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Öğe A new integrated methodology for constructing linguistic pythagorean fuzzy statements for decision making problems(IOS PRESS, 2022) Işık, Gürkan; Kaya, IhsanAs a combining concept of Pythagorean fuzzy sets (PFSs) and linguistic fuzzy sets (FSs), linguistic PFSs (LPFSs) has been suggested in the literature to deal with the uncertain and inconsistent information in multi-criteria decision making (MCDM) process. The LPFSs based procedure has been built by assuming that the experts make assessments suitable with PFS. It does not provide a mechanism to ensure the suitability of the assessments with theory of PFSs but there are other type of non-standard fuzzy sets such as Neutrosophic sets (NSs) used for modeling with inconsistent information. The main motivation of this study is to offer an assessment collection method to guarantee that the input statements will be Pythagorean fuzzy linguistic expressions. As a second motivation, it is aimed to extend the PFS method for the fuzzy modeling of the other type of decision-making problems apart from MCDM which do not require aggregation and comparison operations and continue with precise fuzzy modeling (PFM). The third motivation of this study is to offer enhancements on the LPFSs method to increase the sensitivity of the modeling while protecting the interpretability. For these purposes, a newmethodology based on LPFSs has been proposed and applied on a decision-making problem in a comparative way.Öğe A Novel Approach for Optimum Planning of Bobbin Boilers in Textile Industry(Ege Universitesi, 2022) Demir, Yunus; İnan, KemalAs in all sectors, the fierce competition in the world affects the textile sector deeply. It is an inevitable necessity for companies to reduce their costs in order to survive while maintaining their profitability. In this study, an applied efficiency study was conducted for the bobbin dyeing process, which is one of the important elements of the textile industry. In the application made in Bursah Tekstil Ltd. Sti., the problem of sequencing the lots waiting to be dyed in the bobbin dye boilers has been discussed. Integer linear model and iterative greedy-based heuristic are proposed to solve the problem. Sequencing made with the developed method resulted in an improvement of 17% in terms of the number of boiler washes and 13% in terms of total tardiness compared to the manual sequencing.Öğe A novel hesitant fuzzy linguistic term sets approach and its application on acceptance sampling plans(UNIV SISTAN & BALUCHESTAN, 2022) Işık, Gürkan; Kaya, I.Hesitant fuzzy linguistic term set (HFLTS) is an approach giving ability to obtain more flexible decision-making (DM) process by integrating linguistic fuzzy modeling (LFM) with hesitative expert judgments. Although HFLTS is widely -studied in the literature and many enhancements are made on HFLTS procedure, none of these enhancements gives ability to continue with precise fuzzy modeling (PFM) in decision process. LFM has a big drawback about accuracy because of the dependency between the size of term set and the comprehensiveness of fuzzy sets (FSs). This issue creates a very critical difficulty in modeling of DM problems that need sensitive evaluations by using HFLTS. This paper aims to solve this problem by proposing a novel HFLTS methodology that is usable for DM problems that need sensitive calculations in the decision stage. The proposed methodology integrates 2-tuple LFM and linguistic fuzzy modifiers with HFLTS to overcome the accuracy problem and obtain more sensitive and flexible decision procedure. This paper also presents an envelopment transformation technique to aggregate expert assessments as a fuzzy membership function instead of membership grades. It becomes possible to keep interpretability in a certain level and achieve sensitive results at the same time with the help of these modifications. The proposed HFLTS approach is analyzed on a real case example from manufacturing industry for acceptance sampling plans (ASP) that is a DM problem requiring sensitive calculations. As another originality of the paper, the main formulations of ASP are derived based on hesitant fuzzy defectiveness information. The obtained results are also compared with some existing enhancements of the HFLTS and the success of the proposed methodology is proved in terms of sensitive calculation.Öğe An iterated greedy algorithm for the planning of yarn-dyeing boilers(Wiley, 2022) Demir, YunusYarn dyeing is a critical link in the textile production chain that consumes the most time and energy. Today's dyeing shops receive hundreds of demands with thousands of different colors, different due dates, and different production requirements. This situation has made it very difficult for the human brain to create a minimum-cost production plan by complying with the due dates. In this study, a real-life problem of a company operating in the textile industry is discussed and a solution has been developed for the planning of yarn-dyeing boilers. The application was held in Bursali Textile, which is the major towel manufacturer operating in Turkey. The problem dealt with is basically in the nature of the variable-size bin-packing problem (VSBPP). The limited availability of bins (boilers) of different sizes and the packing of the items (yarn work orders) with due date constraints are the original aspects of this study. Multi-objective mixed integer programming model is developed to minimize two objectives. For the solution, the preemptive method called the lexicographic approach, in which the objectives are solved in order, is preferred. As the first objective, the overcapacity usage is minimized and then the second objective, which is the boiler usage cost, is minimized. Given that the VSBPP is strongly NP-hard, an iterated greedy algorithm with two different decoding approaches is proposed. Computational experiments were conducted on 20 randomly generated benchmark instances and a real-world industrial dataset. The numerical results show that good solutions can be obtained in seconds using the proposed approaches.Öğe A decision support model based on q-rung orthopair fuzzy number for glove design application(Springer, 2022) Efe, Ömer Faruk; Efe, BurakQuality function deployment (QFD) method allows reviewing of customer requirements (CRs) and design requirements (DRs) simultaneously in order to handle the correlations and relationships of CRs and DRs in calculations. It has been often combined with fuzzy numbers because it provides to gather the judgments of experts in vagueness environment more correctly and easily. This paper suggests employing q-rung orthopair fuzzy number (q-ROFN) for improving the fuzzy QFD approach. The proposed q-ROFN based QFD method uses q-ROFN to adjust the weights of CRs based the relationships between CRs and DRs with the help of the correlations and relationships of CRs and DRs. q-ROFN presents more information than numbers such as intuitionistic fuzzy number and Pythagorean fuzzy number about the correlations and relationships of CRs and DRs. VIKOR (VIsekriterijumska optimizacija i KOm-promisno Resenje) approach based on q-ROFN is also used to rank DRs. The new proposed integrated method has been applied for evaluating the anthropometry based glove design. The results show that the most important DR for anthropometry based glove design is ease of hand motion perception.Öğe A framework for choosing an appropriate fuzzy set extension in modeling(Springer, 2022) Işık, GürkanReal-world problems contain uncertainties. Fuzzy Set Theory (FST) is a popular approach to model these uncertainties. FST extensions (FSTEs) have been offered for better modeling of the uncertainties having different natures. It is essential to use the most suitable FSTE in modeling to achieve reasonable, reliable, and realistic results. However, FSTEs are preferred without stating a clear reason in most of the studies. This makes the quality and the reliability of the results of these studies questionable. Because, to obtain reliable models, the dynamics of the problem and environment should be well understood, the scenario should be well analyzed, and the assumptions and limitations of FSTE theories should be well known. In this study, a guiding framework for choosing the most suitable FSTE in modeling to obtain reliable, applicable, and efficient results is proposed. The framework consists of two parts: (i) conceptual analysis of the uncertainty types and FSTEs, (ii) a guiding procedure fed by the first step for deciding the most suitable FSTE. The procedure is illustrated by multiple numerical examples to make its benefits clear. Conceptual analysis and numerical examples show that some FSTEs have some advantages over the others for specific scenarios and problem types. For example, NS is more suitable than PFS for modeling the problems other than Multi-Criteria Decision-Making (MCDM). Another contribution of this study is showing that it is very important to choose the simplest possible FSTE to obtain reliable and applicable models.Öğe A model proposal to examine the effects of ships to marine pollution in terms of internal and external factors(Springer, 2022) Efe, Burak; Efe, Ömer Faruk; Ishizaka, AlessioMarine pollution is an important environmental problem. One of the important causes of marine pollution is ship origin. This study deals with defining the importance degrees of ship origin marine pollution criteria. This paper suggests employing quality function deployment (QFD), interval type-2 fuzzy (IT2F) numbers, TOPSIS (technique for order performance by similarity to ideal solution) and SWOT analysis to determine these importance degrees. Internal factors, which indicate the strengths and weaknesses of the SWOT analysis in this paper, are the infrastructure of the sea to prevent pollution. External factors, which indicate the opportunities and threats of the SWOT analysis in this paper, are ship-related activities that cause pollution of the relevant sea. Five CRs and fourteen DRs are handled to examine ship origin marine pollution. Three experts have presented their judgments about the correlations and relationships of design requirements (DRs) and customer requirements (CRs). The proposed IT2F number-based QFD method uses IT2F numbers to determine the weights of DRs with the help of the correlations and relationships of the DRs and CRs. The most important internal factors are complying with the law and hard supervision, respectively. The most important external factors are direct discharge of waters of tank washing, direct discharge of ballast waters of ships and direct discharge of bilge waters of ships, respectively. Four seas are ranked in terms of ship origin marine pollution by using TOPSIS approach based on IT2F number. The most polluted sea exposed to ship origin marine pollution is Sea of Marmara according to the obtained results.Öğe Systematic Customer Value Analysis: A Case Study in the Automotive Industry(Society of Sytematic Innovation, 2021) Çakmak, Tolga; Altun, KorayProviding high quality with competitive prices is generally essential in the automotive industry because of the customers (directly automotive OEMs and indirectly their end-users) demanding new and costly features without showing additional willingness to pay. For this reason, accurate analysis of customer value can be very helpful for developing new concepts, and hence for correct positioning in this competitive area. Although one of the most important parts of the engine in an automobile is the clutch, there are very limited studies on its value analysis in the literature. Correspondingly, to fill this gap, this paper analyses the customer value of automotive clutch components and their functions by using a two-phase QFD methodology, and a fuzzy-logic based data-fusion methodology. While the former phase determines relative weights of the bene-fit through the House of Quality, the latter phase performs the parts (and cost) deployment to determine the costs of the clutch functions by using a reverse costing analysis incorporating the product teardown cost in-formation. Having obtained benefit, cost, and technical difficulty information, a fuzzy-logic model evaluates the competitive importance of each clutch function. This work identifies the three most important clutch functions and their related subcomponents.Öğe A novel approach based on type-2 fuzzy sets to augment technology roadmaps(GAZI UNIV, 2022) Barip, Semanur; Altun, KorayImportance of RDI outputs is increasing day by day in the business world. Harmony of RDI activities and technology strategies is one of the important guarantees of sustainable success. At this stage, the first thing that comes to mind is the "technology roadmaps", which have been commonly used in order to direct RDI activities. Technology roadmaps are the tools linking technological developments and changes with other relevant layers (products, services, market, etc.), and thus they assist in decision making. To obtain a valid technology roadmap, its inter-element relationships need to be well-established. This study proposes an infographic for the relationships between technology roadmap elements. In this study, importance of the relationships and the relationship degree of element pairs are evaluated through the use of interval type-2 fuzzy systems (IT2FS). The infographic employing these evaluation results augments the technology roadmaps. In order to illustrate how the proposed process executes, a case of three-dimensional (3D) printing technologies is presented. Consequently, it is considered that these augmented technology roadmaps contribute to strategy planning and technology management, especially for large-scale cases.Öğe Design of experiments optimization application in physics: a case study of the damped driven pendulum experiment(Yıldız Teknik Üniversitesi, 2021) Atalan, Abdulkadir; Şahin, HasanThe design of experiment (DoE) approach developed for experiments requiring cost and time is applied in many disciplines. Unfortunately, the insufficient use of the DoE technique in physics led to the emergence of this study. This study aims to demonstrate the applicability of the DoE technique in the field of physics with a case study. The most widely used full factorial experimental design was used for the damped driven pendulum case study. Length (m), dumpling (Newton), and mass (kg) as independent and energy (joule) as dependent variables were defined in this study to apply the DoE approach. As a result of the statistical analyses in DoE, optimization models were created, and optimum values were obtained for the case study. The experiment performed was proved to be statistically significant and valid by calculating the R-square as 0.97. The value of the objective function is calculated as 4.058 (joule). The optimum values for length, dumping, and mass was calculated as 2.719 m, 2.485(Newton), and 2.895 kg, respectively. In conclusion, this study will contribute to the literature to guide the researchers who spend a lot of time in experimental labs and have problems with experiment costs.Öğe An interaction-oriented multi-agent sir model to assess the spread of sars-cov-2(Hacettepe University, 2021) Altun, Koray; Altuntas S.; Dereli T.It is important to recognize that the dynamics of each country are different. There-fore, the SARS-CoV-2 (COVID-19) pandemic necessitates each country to act locally, but keep thinking globally. Governments have a responsibility to manage their limited resources optimally while struggling with this pandemic. Managing the trade-offs re-garding these dynamics requires some sophisticated models. “Agent-based simulation” is a powerful tool to create such kind of models. Correspondingly, this study addresses the spread of COVID-19 employing an interaction-oriented multi-agent SIR (Susceptible-Infected-Recovered) model. This model is based on the scale-free networks (incorporat-ing 10, 000 nodes) and it runs some experimental scenarios to analyze the main effects and the interactions of “average-node-degree”, “initial-outbreak-size”, “spread-chance”, “recovery-chance”, and “gain-resistance” factors on “average-duration (of the pandemic last)”, “average-percentage of infected”, “maximum-percentage of infected”, and “the expected peak-time”. Obtained results from this work can assist determining the correct tactical responses of partial lockdown.Öğe ÜRÜN GELİŞTİRME EKİP YAPISININ ÜRÜN GELİŞTİRME PERFORMANSI ÜZERİNDEKİ ETKİSİ: OTOMOTİV YAN SANAYİİNDE BİR SAHA ARAŞTIRMASI(2017) Yıldız, Aytaç; Yayla, A. YeşimBu çalışmada, otomotiv yan sanayiinde faaliyet gösteren firmalarda, ürün geliştirme ekip yapısının ürün geliştirme performansı üzerindeki etkilerini ortaya koyabilmek amacıyla bir anket çalışması yapılmıştır. Araştırma verilerinin elde edilmesi amacıyla hazırlanan anket, İstanbul ve Gebze'de faaliyet gösteren orta ve büyük ölçekli 51 firmaya uygulanmıştır. Anketten elde edilen veriler SPSS istatistik programında faktör, güvenilirlik, korelasyon ve regresyon analizi ile değerlendirilmiştir. Elde edilen sonuçlara göre, ürün geliştirme ekibinin yapısının bileşenleri olan; çapraz fonksiyonel ekipler, ekip üyelerinin ortak konumlandırılması, yetkilendirilmiş ekip ve ekip kararlılığının, ürün geliştirme performansını pozitif yönde ve anlamlı bir şekilde etkilediği görülmüştürÖğe ENDÜSTRİ 4.0 İLE BÜTÜNLEŞTİRİLMİŞ DİJİTAL TEDARİK ZİNCİRİ(2018) Yıldız, AytaçSon yıllarda rekabet ortamlarının zorlaşması, küreselleşme, teknolojinin hızlı gelişimi, tedarik zincirindeki ağların karmaşıklığının artması ve ürün yaşam sürecinin kısalması gibi gelişmeler, işletmelerin tedarik zinciri stratejilerini gözden geçirmelerine sebep olmuştur. Bundan dolayı, bu koşullarda rekabet etmek isteyen işletmeler, tedarik zincirlerini etkili ve verimli bir şekilde yönetmelidirler. Tedarik zincirinin etkin olarak yönetilebilmesi için de tedarik zinciri ortakları arasında gerçek zamanlı bilgi paylaşımı ve koordinasyonun sağlanması gerekmektedir. Tedarik zinciri sürecinde satın alma, üretim ve dağıtım süreçlerinin organize edilmesi, stok yatırımlarının yönetilmesi, tedarikçiler ile bağlantıların iyileştirilmesi, müşteri geribildirimlerinin hızlı alınması ve isteklerine hızlı cevap verilmesi gibi faaliyetlerin etkili ve verimli bir şekilde yapılabilmesi geleneksel tedarik zincirlerinin dijitalleşmesi ile mümkün olacaktır. Bu çalışmada, işletmelerin tedarik zincirleri faaliyetlerini kolaylaştıran ve verimli hale getiren dijital tedarik zincirinin genel yapısının anlatılması amaçlanmaktadır. Bu amaç için, dijital tedarik zincirinin genel yapısı, endüstri 4.0 ile olan ilişkisi, geleneksel tedarik zincirinden dijital tedarik zincirine dönüşüm, dijital tedarik zincirinin özellikleri, temel karakteristikleri ve faydaları ile ilgili genel bir literatür taraması yapılmıştır. Ayrıca, nesnelerin interneti ve bulut bilişimin dijital tedarik zinciri süreçlerindeki önemi incelenmiştir.Öğe A Problem-Solving Environment to Teach Students Assembly Line Balancing Techniques(2019) Yılmaz, Hamid; Demir, YunusAssembly line balancing is a production planning strategy that has been widely used in industrial applications. Most line balancing problems are known as nondeterministic polynomial time (NP-hard) problem, and they have different structures and solution methodology approaches. In this study, newly developed production planning software which is called Visual Assembly Line Balancing Software (VALBS) is introduced for educational purposes. The aim of the software is to support teaching activity for assembly line balancing techniques; facilitate understanding characteristics of different assembly lines and solution approaches, and enable to compare the results of them. The proposed VALBS is easy to use in various manufacturing environments, and suitable to support teaching line balancing procedures in undergraduate students. The software was used in classes of industrial and mechanical engineering students and feedbacks of students measured by Likert Scale survey. The results show that proposed visual software is an effective method to teach line balancing procedures.Öğe Yanıt yüzey yöntemi ve genetik algoritma kullanılarak transformatör sargı en sıcak nokta sıcaklığının modellenmesi ve optimizasyonu(2019) Ergül, Engin Ufuk; Gezegin, Cenk; Yıldız, AytaçElektrik enerjisine olan talebin artmasıyla, bu enerjinin iletimi ve dağıtımında kullanılan en önemli donanımlardan birisi olan transformatörlerin önemi de artmaktadır. Transformatörlerin verimli bir şekilde uzun süreli çalışabilmeleri için izlenmesi gereken en önemli parametrelerden birisi sargı en sıcak nokta sıcaklığı (Hot-Spot Temperature-HST) değeridir. Bu parametrenin belirlenmesi için çeşitli termal modeller kullanılmaktadır. Fakat transformatör içindeki termal olaylar karmaşık olduklarından HST değerini tam olarak veren termal modeller geliştirilememiştir. Bu çalışmanın amacı, yanıt yüzeyi yöntemi (Response Surface Method-RSM) ile kombine edilen üç seviye BoxBehnken tasarımı ve genetik algoritma (GA) yöntemlerini kullanarak maksimum HST’nin tahmin edilmesinde kullanılan optimum parametre değerlerini bulmak için regresyon modeli oluşturmaktır. Böylece HST değeri tahmin edilerek transformatörlerin ömrü ve verimi artırılabilecektir. Çalışmada, 5kVA 380/220V tek fazlı kuru tip transformatör ile deney düzeneği hazırlanmıştır. Deneyler, üç farklı akım değeri (4, 8 ve 12 A), akım uygulama süresi (3, 6 ve 9 saat) ve ortam sıcaklığında (20, 25 ve 30 oC) Box-Behnken tasarımı dikkate alınarak yapılmıştır. Deneylerden elde edilen yanıtlar Design Expert 11.0.5 programında analiz edilerek HST için matematiksel bir tahmin modeli geliştirilmiş ve parametrelerin optimum değerleri elde edilerek maksimum HST tahmin edilmiştir. Daha sonra, RSM’den elde edilen matematiksel tahmin modelinden yararlanılarak HST tahmini için GA kullanılmıştır. Çalışma sonunda her iki yöntem vasıtasıyla elde edilen tahmin değerleri karşılaştırılmış ve birbirine çok yakın olduğu görülmüştürÖğe BULANIK TOPSIS YÖNTEMİYLE TÜRKİYE’NİN YERLİ OTOMOBİLİ İÇİN EN UYGUN FABRİKA YERİNİN SEÇİMİ(2019) Yıldız, Aytaç; Demir, YunusGirişimciler için, hangi sektörde faaliyet göstermelerinin yanı sıra işletmeyi nereye kuracakları da önemlidir. Çünkü yanlış bir karardan dolayı uygun olmayan bir yere işletmenin kurulması yüksek maliyetlere, nitelikli işgücüne sahip olamama ve yeterli sayıda müşteriye ulaşamama gibi sorunlara sebep olabilir. Yer seçimi problemi, içerisinde birçok kriteri ve belirsizliği barındıran, bundan dolayı da bulanık bir davranış sergileyen bir karar problemidir. Bu gibi karar problemlerinin çözümünde Çok Kriterli Karar Verme (ÇKKV) gibi bilimsel yöntemlerin kullanılması karar vericilere kolaylık sağlamaktadır. Bu çalışmada, Türkiye için stratejik bir öneme sahip yerli otomobil üretimi için en uygun yerin seçilmesi amaçlanmış ve bu amaç için bulanık ortamlarda karar vermeyi kolaylaştıran bulanık TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) yöntemi kullanılmıştır. Yedi alternatif yer (Kocaeli, Bursa-Gemlik, Sakarya, Konya, İzmir-Aliağa, Adana ve Eskişehir) literatür taraması neticesinde belirlenen beş ayrı kritere göre (ekonomik, coğrafi konum, altyapı, teknik ve sosyal özellik) değerlendirilmiştir. Çalışma sonunda yakınlık katsayısı en yüksek olan Bursa-Gemlik alternatifi, yerli otomobil için en uygun fabrika yeri olarak belirlenmiştir.Öğe Better estimation of origin-destination matrix using automated intersection movement count data(Canadian Science Publishing, 2015) Tuydes-Yaman, Hediye; Altintasi, Oruc; Şendil, NuriIntersection movements carry more disaggregate information about origin-destination (O-D) flows than link counts in a traffic network. In this paper, a mathematical formulation is presented for O-D matrix estimation using intersection counts, which is based on an existing linear programming model employing link counts. The proposed model estimates static O-D flows for uncongested networks assuming no a priori information on the O-D matrix. Both models were tested in two hypothetical networks previously used in O-D matrix studies to monitor their performances assuming various numbers of count location and measurement errors. Two new measures were proposed to evaluate the model characteristics of O-D flow estimation using traffic counts. While both link count based and intersection count based models performed with the same success under complete data collection assumption, intersection count based formulation estimated the O-D flows more successfully under decreasing number of observation locations. Also, the results of the 30 measurement error scenarios revealed that it performs more robustly than the link count based one; thus, it better estimates the O-D flows.Öğe Multi-issue negotiation in quality function deployment: Modified Even-Swaps in new product development(Pergamon-Elsevier Science Ltd, 2016) Altun, Koray; von Zedtwitz, Max; Dereli, TurkayQuality function deployment (QFD) is one of the most powerful methodologies in new product development (NPD) because of its systematic support of knowledge creation and sharing. However, greater product complexity, increasing dynamic customer requirements and further decentralization of innovation teams undermine applicability of QFD in modern NPD. Modifying QFD methodology with a multi-issue negotiation mechanism promises to overcome these obstacles because this negotiation-based structure (i) enables QFD to define a large number of interdependent decision parameters while handling complicated design trade-offs, (ii) includes changing customer requirements in real-time rather than a cycle time determined by length of the product development process, (iii) allows decentralized NPD teams to negotiate with each other and customers concurrently. This study presents a multi-issue negotiation based QFD methodology by using a recently developed mechanism for multi-issue negotiation (namely, Modified Even-Swaps) and illustrates strengths and weaknesses along with practical insights with a case study of the development of a washing machine. The QFD methodology proposed in this study provides new options to assess new product alternatives by allowing customer co-creation which is essential in complex and often tacit-knowledge dependent comparisons and also intrinsically helpful for fine-tuning dynamically evolving customer requirements. Moreover, it supports competition-based interactions of decentralized NPD teams. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Comparison of the Effect of Diameters and Numbers of Cannulated Screws and Headless Compression Screws on the Reduction Stability in Transverse Patellar Fractures: A Finite Element Model Study(Amer Scientific Publishers, 2017) Ugur, Levent; Karadeniz, Selami; Yıldız, AytaçBackground: Patella fractures constitute 1% of skeletal trauma. Transverse patella fractures are the most common types of patellar fractures. A fracture gap more than 2-3 mm or irregularities in cartilage require surgical treatment. There are various surgical options available, and one of these options is the screw fixation. This study aims to investigate the effect of the diameter and number of cannulated screws and headless compression screws on the reduction stability of transverse patellar fractures. Methods: In this study, the knee joint with normal anatomy and the knee joint with transverse patellar fracture were modeled using longitudinal lower extremity computerized tomography (CT) images taken in DICOM format. In the knee model with transverse patellar fracture, two circle divide 3.5 mm cannulated screws and one circle divide 4.5 mm cannulated screw, two circle divide 3.5 mm and one circle divide 4.5 mm headless compression screws were inserted respectively; and the maximum equivalent stresses (MES) occurred in the screws and the stability of the patella were examined in a total of 16 models at 30 degrees, 45 degrees and 60 degrees flexion angles and in the normal position (0 degrees) of the knee. The analysis was performed non-linearly and dynamically using ANSYS (version 17) and the same boundary conditions were applied in all models. Results: As a result of the analysis, the maximum stresses on the screws in the models with cannulated screws and headless compression screws were compared. When the maximum stresses in the screws were examined, it was observed that the maximum stress was lesser in the model with two circle divide 3.5 mm headless compression screws, and the maximum stress was found to increase in the single circle divide 4.5 screws. Sixteen different models were analyzed with the help of the Taguchi method and the most suitable model and parameters were determined according to the maximum equivalent von Mises stress value. Conclusions: The use of a single screw in the treatment of transverse patella fractures can lead to loss of reduction. If screw treatment is preferred, it was observed that the 2-screw application was more stable and the fixation with the headless compression screw was found to be more stable compared to the cannulated screw at various degrees of flexion.Öğe OPTIMIZATION OF CUTTING PARAMETERS USING THE RESPONSE SURFACE METHOD(Yildiz Technical Univ, 2018) Guvercin, Salih; Yıldız, AytaçSome cutting parameters have to be considered in order to obtain high-quality surfaces in machining. Because poorly selected cutting parameters cause both the cutting tools to wear out quickly and the surface to become rough. Therefore, it is of great importance to use experimental design methods to obtain better quality surfaces with an optimal combination of cutting parameters. In this study, optimization of cutting parameters such as feed rate, cutting speed and depth of cut, which affects the surface roughness of AISI 1040 steel the commonly used in the industry, is aimed by three-level Box-Behnken design combined with response surface methodology. For this purpose, 15 workpieces with empty set 70 mm and 200 mm length were prepared and machined on a CNC lathe. Then, the surface roughness values of the workpieces were measured. The obtained surface roughness values were analyzed in the Design Expert 10.0.6 program and the cutting parameters affecting the surface roughness were optimized. According to the results obtained from the study, it was determined that the feed rate is the parameter that has the greatest effect on the surface roughness. In addition, optimum surface roughness was determined by a feed rate of 0.2 mm/rev, a cutting speed of 397.58 m/min and a depth of cut 1.5617 mm.
