Mühendislik Fakültesi / Faculty of Engineering
Permanent URI for this collectionhttps://hdl.handle.net/11727/1401
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Item Investigation of the Additional Powder Effect on the Strength of Joined Aluminum Alloy Plates in Friction Stir Welding Using the Topsis-Game Theory Model(Başkent Üniversitesi Mühendislik Fakültesi, 2024-05-03) Yurdakul, Mustafa; Ulke, Ibrahim; Tansel, Yusuf I. C.Friction stir welding (FSW) is a process that can join many materials by causing minimal internal stress without the need for a direct electric current, contrary to traditional welding methods. The effects of SiC and Al2O3 reinforcing powders on the joining of AA6061-T6 and AA7075-T6 plates, which are difficult to join with conventional welding methods by FSW, are investigated in this study. The metallurgical properties of the combined samples are examined in terms of strength characteristics to investigate the effects of the reinforcement powder. In addition, elemental analysis is carried out for the mixing behavior of the powders. Finally, we used the TOPSIS method to select the most appropriate powder types to improve welding quality. Furthermore, a game theory application is presented to determine which powder type is suitable considering the joined aluminum plate's strength expectations.Item A Fuzzy Computing Approach To Aggregate Expert Opinions Using Parabolic And Exparabolic Approximation Procedures For Solving Multi-Criteria Group Decision-Making Problems(Başkent Üniversitesi Mühendislik Fakültesi, 2024-03-02) Ic, Yusuf TanselTriangular fuzzy numbers (TFNs) are widely used for selection problems to determine expert opinions using linguistic expressions. Some aggregation procedures are developed to determine expert opinions more accurately. However, there is a need for a simple and more useful procedure to solve the selection problems more suitably. For this purpose, our study offers a triangular, exparabolic, and parabolic area calculation-based approximation approach for TFNs to aggregate the possible hedges (very and more or less) for TFNs. Hence, this aggregation procedure provides a tuning opportunity for classical TFN expressions to capture possible tuning processes to reflect the hesitancies of experts. The technique for order preferences by similarity to ideal solution (TOPSIS) method is applied in the two studies from extant literature, and suitable alternatives are determined as a result of the ranking process. Finally, a comparative analysis is presented to illustrate the efficiency of the proposed procedure. The conventional TOPSIS model's ranking scores are very close for exemplified examples (i.e., 0.5308, 0.4510, 0.4550 and 0.5304, 0.4626, 0.4940), but the proposed model's result has fluctuated for the same examples (i.e., 0.346, 0,669, 0,567 and 0.208, 0.991, 0.148). So, the main advantage of the proposed aggregation procedure is the alternative ranking scores separation capability analyzed with their linguistic diversification.Item Optimization Of Drilling Process Parameters For Additive Manufacturing Parts Produced Using The Fdm Method(JOURNAL OF THE FACULTY OF ENGINEERING AND ARCHITECTURE OF GAZI UNIVERSITY, 2024-09-15) Zorer, Ezgi Selen; Ayhan, Emre; Yurdakul, Mustafa; Ic, Yusuf TanselThe melt deposition modeling method (FDM) is one of the increasingly widespread additive manufacturing methods, known as 3D printing, based on the layered assembly of material filaments. However, it is seen that the parts produced with FDM in the aviation industry do not have the desired dimensional and geometric tolerance values. For this reason, different manufacturing methods are used to bring the parts produced by the FDM method to the desired tolerance values. In this study, experiments were carried out to improve the tolerance values of the holes on the plates made of polycarbonate material, which is widely used in prototyping and production tools (welding, drilling, fixing) with FDM, and the optimum processing parameters were determined using the integrated design of experiment and TOPSIS methods. According to the obtained results, the optimum drilling parameters for the plate without pre-drilling case could be obtained by selecting HSS as the drill material, using cutting fluid, and setting the feed rate to 390.9091 mm/min and the spindle speed to 1000 rpm. For the pre-drilled plate, the optimum drilling parameters were again obtained by selecting the drill material HSS, using cutting fluid and applying the feed rate to 369.6970 mm/min and the spindle speed to 781.8182 rpm.Item Operating window perspective integrated TOPSIS approach for hybrid electrical automobile selection(2019) Ic, Yusuf Tansel; Simsek, Esra; AAI-1081-2020To reduce vehicle-related environmental pollution, environmental regulations should be taken into account in different levels of sustainable product development process. As a result of the increasingly emitted CO2 and serious energy shortage electrical or hybrid automobiles are one of the possible alternatives for customers. In this study, an operating window perspective based Taguchi-TOPSIS model is developed for the hybrid electrical automobile selection problem. Operating window is a range of attributes' values that the operating parameters meet the specified functional parameters yielding the best results in economic and technological terms. The operating window's upper and lower boundaries are defined as limits. More than two limit modes usually cannot be characterized by a one-dimensional operating window. After obtaining attribute values for the hybrid electrical automobile alternatives, the TOPSIS method is used for the ranking of the alternatives. The developed selection model is tested on a case study and satisfactory results are obtained.Item A Comparative Holistic Fuzzy Approach for Evaluation of the Chain Performance of Suppliers(2014) Eraslan, Ergun; Atalay, Kumru DidemThe competition between the companies in the dynamic market conditions has made the Supply Chain Management (SCM) a more important issue. The companies which have organized their supply chain effectively have obtained more flexibility in their manufacturing processes in addition to delivery of the customer demands. In this study, two different multicriteria decision making algorithms composed of the FAHP and a holistic hybrid method using FTOPSIS were utilized for an electronic company in wholly fuzzy processes. The FAHP is used for determination of the global weights of the factors and the performances of alternative suppliers are evaluated by using both FAHP-based and FAHP-FTOPSIS hybrid methods for synthetic extent values of pairwise comparisons. The sequences of the suppliers differed for the algorithms. The performances of the proposed approaches are quite successful and flexible in a narrow interval. The managerial advantages obtained from the proposed fuzzy algorithms are also analyzed and interpreted.Item Geographic Information System-Based AHP-TOPSIS Approach for School Site Selection: A Case Study for Ankara(2017) Uslu, Aysenur; Kiziloglu, Kubra; Isleyen, Selcuk Kursat; Kahya, ErkayIdentification of school zones is a multi-criteria decision-making problem, which requires a collective evaluation of many criteria, including population density, transportation facilities, level of the population covered, safety of the region. One of the important points that need to be considered during the decision-making phase is the legal restrictions. In this study, a new solution approach is suggested that uses Analytic Hierarchy Process (AHP) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) methods based on Geographical Information System (GIS) for identification of the most convenient location for a primary school to be opened. First, state lands that can accommodate a school in accordance with the development plan have been identified as candidate locations. Among these candidate locations, lands that comply with legal restrictions and cover students within given walking distances with other existing schools were identified as alternative locations by using ArcGIS ESRI software. Then, weights of criteria that were determined by literature reviews were calculated with AHP and alternative locations were ranked with TOPSIS method by using these weights. Suggested approach has been applied to Cankaya district of Ankara city, and results have been presented.Item A COMPARATIVE STUDY OF THE CAPABILITY OF ALTERNATIVE MIXED INTEGER PROGRAMMING FORMULATIONS(2018) Keseci, Baris; Derya, Tusan; Dinler, Esra; Ic, Yusuf Tansel; AAC-4793-2019; F-1639-2011; AAI-1081-2020In selecting the best mixed integer linear programming (MILP) formulation the important issue is to figure out how to evaluate the performance of each candidate formulation in terms of selected criteria. The main objective of this study is to propose a systematic approach to guide the selection of the best MILP formulation among the alternatives according to the needs of the decision maker. For this reason we consider the problem of "selecting the most appropriate MILP formulation for a certain type of decision maker" as a multi-criteria decision making problem and present an integrated AHP-TOPSIS decision making methodology to select the most appropriate formulation. As an example the proposed decision making methodology is implemented on the selection of the MILP formulations of the Capacitated Vehicle Routing Problem (CVRP). A numerical example is provided for illustrative purposes. As a result, the proposed decision model can be a tool for the decision makers (here they are the scientists, engineers and practitioners) who intend to choose the appropriate mathematical model(s) among the alternatives according to their needs on their studies. The integrated AHP-TOPSIS approach can simply be incorporated into a computer-based decision support system since it has simplicity in both computation and application.