Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Author: search.filters.author.Artem, Hatice SeçilPublisher: search.filters.publisher.01. Izmir Institute of Technology

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Now showing 1 - 9 of 9
  • Master Thesis
    Design of Cnt Fiber Reinforced Laminates for Minimum Weight
    (01. Izmir Institute of Technology, 2024) Karaosmanoğlu, Burhan Burak; Artem, Hatice Seçil
    Kompozit malzemeler günümüzde üretim ve uygulamalardaki yüksek işlevsellikleri nedeniyle birçok alanda yer bulmaktadır. Özellikle, yüksek performans özellikleri kazandırmak amacıyla kompozit güçlendirme malzemesi olarak Karbon Nanotüplerin (CNT) kullanımına olan ilgi giderek artmaktadır. Bu tezde 16 katmanlı, simetrik ve dengeli CNT-fiber takviyeli kompozit laminalar minimum ağırlık tasarımı için incelenmiştir. Yenilik olarak, klasik lamina teorisi dahilinde tanımlanan burkulma problemi bağlamında iki farklı minimum ağırlık tasarım yaklaşımı iki farklı problem altında sunulmuş ve karşılaştırılmıştır. Karşılaştırma kritik burkulma yükü faktörünün ağırlığa oranı şeklinde tanımlanan dizayn verimliği kriteri üzerinden yapılmıştır. Tek ve çok amaçlı genetik algoritmalar kullanılmış; ayrıca tam sayı problemlerine uyarlanmış önerilen bir benzetilmiş tavlama algoritması da test edilmiştir. CNT'lere ek olarak epoksi matris, cam fiber malzemelerinden oluşan laminanın etkin malzeme özellikleri fiber mikromekanik ve Halpin-Tsai modelleri kullanılarak belirlenmiştir. İlk problemde, kritik burkulma yükü faktörünün maksimize edilmesi için çözüme geçmeden önce her bir katmanda CNT ve fiber içerikleri fonksiyonel olarak dağıtılmış, tam sayı fiber açıları ise tasarım değişkenleri olarak alınmıştır. İkinci problemde, kritik burkulma yükü faktörü ve ağırlık çok amaçlı optimizasyon olarak ele alınmış, CNT'lerin ağırlık oranı, fiberlerin hacim oranı ve tam sayı fiber açıları tasarım değişkenleri olarak kullanılmıştır. Sonuç olarak, CNT'lerin ve fiberlerin dağılımının tasarım etkinliğini nasıl etkilediği gösterilmiş ve çok amaçlı optimizasyon yaklaşımın tek amaçlı alternatife kıyasla daha yüksek tasarım verimliliği sağladığı ortaya konulmuştur.
  • Master Thesis
    Process Parameter Optimization of Additively Manufactured Maraging Steel
    (01. Izmir Institute of Technology, 2024) Sivri, Burak; Artem, Hatice Seçil
    Bu çalışmada lazer toz yatak füzyonu ile üretilen maraşlama çeliği parçaların üretim parametleri araştırılmaktadır. Lazer toz yatak füzyonu, hafif ve mukavim parçaların hızlı üretilmesini sağlar ancak lazer gücü, tarama hızı ve katman kalınlığı gibi proses parametrelerinin hassas bir şekilde kalibre edilmesi gerekmektedir. Üretim yönteminin karmaşıklığı ve maliyetleri nedeniyle parametreler arası uyumun ve parça kalitesinin öngörülebilir olması kritiktir. Maraşlama çeliği yüksek mukavemet, sertlik ve süneklik gibi mekanik özelliklere sahiptir. Maraşlama çeliği, metal eklemeli imalat esnasında gerçekleşen katmanlı üretim nedeniyle peş peşe ısınma ve soğuma döngülerine maruz kalır ve süreç boyunca östenit ve martenzit fazları arasında geçiş yapar. Bu çalışma, içerisinde faz dönüşümü bilgisi içeren bir maraşlame çeliği malzeme modelini kullanmayı, lazer toz yatağı füzyonunun sonlu elemanlar analizini oluşturmayı, analize yapay faktörler ekleyerek analiz modelini literatürden alınan fiziksel test sonuçlarıyla uyumlu çıktılar verecek şekilde direkt optimizasyon metotlarıyla kalibre etmeyi içermektedir. Sonrasında ise simülasyon ve literatür çıktıları ile optimum öngörü sağlayacak bir metamodel oluşturulmaktadır. Stokastik optimizasyon metotları incelendikten sonra evrimsel bir algoritma metamodel verisi ile eğitilmekte, üretim parametreleri arası uyum ve ideal eklemeli imalat parametreleri elde edilmektedir. Bu araştırmada üretim sebebiyle oluşan deformasyon başlıca optimizasyon problemi olarak belirlenmiştir ve bu etkinin minimuma indirgenmesi hedeflenmiştir. Araştırmada elde edilen bulgular, maraşlama çeliğinin simülasyon ve optimizasyon metotları sayesinde sıfıra yakın deformasyon ile üretilebileceğini göstermektedir. Bu çalışmada maraşlama çeliği eklemeli imalatının doğruluğunu ve verimliliğini artırmak adına bir yöntem önerilmekte olup, bu doğrultuda sonlu elemanlar analizi ve optimizasyon yöntemlerinin faydaları vurgulanmaktadır.
  • Master Thesis
    Experimental Analysis and Modeling of Shear Strength of Adhesive-Bonded Single-Lap Glass Fiber Reinforced Composites
    (01. Izmir Institute of Technology, 2024) Artem, Hatice Seçil; Serbest, Sertaç; Artem, Hatice Seçil
    Composite materials are being used in many fields of industry day by day. With this increasing interest in composites, the methods of joining composites have also become the focus of attention. Mechanical fasteners cause damage to the composite, increase in weight, and stress accumulation in the joint area. Recently, joining composites with adhesives has attracted the attention of researchers. In this study, glass fiber reinforced polymer composites were combined with two paste adhesive thicknesses, using two brands of paste adhesives as fast-curing and slow curing, and three different peel plies and the effects of these three different parameters on the bonding strength were investigated both experimental and numerical analyses. In the experimental part of the thesis, glass fiber reinforced polymer composites were produced by the vacuum infusion method. The surfaces modified with different peel plies were combined with two different paste adhesives. A single-impact shear test was performed to examine the bond strength. As a result, it was observed that the fast-curing paste adhesive showed better performance in bond strength. At the same time, it has been experimentally demonstrated that the paste adhesive thickness of 0.6 mm has a positive effect compared to the paste adhesive with a thickness of 0.4 mm. It has been observed that the different peel plies used did not make a critical difference in the bond strength. In the numerical part of the thesis, six different regression models were used to model the shear strength of adhesive-bonded composites and then an optimization study was carried out by selecting the two best regression models that accurately express the physical model. Using the stochastic optimization methods, Differential Evolution and Nelder Mead algorithms, the optimum shear strength values possible with the existing parameters were found. This thesis contributes to determination of the bonded samples with the highest shear stress value by determining the optimum parameters.
  • Master Thesis
    Optimization of Injection Molding Process Parameters for Cycle Time
    (01. Izmir Institute of Technology, 2024) Kaplan, Anıl; Artem, Hatice Seçil
    Plastic, an integral part of modern life, is widely used in various sectors such as automotive, aerospace, and healthcare. The rapid advancements in the plastic industry have improved plastic processing technologies. Among contemporary production methods, plastic injection molding has become one of the most commonly used techniques. As industrial markets evolve rapidly, the need to shorten product cycle times, reduce production costs, and increase production speeds to respond swiftly to demand has become increasingly urgent. In this context, the thesis addresses the reduction of cycle times through the optimization of process parameters in the injection molding process. By utilizing experimental data available in the literature, a mathematical model of the injection molding process has been developed using a hybrid method known as Neuro-regression approach and cross-validation technique. To minimize the cycle time of the injection molding process, multi-objective optimization scenarios were created using seven different process parameters and two parameters affecting product quality. Optimization studies were carried out using stochastic optimization methods with the 'Simulated Annealing,' 'Random Search,' 'Nelder-Mead,' and 'Differential Evolution' algorithms in the 'Wolfram Mathematica' program with the help of the 'NMinimize' tool. When comparing the obtained optimization results with those in the literature, it was found that the model and optimization methods used in the study are reliable and applicable.
  • Master Thesis
    Design and Optimization of Hydraulic Actuator Used in Jet Fighter
    (01. Izmir Institute of Technology, 2024) Denizci, Ahmet; Artem, Hatice Seçil
    Actuators have been used in many areas from past to present. It is an indispensable equipment in the areas of use in today's technology. They are classified according to their usage areas and drive type. Depending on the type of drive, there are hydraulic, pneumatic and electrical actuators. It also has many uses: construction, manufacturing, automotive, robotics and aerospace industries. Hydraulic actuators are frequently used equipment in the aviation industry. In this thesis, the hydraulic actuator rod used in jet fighters was examined. This actuator is used to move the flight control surfaces in the jet fighter. So hydraulic actuator is vital for jet fighters. First, by conducting a literature search, boundary conditions and parameters were determined for actuator design and analysis. The design of rod was made using the determined parameters and the design parameters were analyzed using the finite element method. Neuro-regression approach was used to model a compact, lightweight and durable actuator. After regression analysis, many scenarios were created to optimize the mass and von Mises stress of the rod. The design and optimization of the hydraulic actuator rod were achieved by using Differential Evolution, Nelder-Mead, Random Search and Simulated Annealing algorithms. It has been concluded that the model and optimization algorithms are reliable and applicable to the problem.
  • Master Thesis
    Optimum Design and Analysis of Torsion Spring Used in Series Elastic Actuators for Rehabilitation Robots
    (01. Izmir Institute of Technology, 2021) Erten, Hacer İrem; Artem, Hatice Seçil
    Along with the developing technology, robotic systems have started to take place in areas where there is one-to-one interaction with people, as well as their use in industrial areas. As the robotic system began to take place in daily life, safety and reliability between humans and robots have become a critical issue. In this context, a series elastic actuator has been developed for the aforementioned robotic systems, which has an elastic element placed in series between the motor output and the mechanical output. In this thesis, the torsion spring, as a critical part for the rotary series elastic actuators of rehabilitation robots, which helps support the extension and flexion of the knee joint during physical therapy of individuals with lower extremity disorders, is discussed. First of all, the data required for modeling was produced by making analyses with the design of experiment and finite element method. In line with the design goal of a light, compact, durable and stiff spring, the torsion spring whose topology was determined was modelled using a hybrid method: Neuro-regression approach and cross-validation technique. To minimize the mass and von Mises stress of the torsion spring, the thickness of the spring and the inner corner radius of the flexible leg are taken as the design variables and multi-objective optimization problems are created. The design and optimization of the torsion spring was done with the help of Differential Evolution, Nelder-Mead, Random Search and Simulated Annealing algorithms. By comparing the obtained optimization results with the finite element method and the results in the literature, it has been seen that the model and optimization methods used in the study are reliable and applicable.
  • Master Thesis
    Optimization of Buckling Behavior of Hybrid Composite Beam Under Axial Compression
    (01. Izmir Institute of Technology, 2021) Altıntaş, Hayri; Artem, Hatice Seçil
    The use of lighter and high-performance materials in the aerospace sector is of great importance. Optimization methods, which have become very popular with the technological development in the production methods of composite structures in recent years and provide the most suitable design for the purpose, are frequently preferred in the design of parts in the aviation industry. Determining the buckling load capacity of a composite beam under compression load is very important for the design of composite structures. The buckling load capacity of a hybrid composite beam with fiber metal laminate (FML), which is frequently used between aircraft wing and fuselage. The optimum design of the anti-buckling behavior of the hybrid composite beam, which is subjected to compression load, fixed by simple support on both sides, was performed by a genetic algorithm (GA) based on the Tsai-Wu fracture criterion. The robust design of composite hybrid laminates was developed using a design optimization process based on GA with the finite element method. A multi-objective genetic algorithm (MOGA) was used to optimize the design of a hybrid composite beam subjected to buckling. Design variables in the optimization process are considered as fiber material and angle orientations. The purpose of the objective function is to reduce the equivalent stress of hybrid composites while increasing critical buckling load. The design constraint was the Tsai-Wu failure index. As a result, it has been observed that the buckling performance of the beam depends on the structure of the metal material in FML composites. Carbon/epoxy and glass/epoxy structures were proposed and a design was aimed according to the maximum buckling load in the best stacking sequence, taking into account the data in the design constraints.
  • Master Thesis
    Gravity Compensation of a 2r1t Mechanism With Remote Center of Motion for Minimally Invasive Transnasal Surgery Applications [master Thesis]
    (01. Izmir Institute of Technology, 2021) Aldanmaz, Ataol Behram; Artem, Hatice Seçil; Dede, Mehmet İsmet Can; Artem, Hatice Seçil; Dede, Mehmet İsmet Can
    In this work, gravity balancing of a 2URRR-URR parallel manipulator is issued. The manipulator is designed as an endoscope holder for minimally invasive transnasal pituitary gland surgery application. In the surgery, the endoscope is placed through the nostril of the patient where there is a natural path to the pituitary gland. In case of a motor failure, in order to protect the patient and to ease the control of the manipulator static balancing for this manipulator is worked out, the manipulator prototype is balanced and tested. The parallel manipulator has three legs. The payload mass has been distributed to side legs due to workspace limitations. By using counter-mass for two links in each leg, the center of mass of each leg has been reduced to the proximal link which simplified the balancing problem to balancing of a two degree-of-freedom inverted pendulum. By connecting a zero free length spring to the proximal link the total mass of the leg the manipulator has been kept in static balance in its desired workspace. Simulations show that with the applied design, torque effects on the motors have been reduced by 93.5%. Finally, the balancing solution is applied on the manipulator with active motors and the manipulator has been balanced, the torque values mostly has been decreased where the joint clearance, spring tension adjustments and mechanical constraints has affected the results. With the elimination of the joint clearance, mechanical constraints and rearranging the spring tension the required torque could be minimized.
  • Master Thesis
    Design and Optimization of Shaft Bracket of Drum Brake for Heavy Duty Vehicle
    (01. Izmir Institute of Technology, 2021) Çetin, Mert; Artem, Hatice Seçil
    The automotive industry is one of the leading sectors with a wider market share than any other sector which can quickly adapt to the increasingly competitive environment. However, in addition to the increasing product costs, regulations aiming to reduce fuel consumption and carbon emissions require an optimal design that satisfies design requirements depending on seriously increasing competition in this sector. This situation aims to design lightweight and high-performance vehicle products in a shorter period. In this sense, optimization methods have become very popular especially with the development of computer technologies in recent years. Therefore, they are often preferred in the design of vehicle products which enable to achieve the most suitable design for the specified purpose in a short time. This thesis study aims to realize a new shaft bracket design to be used in Z-Cam drum brakes of heavy duty vehicles by optimization methods. In line with this goal, firstly, the boundaries of material distribution in the given design space for vehicle axle application were obtained with the help of topology optimization. Then shape optimization was applied to bring material distribution having the suitable rough surfaces into the manufacturable form. Here, the Solid Isotropic Microstructure with Penalization (SIMP) algorithm was used for topology optimization and Response Surface Method (RSM) for shape optimization. Finite element analysis (FEA) of the final design obtained due to optimization was repeated and design verification tests were performed on the shaft bracket prototype manufactured according to the final design. The effectiveness and applicability of the optimization method used in the study were examined by comparing the performed test results with the final FEA. As a result of this study, a lighter design having a 72% weight advantage was obtained instead of the existing shaft bracket and the new design showed the similar structural strength compared with the existing shaft bracket as a result of experimental verification tests. Consequently, it has been seen that the optimization methods are very effective for the structural design of vehicle products.