162
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3
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Archived Theses
Narin saplı tahıl bitkilerinde mukavemet ve titreşim analizi ve teknolojiye aktarımı
Bu çalışmada makarnalık buğday (Triticum durum L.), ekmeklik buğday (Triticum aestivum L.), arpa (Hordeum vulgare L.), tritikale (Triticosecale L.), yabani arpa (Elymus L.) ve yabani yulaf (Avena fatua L.) gibi uzun saplı ve küçük çaplı olan bitkilerin fiziksel ve mekanik özellikleri incelenmiştir. Tüm bitkilerden otuzar tane toplanıp çap ve başak ağırlığı ölçümleri yapılmış ve grafiklerle sonuçlar sunulmuştur. Tüm bitkilerden dörder tane toplanıp bitkilerin sapları test makinesi ile çekilmiştir. Özel yöntemlerle preparatlara alınan bitki sap kesitleri optik mikroskopta büyütülmüştür. Yarıçap boyunca malzeme yoğunluğu değişimi ölçülmüş ve bir matematik modelle yaklaşık olarak ifade edilmiştir. Elde edilen verilerden hareketle eğilme ve burkulma direnci daha yüksek ve aynı zamanda bazı modlarda yüksek tabi frekansa sahip yeni bir kiriş/kolon tasarımı önerilmiştir. Bu yeni tasarımlar ile mevcut tasarımların gerilme dağılımı, kritik burkulma yükleri ve tabi frekansları ANSYS programı kullanılarak karşılaştırılmıştır.
An experimental investigation of electrical discharge machining (EDM) fast hole drilling of Inconel 718 and Ti6Al4V
Aerospace manufacturing industry demands high level of quality, accuracy, skilled work and precision manufacturing operations. Electrical discharge machining (EDM) which is very prominent amongst the non-conventional machining methods is effectively used in aerospace manufacturing applications. EDM hole drilling is a variation of EDM process and it is preferred to drill holes with high-aspect ratios. This work was undertaken to investigate EDM hole drilling processes and study EDM hole drilling performance on aerospace alloys, namely Inconel 718 and Ti-6Al-4V. Effects of EDM process parameters, such as discharge current, pulse on/off time and capacitance on material removal rates (MRR), electrode wear (EWR) and surface roughness (SR) were analysed throughout the experimental works. The experimental plan was conducted according to the design of experiment (DOE) and the results were statistically evaluated using analysis of variance (ANOVA). Response surface methodology (RSM) was employed in evaluating the drilling performance of the EDM process and mathematical models and optimisation attempts for MRR, EWR and SR were established. The results obtained from the mathematical models and optimisation attempts were verified additional validation experiments.Key Words: EDM, Hole-drilling, Aerospace Alloys
Development of neuro-fuzzy models for hole drilling on Ti-6Al-4V and Inconel 718 using electrical discharge machining
The aim of this study is to develop ANFIS models for prediction of input-output relationships in hole drilling EDM process. It is a nontraditional machining process preferred to produce holes on difficult-to-cut materials, particularly aerospace alloys, in a fast and accurate way with a good surface finish. There are many parameters in this process, and their effects on the process outputs are very complicated. It is usually not possible to define such complex relationships by means of conventional modeling techniques. Fuzzy logic and neural networks are intelligent modeling techniques to predict the response of a process in accordance with the given inputs.For this purpose, an Adaptive Neuro-Fuzzy Inference System (ANFIS) has been implemented to develop neuro-fuzzy models. The experimental data were obtained by making several holes on specimens of Ti-6Al-4V and Inconel 718 using copper and brass electrodes (Ø2 mm) with input parameters of current, pulse-on and pulse-off times, and capacitance. The output parameters were material removal rate, electrode wear rate, and surface roughness. The comparison between experimental and ANFIS results reveal that developed models can predict the values of process outputs for given input parameters within the lowest error range.
CFD modelling of two-phase pulsatile tubular flows
The analysis of pulsatile tubular flow problems is studied by using FLUENT CFD (Computational Fluid Dynamics) software. Modelling and analysis are realized by three main steps:Firstly, single-phase, Newtonian, intermediate laminar pulsatile flow in rigid pipe flow at different flow conditions is studied for the evaluation of characteristic flow parameters. The computational and experimental data on axial velocity confirm each other except the near-wall region for 0.95Keyword: Euler = Euler ; Kan = Blood ; Koroner damarlar = Coronary vessels ; Sürükleme katsayısı = Drag coefficient ; İki fazlı sistemler = Two phase systems
Computer simulation of the long-term performance of a summer air conditioning system with a man -made sea sonal thermal energy store
ABSTRACT COMPUTER SIMULATION OF THE LONG-TERM PERFORMANCE OF A SUMMER AIR CONDITIONING SYSTEM WITH A MAN-MADE SEASONAL THERMAL ENERGY STORE YİLDİRİM, Murtaza M. S. In Mechanical Engineering Supervisor: Prof. Dr. Mazhar ÜNSAL February 1991, 97 Pages Modelling and computer simulation of the long-term performance of a summer air conditioning system with a man-made seasonal thermal energy store is the subject of this investigation. The performance of two different models as hot and cold time active systems were investigated for daily and seasonal storage. In both cases, winter air is the natural source for cooling. For hot time active system, the cold storage tank is cooled by low temperature atmospheric air via an air/water heat exchanger and the air conditioning system condenser is cooled fully or partially by the water in the cold storage tank during hot time when the air conditioning system is operational. In cold time active system, the air conditioning system is operational at cold time. The condenser is cooled by cold time atmospheric air. Water is cooled and stored during cold time.The water is then circulated between the tank and fan-coils. The purpose of this study is the estimation of the effect of systems components cm the coefficient of performance (COP) by an interactive computer program that is prepared in the Fortran 77 language. Results of these two models are compared with the results of a conventional system. Key words: thermal storage, energy storage, thermal energy store, cold storage, seasonal thermal energy store. ni
2B büyük deformasyon problemleri için ağsiz yöntemler
In this work, PIM and RPIM are used in the solution of 2D geometrical nonlinear and elasto-plastic problems. The effect of shape parameters are investigated in the solutions. The optimum values of shape parameters are either validated or proposed.The singular moment matrix problem in the PIM is discussed in detail and two new algorithms are proposed: A diagonal offset algorithm and Regular based algorithm. They are numerically tested and applied in the solution of 2D elastic problems. The regular basis algorithm gives excellent results with regular distributed field nodes.A number of programs are developed for the solution of 2D geometrically nonlinear and elasto-plastic problems. Mathematica, Fortran 95 and Matlab are used in the programming stages. The PIM and RPIM shape function are successfully implemented in these programs.
Computer simulation of solar aided heat pump systems with underground spherical thermal energy stores
l ABSTRACT COMPUTER SIMUIATION OF SOLAR AIDED HEAT PUhP SYSTEMS WITH UNDERGROUNO SPHER1CAL THERMAL ENERGY STORES YUMRUTAŞ, Recep M. S. in Mechanical Engineering Supervisior : Prof. Dr. Mazhar Unsal April 1991,84pages Thls study contains two computational simulation models Tor predicting long term performance of solar alded heat pump systems with spherical thermal energy stores. Two models are developed for predlction of the transient ternperature f ield outside an underground sphertcal thermal energy store. Solutions of the transient heat transfer problems are obtained by applications of a similarity transformation and a complex flnlte Fourier transformation. Solutions obtained are used to tnvestlgate the long term performance of the systems under constderation. Two interactive computer programs were developed in Fortran 77. The computer programs are utilized to ftnd the transient storage temperature and long term system performance. Results obtained from execution of the programs are presented in graphical form. Key words : Solar energy, heat pump, thermal storage, solar heatlng iii
Design, construction and testing of a model blower type wind tunnel
ABSTRACT DESIGN. CONSTRUCTION AND TESTING OF A MODEL BLOWER TYPE WIND TUNNEL USKANER, Fatma. M.S. in M.E. Supervisor: Prof." Dr. Ömer T. GÖKSEL September 1991, İ&5 pages. In the work presented in this thesis, a prototype blower wind tunnel and 1/7 model of it were designed by developing a similarity analysis, for the similar tunnels. The model tunnel was constructed and instrumented. The flow quality in the test section and in other tunnel components were investigated. Additionally, the test results of the model tunnel were compared with the theoretical results. Key words; Prototype, Model, Similitude, Blower Wind Tunnel, Wind Tunnel Design. Scientific Code: 825.04.83 IV
Computer aided optimisation of cutting conditions in multicut turning operations
ABSTRACT COMPUTER AIDED OPTIMISATION OF CUTTING CONDITIONS IN MULTICUT TURNING OPERATIONS BAYKASO?LU, Adil M. Sc. In Mechanical Engineering Supervisor: Assoc. Prof Dr. A. İhsan Sönmez May 1995, 119 pages In this study, a computer program is developed for the optimisation of cutting conditions in turning operations such as; roughing, boring, facing, drilling, threading, grooving and parting-off. By using minimum cost criterion as the objective function a direct search procedure is used for the optimisation of cutting conditions in turning operations namely; roughing, boring and facing. For the other operations which are drilling, threading, grooving and parting-off feasibility check methods are used for the optimisation of cutting conditions. The following costraints were considered in the optimisation: maximum and minimum depth of cuts and feeds for the tool and workpiece materials, maximum allowable tool force, holder strength and rigidity, spindle and feed-drive motors torque-speed characteristics, work holding limitations, deflection of the workpiece, geometrical accuracy, bearing design loads, cutting tool velocities, tool wear and surface roughness. The program is written in Turbo C++ and CLIPPER programming languages on an IBM compatible personal computer. The use of the system is illustrated with practical examples. Key Words: Metal cutting in turning, Optimisation, Cutting Conditions HI
Computer aided design of machine elements
ABSTRACT COMPUTER AIDED DESIGN OF MACHINE ELEMENTS DEM I RH AN, Necdet M.S. in Mechanical Engineering Supervisor. Prof. Dr. İ. Hüseyin FİLİZ August 1996, 155 pages In this thesis, a computer aided design (CAD) package for the machine elements is prepared. Shafts, bolts, anti-friction bearings, journal bearings, helical springs, brakes and V-belts are the elements considered in this study. The developed design package has a modular structure. For each of the machine elements specified above, an interactive computer aided design/selection program is written. A database which consists of material properties, design parameters like stress concentration factors, charts, standard values from manufacturer's catalogues, etc., is prepared to ease the design and selection procedure. The modules were combined under a supervisor program. Programs are written in QuickBASIC and colour graphics are sometimes utilised to communicate with the user. The entire system is implemented on an IBM compatible PC. The use of CAD package for each module is illustrated with examples. Key Words: Computer Aided Design, Machine Elements m