Raylı taşıtlarda teker bandajlı –ray sisteminde dolgu kaynağı ve sabo parçaların aşınma ve yorulma davranışlarının incelenmesi

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.THE WEAR AND FATIGUE BEHAVIOUR INVESTIGATION OF FILLET WELDING AND BRAKES IN WHEEL TYRE-RAIL SYSTEM OF RAILWAY VEHICLES SUMMARY Keywords: Wear, Fatigue, Wheel/Rail Interactions, Fillet Welding Steel wheels rolling on steel rails are the principal characteristic that distinguishes railways from other forms of transport. For effective and economical railway operation, important tribological issues must be addressed at the wheel/rail interface. Wheel and rail meet at a contact patch that is small and carries the full wheel load through which all steering, traction and breaking forces are transmitted. This contact patch sees a severe working environment. Stresses normal to the plane of contact can reach values several times the wheel or rail tensile strength and sometimes shear.s&esses in the plane of contact can exceed the shear yield stress. Rapid temperature rises, caused by relative slip between the wheel and rail, can reach several hundred degrees Celsius in routine operation, and over 10.00 °C in extreme circumstances. These stress and temperature conditions inevitably lead to wear, deformation and damage to the wheels and rails and a major goal of railroads is to arrange service conditions and maintenance procedures to minimize deterioration and hence extend component life. This is important, because rails-and to lesser extent wheels- constitute a large part of a railroad's asset base. Railways have more money invested in rail than in any other asset. Extending the life of these components and especially that of the rail, has a major impact on railroad profitability. An understanding of the tribology of the wheel/rail system is essential if wheel/rail life is to be extended. This system is complex and its behaviours depends on interactions between the materials (wheel, rail and any third body introduced, such as lubricant/debris mixtures) and environmental factors such as rain, snow, ice, etc. The material in and around the contact area is therefore highly stressed. High rates of wear might be expected for such a contact but. in addition, because the load is applied and removed many times during the passage of each train, there is the possibility of fatigue of the rail surface. The ideal material, which does not wear or suffer fatigue and yet is economically viable as a rail or wheel material, has not yet been found. However, service life extension of railroad components such as rail, wheel, wheel tyre and brake pads becomes an important achievement for engineers dealing with railways. XVIITherefore, the wear and fatigue behaviour investigations of rails, wheel tyres and brake pads were performed and occurred damages were characterized in this study. Then fillet welding operation was applied to worn surfaces of wheel tyres with two different electrodes by electric arc welding technique and by Gas Metal Arc welding method used in industry called Boden welding. After that wear and fatigue tests of specimens obtained from welded surfaces and joints were done. For wear tests, pin- on-disc testing method was used and the experiments were performed at four different loads as ION, 20N, 30N and 40N with 1 m/s constant sliding speed. The total sliding distance was 3600 m for every experiment. In the light of results of wear experiments, coefficient of friction, weight loss (mg), volumetric loss (mm3) and specific wear rate (g/N.m) values of specimens were calculated and advices were submitted to users. In addition, fatigue strengths and endurance limits of specimens were tried to detect during the fatigue tests performed for 300, 400 and 500 MPa stress amplitudes. XVII

Endüstriyel yatak alaşımlarının aşınma davranışlarının karakterizasyonu

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.ÖZET Anahtar Kelimeler: Sürtünme, Aşınma, Yatak, Bronz, Çinko- Alüminyum Alaşımı Bu çalışmada yatak malzemesi yapımında geleneksel olarak kuüanüagelen yataklık fosfor bronzu (RB1) ile kurşunlu kalay bronzları (RB4 ve RB7) ile son yıllarda geliştirilmiş olan çinko-alüminyum alaşımlarının (ZA-8, ZA-12 ve ZA-27) aşınma davranışları incelenmiştir. İncelemelerde iki değişik deney türü uygulanmıştır. Bunlardan ilki disk üstü-pim (pin- on-disc)'dir. İkinci tür deney için yatak aşınması yapılan bir deney cihazı sanayide imal edilmiştir. Deneyler 10 N, 20 N ve 40 N'luk yükler altında ve 1 m/s ve 0.5 m/s hızlarda yapılmıştır. Yapılan deneyler sonucunda malzemelerin aşınması, ağırlık kaybı (mg) ve hacim kaybı (mm3) olarak ölçülmüş yatak malzemelerinin sürtünme katsayıları hesaplanmıştır. Bu çalışmadan elde edilen sonuçlara göre ZA alaşımlarının, geleneksel olarak kullanılan bronz alaşımlannınkinden daha düşük sürtünme katsayılarına sahip oldukları görülmüştür. Bu durum hem disk-üstü-pim hem de yatak aşınması deneyleri için geçerlidir. Buna paralel olarak ZA-alaşımlannın ağırlık kayıplarının bronz alaşımlanyla kıyaslandığında çok düşük düzeyde olduğu görülmüştür. Yapılan ölçümler sonucu bronz alaşımlarının, ZA-alaşımlanndan iki saatlik süre içinde; 10 N'da yaklaşık olarak 4 kat, 20 N'da 9 kat, 40 N'da da 14 kat daha fazla ağırlık kaybına uğradığı tespit edilmiştir.Bu araştırmanın sonunda aşınmanın sözkonusu olduğu mühendislik uygulamalarında, eskiden beri kullanılan bronz alaşımlarının yerine aşınma dayanımları yüksek, mekanik özellikleri daha iyi olan ZA-alaşımlannın kullanılabileceği görülmüştür. XIITHE CHARACTERIZATION OF WEAR BEHAVIORS OF INDUSTRIAL SLIDING-BEARING ALLOYS KEYWORDS: Friction, Wear, Shding-Bearing, Bronze, Zinc-Aluminum Alloys SUMMARY In this study, the wear behaviors of conventionally used bearing phosphorus bronze (RBI) and leaded tin bronzes (RB4 and RB7) and recently developed zinc-aluminum alloys (ZA-8, ZA-12 and ZA-27) were investigated. Two types of testing were applied during the research. First one was pin-on-disc testing. The second type of testing was a sliding-bearing testing. A machine for the later testing was designed and built particularly for this research in the university. Tests have been performed under 10 N, 20 N and 40 N loads with 1.0 m/s and 0.5 m/s speeds. After the applied tests wear rates of materials were measured in terms of weight loss (mg) and volume loss (mm3). In addition, the coefficient of friction of all materials tested have been determined. According to the result obtained from this study, it has been seen that the coefficients of friction of ZA-alloys are lower than that of conventionally used bronze-alloys. This is valid for both pin-on-disc testing and sliding-bearing testing. Similarly, weight loses of ZA-alloys are lower than that of bronze-alloys. As a result of the measurements, the bronze-alloys have been subjected to the weight loses approximately four timesgreater than that of ZA-alloys under 10 N force and nine times greater under 20 N and also fourteen times greater under 40 N force in the period of two hours. As result of this research, it has been understood that the zinc-based alloys showing considerably higher wear resistance and having better mechanical properties can be used instead of conventionally used bronze alloys. XI

The effect of process parameters on penetration in gas metal arc welding processes

The welding currents were chosen as 95, 105, 115 A, arc voltages were chosen as 22, 24, and 26 V and the welding speeds were chosen as 40, 60 and 80 cm/min for all experiments. As a result of this study, it was obvious that increasing welding current increased the depth of penetration. In addition, arc voltage is another parameter in incrimination of penetration. However, its effect is not as much as current's. The highest penetration was observed in 60 cm/min welding current. (c) 2005 Elsevier Ltd. All rights reserved

The wear behaviour investigation of sliding bearings with a designed testing machine

In this study, firstly a new wear testing machine was designed and produced in the university in order to investigate the wear behaviour of conventionally used sliding bearing alloys. Secondly, the wear tests of these bearings were performed by using this new machine. Three types of specimens' wear behaviours were tested in this constructed machine. These were tin bronzes called RB-1 and RB-7 and tin-based lead bronze called RB-4. The wear tests were performed under 10, 20 and 40 N loads with 0.5 m/s sliding speed by using ring shaped specimens. During the experiments, these specimens are put in their location in the test machine and tightened and then vertically loaded against the mile located at the center of the motor. When the experiment was started the mile turns and a force occurs to put up with the friction occurred between mile and ring interface. This force creates a moment along the mile axis and tries to turn the specimen. As a result, a deflection was observed in a plate located on the top of the machine and it is recorded by means of a transducer as a voltage (V). These data were recorded in every 10 s and stored in a data acquisition card inside the computer. The experiments were conducted for 2 h. Having finished the tests, the weight losses of the specimens were measured, the coefficient of friction values were calculated, optical and SEM investigations were performed and finally the wear behaviour of conventionally used sliding bearing alloys was characterized. (c) 2005 Elsevier Ltd. All rights reserved

Welding time effect on mechanical properties of automotive sheets in electrical resistance spot welding

In this study, the effects of welding time on the tensile-peel strength and tensile-shear strength of welding joints in electrical resistance spot welding of chromate micro-alloyed steel sheets having 1.2 mm thicknesses were investigated. A timer and current controlled electrical resistance spot welding machine having 120 kV A capacity and a pneumatic application mechanism with a single lever was used to prepare the specimens. Welding current periods of 5-10 kA and 12 kA were selected, and it was adjusted by increasing 5 cycle from 5 cycle to 15 cycle during the welding process. The electrode pressure was fixed at 6 kN. The welding joints were exposed to tensile-peel and tensile-shear tests, and the effect of welding time on tensile-peel strength and tensile-shear strength was researched by using related period diagrams. The optimum welding times were obtained. (C) 2007 Elsevier Ltd. All rights reserved

The effect of Ti-B and Sr on the mechanical behaviour of the zinc-aluminum-based ZA-12 alloy produced by gravity casting

In this study, the effect of Ti-B (0.05-0.7 wt.% Ti, 0.01 - 0.13 wt.% B) and Sr additions (0.05-0.7 wt.%) on the hardness, ultimate tensile strength (UTS), strain and fatigue properties of the gravity cast Zn-Al-based ZA-12 alloy was investigated. While the Ti-B additions had no significant effect on the hardness of the alloys, the Sr additions lowered the hardness by a small amount. UTS and fatigue resistance of the ZA-12 alloy increased with 0.05 wt.% Ti, but the addition of 0.05 wt.% Sr to the standard alloy did not change these properties significantly. In excess of 0.05 wt.% Ti and Sr, the UTS and fatigue resistance of the alloys decreased and reached a lower value than that of the standard alloy. The failure strain only increased for the ZA-12 alloy containing 0.05 wt.% Ti, then decreased with further increase in Ti content. The failure strain values of the alloys decreased with addition of Sr. Metallographic examination indicated that the addition of Ti-B strongly modified the microstructure of the standard ZA-12 alloy, but Sr did not. Ti and Sr have also formed complex-shaped intermetallic compounds, which were identified as Al5Ti2Zn and Zn5Al3Sr by X-ray diffraction and EDS analyses. It can be suggested that these particles cause a decrease in UTS, fatigue resistance, and strain to failure of the ZA-12 alloy

Effect of welding current on mechanical properties of galvanized chromided steel sheets in electrical resistance spot welding

In this study, the effect of welding current on the quality of weld joint and obviously on tensile-shear and tensile-peel strengths of galvanized chromate steel sheets having 1.2 mm thickness in electrical resistance spot welding was investigated. A timer and current controlled electrical resistance spot welding machine having 120 kVA capacity and pneumatic application mechanism with a single lever was used to prepare the specimens. Welding periods were chosen as 5, 10, 12 and 15 cycles and also welding currents were increased from 4 kA up to 12 kA by rise of 1 kA. The electrode force was kept constant at 6 kN. The prepared welding specimens were exposed to tensile-shear and tensile-peel tests and the obtained results were supported by diagrams and, finally, appropriate welding parameters were advised to the users. (c) 2005 Elsevier Ltd. All rights reserved

The experimental study of titanium-ions into hydroxyapatite by chemical precipitation

Hydroxyapatite (HA) is an important material for biomedical implants, because its chemical composition is similar to that of bone tissue. This study focuses on the effect of sintering temperature and the amount of reinforcement phase on the mechanical properties of HA-Ti composites. Firstly, the production of hydroxyapatite powders that are consistent with the natural bone tissue was planned by means of chemical precipitation method. Secondly, the titanium element was added into this hydroxyapatite powder mixture by different amounts to investigate the change of mechanical properties. Titanium isopropoxide, Ti(OCH(CH3)(2))(4), was used as titanium supplier. These were solved and added into calcium solution without phosphate solution addition. In total, 0.5, 1, 2 and 4 mol% Ti were added into pure hydroxyapatite obtained by chemical precipitation method. The powders including different amounts of Ti additions were dried after the precipitation process and exposed to calcination at different temperatures in order to detect the phases obtained during the process. Microstructures have been investigated by SEM and EDS, and the phase analysis has been determined by the X-ray diffraction analysis, FTIR, DTA-TG and Raman spectrometers. The grain size and apparent density were measured. These results showed that titanium could enter into HA

Effect of welding time on tensile-shear load in resistance spot welded TRIP 800 and microalloyed steels

355-357In recent years, some topics in Automotive industry has become important such as energy saving, carbon emission and automotive safety issues. The main motivation to meet these requirements is employing high strength and low weight materials for vehicles. Therefore, the conventional materials have been substituted with Advanced High Strength Steels (AHSS) and High Strength Low Alloy (HSLA) steels that have high strength-to-weight ratios. However, in addition to material investigation, the joining and welding of these materials is of high importance cannot be underestimated. In this work, weldability of TRIP 800 (transformation induced plasticity), a AHSS steel, and microalloyed steels, a HSLA steel, with resistance spot welding has been investigated. The effect of welding time parameter on tensile-shear properties was analyzed. The optimum parameters for tensile-shear strengths and the encountered separation modes have been examined. The highest tensile-shear loads was obtained using 15 periods