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 A multiobjective mathematical model to form the best team at sports clubs: team harmony and player performance objectives(2022) Budak, Gercek; Kara, ImdatPurpose Team coaches of sports clubs are highly concerned when forming the best team to win the upcoming match at the stage before that particular game. Even if a team squad is comprising of a limited number of players, the combination of them makes a complicated problem with a huge number of possible line-ups. This study aims to build a mathematical model to solve this problem with the objectives of maximum player performance and team harmony. Design/methodology/approach This paper proposes a novel approach of a multiobjective mathematical model on team harmony and player performance. Two objectives are chosen as these are the most important perspectives that define the best team. The model outputs are nondominated solutions of these two objectives. Findings These solutions are displayed to the team coach to decide the best team according to strategical, psychological and conditional preferences of him/her. A real-life example is demonstrated to show the model validity and interpretation of the results by using the technique for order preference by similarity to an ideal solution on a volleyball team formation problem. Originality/value This paper proposes a multiobjective mathematical model on team harmony and player performance to solve the team coach's hard and complicated problem.Item Analysis of the manufacturing flexibility parameters with effective performance metrics: a new interactive approach based on modified TOPSIS-Taguchi method(2022) Ic, Yusuf Tansel; Sasmaz, Turgut; Yurdakul, Mustafa; Dengiz, Berna; 0000-0001-9274-7467; AGE-3003-2022Flexibility is one of the most important strategy parameters to achieve a long-term successful performance for a manufacturing company. Studies in the literature aim to operate a manufacturing system at optimum levels of flexibility parameters under its own manufacturing environment. This study aims to present an interactive analysis framework based on TOPSIS and Taguchi parameter design principles for investigating the effects of different levels of flexibility parameters on the performance of a flexible manufacturing cell (FMC). The main performance metric used in this study is manufacturing lead time. Other important metrics to evaluate quality control and inspection policies are also investigated in this study. To conclude, a combined model of an interactive approach based on TOPSIS and Taguchi methods are used to assess the effectiveness of the flexibility parameters for a FMC.Item The development of a reviewer selection method: a multi-level hesitant fuzzy VIKOR and TOPSIS approaches(2021) Kocak, Serdar; Ic, Yusuf Tansel; Atalay, Kumru Didem; Sert, Mustafa; Dengiz, Berna; 0000-0001-9274-7467; AGE-3003-2022This paper proposes a new approach for the selection of reviewers to evaluate research and development (R&D) projects using a new integrated hesitant fuzzy VIKOR and TOPSIS methodology. A reviewer selection model must have a multi-level framework in which reviewer selection strategies and related objectives guide the second level of the reviewer performance ranking process. The model must measure reviewer performance related to the activities that are necessary for the R&D project evaluation to be successful. A novel model is presented in this paper. In the proposed methodology, the aim is to select a reviewer in a hierarchical decision-making structure. The selection criteria values and their weights were obtained using the hesitant fuzzy VIKOR method. For the selection of a suitable reviewer, the conventional TOPSIS model was used. We developed a simpler procedure for effectively performing the reviewer selection process. The new approach was tested with a real case study and satisfactory results were obtained. A comparative analysis is also included in the article for illustrative purposes.Item A knowledge-based material selection system for interactive pressure vessel design(2020) Yurdakul, Mustafa; Balci, Arif; Ic, Yusuf Tansel; AAI-1081-2020Continual introduction of new materials and improvements in existing materials increase the variety of materials that can be used for pressure vessel components. Among wide variety of materials, the most suitable one must be selected for a component by matching its functional requirements with various available materials' specifications. This study proposes an interactive knowledge-based decision support system for selecting the most suitable material for a given pressure vessel component and its working environment. The developed decision support system, namely Pressure Vessel SELection (PVSEL), consists of two separate phases. In the first elimination phase of PVSEL, the user obtains a feasible set of alternative materials by answering various questions and providing lower-limit values at materials' critical specifications. PVSEL, then, uses a ranking phase which uses ELECTRE, TOPSIS and VIKOR methods to rank the feasible materials. In the second phase, each alternative material's ranking is determined by combining its performance values at weighted critical specifications (selection criteria), which are considered as important in meeting the functional requirements of the component. Usage of PVSEL is illustrated in the paper and the results show that the proposed PVSEL is an effective selection tool and provides meaningful results for the designers.