Makine Mühendisliği Bölümü Koleksiyonu

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

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An accurate investigation of the mechanical response and damage model of aluminum 7068
(Abdullah Gül Üniversitesi, 2018) Karaveli, Kadir Kaan; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Karaveli, Kadir Kaan
The promising combination of high strength, high toughness, low density and corrosion resistivity have made aluminium (Al) alloys the material of choice in various applications, from buildings to aerospace, for decades. Especially, Al 7068 alloy is one of the recently developed materials used mostly in defence and automobile industries due to their exceptional mechanical properties. In this master thesis, the mechanical response and Johnson-Cook damage model of Al 7068-T651 alloy was investigated. Specifically, different Johnson-Cook damage parameters were determined for different application areas considering the maximum, minimum and average results. These damage parameters can be used for accurate Finite Element Analysis simulations. To determine these damage parameters tensile tests were conducted on notched and smooth specimen son both rolling direction and perpendicular to the rolling direction. The notch radius were selected as smooth, 0.4 mm, 0.8 mm and 2 mm to provide different stress triaxiality values and observe the mechanical response at these triaxiality values. Tensile tests were repeated seven times to obtain the accurate results. The final cross-sectional areas of fractured specimens were calculated through optical microscopy. The effects of stress triaxiality factor and rolling direction on the mechanical properties of Al 7068-T651 alloy were successfully investigated. All damage parameters were calculated via LevenbergMarquardt optimization method. Overall, three different Johnson-Cook damage parameters based on minimum, average and maximum equivalent strain values were calculated. These Johnson-Cook ii damage parameters can be utilized for the accurate damage simulations of different applications in Finite Element Analysis, which is a computational technique and is used to obtain approximate solution of several engineering problems
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.
Anhydrous proton conducting poly(vinyl alcohol) (PVA)/ poly(2-acrylamido-2-methylpropane sulfonic acid) (PAMPS)/1,2,4-triazole composite membrane
(Elsevier Ltd, 2016) Erkartal, Mustafa; Aslan, Ayse; Erkilic, Ufuk; Dadi, Seyma; Yazaydin, Ozgur; Usta, Hakan; Sen, Unal; 0000-0002-9772-128X; 0000-0003-1849-9180; 0000-0001-8562-723X; 0000-0002-0618-1979; 0000-0003-3736-5049; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Erkartal, Mustafa; Erkılıç, Ufuk; Dadı, Şeyma; Usta, Hakan; Şen, Ünal
The design and fabrication of anhydrous proton exchange membranes are critically important for high temperature proton exchange membrane fuel cell (HT-PEMFC) operating between 100 and 200 °C. Herein, we demonstrate a novel proton conducting membrane consisting of poly(vinyl alcohol) (PVA), poly (2-acrylamido-2-methylpropane sulfonic acid) (PAMPS) and 1,2,4-triazole, which was fabricated by physical blending, casting and solvent evaporation techniques. The in-situ chemical cross-linking was performed by glutaraldehyde (GA) to improve the water management of the membranes. The molecular structure of the membranes and intermolecular interactions between the constituents were confirmed by Fourier-transform infrared spectroscopy (FT-IR). The surface and cross-section morphologies of the membranes were observed by scanning electron microscopy (SEM). The thermal stability performance of the membranes was studied with thermogravimetric analysis (TGA). In order to determine the physico-chemical properties of the membranes, water uptake (WU), dimensional change and ion exchange capacity (IEC) tests were carried out. The proton conductivities of composite membranes increase with the temperature and the temperature dependencies exhibit an Arrhenius behavior. Proton conductivity measurements revealed an optimum ratio between PAMPS and 1,2,4-triazole content to achieve higher proton conductivity. In anhydrous state at 150 °C, the highest proton conductivity measured was 0.002 S/cm for PVA:PAMPS:1,2,4-triazole (1:1:1) composition. Overall, our investigation showed that 1,2,4-triazole is a promising proton carrier reagent above 100 °C when it is embedded into appropriate host polymers.
Application of Classical Lamination Theory to Fused Deposition Method 3-D Printed Plastics and Full Field Surface Strain Mapping
(Afyon Kocatepe Üniversitesi, 2022) Yılmaz, Çağatay; ALI, Hafiz Qasim; Yıldız, Mehmet; 0000-0002-8063-151X; 0000-0001-8288-2737; 0000-0003-1626-5858; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Yılmaz, Çağatay
In this study, five differently oriented sets of 3D-printed tensile samples are produced using the Fused Deposition Method (FDM). Among these five sets, three are used to determine the elastic constant to be used in Classical Lamination Theory (CLT), which is generally used to model fiber-reinforced polymers (FRP). Based on the obtained results, CLT is further applied to the remaining two sets of unreinforced 3D-printed polymer samples where the deposition direction varies in each layer. The stress and strain calculated with CLT are then compared with experimental results obtained through tensile testing. The comparison depicts that experimental and CLT results are in good agreement at lower strain levels. In contrast, the stress calculated with CLT deviates from the experimental result at the higher strain levels.Thereafter, a full-field surface strain mapping is applied by using Digital Image Correlation (DIC) Techniques to reveal the damage progression and failure of Fused Deposition Method 3-D Printed Plastics.
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.
An atomistic study on the HELP mechanism of hydrogen embrittlement in pure metal Fe
(PERGAMON-ELSEVIER SCIENCE LTD, 2024) Hasan, Md Shahrier; Kapci, Mehmet Fazil; Bal, Burak; Koyama, Motomichi; Bayat, Hadia; Xu, Wenwu; 0000-0002-7389-9155; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Kapci, Mehmet Fazil; Bal, Burak
The Hydrogen Enhanced Localized Plasticity (HELP) mechanism is one of the most important theories explaining Hydrogen Embrittlement in metallic materials. While much research has focused on hydrogen's impact on dislocation core structure and dislocation mobility, its effect on local dislocation density and plasticity remains less explored. This study examines both aspects using two distinct atomistic simulations: one for a single edge dislocation under shear and another for a bulk model under cyclic loading, both across varying hydrogen concentrations. We find that hydrogen stabilizes the edge dislocation and exhibits a dual impact on dislocation mobility. Specifically, mobility increases below a shear load of 900 MPa but progressively decreases above this threshold. Furthermore, dislocation accumulation is notably suppressed at around 1 % hydrogen concentration. These findings offer key insights for future research on Hydrogen Embrittlement, particularly in fatigue scenarios.
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.
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.
Biogas intake pressure and port air swirl optimization to enhance the diesel RCCI engine characteristics for low environmental emissions
(Institution of Chemical Engineers, 2024) Dalha, Ibrahim B.; Koca, Kemal; Said, Mior A.; Rafindadi, Aminu D.; 0000-0003-2464-6466; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Koca, Kemal
Exhaust emission and combustion control in RCCI (reactivity-controlled compression ignition) focused mainly on the direct-injected fuel parameters, urging to investigate the advantages of port-fuel intake parameters. The engine was modified for port injection of Biogas at the valve and RCCI mode. The influence of port swirl ratio (PSR, 0 – 80%) and biogas injection pressure (BIP, 1 – 4 bar) on the diesel RCCI combustion and emissions was tested and optimized at varied loads and 1600 rpm in a port injection at the valve (PIVE) approach. Established kinetic mechanisms were combined with multi-objective optimization to further investigate, predict, and analyze emissions occurrence and trade-offs for reduced environmental impacts. The results show that the radiation absorption triggered by increased CO2 lowers combustion temperature, resulting in prolonged ignition. Setting the airflow to swirl lowers the in-cylinder pressure at elevated BIP while raising the heat generated across the BIPs. Increasing the PSR slows the combustion while BIP speeds up the process. BIP and PSR show great trade-off reduction ability among all emission parameters. The optimum unburned hydrocarbon, nitrogen oxide, particulate, and carbon monoxide emissions for the injection at the valve were found to be 109.58, 0.577, and 2.336 ppm, and 0.103%, respectively, at low-load, low-BIP, and high-PSR. The emissions were lowered by 6.58, 91.26, 80.65, and 13.45% compared to the premixed RCCI mode, respectively. Therefore, introducing lowpressure biogas amid high swirling air at the valve elevates the in-cylinder condition while lowering the emissions, mitigating their environmental implications.
Characterization of 3D fabric permeability with skew terms
(ELSEVIER SCI LTDTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 2017) Yun, Minyoung; Sas, Hatice; Simacek, Pavel; Advani, Suresh G.; 0000-0002-5179-2509; 0000-0002-2670-903X; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü
Flow simulations can predict resin flow behavior and void formation locations in a preform. One important parameter for simulation is the preform permeability. For thick parts with distribution media on the surface, resin flow is three dimensional and through the thickness permeability is required for simulation. If the fabric is a 3D preform or unbalanced, the through the thickness (Kzz) and two skew components (Kxz and Kyz) must be characterized. The skew terms influence the flow behavior and hence the void formation. In this study, we present a measurement station that provides all six independent components of the permeability tensor from one experiment. The methodology uses the location data of the flow front with time and then couples it to an optimization algorithm and our flow simulation tool, LIMS (Liquid Injection Molding Simulation). The process is automated and experimental results are superimposed on the simulation results to confirm fidelity of the values determined. (C) 2017 Elsevier Ltd. All rights reserved.
Çok Ölçekli Malzeme Modellemesi Yoluyla Talaşlı İmalat Çıktılarının Daha Kapsamlı Ve Doğru Analizi
(TUBİTAK, 2020) Bal, Burak; LAYEGH KHAVIDAKI, SEYD EHSAN; 0000-0002-7389-9155; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Bal, Burak; LAYEGH KHAVIDAKI, SEYD EHSAN
İnconel 718 savunma sanayi, uzay-havacılık ve otomotiv için kullanılan ve ileride kullanım alanı daha da genişleyebilecek olan süper alaşımdır. Bu projede Inconel 718 süper alaşımının talaşlı imalat sonucunda yüzeyinde oluşan kalıntı gerilimler, sertlik değişimleri ve kesici takımda oluşan aşınmalar gözlenmiştir. Talaşlı imalat simülasyonları için kullanılan Deform 2D programına, klasik Johnson-Cook malzeme modeli yerine, kristal plastisite tabanlı çok ölçekli malzeme davranışı tanıtılarak daha kapsamlı ve deneysel veriye daha yakın analizler yapılmıştır. Bu konunun seçilme nedeni, gerçek deneysel sonuçlara daha yakın sonuçlar elde edilip beklenmedik üretim hataları ve denemeleri en aza indirebilecek bir yöntem geliştirmektir. Bugüne kadar gerçekleştirilen talaşlı imalat simülasyonlarında malzeme davranışı genellikle tek ölçekli gerinim pekleşmesi, gerinim hızı pekleşmesi ve sıcaklık yumuşamasını kapsayan Johnson-Cook malzeme modelleri ile gerçekleştirilmiştir ve bu modeller malzemelerin mikroyapısal girdilerini içermemektedir. Bu projede ise Johnson-Cook malzeme modeli ile ve karşılaştırmalı olarak çok ölçekli kristal plastisite tabanlı malzeme modeli ile 2D deform programında farklı kesme hızlarında ve farklı ilerleme hızlarında simülasyonlar gerçekleştirilmiştir. Bu projede ilk olarak, Inconel 718 malzemesinin talaşlı imalat deneylerini yapılarak sonuçları gözlenmiştir. Daha sonra Johnson-Cook malzeme modellemesiyle gerçekleştirilen simülasyon sonuçları gözlenmiştir. Son olarak da Inconel 718 süper alaşımının kristal plastisite modelinin yapılması ve mikroyapı girdileri ile elde edilen kristal plastisite modeli ile çıkarılan çok ölçekli ve çok eksenli malzeme davranışının Deform 2D simülasyonlarına tanıtılarak simülasyonu gerçekleştirip, elde edilen sonuçlar gözlenmiştir. Yapılan simülasyonlar ve deney sonucunda, iki farklı malzeme modelin deneysel sonuçlarla karşılaştırılması yapılmıştır. Mikroyapı girdileri ile elde edilen kristal plastisite modeli ile çıkarılan çok ölçekli ve çok eksenli malzeme davranışının, tek ölçekli malzeme davranışı ile karşılaştırıldığında deneysel sonuçlara daha yakın sonuçlar verdiği gözlemlenmiştir. Böylelikle çok ölçekli malzeme modellemesiyle gerçekleştirilen simülasyonların daha gerçekçi ve güvenilir sonuçlar gösterdiği kanıtlanmıştır.
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.
A Comparison of Ensemble and Base Learner Algorithms for the Prediction of Machining Induced Residual Stresses in the Turning of Aerospace Materials
(Bitlis Eren Üniversitesi, 2022) Buyrukoğlu, Selim; Kesriklioglu, Sinan; 0000-0002-2914-808X; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Kesriklioglu, Sinan
The estimation of residual stresses is essential to prevent the catastrophic failures of the components used in the aerospace industry. The objective of this work is to predict the machining induced residual stresses with bagging, boosting, and single-based machine learning models based on the design and cutting parameters used in the turning of Inconel 718 and Ti6Al4V alloys. Experimentally measured residual stress data of these two materials was compiled from the literature, including the surface material of the cutting tools, cooling conditions, rake angles, as well as the cutting speed, feed, and width of cut to show the robustness of the models. These variables were also grouped into different combinations to clearly show the contribution and necessity of each element. Various predictive models in machine learning (AdaBoost, Random Forest, Artificial Neural Network, K-Neighbors Regressor, Linear Regressor) were then applied to estimate the residual stresses on the machined surfaces for the classified groups using the generated data. It was found that the AdaBoost algorithm was able to predict the machining induced residual stresses with a mean absolute error of 18.1 MPa for the IN718 alloy and 31.3 MPa for Ti6Al4V by taking into account all the variables, while the artificial neural network provides the lowest mean absolute errors for the Ti6Al4V alloy. On the other hand, the linear regression model gives poor agreement with the experimental data. All the analyses showed that AdaBoost (boosting) ensemble learning and artificial neural network models can be used for the prediction of the machining induced residual stresses with the small datasets of the IN718 and Ti6Al4V materials.
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.
A comprehensive experimental and modeling study of the strain rate- and temperature-dependent deformation behavior of bio-degradable Mg-CeO2 nanocomposites
(ELSEVIER, 2024) Deka, Surja; Mozafari, Farzin; Mallick, Ashis; 0000-0001-8218-4410; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Mozafari, Farzin
A comprehensive study was undertaken on the temperature-dependent and strain rate-sensitive deformation behavior of near-dense low-volume fraction magnesium-cerium dioxide (Mg-CeO2 ) nanocomposites synthesized by powder metallurgy technique. The process involved ball milling of elemental powders → cold compaction → sintering in an inert atmosphere, and in-situ hot extrusion. The Mg-CeO2 nanocomposites displayed strain rate and temperature sensitivity, exhibiting higher yield strength, superior compressive characteristics, greater hardness, and improved ductility compared to pure Mg and most commercial Mg alloys. Furthermore, a thorough micro-structural investigation was conducted to characterize the distributions of ceria nanoparticles, grain refinement degree, ceria-magnesium interface, formation of deformation twins and interfacial bonding between the reinforcement and matrix. The present study has proposed two modeling approaches, the Johnson– Cook (J–C) constitutive model and a machine learning-assisted model, to predict the mechanical behavior of monolithic Mg and Mg-CeO2 nanocomposites. The models effectively explained the deformation behavior under various strain rates and temperatures.
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.
Computational fluid dynamics for the optimization of internal bioprinting parameters and mixing conditions
(WHIOCE PUBL PTE LTD, 2023) Ates, Gokhan; Bartolo, Paulo; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Ates, Gokhan
Tissue engineering requires the fabrication of three- dimensional (3D) multimaterial structures in complex geometries mimicking the hierarchical structure of biological tissues. To increase the mechanical and biological integrity of the tissue engineered structures, continuous printing of multiple materials through a printing head consisting of a single nozzle is crucial. In this work, numerical analysis was carried out to investigate the extrusion process of two different shear-thinning biomaterial solutions (alginate and gelatin) inside a novel single-nozzle dispensing system consisting of cartridges and a static mixer for varying input pressures, needle geometries, and outlet diameters. Systematic analysis of the dispensing process was conducted to describe the flow rate, velocity field, pressure drop, and shear stress distribution throughout the printing head. The spatial distribution of the biopolymer solutions along the mixing chamber was quantitatively analyzed and the simulation results were validated by comparing the pressure drop values with empirical correlations. The simulation results showed that the proposed dispensing system enables to fabricate homogenous material distribution across the nozzle outlet. The predicted shear stress along the proposed printing head model is lower than the critical shear values which correspond to negligible cell damage, suggesting that the proposed dispensing system can be used to print cell-laden tissue engineering constructs.
Convenient Site Selection of a Floating PV Power Plant in Türkiye by using GIS-Fuzzy Analytical Hierarchy Process
(SPRINGER, 2024) Karipoğlu, Fatih; Koca, Kemal; İlbahar, Esra; 0000-0003-2464-6466; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Koca, Kemal
Floating photovoltaics (FPVs) are appearing as a promising and an alternative renewable energy opinion in which PV panels are mounted on foating platforms in order to produce electricity from renewable energy on water such as seas, dams, rivers, oceans, canals, fsh farms, and reservoirs. So far, such studies related to the body knowledge on fnancial, technical, and environmental aspects of installation of FPV have not been performed in Turkey while expanding steadily in other countries. In this study, suitable site selection for installation of FPV power plants on three lakes in Turkey was studied by performing geographic information system (GIS) and the fuzzy analytic hierarchy process (FAHP) as multi-criteria decision-making (MCDM) method. This detailed study revealed that the criterion of global horizontal irradiance (GHI) was determined as the most crucial criterion for the installation of FPV on Beysehir Lake, Lake of Tuz, and Van Lake. Additionally, it was clearly seen that the Beysehir Lake had the highest value approximately 52% among other lakes for installation, that is why Beysehir Lake is selected as the best option for installation of an FPV system with this multi-criteria approach.
Corrosion behavior of novel Titanium-based high entropy alloys designed for medical implants
(ELSEVIER SCIENCE SA, PO BOX 564, 1001 LAUSANNE, SWITZERLAND, 2020) Yagci, Mustafa Baris; Bal, Bekir Cihad; Canadinc, Demircan; Gurel, S.; 0000-0001-9961-7702; 0000-0002-3176-2388; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü
This paper reports on the corrosion behavior of three TiTaHf-based high entropy alloys (HEAs) in simulated body fluid (SBF) and artificial saliva (AS) in order to assess their potential utility as implant materials. Specifically, TiTaHfNb, TiTaHfNbZr and TiTaHfMoZr HEAs were subjected to static immersion experiments in SBF and AS, and both the surfaces of the samples and the immersion fluids were thoroughly examined with the state of the art techniques. The experimental results presented herein revealed that the presence of Zr and Nb in the TiTaHf-based samples enhanced corrosion performance with reduced ion release and better surface properties, while Mo addition resulted in an inhomogeneous microstructure, leading to dendrite structures and significant amount of ion release upon immersion in both media. Furthermore, a protective passive layer formation or crystallization was present on all HEA surfaces, implying that corrosion resistance can be sustained in long-term applications. Overall, the set of findings presented herein constitute an early indication of the potential of the TiTaHf-based HEAs to be utilized as implant materials.

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