Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
Browse
186 results
Search Results
Master Thesis Hydraulic Design Optimization and Performance Evaluation for a Dishwasher(Izmir Institute of Technology, 2019) Erik, Ömer Berhan; Çetkin, ErdalHydraulic designs of dishwashers with 12 (2 baskets) and 15 (3 baskets) place settings with diverter which distributes the water to bottom and upper spray arms separately were analyzed. First, both hydraulic systems were modeled analytically, so continuous and local losses were calculated based on them. Besides, operating point of systems were determined based on the curve of the pump and head loss. All parameters were also verified by experimental tests. An asynchronous circulation pump (fixed pump rpm and outlet pressure) with the same hydraulic outlet pressure is used in both products. Hydraulic design is evaluated with parameters obtained from the analytical model and then the design of equipment along the hydraulic path was improved. Once parameters improving the designs are determined, modified parts were analyzed numerically with finite volume method. The results were also validated with experimental studies. Lastly, prototype with improved design parameters was produced and installed on a dishwasher. Dishwasher performance index was calculated according to IEC standards to see the effect of new design on dishwasher washing performance. The results show that the energy requirement decreases 25% whereas performance index stays the same.Master Thesis Microscale Precise Position Measurement and Monitoring of Sliding Valves(Izmir Institute of Technology, 2019) Tanrıyapısı, Önder Mahir; Özdemir, Serhan; Özdemir, SerhanIn present study, a sensor, Accuciser, is presented to know the position of sliding valves which have ferromagnetic or diamagnetic guide. The main objective is to develop a sensor, which has low cost and high resolution, that measures the displacement of engine valves or SCR injectors which are used in especially in the automotive industry. For now, the position of the valves, which are using in propulsion systems, or SCR injector cannot be known with a signal from an analog sensor. Instead of analog sensor, the mapping is used from experimental data. However, this mapping gives inaccurate results due to driving style or usage of the system. After seeing the gap in these systems, the sensor was developed, and it fulfils this gap. The sensor is developed based on Faraday’s Law of Induction which was discovered by Michael Faraday in 1830. The sensor consists of two coils and one coil located on top of the other. The most important property of the proposed sensor is working with a direct current. In fact, if the valve is actuated by an electromagnetic force, there is no power consumption on the sensor. The experimental results, for the latter property, are corroborated by theoretical calculations. The output of the sensor is directly proportional to the displacement of the core and it has high signal-to-noise ratio because of the nature of magnetism. The results show that using Accuciser, the proposed sensor, to monitor valve displacement gives more reliable results than current technology.Master Thesis Dynamic Crushing Behaviour of Cactus Geometry Inspired Core Structure(Izmir Institute of Technology, 2019) Balya, Ozan; Taşdemirci, Alper; Güden, MustafaCactus geometry inspired core structure was manufactured with the fused deposition modelling method by a 3D printer using Acrylonitrile Butadiene Styrene (ABS) material filament. The characterization of ABS was made by performing compression tests to take some parameters for numerical models. Numerical preliminary studies were carried out by using the areal density concept and direct-impact Hopkinson pressure bar test method to compare the cactus geometry with the conventional ones in point of the specific energy absorption capacity (SEA). It was understood that from the preliminary work, the cactus inspired structure is intriguing to investigate the dynamic crushing behaviour at least. Quasi-static, drop weight and direct-impact Hopkinson pressure bar tests were conducted to comprehend the energy absorption and crushing behavior in all cases, then to investigate the strain rate and inertia effects on the structure. Implicit and explicit numerical models were made by using LS-DYNA software to validate experiments and to set a precedent for future works. It was seen that the result of numerical models is in harmony with that of experiments excluding the non-fracture structure at the quasi-static implicit model. Moreover, although quasi-static compression gave the structure more stable deformation behavior compared to drop weight impact, higher energy absorption capability was observed on drop-weight tests. In addition, the strain rate effect is more forceful in point of loading carrying capacity compared to the inertia effect despite the fact that it provides the development of buckling and damage formation.Master Thesis Development of Fiber Reinforced Cylindrical Composite Structures by Filament Winding Technique(Izmir Institute of Technology, 2019) Aydın, Mustafa; Tanoğlu, MetinFiber reinforced composite structures with superior properties are used for cylindrical structure systems in many application areas nowadays. The major aim of this thesis is development of filament wound composite cylindrical structures with various fiber types on different ply sequence and investigate their mechanical properties. For this purpose, 4 layered glass, carbon and glass/carbon hybrid fiber reinforced cylindrical structures were manufactured with 55 degree winding angle by utilizing filament winding technique. Produced 6 different composite structures have 1 m length and 60 mm inner diameter. Glass/carbon fiber reinforced systems were developed to reduce the cost by reducing carbon fiber usage. Apparent hoop tensile strength and radial compression tests were applied to the manufactured composite structures. In addition to these studies, two different composite plate with glass fiber and carbon fiber reinforcements were produced by filament winding to investigate glass transition temperature. These plates were manufactured with 4 layered by using the same fiber and matrix as used in the previous tube production. Dynamic mechanical analysis was performed with samples which is sectioned from plates to obtain glass transition temperature. Consequently, apparent hoop tensile strength test results showed that hoop strength of glass fiber reinforced cylindrical structures can be improved significantly by hybridization. Based on the radial compression test results, deflection of the structures decreases by hybridizationMaster Thesis The Dynamic Mechanical Characterization of a Bio-Inspired Sandwich Structure(Izmir Institute of Technology, 2019) Ramyar, Ayda; Taşdemirci, Alper; Güden, MustafaIn this study, the sandwich structure consisting of novel-3D-printed-polymeric base core was examined in terms of crashworthiness. The designed core structure for energy absorption purpose is inspired by the geometry of the human fingerprint. The fingerprint geometry is a spiral-shaped, asymmetrical and complex structure; therefore, the manufacturing of the geometry is difficult by conventional manufacturing methods. Fused Deposition Modeling (FDM) which is one of the additive manufacturing (AM) methods was used for fingerprint core preparation by layer by layer production technique with low-density material. After the material characterization of 3D printed thermoplastic specimens, optimum geometric parameters of fingerprint were determined via experimental and numerical studies by changing the height and thickness. The fingerprint performed better crushing performance compared to other conventional geometries. Quasi-static and dynamic crushing experiments were conducted, and the results were verified with models by non-linear finite element code LS-DYNA. The results showed that the energy absorption capacity and peak crushing force of fingerprint geometry increases with strain rate increment. However, the deformation behavior of the structure under dynamic loads changes and the material becomes more brittle. This is caused by the change in deformation mechanism due to AM and material itself. It was found that the 3-D printed core structure is suitable to be employed at low-to-medium strain rates due to its multi-stage deformation behavior. It was observed that the bio-inspired sandwich structure consisting of 4 fingerprint-core can absorb 10% more impact energy than fourfold individual 3-D printed core geometry, which indicates the promising potential of the novel sandwich structure for crashworthiness applications.Master Thesis Sub-Kilowatt, Efficient Capacitive Power and Data Transfer for Monitoring the Major Mechanical Variables(Izmir Institute of Technology, 2019) Karabulut, Abtulgalip; Özdemir, SerhanThe main aim of this thesis is to design and prototype a sub-kilowatt, efficient capacitive data and power transfer (CPT) system that for example, monitors the loads on an axle of a vehicle. The data and power are transmitted wirelessly. In a separate case study, the power is provided for the weight measurement system by an E class power amplifier. In the industry, today, wireless power and data transfer methods have become quite popular. Some of those methods are inductive power transfer (IPT), capacitive power transfer, micro-wave power transfer (MCP). One of these techniques, which is the theme of this thesis, is the capacitive power and data transfer. The capacitive power system is quite compact and does not create electromagnetic interference (EMI), which is one of the strengths of the CPT. Hence, the stability of the embedded electronics system is preserved. Another attractive feature of CPT is that data and power can be transferred at the same frequency over a short distance. This thesis addresses the various facets of the CPT system. The historical development of the CPT technique has started with Nicola Tesla. Wireless power transfer methodology could safely be attributed to him. The system consists of two main parts which are the weight measurement system and power transmitting system. The power is transferred by the copper capacitive plates with 100 cm2 surface area. Average error of the measurement system is computed as 1.1% with high signal-to-noise ratio (SNR). Finally, the capacitive power and data transfer system has been designed with 83.8% efficiency at 1.7 MHz frequency and high SNR.Master Thesis Investigations on Surface Electric Charge of Silica Nanoparticles With Different Surface Roughnesses(Izmir Institute of Technology, 2019) Alan, Büşra Öykü; Barışık, MuratSilica nanoparticles have been receiving more attention from diverse research areas recently due to their significant physical properties such as large pore volume and high internal surface area, colloidal stability, high biocompatibility, and tunable pore sizes. These silica nanoparticles are great candidates for drug delivery applications because they can transport a large amount of drugs into selective organs and tissues due to their high surface area and large pore volume. However, there are important drug delivery mechanisms that need to be understood properly such as cellular uptake, endosomal escape, drug loading and release, and crossing physical barriers. Physicochemical properties of nanoparticles (size, shape, surface charge, or surface chemistry) are important for understanding these mechanisms in order to develop successful drug delivery applications. This research investigates how these surface charge properties change with different particle, pore diameters, roughness structure on the nanoparticle surface, and different temperature and solution conditions. Also, we investigate how the surface charging behavior of rough nanoparticles interacts with a flat plate. Rough nanoparticles and their interactions with surfaces theoretical assumptions can be wrong and ionic distribution can show variation locally. In order to calculate ionic distribution and surface charge properties in these systems, proper equations and boundary conditions were employed. The charge regulation model was used as a boundary condition because of the electric double layer overlap effect. Results showed that there was a considerable variation on surface charge properties due to the roughness structure with different roughness and particle sizes and temperature difference.Master Thesis Experimental and Numerical Analysis of the Strain Rate Dependent Compressive Strength of a Cellular Concrete(Izmir Institute of Technology, 2019) Akyol, Burak; Güden, Mustafa; Taşdemirci, AlperExperimental and numerical quasi-static and high strain rate tests, including compression, indentation and direct impact, were performed on a cellular concrete in order to investigate the effect of strain rate on the compressive strength. The results of compression tests indicated three distinct regions of the compressive strength dependence on strain rate. A relatively lower strain rate dependent compressive stress was found in the quasi-static strain rate-regime, 2x10-3-2x10-1 s-1, a relatively high strain rate dependent compressive stress in the dynamic strain rate-regime, 180-103 s-1 and a cut-off strength above 103 s-1. The dynamic increase factor (DIF=dynamic/static fracture strength) varied between 1 and 2.5 from quasi-static to dynamic strain rate-regime with a sharp increase after about 100 s-1. The indentation tests using 25 and 30 mm-diameter indenters in the quasi-static strain rate-regime (uniaxial state of strain) and resulted in moderate DIF values (1-1.13), very similar with those of the quasi-static compression tests (1-1.15). In the indentation tests, the DIF values significantly and also confirmed the numerically determined DIF values of concrete at 1000 s-1 (~1.30) without radial and axial inertia. The compression and direct impact tests in the Split Hopkinson Bar (SHPB) set-up were implemented numerically in LS-DYNA using an anisotropic strain rate insensitive material model, MAT_096 (MAT BRITTLE DAMAGE). The stress readings were performed at the specimen different locations of the SHPB and indicated that radial and axial inertia were dominant between 1 and 30 m s-1 (30-1000 s-1).Master Thesis Optimization of Oxide Additives in Boron Carbide Powders Using Precipitation Method(Izmir Institute of Technology, 2019) Elçi, Caner; Toksoy, Muhammet FatihThis study aims to precipitate oxides to boron carbide powders to achieve homogeneous dispersion of additive which is essential for sintering. Fine boron carbide powders were suspended in distilled water, then nitrate salts were solved in alcohol. Solved nitrate salts were fed to mixture in high pH levels. Mixing stage of the precipitation was done with both magnetic stirrer and ultrasonic treatment to investigate the effect of the mixing method. After the precipitation, synthesized powders were calcined under various atmospheres to eliminate the inorganic residues from the precipitation process. The examination of the XRD graphs showed that the calcination atmosphere is important for the oxide layer of the boron carbide powders. Inert atmosphere restrained the formation of the boron oxide layer due to the lack of oxygen. Methanol washing also eliminated the boron oxide layer. According to the zeta potential analysis, surface characteristics were obtained better when the ultrasonic treatment was applied during the precipitation. Ultrasonic treatment increased the dispersion of the additives between the particles during the suspension stage of the precipitation. Calcination time also affected the dispersion of the yttrium oxide at the sintered compacts when the SEM images were observed. When the calcination time increased, dispersion of the yttria was getting more agglomerated.Master Thesis Investigation of Mechanical Properties and Fatigue Performance of Carbon-Glass Fiber Reinforced Epxy Hybrid Composites(Izmir Institute of Technology, 2019) Sandallı, Hatice; Tanoğlu, MetinRecently, hybrid composites have known as high performance engineering materials and they have been used broadly in engineering applications where high strength to weight ratio, reasonable cost and ease of fabrication are requested. Since these composites offer combination of benefits of different kinds of fibers, their usage is increasing day after day. The objective of this thesis is to examine the mechanical properties of carbonglass fiber reinforced epoxy hybrid composites in two different configurations. Also, the fatigue performance under bending tests of these composites were investigated. The hybrid composites were manufactured by using vacuum infusion technique at ambient temperature. To examine the mechanical properties of manufactured composites, a series of mechanical tests such as compression, tensile and three-point bending tests were performed on the samples which were prepared in accordance with the relevant ASTM standards. Load-controlled three-point bending fatigue tests were also carried out to investigate the performance of manufactured composites under fatigue. The fatigue tests were performed at different stress levels varied from 30 percent to 90 percent of average ultimate flexural strength of the samples which were determined from static three-point bending tests. Subsequently stiffness loss and Wöhler curves were constructed using a specific failure criterion.