Makine Mühendisliği Bölümü Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/206

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Axial free vibration analysis of a tapered nanorod using Adomian decomposition method
(TECHNO-PRESS, 2025) Coskun, Safa B.; Kara, Ozge; Atay, Mehmet T.; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Atay, Mehmet T.
This study aimed to conduct an analysis of the axial free vibration of tapered nanorods based on nonlocal elasticity theory. The small-scale effect on the free axial vibration of a tapered nanorod was studied employing the Adomian decomposition method (ADM) and the finite difference method (FDM) as a checking tool where a contradiction existed between the results of this study and available results in one highly cited work in the literature, which was used for comparison purposes in this work. Different boundary conditions for the nanorod were considered: fixed-fixed nanorod, fixed-free nanorod, and fixed-linear spring nanorod. The governing equation of the problem is a variable coefficient differential equation for which analytical solutions are strictly limited. For this type of problem, analytical approximate methods are effective, and there are many studies available in the literature on the application of these methods to solve linear/nonlinear ordinary/partial differential equations. ADM is one of the methods and was successfully used in this study to analyze the free vibration of nanorods. The results obtained in this study have shown that the presented technique is so powerful and has potential for applications in nanomechanics based on nonlocal elasticity theory.
Effect of bio-mimicked surface texturing on the shear strength of additively manufactured metal single-lap joints: An innovative approach
(PERGAMON-ELSEVIER SCIENCE LTD, 2025) Atahan, M. Gokhan; Maskery, Ian; Ashcroft, Ian; Apalak, M. Kemal; Pappas, Athanasios; 0000-0002-8180-5876; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Atahan, M. Gokhan
In this paper, we investigate the mechanical performance of metal single-lap joints featuring bio-mimicking surface textures. The inspiration for the surface textures was the foot and toe of the gecko, a creature whose ability to climb smooth shear surfaces is attributed to the mesoand micro-structures of its feet. Three surface textures were investigated: a hexagonal texture based on the central region of the foot, a lamellae-like texture based on the toe, and a mixed texture of both. Metal adherends with these textures were produced using the laser powder bed fusion (LPBF) additive manufacturing method. Finite element analysis was performed to examine the influence of surface texture on stress distribution in the adhesive layer, while mechanical testing was used to determine joint strength and failure mode. Compared to the as- printed surface texture, bio-mimicking surface textures improved the wettability of the bonding surfaces, and significantly improved the lap shear strength of the joints. Mechanical interlocking due to surface texture was more effective than the increase in bonding surface area in enhancing joint strength. The bio-mimicking textures improved the damage tolerance capacity of the joints by reducing local stress concentrations at the overlap edges of the adhesive layer and ensured that the adhesive failure type was mixed mode due to the mechanical interlocking effect. The presented novel bio-mimicked surface texture method offers promising results for both industrial applications and scientific studies.
Basalt Fiber Reinforced Polymers: A Recent Approach to Electromagnetic Interference (EMI) Shielding
(WILEY Online Library, 2025) Fareez, Umar Naseef Mohamed; Loudiy, Aymen; Erkartal, Mustafa; Yilmaz, Cagatay; 0000-0001-9763-6598; 0000-0002-9772-128X; 0000-0002-8063-151X; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Fareez, Umar Naseef Mohamed; Loudiy, Aymen; Yilmaz, Cagatay
Electromagnetic wave (EMW) radiation pollution is getting more severe as result of the advancement of electronic technology. Researching shielding materials with superior EMI (electromagnetic interference) shielding characteristics is therefore crucial. Basalt fibers (BFs) have been an emerging candidate in the fiber-reinforced polymer (FRP) category due to their favorable mechanical and chemical properties, along with being favorites in sustainability and having low production costs. Therefore, due to the rising need for cheaper and efficient alternatives in the EMI shielding industry, the EMI shielding is covered in terms of BF composite materials and their properties in this review, starting with the EMI shielding mechanism and followed by how BF composites affect the EMI properties. This review then covers the post-treatments of BF composites and, finally, the factors of the composites that affect the EMI properties. Moreover, the EMI shielding applications in which BFRPs are used are comprehensively discussed as well. This review aspires to bridge an understanding between EMI shielding as a material property and the BF composites that are developed to aid in the EMI shielding application.
APPLICATION OF HOOKE’S LAW TO ANGLE PLY LAMINA
(ESKİŞEHİR TEKNİK ÜNİVERSİTESİ, 2022) Yılmaz, Çağatay; Ali, Hafiz Qasim; Yıldız, Mehmet; 0000-0002-8063-151X; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Yılmaz, Çağatay
Aerospace-grade carbon fiber reinforced polymer composite plates with four different fiber orientations 0º, 30º, 45ºand 60º is produced with the autoclave curing method and subjected to tensile testing. The stress-strain curves of the composite specimens are compared with Hooke’s law. It is observed that Hooke’s law coincides precisely with the experimental results for samples containing fibers parallel to the loading direction. However, it does not coincide with samples where the fibers make a certain angle with the applied load direction. Moreover, it is reported that Hooke’s law converges the experimental results for small strain values but diverges significantly from the experimental results at higher strain values.
Compression performance of 3D-printed ant-inspired lattice structures: An innovative design approach
(Sage Journals, 2025) Atahan, Mithat Gokhan; Saglam, Selman; 0000-0002-8180-5876; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Atahan, Mithat Gokhan; Saglam, Selman
In this study, three different ant-inspired lattice design types: single, double, and inverted double structures were considered due to ants' excellent load-carrying weight ratio. Lattice structures were fabricated using the 3D printing method and polylactic acid filament was used as a printing material. The true blueprint images of the ant were used to obtain the parametric dimensions of the ant-inspired lattice structure. Hence, the presented innovative method for designing lattice structures can be a promising option for industrial sectors requiring high-strength structures. The quasi-static axial compression tests were conducted to evaluate the compression performance of the novel lattice structures. The compression performance of ant-inspired single lattice structures was compared based on specific force, specific energy absorption, and specific stiffness at different height values. The deformation stages and damage regions of ant-inspired lattice structures were analyzed to identify their critical regions during compression tests. The results indicated that as the height value increased, there was a notable decrease in specific force, specific energy absorption, and specific stiffness, along with buckling damage in the ant-inspired single lattice structures. Among the three design types, the ant-inspired inverted double lattice structure showed better compression performance compared to the ant-inspired double lattice structure; however, the ant-inspired single lattice structure with a height of 30 mm exhibited the highest overall compression performance.
Computational Fluid Dynamics (CFD) Analysis of Bioprinting
(John Wiley and Sons Inc, 2024) Fareez, Umar Naseef Mohamed; Naqvi, Syed Ali Arsal; Mahmud, Makame; Temirel, Mikail; 0000-0002-8199-0100; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Fareez, Umar Naseef Mohamed; Naqvi, Syed Ali Arsal; Mahmud, Makame; Temirel, Mikail
Regenerative medicine has evolved with the rise of tissue engineering due to advancements in healthcare and technology. In recent years, bioprinting has been an upcoming approach to traditional tissue engineering practices, through the fabrication of functional tissue by its layer-by-layer deposition process. This overcomes challenges such as irregular cell distribution and limited cell density, and it can potentially address organ shortages, increasing transplant options. Bioprinting fully functional organs is a long stretch but the advancement is rapidly growing due to its precision and compatibility with complex geometries. Computational Fluid Dynamics (CFD), a carestone of computer-aided engineering, has been instrumental in assisting bioprinting research and development by cutting costs and saving time. CFD optimizes bioprinting by testing parameters such as shear stress, diffusivity, and cell viability, reducing repetitive experiments and aiding in material selection and bioprinter nozzle design. This review discusses the current application of CFD in bioprinting and its potential to enhance the technology that can contribute to the evolution of regenerative medicine.
Hydrogen susceptibility of Al 5083 under ultra-high strain rate ballistic loading
(Walter de Gruyter GmbH, 2024) Baltacioglu, Mehmet Furkan; Mozafari, Farzin; Aydin, Murat; Cetin, Baris; Oktan, Aynur Didem; Teoman, Atanur; Li, Yang; Bal, Burak; 0000-0001-8218-4410; 0000-0002-7389-9155; 0000-0001-6476-0429; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Baltacioglu, Mehmet Furkan; Mozafari, Farzin; Bal, Burak
The effect of hydrogen on the ballistic performance of aluminum (Al) 5083H131 was examined both experimentally and numerically in this study. Ballistics tests were conducted at a 30° obliquity in accordance with the ballistic test standard MIL-DTL-46027 K. The strike velocities of projectiles were ranged from 240 m s−1 to 500 m s−1 level in the room temperature. Electrochemical hydrogen charging method was utilized to introduce hydrogen into material. Chemical composition of material was analyzed using energy dispersive X-ray (EDX) analysis. Instant camera pictures were captured using high-speed camera to compare H-uncharged and H-charged specimen ballistics tests. The volume loss in partially penetrated specimens were assessed using the 3D laser scanning method. Microstructural examinations were conducted utilizing scanning electron microscopy (SEM). It was observed that with the increased deformation rate, the dominance of the HEDE mechanism over HELP became evident. Furthermore, the experimental findings were corroborated through numerical methods employing finite element analysis (FEM) along with the Johnson–Cook plasticity model and failure criteria. Inverse optimization technique was employed to implement and fine-tune the Johnson–Cook parameters for H-charged conditions. Upon comparing the experimental and numerical outcomes, a high degree of consistency was observed, indicating the effective performance of the model.
A phenomenological hydrogen induced edge dislocation mobility law for bcc Fe obtained by molecular dynamics
(ELSEVIER, 2024) Baltacioglu, Mehmet Furkan; Kapci, Mehmet Fazil; Schön, J. Christian; Marian, Jaime; Bal, Burak; 0000-0002-7389-9155; 0000-0001-6476-0429; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Baltacioglu, Mehmet Furkan; Kapci, Mehmet Fazil; Bal, Burak
Investigating the interaction between hydrogen and dislocations is essential for understanding the origin of hydrogen-related fractures, specifically hydrogen embrittlement (HE). This study investigates the effect of hydrogen on the mobility of ½<111>{110} and ½<111>{112} edge dislocations in body-centered cubic (BCC) iron (Fe). Specifically, molecular dynamics (MD) simulations are conducted at various stress levels and temperatures for hydrogen-free and hydrogen-containing lattices. The results show that hydrogen significantly reduces dislocation velocities due to the pinning effect. Based on the results of MD simulations, phenomenological mobility laws for both types of dislocations as a function of stress, temperature and hydrogen concentration are proposed. Current findings provide a comprehensive model for predicting dislocation behavior in hydrogen-containing BCC lattices, thus enhancing the understanding of HE. Additionally, the mobility laws can be utilized in dislocation dynamics simulations to investigate hydrogen-dislocation interactions on a larger scale, aiding in the design of HE-resilient materials for industrial applications.
Experimental and statistical damage analysis in milling of S2-glass fiber/epoxy and basalt fiber/epoxy composites
(John Wiley and Sons Inc, 2024) Sayin, Ahmed Cagri; Danisman, Sengul; Ersoy, Emin; Yilmaz, Cagatay; Kesriklioglu, Sinan; 0000-0002-8063-151X; 0000-0002-2914-808X; 0009-0008-8666-7995; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Sayin, Ahmed Cagri; Yilmaz, Cagatay; Kesriklioglu, Sinan
S2-glass fiber reinforced plastics (S2-GFRP) and basalt fiber reinforced plastics (BFRP) have emerged as crucial materials due to their exceptional mechanical properties, and milling of composite materials plays an important role in achieving desired properties. However, they have proven challenges due to relative inhomogeneity compared with metals, resulting unpredictability in quality of milling operations. The objective of this work is to investigate the effect of cutting parameters, tool geometry and tool surface materials on the surface quality of composites using burrs as a metric. S2-GFRP and BFRP composites were produced by the vacuum infusion method. Helical and straight flute end mills were manufactured from high-speed steel (HSS) and carbide rounds, and half of them were coated with titanium nitride using reactive magnetron sputtering technique. Taguchi L18 orthogonal array is used to determine the effect of tool material, tool angle, coating, cutting direction, spindle speed, and feed rate on the machining quality of S2-GFRPs and BFRPs with respect to burr formations. Milling experiments were conducted under dry conditions and then the burrs were imaged to calculate the total area and length. Statistical analysis was also performed to optimize the machining parameters and tool type for ensuring the structural integrity and performance of the final composite parts. The results showed that the selection of tool material has the most significant impact on the burr area and length of the machined surface. The novel image analysis allows to analyze the extent of the burr size with a desirable operation speed for industrial applications. Highlights: Aerospace grade S2-Glass (S2-GFRP) and basalt fiber reinforced plastics (BFRP) were manufactured. Carbide and HSS end mills were fabricated and coated with titanium nitride protective layer. FRPs were machined at various process parameters designed by Taguchi method. Distinctive image processing was firstly used to compute milling induced Burr area and length. Statistical analysis was performed to quantify the contribution of parameters and optimize milling.
Design analysis of a wave energy converter for hydrogen generation near shoreline of Black Sea
(Institution of Chemical Engineers, 2024) Bekçi, Eyüp; Koca, Kemal; Bashir, Muhammad Farhan; 0000-0003-2464-6466; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Bekçi, Eyüp; Koca, Kemal
The generation of electricity from waves has attracted a lot of attention from researchers lately. Despite the vastness and accessibility of wave energy across the majority of the planet, there is a dearth of literature on the production of electricity and hydrogen from wave power. In this paper, a comprehensive simulation related to hydrogen production with an oscillating wave surge converter (OWSC) system was employed for the Black Sea region. The simulations were performed by means of Homer-Pro software and the data were provided thanks to European Marine Observation and Data Network (EMODnet) as well as a novel web-based tool with regards to wave resources. Initial results of web-based tool showed that the hydrogen generation was directly impacted by considerable wave height and wave energy period. As a result, it may change based on the days and months. May had the lowest monthly energy production (3 MWh), while December had the highest monthly energy production (27 MWh). Moreover, the electrolyzers with different efficiencies were investigated with Homer-Pro. The electrolyzer with an efficiency of 85% at 100 kW produced 3301 kg annually, whereas the electrolyzers with 90% and 95% efficiency at 100 kW produced 3419 kg annually and 3422 kg annually, respectively. Apart from those findings, when more efficient electrolyzers were employed in the system, both the capital and replacement costs dropped at the same time.
Compensating energy demand of public transport and yielding green hydrogen with floating photovoltaic power plant
(Institution of Chemical Engineers, 2024) Koca, Kemal; 0000-0003-2464-6466; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Koca, Kemal
The last three decades have seen a dramatic increase in the renewable energy sector as a result of increased human energy consumption and environmental concerns about fossil fuels. Offshore renewable energy sources are the most alluring and promising technologies because of more energy potential, less space, and visual restrictions than onshore ones. Among those, floating solar photovoltaic (FPV) has a remarkable reputation. The present study focuses on a viable way to replace energy resources derived from fossil fuels with renewable solar energy. In this regard, electrical energy demand is investigated where a floating photovoltaic system and integrated hydrogen production unit are employed on water surface of Yamula Dam. Energy demand of public trams would be compensated with electricity generated by FPV and rest of energy would be utilized for hydrogen production. Key results illustrated that in various scenarios, the energy generation amounts were around 31×106 kW, 32×106 kW, and 39×106 kW, while the energy consumption amounts were approximately 24×106 kW. It was evident that the energy created more than offset the amount consumed. It was also note that the total costs of entire system were $94.1 M, $78.5 M and $71.2 M according to the different cases. It was also observed that in October and November, the remaining energy from the Bozankaya tram produced the most hydrogen with 125 kg, whereas in September and October, the remaining energy from the Sirio tram produced approximately 70 kg.
Edge dislocation depinning from hydrogen atmosphere in α-iron
(Acta Materialia Inc, 2024) Kapci, Mehmet Fazil; Yu, Ping; Liu, Guisen; Shen, Yao; Li, Yang; Bal, Burak; Marian,Jaime; 0000-0002-7389-9155; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Kapci, Mehmet Fazil; Bal, Burak
Understanding the dislocation motion in hydrogen atmosphere is essential for revealing the hydrogen-related degradation in metallic materials. Atomic simulations were adopted to investigate the interaction between dislocations and hydrogen atoms, where the realistic hydrogen distribution in the vicinity of the dislocation core was emulated from the Grand Canonical Monte Carlo computations. The depinning of edge dislocations in α-Fe at different temperatures and hydrogen concentrations was then studied using Molecular Dynamics simulations. The results revealed that an increase in bulk hydrogen concentration increases the flow stress due to the pinning effect of solute hydrogen. The depinning stress was found to decrease due to the thermal activation of the edge dislocation at higher temperatures. In addition, prediction of the obtained results was performed by an elastic model that can correlate the bulk hydrogen concentration to depinning stress.
Role of Partial Flexibility on Flow Evolution and Aerodynamic Power Efficiency over a Turbine Blade Airfoil
(MDPI, 2024) Koca, Kemal; Genç, Mustafa Serdar; 0000-0003-2464-6466; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Koca, Kemal
In this study, the aerodynamic performance of a cambered wind turbine airfoil with a partially flexible membrane material on its suction surface was examined experimentally across various angles of attack and Reynolds numbers. It encompassed physical explanation at the pre/post-stall regions. The results of particle image velocimetry revealed that the laminar separation bubble was diminished or even suppressed when a local flexible membrane material was employed on the suction surface of the wind turbine blade close to the leading edge. The results of the deformation measurement indicated that the membrane had a range of flow modes. This showed that the distribution of aerodynamic fluctuations due to the presence of LSB-induced vortices was reduced. This also led to a narrower wake region occurring. Aerodynamic performance improved and aerodynamic vibration significantly lowered, particularly at the post-stall zone, according to the results of the aerodynamic force measurement. In addition to the lift force, the drag force was enormously reduced, corroborating and matching well with the results of PIV and deformation measurements. Consequently, significant benefits for a turbine blade were notably observed, including aerodynamic performance enhancement, increased aerodynamic power efficiency, and reduced aerodynamic vibration.
Comparative study on bending behavior and damage analysis of 3D-printed sandwich core designs with bio-inspired reinforcements
(ELSEVIER, 2024) Atahan, M. Gokhan; Erikli, Merve; Ozipek, Enes; Ozgun, Fulya; 0000-0002-8180-5876; 0009-0009-4624-3319; 0009-0009-9408-077X; 0009-0002-8198-4525; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Atahan, M. Gokhan; Erikli, Merve; Ozipek, Enes; Ozgun, Fulya
In this study, novel sandwich core designs with bio-inspired reinforcements were proposed and their bending behaviors were comparatively examined. The geometrical shapes of alligator osteoderm and chambered nautilus shell were utilized as bio-inspired reinforcements for sandwich core structures. Sandwich core structures were produced through the additive manufacturing method. Experimental tests and finite element analysis were performed to determine the bending performances of the proposed sandwich core structures. The loadcarrying capacity, deformation ability, damage-tolerant capability, energy absorption, and damage mechanisms of the proposed sandwich core structures were comparatively investigated through experimental and numerical methods. The orthotropic material model and Hashin’s damage criterion were used in the numerical model of 3D-printed sandwich core structures to consider the effect of the filament raster orientation on the elastic and damage behavior of the sandwich core structures. Compared to the classical honeycomb sandwich core structure, while bio-inspired reinforcements improved the load-carrying capacity and damage-tolerant capability of sandwich core structures, they reduced the energy absorption ability of sandwich core structures due to reducing the vertical deformation ability of sandwich core structures. Bio-inspired reinforcements significantly affected the stress distribution and damage behavior of the sandwich core structures. They reduced von Mises stress level at the outer cell edges of the sandwich core structures and caused reinforcement damage instead of outer cell damage.
Indirect internal reforming SOFC accommodating graded-catalytic domain fabricated by paper-structured catalyst
(Electrochemical Society Inc., 2019) Aydin, Özgür; Matsumoto, Go; Kubota, Atsushi; Tran, Dang Long; Sakamoto, Mio; Shiratori, Yusuke; 0000-0002-8814-6025; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Aydin, Özgür
Biogas can be directly utilized in Solid Oxide Fuel Cells (SOFCs), as it can be reformed to H2-rich mixture in the anode of SOFCs. However, the rate of reforming reaction significantly changes along the flow field due to the rapid conversion of CH4 in the inlet region. Since the reforming reactions are endothermic, a dramatic temperature gradient develops along the flow field, resulting in thermal stresses on the adjacent SOFC components. Taking the reforming reactions out of SOFC domain by indirect internal reforming reduces the thermal stresses to an extent, which can be further mitigated by designing a graded catalytic domain for an even temperature distribution. In this study, we demonstrate a reliable and durable operation of SOFC equipped with an indirect internal reformer graded in terms of catalyst loading.
INVESTIGATION OF TEMPERATURE AND PRESSURE EFFECT ON THE HYDROGEN SORPTION KINETICS IN THE INTERFACE OF Mg/MgH2 BY MOLECULAR DYNAMICS
(International Association for Hydrogen Energy, IAHE, 2022) Kapçı, Mehmet Fazıl; Wu, Zhen; Bal, Burak; 0000-0002-7389-9155; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Kapçı, Mehmet Fazıl; Bal, Burak
Molecular dynamics simulations were performed in order to analyze the hydrogen sorption kinetics between αMgH2 and hcp Mg structures under different temperatures and pressures. Results showed that hydrogen desorption from magnesium hydride and absorption by hcp magnesium increase at the higher temperatures. During the hydrogen desorption from magnesium hydride and absorption into hcp magnesium, crystallographic orientation change in the magnesium atoms was observed. At 400 °C, the pressure was found to have a negative impact during the hydrogen desorption from magnesium hydride due to the prevention of recrystallization.
The Digitized Shoulder: From Preoperative Planning to Patient-Specific Guides
(SPRINGER LINK, 2022) Sadeghi, Majid Mohammad; Kapicioglu, Mehmet; Kececi, Emin Faruk; Bilsel, Kerem; 0000-0001-8561-6960; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Kececi, Emin Faruk
As the information and computer technologies improve, it can change how the shoulder surgeries and treatments are done. Digitalization of the shoulder joint acquired via MR and CT (1) shows the surgeons the pathology in a more easily understandable way, (2) generates models for preoperative planning, and (3) uses special software to generate patient-specific instruments. Digitalization of the shoulder will make the shoulder disorder’s treatment easier and more accurate in the future.
Accurate Prediction of Residual Stresses in Machining of Inconel 718 Alloy through Crystal Plasticity Modelling
(Afyon Kocatepe Üniversitesi, 2023) Kesriklioglu, Sinan; Kapci, Mehmet Fazil; Büyükçapar,Rıdvan; Çetin , Barış; Yılmaz, Okan Deniz; Bal, Burak; 0000-0002-2914-808X; 0000-0003-3297-5307; 0000-0002-2550-7911; 0000-0002-7389-9155; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Kesriklioglu, Sinan; Kapci, Mehmet Fazil; Büyükçapar, Rıdvan; Bal, Burak
Determination and assessment of residual stresses are crucial to prevent the failure of the components used in defense, aerospace and automotive industries. The objective of this study is to present a material method to accurately predict the residual stresses induced during machining of Inconel 718. Orthogonal cutting tests were performed at various cutting speeds and feeds, and the residual stresses after machining of Inconel 718 were characterized by X-ray diffraction. A viscoplastic self-consistent crystal plasticity model was developed to import the microstructural inputs of this superalloy into a commercially available finite element software (Deform 2D). In addition, same simulations were carried out with classical Johnson - Cook material model. The simulation and experimental results showed that the crystal plasticity based multi-scale and multi-axial material model significantly improved the prediction accuracy of machining induced residual stresses of Inconel 718 when compared to the existing model, and it can be used to minimize the surface defects and cost of production trials in machining of difficult-to-cut materials.
GIS-AHP APPROACH FOR A COMPREHENSIVE FRAMEWORK TO DETERMINE THE SUITABLE REGIONS FOR GEOTHERMAL POWER PLANTS IN IZMIR, TÜRKİYE
(Konya Mühendislik, 2024) Koca, Kemal; Karipoğlu, Fatih; Öztürk, Emel Zeray; 0000-0003-2464-6466; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Koca, Kemal
Geothermal energy is gaining more reputation and importance around the world. Correspondingly, suitable location selection is a critical step and has become necessary for the successful installation and operation of geothermal power plants. This study investigated suitability of İzmir region, located in the Aegean part of Türkiye, in terms of geothermal power plants applications by using the combination of Geographical Information System and Analytic Hierarchy Process. Based on the request of power plants, thirteen important criteria were evaluated under three main categories named as physical (C1), environmental (C2) and technical (C3). Moreover, expert’s opinions were taken into consideration to calculate the importance of these criteria. Key results showed that İzmir was suitable for geothermal power plants. The final suitability map layer pointed out that %8.73 (1.037 km2) of total area were determined as highly suitable regions in terms of installation. In addition, the obtained suitability map layer was compared with actual geothermal power plants. Based on the comparison study, power plants in Seferihisar were moderately suitable for geothermal power plants while the location of Balçova power plant was highly suitable. Regarding the suitability assessment in the present study, the location of Dikili power plants had the least suitability score.
Flow properties of an Ahmed Body with different passive flow control methods
(Gazi Üniversitesi, 2024) Koca, Kemal; Özden, Mustafa; 0000-0003-2464-6466; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Koca, Kemal
A numerical simulation by utilizing the FloEFD software was carried out in order to investigate the flow topology formed on slant surface and wake region of an Ahmed Body with and without passive flow control techniques. The effects of those flow controllers on flow at the slant surface and wake region by influencing the flow topology as well as aerodynamic drag coefficient examined carefully. The numerical findings clearly revealed that the best performance in terms of providing the drag reduction obtained when sphere and hemispherical shape flow control techniques were applied at the rear part of slant surface of Ahmed Body. Sphere and hemispherical shape flow controllers positioned at the rear part of slant surface led to have drag reduction of 6% and 7%, respectively. Besides, the results of current study compared with the results obtained from published studies in the literature. It was clearly observed that they are consistent with each other even though they were found by different software.

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