damage model, models based on modified J-C material models (MJ-C) with strain softening terms, and material model with power-law type strain hardening and strain rate sensitivity, with polynomial thermal softening and polynomial temperature-dependent damage. The results of the finite element models are verified using orthogonal cutting experiments in terms of chip morphology and machining forces. Metallography techniques are used along with SEM observations to elucidate the distinction between continuous and shear localized chips. The results of this study indicate that three models are capable of predicting shear localization onset. However, when compared to the experiments, where a critical cutting speed of 2.8 m/min is obtained for shear localization onset, the results revealed that the model proposed by Sima and Ozel (2016) which is a model based on MJ-C model with temperature-dependent overarching modifier and temperature-dependent material model parameters is more accurate for the prediction of shear localization onset during machining Ti6Al4V. This model is shown to reveal a good prediction for the machining forces as well.

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