Mühendislik Fakültesi / Faculty of Engineering
Permanent URI for this collectionhttps://hdl.handle.net/11727/1401
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Item Determination of periodic inspection time in pressurized equipment exposed to fatigue by estimating the probability of fracture(2021) Sozen, Levent; Yurdakul, Mustafa; Ic, Yusuf Tansel; 0000-0001-9274-7467; AGE-3003-2022It is essential to inspect the pressurized equipment such as vessels, pipes, heat exchangers, boilers, etc., which are under the influence of variable load periodically to minimize the possibility of damage occurring or early disclosure of existing damage. These inspections may be carried out at fixed time intervals or can be carried out at determined intervals depending on a risk assessment that considers settlement of the equipment, operating conditions, and the potential danger of the equipment's chemical contained. Within the scope of this study, we evaluate the thin-walled pressurized equipment under variable internal pressure load. Special attention is crucial to the hot points where the stress is relatively high for inspection of fatigue-related damage on the equipment. We know that stress concentration factors are critical in welded zones in thin-walled pressure vessels. Therefore, the fatigue crack formation in the welded joints is more likely than the equipment's base metal. As a result of the study, we present the probability of time-dependent damage under the effect of fatigue caused by variable internal pressure for butt welded joints. Also, we propose a new approach for periodic control planning. As a case study, damage probabilities of the fuel or gas pipelines operating under variable pressure are calculated based on the diversity of the mentioned parameters, and a new approach is provided to determine the most suitable periodic inspection interval.Item A New Multi-Echelon Repair Network Model with Multiple Upstream Locations for Level of Repair Analysis Problem(2021) Bicakci, Ismail; Ic, Yusuf Tansel; Karasakal, Esra; Dengiz, Berna; 0000-0001-9274-7467; AGE-3003-2022Level of repair analysis (LORA) determines (1) the best decision during a malfunction of each product component; (2) the location in the repair network to perform the decision and (3) the quantity of required resources in each facility. Capital goods have long life cycles and their total life cycle costs are extremely high. LORA, which can be done repeatedly during the life cycle of the product, both at design and product support phase, plays an important role in minimising the total life cycle costs of capital goods. It is mostly applied to systems that operate in different geographical areas and deployed in different regions, which include different subsystems with special technology and expertise, and have a complex product structure. In this study, we propose a new mathematical model to the LORA problem, which is more comprehensive and flexible than the other pure LORA models in the literature. The proposed model uses the multiple upstream approach that allows the transfer of the components from a location in the lower echelon to the predefined locations in the upper echelon and determines the material movement paths between each facility, defining the facilities' locations in the repair network. The performance of the proposed model is tested on benchmark instances and the results are compared with the single upstream model. Computational experiments show that the proposed model is more effective than the single upstream model and reduces the total life cycle costs by 4.85% on average, which is an enormous cost saving when total life cycle costs of capital goods are considered.Item Analysis of the effect of the number of criteria and alternatives on the ranking results in applications of the multi criteria decision making approaches in machining center selection problems(2020) Ic, Yusuf Tansel; Yurdakul, MustafaMulti criteria machining center selection models are widely used in the literature. In the applications of multi-criteria decision making models, machining center selection criteria are directly taken from catalogues. It is known that to have a ranking model sensitive to the weights of the selection criteria, it is especially important to limit the number of selection criteria to 7 +/- 2. A similar proposal can be put forward for the number of machining centers. In this study, whether or not reducing the number of criteria and alternative machining centers make the ranking results more sensitive to the changes in the criteria weights is studied using Spearman's rank correlation test. The study results show that the ranking results become more sensitive with a reduced number of criteria and alternative machining centers.Item Fuzzy failure mode and effect analysis application to reduce risk level in a ready-mixed concrete plant: A fuzzy rule based system modelling approach(2020) Simsek, Baris; Ic, Yusuf TanselIn this study, failure mode and effect analysis were applied to evaluate and eliminate potential failure modes in a Ready-Mixed Concrete Plant using a fuzzy-rule-base system. The questionnaires were specially prepared for each sub-department such as production plant, workshop and maintenance, dumping grounds, materials transportation and storage, utilities, administrative office, social facility, quality control laboratory and wastewater pool and recycling facilities. The questions were answered by the workers in each section. Risk Priority Numbers (RPNs) and Fuzzy Risk Priority Numbers (FRPN), which measure potential failure modes, were calculated using the risk parameters. High-risk areas were identified, and some suggestions were made to reduce accident risk at the Ready-Mixed Concrete Plant. Three questionnaires were prepared, based on these suggestions, and distributed to workers to determine whether the suggestions would reduce the risk or not. Based on conditions at the time the recommendations were implemented and improvement rates were calculated. The results showed that the fuzzy failure mode and effect analysis methodology were effective in identifying and eliminating potential failure modes at the Ready-Mixed Concrete Plant. The results can also be used by other ready-mixed concrete manufacturers who want to improve the safety of their operations. (C) 2020 International Association for Mathematics and Computers in Simulation (IMACS). Published by Elsevier B.V. All rights reserved.Item An optimization for milling operation of Kevlar fiber-epoxy composite material using factorial design and goal programming methods(2019) Ic, Yusuf Tansel; Elaldi, Faruk; Kececi, Baris; Uzun, Gozde Onder; Limoncuoglu, Nur; Aksoy, Irem; 0000-0003-0592-6868; 0000-0002-2730-5993; AAI-1081-2020; AAG-5060-2019; F-1639-2011; AAC-4793-2019Kevlar fiber-epoxy composite material is extensively used in manufacturing areas because of the advantages of composite material's characteristics. It is usually processed by traditional machining methods but the drawbacks for determination of optimum cutting parameters might cause some material deformations during machining process. In this study, the cutting parameters are concurrently optimized by using the integrated 2k factorial design and goal programming methods for minimum delamination and minimum surface roughness of Kevlar fiber-epoxy composite and the best machining parameters have been obtained for the material. The results were compared with the results of the multi-criteria decision-based Taguchi methods.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 Hybridizing a fuzzy multi-response Taguchi optimization algorithm with artificial neural networks to solve standard ready-mixed concrete optimization problems(2016) Simsek, Baris; Ic, Yusuf Tansel; Simsek, Emir HuseyinIn this study, a fuzzy multi-response standard ready-mixed concrete (SRMC) optimization problem is addressed. This problem includes two conflicting quality optimization objectives. One of these objectives is to minimize the production cost. The other objective is to assign the optimal parameter set of SRMC's ingredient to each activity. To solve this problem, a hybrid fuzzy multi-response optimization and artificial neural network (ANN) algorithm is developed. The ANN algorithm is integrated into the multi-response SRMC optimization framework to predict and improve the quality of SRMC. The results show that fuzzy multi-response optimization model is more effective than crisp multi-response optimization model according to final production cost. However, the ANN model also gave more accurate results than the fuzzy model considering the regression analysis results.Item Development of a decision support system to select materials for pressure vessels(2018) Ic, Yusuf Tansel; Balci, Arif; Yurdakul, Mustafa; AAI-1081-2020Improvements in technologies applied in material field and continual increase in the number of material types force to develop and use new approaches in material selection. In this paper, a multi-criteria decision support system, called MATSEL, is developed to make material selection decisions for pressure vessel components more thorough and inclusive. MATSEL consists of two separate stages. In the first elimination stage of the MATSEL, it obtains a feasible set of materials for a specified pressure vessel component. MATSEL, then, uses three different multi criteria approaches namely ELECTRE, TOPSIS and VIKOR in the second stage to rank the feasible materials. An overall total score is obtained by summing the rankings of every feasible material and MATSEL proposes the material with the lowest total score as the most suitable one for the specified component. In this study, the statistical similarities between the rankings are also calculated to analyze the differences between rankings if there are any. Instead of inputting the materials every time MATSEL is used, a material data base is formed with the usage of ASME (American Society of Mechanical Engineers) and Ashby material selection diagrams for selection of alternative materials for the specified application.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.Item Optimization of the Factors That are Critical in External Surface Grinding of Roller Followers Using Design of Experiments(2018) Ic, Yusuf Tansel; Gunay, Ezgi; Yurdakul, Mustafa; Mizrak, Haci Veli; Gunes, Serkan; AAI-1081-2020In this study, it is aimed to experimentally optimize the parameters of the grinding of external surface of the roller followers which are used in internal combustion engines to operate the inlet and exhaust valves. 2k factorial experimental design methodology is applied to optimize the grinding process such that after this last finishing operation the rollers' external surface quality and cycle time meets the customers' special and strict requirements. In the application of the experimental design methodology, the critical parameters that are important in the optimization of two different surface roughness values along with cycle time are first determined. Then, the values of critical parameters are calculated with the application of the multi-objective optimization of the two surface roughness measures and cycle time. As a result of the optimization, the surface roughness values that are important in the working of the roller followers and cycle time are improved.