LEE- Otomotiv Lisansüstü Programı
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ÖgeSistem mühendisliği yaklaşımı ile elektronik donanım entegrasyonu ve yapısal analizleri(Lisansüstü Eğitim Enstitüsü, 2022) Özbaş, Halit Alper ; Arslan, Hikmet ; 719692 ; Otomotiv Bilim DalıBu çalışmada, askeri sektörde ürün geliştirme süreçleri ile ilgili sınırlı literatür kaynağına katkıda bulunmak amacıyla sistem mühendisliği yaklaşımı ile, bir elektronik ürünün sağlaması gereken gereksinimler belirlenmiş, bu gereksinimlerin doğrulama planları oluşturulup ürünün kullanılacağı sistem ile olan entegrasyonu sağlanması amacıyla, ilgili standartlarda verilen direktifler işlenerek kullanılmıştır. Bu kapsamda oluşturulan doğrulama planı üzerinden, rafta hazır kapsamda bulunan elektronik bir ürün incelenmiş ve entegrasyon stratejisinde kullanılan braket ve bağlantı elemanlarının uygunluğu değerlendirilmiştir.
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ÖgeReduction of engine torsional vibrations via hydrodynamic dampers(Graduate School, 2022-02-10) Aslan, Yavuz ; Akalın, Özgen ; 503191710 ; AutomotiveWithin the scope of this master's thesis, the vibration damper used to dampen the torsional vibrations of internal combustion engines has been examined. In this manner, the hydrodynamic damper, which is a special type of vibration damper, is investigated. The calculation methods of the stiffness coefficient and damping coefficient, which are the two main characteristics of the hydrodynamic damper, have been studied. CATIA and Hypermesh software programs are used in order to perform the needed 3D model creation and analysis. Values obtained from the calculation by analytical and numerical methods are compared with test results performed on measurement systems. After the determination of these characteristic parameters, a crank train model is built over the AVL EXCITE program to examine the effect of the hydrodynamic damper in an 8-cylinder diesel engine. This established model is considered as two different sub-models, with and without vibration damper, and the differences between both cases are determined. Angular displacement and stress values in different sections of the crankshaft are used as the output of the analysis. Thus, the effect of the hydrodynamic damper used on the crank train and the engine has been clearly demonstrated. Currently, efficiency of the engine is increased by increasing power density and reducing engine volumes in internal combustion engines. On the other hand, this trend increases the loads on the components and affect the strength limits. In an 8-cylinder diesel engine with a high power density, the vibrations observed with increasing cylinder pressures and loads also increase. These vibrations seen in the crank mechanism directly affect the operation of the engine and the lifetime of the parts. For this reason, vibration dampers are used for the damping of these vibrations and for the safe operation of the engine by reducing their amplitudes. In this thesis, a hydrodynamic vibration damper coupled to the free end of the crankshaft is used. The hydrodynamic damper is a vibration damper that consists of leaf springs arranged in an inner part and that creates damping by providing oil flow between these spring packages. Firstly, the stiffness coefficient of this damper is determined. For this purpose, finite element analysis is applied to the damper, which is 3D modeled, through the Hypermesh program. As a result of the analysis, the angular displacement values against the acting torque are obtained and the related stiffness coefficient is determined. Also, a test system is designed to measure the stiffness coefficient. The stiffness coefficient value is obtained by the measurement made on this test system. The stiffness coefficient calculated by the numerical method is compared with the stiffness coefficient measured from the test system. As a result of the comparison, it is seen that both values coincided with each other within a certain margin of error. Analytical calculations have also been made to determine the damping coefficient, which is another specific feature of the hydrodynamic damper. The passage of the oil in the damper between the chambers next to each other creates a damping effect. In this context, the damping coefficient is tried to be calculated with two different methods. The first of these methods is the control oriented transient method, which is used in a similar study before. With this method, the damping coefficient is calculated over different coefficients based on the oil flow. However, since the geometry is very small and there are many parameters affecting the flow, the damping coefficient calculated with this method is found to be quite different from the damper coefficient in the catalog information from the manufacturer. The second method is to reduce the damper to an equivalent dashpot system. With this reduction, the damping coefficient is calculated from the dashpot. With this method, the damping coefficient differs from the value in the catalog, depending on the assumptions and reductions used. In addition to the calculations, a test system is designed for a static damping coefficient and it is measured on this system. The damping coefficient is obtained from the measurement result using the logarithmic decrement method. Since the engine operating conditions cannot be reflected in the test system and the damper is tested statically, not dynamically, the value obtained from the measurement does not represent the dynamic damping coefficient. For this reason, the values obtained from the calculations and the values in the catalog have not been compared. Finally, after determining the characteristics, a crank train model is created using the AVL EXCITE program to examine the effect of the hydrodynamic damper on the engine and to reveal the damping effect of the hidrodynamic damper. In this model, the crankshaft, connecting rod, piston and flywheel are modeled under the forces after combustion pressure and inertia forces. In order to see the effect of the damper on the system, two models, with and without the damper, are created. From these two models, the angular displacement and the resulting stress values in different parts of the crankshaft are investigated. The results from the model with the damper obviously stated that the hydrodynamic damper effectively reduces the torsional vibrations in the engine compared to the model without the damper. It can be said that the lifetime of the components and therefore the engine is extended since the stress values on the parts are reduced at the same time. It is claimed that adding torsional vibration damper into the crank train has no negative effect on the engine in terms of torsional vibrations. According to the results of the torsional vibration analysis, almost every part of the crank train elements has minimized amplitude level of torsional vibration and angular displacements with hydrodynamic damper. Additionally, 7 different damper case studies are revealed in order to determine the possible optimized stiffness and damping coefficients of the current hydrodynamic damper. In order to compare the different cases, the existing stiffness and damping coefficients of the current damper are changed by 25%. Updated stiffness and damping coefficients of the damper are applied into the torsional vibration analysis and corresponding results are obtained, respectively. These results are compared with the results of the current hydrodynamic damper. In some cases, the angular displacements and the shear stresses are increased due to the change in the stiffness and damping coefficients. On the other hand, some cases have improved results due to the higher stiffness and damping coefficients compared with the current hydrodynamic damper. These improved cases are investigated in order to determine the possible optimized version of the existing damper. It is not hundred percent possible to claimed that the revised damper has better results in the all speed intervals, but it can be said that the updated dampers with high stiffness and damping coefficients have better torsional vibration results in the most of the engine operating speeds. Regarding this aspect, Case 5 and Case 7 have better results than the other cases and the current hydrodynamic damper. Moreover, Case 5 has less angular displacements and shear stresses in the most speed ranges than the Case 7. Although Case 7 has better results in some speeds than the Case 5, there are some speed intervals that the Case 7 has higher angular displacements and shear stresses than the current hydrodynamic damper. Also, the reduction of the results in Case 7 is less than the increase coming from the Case 7 for specific speeds. Thus, the hydrodynamic damper in Case 5 has better results than the Case 7. It can be concluded that the revised hydrodynamic damper in Case 5 can be the optimized version of the current hydrodynamic damper in terms of torsional vibrations. Lastly, the needed structural changes in order to obtaine the stiffness and damping coefficients of the hydrodynamic damper in Case 5 are determined by using the formulations derived in previous sections.
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ÖgeParallel hybrid electric truck design(Graduate School, 2022-05-06) Darıcı, Onurcan ; Şen, Osman Taha ; 503171719 ; AutomotiveAutomotive industry has been developed since years by beginning of first patent of it. In those years automotive companies has been dealt with different type of issues. One of the biggest challenge is fuel consumption and CO2 emissions for the automobiles. Nowadays CO2 emissions are one of the trend topics in the era. CO2 is harmful for human body besides it creates green gases effect and due to that the average temperature of the planet increases which is called "global warming" in other terms. CO2 emissions have a direct relation with fuel consumption of the engine. After reactions in the engine gasoline or diesel create CO2 as a result. To decrease CO2 emissions of the vehicle one of the key element is to decrease fuel consumption. To decrease fuel consumption there are different methods. On of the common solution is hybridization. Hybridization can be done by including two different energy sources into the specific vehicle. In the common sense, modern-day vehicles are equipped with gasoline or diesel engines. The appropriate way to hybridize a gasoline/diesel engine can be done by adding an electrical source to the vehicle. Hybridization has different types and each type has its own advantage and disadvantage. One of the common hybrid electric vehicle type is parallel hybrid electric. In this thesis, a heavy-duty parallel hybrid electric truck has been investigated. The conventional model is selected as an 18t 4x2 heavy-duty commercial vehicle, Mercedes – Benz Actros. It is one of the most sold truck in 2020 Turkey truck market. 18t 4x2 Mercedes-Benz Actros truck is modelled in AVL Cruise system to compute conventional vehicle's fuel consumption. After that, conventional truck is hybridized by electric motor that is coupled to its transmission exit. Model B parallel hybrid truck is computed again on the same VECTO cycles and fuel consumptions and CO2 emission of the vehicles are compared. The last model is selected which is equipped with a downsized engine. Parallel hybrid+downsized, Model C, is computed and compared with other models. All these three models are created in AVL Cruise and simulations are done in the programme. At the end of the results, advantages and disadvantages are noted in the conclusion chapter.
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ÖgeFonksiyonel güvenlik kapsamında elektrik motoru takviyeli direksiyon sisteminin model tabanlı yazılımının geliştirilmesi(Lisansüstü Eğitim Enstitüsü, 2022-07-04) Aydın, Cengiz ; Şen, Osman Taha ; 503181703 ; OtomotivKarayolları ulaşımında yaşanan kazalar nedeniyle her yıl yüz binlerce kişi hayatını kaybetmekte, sakat kalmakta veya ağır yaralanmalar geçirmektedir. Bu nedenle otomotiv üreticileri geliştirdikleri teknolojilerle insan hayatını koruyucu önlemler almayı hedef haline getirmektedir. Ayrıca markalaşma açısında da güvenilir olarak anılan markaların değeri ve prestiji diğer üreticilere göre oldukça yüksektir. Bu kapsamda elektronik kontrol ünitelerinin otomotiv sektöründe kullanımının artmasıyla birlikte pek çok elektronik güvenlik sistemi hayatımıza girmiştir. Peki bu hayatlarımızı emanet ettiğimiz elektrik elektronik sistemlerin güvenliğinden nasıl emin olabiliriz? İhtiyacımız olduğunda bu sistemler sağlıklı bir biçimde fonksiyonlarını yerine getirebilecek mi? Bu şüpheler sadece elektronik güvenlik sistemleri için değil tüm elektronik kontrol üniteleri için geçerlidir. Amacı hayatımızı kolaylaştırmak olan bir elektronik kontrol ünitesindeki bir arızanın hayatımızı tehlikeye atmayacağından nasıl emin olabiliriz? Bu tehlikelere karşı hiçbir önlem almadan bu sistemleri kullanmak oldukça risklidir. Tabi ki de tüm riskleri ortadan kaldırmak mümkün değildir ancak bu sistemleri tasarlayan mühendislerden iyi bir risk yönetimi yaparak güvenli sistemler meydana getirilmesi beklenir. Risk ettiğimiz şey insan hayatı olduğunda, risk yönetimini standartlaştırmak kaçınılmaz olmaktadır. İşte bu nedenle 2011 yılında ISO 26262 – Kara Araçları Fonksiyonel Güvenlik Standardı hayatımıza girdi. Bu çalışmada, otomotiv sektöründe çalışarak veya akademide yayınlar yaparak sektöre katkı yapanlar için ISO 26262 – Kara Araçları Fonksiyonel Güvenlik Standardı hakkında bilinmesi gerekenleri özetlemek, süreç hakkında bilgiler paylaşmak ve sektörel kabul görmüş yaklaşımları incelemektir. Tezin literatür taraması sürecinde sadece ISO 26262 – Kara Araçları Fonksiyonel Güvenlik Standardı ile ilgili yapılan çalışmaları referans vermekle yetinilmemiş, sektörel olarak kabul edilen mimari ve konseptler de incelenmiştir. Uygulama kısmında bir konsept oluşturabilmek için referans bir elektronik kontrol sistemine ihtiyaç duyuldu. Bunun için popüler elektronik kontrol sistemlerinden EPS (Electric Power Steering) seçildi ve sistem hakkında temel bilgiler paylaşıldı. Yeterli temellerin oluşmasıyla detay tasarım konularına giriş yapıldı. Konsept aşamasında ve fonksiyonel güvenlik mühendisliğini ilgilendiren kısımlarda NHTSA (National Highway Traffic Safety Administration) tarafından yayınlanan "Functional Safety Assesment of a Generic Electric Power Steering System with Active Steering and Four-Wheel Steering Features" çalışması referans alınarak alıntılar yapıldı. Potansiyel tehlikeler ve riskler tanımlandı. HARA (Hazard Analysis and Risk Assesment süreci açıklanarak ASIL'ler (Automative Safety Integrity Level) tanımlandı. Konsept belirlendikten sonra, sistem seviyesinde fonksiyonel güvenlik gereksinimlerini sağlayacak teknik yaklaşımlardan bahsedilerek güvenlik mekanizmalarına kısaca değinildi. Güvenlik mekanizmalarının sistem seviyesinde doğrulanması için standart tarafından önerilen yöntemler açıklandı. Sistem seviyesi sadece yazılım geliştirme sürecine geliştirilecek fonksiyonları tanımlamakla değil aynı zamanda sistem entegrasyonu ve kabul testleri süreçlerinde de aktif rol almaktadır. Bu nedenle geliştirilen yazılımın, performans, tutarlılık, zamanlama, arayüz entegrasyonu, yetkinlik ve sağlanlık gibi kriterleri test ederken standart tarafından önerilen yöntemler incelendi. Yazılım geliştirme sürecinde, iş akış organizasyonunun belirlendiği V-Döngüsüne değinildi. Modelleme ve yazılım geliştirme sürecinin bütünlüğünün önemi vurgulanarak seçilen geliştirme methodları için şartnamelerin belirlenmesinin sisteme katacağı değerler vurgulandı. Yazılım test sürecinde MiL (Model in the Loop), SiL (Software in the Loop), PiL (Processor in the Loop), HiL (Hardware in the Loop), Gerçek donanımla test gibi farklı test ortamlarında yapılan testlerin farklılıkları geliştirme sürecine katkıları açıklandı. Uygulama bölümünde, EPS sistemi direksiyon sensör modülü için yazılım gereksinimleri belirlendi. Mimari tasarım hakkında bilgi vermek adına Data Flow Diagram, Sequence Diagrams ve State Machine Diagramları paylaşıldı. Yazılım birim tasarım bölümünde Model Based Software Design teknikleri kullanılarak geliştirme süreci açıklandı. Yazılım birim doğrulama bölümünde statik kod analizi, dinamik testler, test koşum ortamları, kapsama analizleri gibi teknikler gösterildi Model seviyesinde doğrulama yapabilmek için simülasyon ortamı oluşturuldu. Sistemin test edilebilmesi için EPS sistemi MATLAB/Simulink Simscape aracı kullanılarak modellendi ve kontrol algoritmaları sisteme entegre edildi. Farklı kullanım senaryoları için test senaryoları olışturuldu ve sistem sonuçları paylaşıldı. Son olarak elde edilen çıktılar değerlendirilerek gelecek çalışmalar için fikirler verildi. Elektrik/Elektronik sistemlerde fonksiyonel güvenlik kopseptinin gelişmekte olduğuna vurgu yapılarak çalışma tamamlandı.
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ÖgeOptimization design parameter of dual mass flywheel coupled with a non-linear elastic path(Graduate School, 2023) Karakuş, Gökay ; Şen, Osman Taha ; 807252 ; Automotive ProgrammeToday, expectations from automotive industry are high in the fields of performance, comfort, economy and environmental protection. That is why, the automotive industry must have a knowledge, experience, development processes, and strong research. Hence, the design of the components that transmit power from the internal combustion engine to the wheels via axes in a vehicle are crucial research topics. The flywheel, which is the primary element in power transmission system, works in engine in order to reduce the speed fluctuations on the crankshaft. Along with the studies in the field of flywheel development, dual-mass flywheels have been started to be used as an alternative to the single-mass flywheel. Briefly, the dual mass flywheel can be defined as the combination of two single mass flywheels. The spring damper system is combined with these two single mass flywheels. The dual-mass flywheel, which is used in diesel engines, is thought to have favorable effects on the dynamics of the power transmission system compared to the single-mass flywheel. In 1985, the first dual mass flywheel (DMF) was manufactured in automotive sector. In begin, dampers in flywheel were not lubricated and the springs are stand away from outside and created some wear problems. In 1987, DMF is lubricated with grease oil for the first time. Service life problem was no longer an issue thanks to grease oil application. Around 1989, arc spring damper was innovation for the DMF, and it had pretty much solved all resonance problems. Alson manufacturing costs were continually reduced. The primary mass of flywheel was made by casting or forged steel at first production batches. Over time, the primary mass was formed from sheet metal parts by metal-forming specialists. In 1995, folded masses were developed from sheet metal in order to increase inertia moment of primary mass of flywheel. This development led to the widespread use of the DMF. However, there is some disadvantages such as cost, the achievable improvements are seen clearly, therefore, DMF are used widespread in vehicles. There are some advantages of dual mass flywheel such as isolation from torsional vibration, relief of transmission and crankshaft. Within the scope of this study, firstly, give information about flywheel, parts of dual mass flywheel and its advantages. Then, while engine is running, the working principles of dual mass flywheel is mentioned. Also, the single mass flywheel and dual mass flywheel are compared and it has been observed that the resonance regions are reduced below the engine idle speed with the use of dual-mass flywheel. After all crucial information was explained, mathematical model of DMF is built. The model was solved in Matlab for all optimization. Sensitivity analysis was done in order to determine the parameter effects on system. The design parameters were determined as stiffness ratio, damping ratio and inertia ratio. Also, the system was running on non-linear cubic path, that is why, non-linear stiffness ratio is also important parameter to examine system correctly. The primary body represent not only primary flywheel itself but also engine side dynamic properties.
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ÖgeInvestigation of regenerative braking efficiency in different drive cycles(Graduate School, 2023-06-23) Barın, Berkay ; Şen, Osman Taha ; 503201705 ; AutomotiveAs being an important fact, climate change threatens the world population and its impact has become crucial recently. Thus, the world is being prepared for a very fresh era: green energy and electrification era. The European Union proposes the EU7 emission regulation, which has lower limits compared to prior regulations; and net zero emission policies are already adopted by several governments throughout the world. These developments increase the importance of electric vehicles (EVs), which have already start to replace the conventional vehicles due to their zero tailpipe emissions. Furthermore, the high efficiency, quiet operation and improved performance characteristics of EVs make them more preferable, and the recent advancements in battery technology bring this preference to the fore. Though, EVs still have significant disadvantages such as limited driving range and long charging time. The concept of regenerative braking becomes crucial in increasing the battery state of charge, which improves the driving range and reduces the required charging duration. Thus, the optimization of the regenerative braking system operation becomes critical. The chief objective of this study is to investigate the utilization rate of regenerative braking in different drive cycles, which depends on braking rate and road conditions. Consequently, seven well-known different drive cycles are selected, which vary with distance, urban / highway scenario, traction per kilometres, etc. An E class sport utility battery electric vehicle is selected for modelling purposes and it is subjected to all drive cycles. The driving resistances are calculated and the instantaneous electric motor torque demand is obtained for all drive cycles. Furthermore, the total braking and traction force ratios are evaluated for all drive cycles. It is observed that the comparison of these drive cycles based on total braking and traction force values does not provide reasonable conclusions due to the variation of drive cycle range. Thus, results are compared by normalizing the traction and braking forces by the range of each drive cycle. Finally, a braking to traction ratio is determined for all drive cycles, and the tendency of regenerative braking utilization rate change is investigated. Based on the results, it is observed that the braking to traction ratio of the vehicle significantly reduces when the vehicle moves from urban to highway drive cycle. Furthermore, the utilization rate of the regenerative braking also drops down to %13 from %53, when the drive cycle transition from urban to highway occur. The low braking to traction ratio shows that the recovered energy begins to be insufficient in highway driving conditions, and enough energy cannot be provided for the charging of the battery pack. In addition, the test vehicle's weight has increased to its gross weight. Subsequently, results were reanalyzed in the view of weight change. Finally, it is observed that weight change has not a significant effect on utilization rate in city conditions, whereas it increases the efficiency around %6 in highway conditions.
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ÖgeRide quality and handling characteristics of an off-road vehicle with active anti-roll bar suspension(Graduate School, 2024-01-17) Canpolat, Berkay ; Akalın, Özgen ; 503201707 ; AutomotiveA vehicle's suspension system isolates the car from road vibrations, resulting in a comfortable ride. In addition, it provides sufficient handling in the vehicle and helps the vehicle to drive stably and reliably. The anti-roll bar system contributes significantly to safety by reducing body roll during cornering. However, when used passively, this system negatively affects the vehicle's ride quality. Active anti-roll bar systems can adjust stiffness according to the driver's input or road conditions. Most current studies have focused on this feature to improve the stability and handling of the vehicle. However, ride quality is essential for many reasons in military vehicles. It is possible to observe effects such as loss of attention and discomfort and the emergence of health problems when the driver is exposed to poor road conditions. In this study, it is desired to examine the effect of the anti-roll bar on the system. According to the results, the goal is to develop a controller for a vehicle with better ride quality. In this context, analyses were made on roads with the same waviness and roughness values to compare each result clearly. In addition, analyses were made on roads with different phase angles to observe the vehicle's response to various conditions. It would need to be important to check essential parameters such as road holding and stability by increasing the ride quality while performing analyses on the off-road vehicle. As a result, analyses of these suspension systems, which are essential for vehicle dynamics such as cornering and lane change, should also be made. The aim is to create a system that will not adversely affect road holding and stability while contributing to the improvement of ride quality. Four different suspension systems were installed in the analyses to examine the ride quality with different anti-roll bar thicknesses. One of them is a thicker anti-roll bar. A front suspension produces higher torsional stiffness and load transfer in this case. The second is the anti-roll bar, which is actively used in the vehicle. The third one is a lower-thickness anti-roll bar. Thus, the results in the case where the effect of the anti-roll bar is reduced wanted to be examined. Finally, the anti-roll bar has been removed from the suspension system. The anti-roll bar model used does not have a complex structure. For this reason, the calculation method created by the SAE (Society of Automotive Engineers) was used while calculating the torsional stiffness. There are standards and methods such as ISO 2631, BS 6841, absorbed power, and VDI 2057 to evaluate ride quality. Within the scope of this study, the absorbed power method, frequency-weighted RMS, and vibration dose value (VDV) have been used to evaluate ride quality. The absorbed power is expressed in Watts to represent how much power the human body absorbs to measure the level of discomfort. In this method, which shows a number mathematically, high values indicate an increase in discomfort, while the limit value is determined as 6 Watts. In calculating the comfort level, getting data from the driver or passenger locations is more accurate. Therefore, acceleration data at the driver's location were taken for calculations. In order to extract acceleration values, first of all, analyses should be made in the multibody dynamics program. Then, with the acceleration values obtained from here, the absorbed power value can be transformed with the transfer functions specified by TARADCOM. Graphical programming and numeric computing environments were used simultaneously for this transformation, and the transfer functions provided are analyzed. Absorbed power values in all three global axes were obtained, and the results were transferred to tables and graphics. Another assessment criterion was ISO 2631. Examining the frequency-weighted RMS and vibration dose value (VDV) results, comments on ride quality were given. To determine these values, the signal processing application examined the acceleration data in all three axes. While analyzing the ride quality, the vehicle travels 300 meters to make the assessment correctly. In addition, the speed values between 12.87 km/h and 32.19 km/h were examined to observe different speed conditions. In order to examine different phase conditions, analyses were made on the paths at 0, 45, 90, and 180-degree phase angles, and their effects were examined. Anti-roll bars with different torsional stiffness values have been investigated for their impact on ride quality. According to the results obtained, the change in thickness did not have much effect on ride quality at a 0-degree phase angle due to the low effect of the anti-roll bar on the system. It also allows the vehicle to remain more stable at this phase angle. With the increase of the phase angle, significant increases were observed in the absorbed power values of the lateral axis. It has been determined that this difference widens even more, especially in the 180-degree phase angle. The presence of an anti-roll bar significantly increases the discomfort in the lateral axis. In addition, it was determined that the highest absorbed power values were on the vertical axis. It has been observed that the anti-roll bar has a negative effect on the vertical axis at the 180-degree phase angle. As a result, it has been deduced that the anti-roll bar has negatively affected ride quality, especially with the increase in the phase angle. According to the results, the lowest absorbed power values were achieved in the vehicle's longitudinal axis (x-axis). When frequency-weighted RMS and vibration dose value (VDV) values were also analyzed, it was found that similar results were obtained with the absorbed power method. In vehicle dynamics analyses such as cornering and double-lane change, it has been observed that vehicles with anti-roll bars in the front suspension have lower roll angle values. In addition, vehicles with and without an anti-roll bar were subjected to lane change analyses by the ISO 3888-2 standard. This analysis consists of an obstacle avoidance course and is based on double-lane change. According to ISO 3888-2 results, it has been observed that the vehicle with an anti-roll bar can complete the track at higher speeds. When the results of the model with active anti-roll bars operating according to the specified algorithm are analyzed, it is observed that the ride quality values of the vehicles have improved considerably, especially at high phase angles. In the analyses where the handling is evaluated, it is observed that the vehicles with the active anti-roll bar system produced similar results to the standard vehicle and performed better than the vehicles without an anti-roll bar. As a result, while the ride quality of the vehicle with the active system is better, there is no change in handling characteristics.
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ÖgeKauçuk ömür testi için bir test düzeneğinin validasyonu(Lisansüstü Eğitim Enstitüsü, 2024-06-12) Çorbacıoğlu, Baybora ; Çalık, Alper Tolga ; 503191712 ; OtomotivKauçuk malzemeler, özellikle tekrarlı yükleme koşullarına maruz kalmakta ve çeşitli mühendislik uygulamalarında gerek birincil gerek ikincil fonksiyonlarda kritik bir rol oynamaktadır. Kauçuğun yorulma özelliklerini anlamak, ürün performansını ve dayanıklılığını öngörebilmek; kaliteyi ve emniyeti garanti ederken ticari olarak rekabetçi kalabilmek için hayati önem taşır. Kauçuk yorulma testi cihazları, kauçuğun tekrarlayan yüklemelere karşı performansını test etmek için kullanılan makinalardır. Kauçuğu sabitlemek ve ölçüm sonuçlarının gürültüden etkilenmemesi için sağlam bir çerçeveye, gerilmeyi uygulamak için aktüatörlere ve bunu ölçmek için sensörlere sahiptirler. Kontrol sistemi, gerilme seviyelerini ayarlar, verileri kaydeder. Bazı cihazlar farklı ortamları (sıcaklık, frekans, ...) taklit edebilirler. Bu cihazlar, kauçuk ürünlerin kalite standartlarını karşıladığından ve parçalar gerçek koşullarda kullanıldığında istenen ömür dayanımına sahip olmasını sağlar. Kauçuk ömrü; malzeme özellikleri, çevresel faktörler, yükleme koşulları, yükleme geçmişi, parça geometrisi, imalat süreçleri, işletme koşulları ve yaşlanma etkileri gibi birçok faktörün kombinasyonuna bağlıdır. Tüm bu faktörlerin takip edilerek kauçuk yorulma davranışının incelenmesini zorlaştırmaktadır. Bu nedenle test cihazları belli başlı karakteristiklere, birbirine göre avantajlı ve dezavantajlı olduğu senaryolara sahiptir. Bu farklılıklara; test edilebilen sıcaklık aralığı, frekans aralığı, yükleme tipleri, ölçüm hassasiyetleri, parça boyutları vb. birçok etken örnek verilebilir. R = -1, bileşenlerin simetrik tekrarlı yükleme koşullarına maruz kaldığı durumu temsil etmektedir. İncelenen test cihazının doğrulaması bu yükleme tipinde kauçuk ömrünün tespiti içindir. Kauçuk sektöründe genelgeçer kabul edilen standart R = 0 durumu sadece çekme durumu için ömür testine yöneliktir. İncelenen diğer çalışmalarda farklı yükleme tipleri haricinde, R = -1 koşulunun farklı bir mekanizmayla sağlandığı ya da cihaz validasyon çalışmalarının zayıf olduğu gözlemlenmiştir. Bu çalışmayla silindirik numuneleri eksenine göre farklı açılarda gerdirerek konumlandırdıktan sonra motordan alınan güç aracılığıyla numunelere dönme hareketi vermek suretiyle numunede sıkışan bölgede basma, genleşen bölgede çekme gerilmesi uygulamak suretiyle; sinüzoidal basma-çekme yükleme koşulunda kauçuk numunelerin ömür dayanımları tespit edilebilecektir. Yeni cihazla ve bu cihaza uygun test takozlarından elde edilen Wöhler eğrisiyle hesaplanan ömür tahminlerinin fiziki şaft askı lastiği ömür testlerinden çıkan sonuçlarla örtüşüp örtüşmediği irdelenmiştir.
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ÖgeDizel motor silindir devre dışı bırakma teknolojisinin farklı sürüş çevrimleri boyunca araç yakıt tüketimine etkisinin incelenmesi(Lisansüstü Eğitim Enstitüsü, 2024-07-05) Özdemir, Adem ; Doğru, Barış ; 503131701 ; OtomotivEmisyon regülasyonlarını sağlayabilmek ve daha çevre dostu araçlar üretebilmek için taşıt üreticileri geçmişten günümüze yakıt tüketimi azaltma çalışmalarına devam etmektedir. Özellikle yakıt tüketiminin ulaştırma amaçlı kullanılan dizel motorlarda yakıt ekonomisi iyileştirme çalışmalarının önemli ölçüde artması beklenmektedir. Silindir devre dışı bırakma (CDA), dizel motorlarda yakıt ekonomisini önemli ölçüde iyileştiren ve emisyonları azaltabilen önemli teknolojilerden biridir. CDA, özellikle düşük yük çalışma koşulundaki yakıt tüketiminin tam yüke göre daha fazla olduğu durumlarda devreye giren bir yakıt tüketimi azaltma teknolojisidir ve çok silindirli motorlarda yaygın olarak kullanılmaktadır. Düşük yüklerde silindirlerin bir ya da daha fazlasının devre dışı bırakılması ile yakıt kesilir ve emme ve egzoz supapları kapatılarak aktif silindirlere daha fazla yük verilir. Böylece CDA modunda motorun, daha yüksek termal verim ve dolayısıyla daha düşük yakıt tüketimi ile çalışması sağlanır. Düşük yüklerde gaz kelebeğinden kaynaklı kısılma kayıplarının yüksek olmasından kaynaklı olarak CDA teknolojisi benzin motorlarında yaygın olarak kullanılmaktadır. Dizel motorda gaz kelebeği kaynaklı kısılma kaybı olmayacağı için CDA teknolojisinin dizel motor uygulaması konusundaki çalışmalar kısıtlı olmuştur. Simülasyon çalışmaları kapsamında, otomotiv sektöründe araç ve motor performans uygulamalarında sıklıkla faydalanılan GT-Suite 1-Boyutlu (1D) modelleme yazılımı kullanılmıştır. Bu çalışmada ise GT-Suite yazılımı, CDA teknolojisinin dizel motor yakıt ekonomisine etkisinin incelenmesi için yapılacak 1D simülasyon çalışmalarında kullanılacaktır. Simülasyonlar için bazı önemli adımları içeren bir metodoloji izlenmiştir. Birinci adımda, tam yük koşulunda elde edilmiş deney datasından beslenen tam yük motor performans modeli oluşturularak deney sonuçlarıyla karşılaştırılmış ve doğrulanmıştır. Burada tam yük modeli 800 ve 2100 dev/dk motor hızı aralığında 14 ayrı noktada kararlı hal sonuçları elde edilmiş olup motorun maksimum fren ortalama efektif basıncı 1100 dev/dk'da 23 bar değerine karşılık gelmektedir. Daha sonra doğrulanmış model, ikinci adımda, düşük yüklerde CDA mod (2. ve 3. Silindirler devre dışı, 1. ve 4. silindirler aktif) ve normal mod (tüm silindirler aktif) motor performans sonuçlarını tahmin etmek üzere düşük yük motor performans modeline dönüştürülmüştür. 1D düşük yok motor performans CDA modunda modellerken talep edilen tork ve güçte herhangi bir kayıp olmaksızın, devre dışı bırakılan silindirlerde yakıt kesilir ve supaplar kapatılır. Son adımda, tam yük normal çalışma ve düşük yükte hem normal hem CDA modunda çalışma koşullarına ait performans verileri araç performans modellerine girdi olarak sağlanır. Bu çalışmanın amacı, literatürde CDA teknolojisinin dizel motor uygulamasına yönelik çalışmaların kısıtlı olmasından dolayı, yakıt tüketimi avantajlarını simülasyon yoluyla tahmin etmek üzere, istenilen silindiri devre dışı bırakma esnekliği sağlayan bir dizi simülasyon metodolojisi izlenmiştir. Simülasyon çalışmasında, ağır vasıta bir araca dört silindirli dizel motor uygulanıp araç performans simülasyonları koşularak, rölanti ve düşük yük çalışma koşullarına sahip sertifikalı sürüş çevrimleri (WHVC, NEDC, FTP75 ve HHDDT) boyunca karşılaştırmalı yakıt tüketimi sonuçları incelenmiştir. Bu çevrimler boyunca, normal mod ve CDA mod karşılaştırmalı 1D araç simülasyon tahminlerine göre CDA modunda %4 civarında yakıt tüketiminde iyileşme sağlanmıştır.