Makale Koleksiyonu | Makine Mühendisliği Bölümü

Bu koleksiyon için kalıcı URI

https://hdl.handle.net/11729/4972

Listeleniyor 1 - 20 / 30

Investigation of residual stresses induced by milling of compacted graphite iron by x-ray diffraction technique
(Springer, 2024-04) Kara, Mehmet Emre; Kuzu, Ali Taner; Bakkal, Mustafa
This study investigates the relationship between residual stresses, cutting parameters, and machining performance in the milling process of compacted graphite iron (CGI). X-ray diffraction (XRD) analysis is employed to measure residual stresses on the cast and milled surfaces, while cutting force modeling is utilized to calculate the tangential force, power, and active work. The results demonstrate that tensile residual stresses are predominant on the milled surfaces, attributed to the both mechanical and thermal loads generated during milling. By analyzing various cutting conditions, it is observed that lower feeds contribute to reduced plastic deformation, resulting in lower residual stress levels. Additionally, higher cutting speeds lead to higher temperatures, but due to the shorter machining time, heat accumulation is limited, resulting in higher residual stresses, especially at low feeds. At high feeds, residual stresses decreased as the cutting speed increased. The interplay between cutting parameters and residual stresses highlights the need for optimizing cutting conditions to enhance fatigue strength in CGI components. These findings provide valuable insights for process optimization and quality control in the milling of CGI materials.
Neural network steering control algorithm for autonomous ground vehicles having signal time delay
(SAGE Publications Ltd, 2024-03) Dinçmen, Erkin
An adaptive neural network–based steering control algorithm is proposed for yaw rate tracking of autonomous ground vehicles with in-vehicle signal time delay. The control system consists of two neural networks: the observer neural network and the controller neural network. The observer neural network adapts itself to the system dynamics during the training phase. Once trained, the observer neural network cooperates with the controller neural network, which constantly adapts itself during the control task. In this way, an adaptive and intelligent control structure is proposed. Through simulation studies, it has been shown that while a proportional-integral-derivative type steering controller fails to perform its control task in case of steering signal delay, the proposed control algorithm manages to adapt itself according to the control problem and achieves reference yaw rate tracking. The robustness of the control algorithm according to the signal delay magnitude has been demonstrated by simulation studies. A rigorous Lyapunov stability analysis of the control algorithm is also presented.
Tribo-corrosion behavior of electroplating, nitrocarburizing, and QPQ processes on barrel finishing
(Walter de Gruyter GmbH, 2023-11-27) Yücel, Aysu Hande; Yılmaz, Alpay; Bakkal, Mustafa; Kuzu, Ali Taner
In this study, the effects of nitrocarburizing, QPQ, and Cr coating on the surface properties of 32CrMoV12-10 gun barrels are discussed. Hardness measurements, pin-on-disc tests, and anodic polarization tests were performed to examine the hardness values, wear resistance, friction coefficient, and corrosion resistance. The hardness of the specimen treated with QPQ was found to be the highest. Comparing the hardness profiles, it was observed that the casing depth of the nitrocarburized sample was shallower than that of the QPQ-treated sample. The pin-on-disc test revealed that the nitrocarburized sample exhibited a high coefficient of friction, while the Cr-coated sample showed the lowest coefficient of friction. Analyzing the Tafel polarization curve, it was determined that the nitrocarburized and QPQ-treated specimens demonstrated similar levels of corrosion resistance. However, it can be noted that the QPQ-treated specimen had a slightly lower corrosion rate.
The development of a hybrid cutting model for workpiece temperature distribution via advection heat partition approach
(Springer Science and Business Media Deutschland GmbH, 2023-04-15) Kara, Mehmet Emre; Kuzu, Ali Taner; Bakkal, Mustafa
This paper presents a novel hybrid cutting model for the prediction of workpiece temperature distribution during the dry milling process of compacted graphite iron (CGI). The hybrid model consists of an analytical force model based on a mechanistic approach and finite element analysis (FEA) based on the thermal model. The heat generated during the milling process transferred to the workpiece is computed via the advection heat partition model. The workpiece temperature distribution obtained through the heat loads, using as boundary conditions in the FEA, was calculated by means of cutting forces. The developed force and thermal models have been experimentally validated, and good agreement between the measured and calculated results has been observed. The energy and active work calculations show that by doubling the feed during CGI milling, an energy saving of about 10% is achieved despite almost doubling the cutting forces.
Jet motorlarinda uygulanan efüzyon film soğutma akış karakteristiklerinin PIV yöntemiyle incelenmesi
(Sürdürülebilir Havacılık Araştırma Derneği, 2018-12-01) Yalçın, Sinan Eren; Yakın, Evren Yılmaz; Kuşhan, Melih Cemal; Karakoç, Tahir Hikmet
Efüzyon soğutma tekniği, modern yanma odalarında kullanılan en gelişmiş soğutma teknolojisidir. Bu çalışmada 1/9 ölçekte boyutlandırılmış bir yanma odası cidarında, efüzyon film soğutmanın ana akım üzerine etkileri Parçacık Görüntülemeli Hız Ölçümü (PIV) yöntemi kullanılarak deneysel olarak incelenmiştir. Bu amaçla bu çalışmada, ana akım Reynols (Re) sayısı 15000 değerine sabitlenmiş, 2.25 mm delik çaplı efüzyon plakası için, delik açıları 30° ve 45° değişiyor iken, efüzyon plakasından 7 farklı üfleme debisi için testler gerçekleştirilmiş ve soğutma filmi oluşumu incelenmiştir. PIV deneylerinden elde edilen veriler incelenerek, çapraz akışta jet karışımlarında meydana gelen akış haritası çıkarılmıştır ve film oluşma karakteristiği belirlenmiştir. Akış haritası sonuçlarına göre, soğutucu deliklerden düşük debili üflemelerde jetler ana akıma yenik düşmekte, tam tersine yüksek debilerde jetler ana akımla eş baskın özellikte olduğu için, film oluşumu gözlemlenmiştir. Ayrıca soğutma deliklerinin açılarının artışının film oluşumuna olumsuz etkisi gösterilmiştir.
Sıcak dövme kalıplarına infrared (kızılötesi) yöntemi ile ön ısıtma uygulanmasına yönelik deneysel ve teorik analiz
(Makina Tasarım ve İmalat Derneği, 2020-09-19) Karagüzel, Umut; Kuzu, Ali Taner; Korap, Vedat; Çilingir, Hasan; Bakkal, Mustafa
Sıcak dövme işlemi, üretim teknolojisinin önemli bir parçasınıoluşturur. Sıcak dövmede uygulanan ısı enerjisi ile parçanın akmadayanımı azalır böylelikle şekil verme kabiliyeti artarak daha karmaşıkgeometrili parçaların üretilmesine imkân tanır. Ancak artan sıcaklıklabirlikte kalıp dayanımında da düşüş yaşanması kalıp ömrünün azalmasınave üretim maliyetlerinin artmasına neden olur. Kalıp ömrünü azaltanetkenlerden biri de kalıbın dövme işlemi süresince karşılaştığı yükseksıcaklık farklarıdır, bunun önüne geçebilmek için dövme işlemi öncesindekalıba ön ısıtma işlemi uygulanır. Bu çalışmada sıcak dövme sırasındadengeli ve homojen bir ön ısıtma için infrared ısıtıcı geliştirilmiş veüretime uygulanmıştır. İnfrared ısıtıcının verimi ısıtılıcak kalıbın yüzeydurumuna da bağlı olduğundan, çalışmada kalıp yüzeyi için çeşitlikaplamalar ve yüzey uygulamaları denenmiş ve bunların verimlerikarşılaştırılmıştır. Çalışmada ısıtma prosesinin sonlu elemanlar modelide geliştirilmiş ve sıcaklık sonuçları deneysel sonuçlarlakarşılaştırılmıştır. Geliştirilen model ile sıcaklıkların en fazla % 9’luk birfark ile tahmin edilebileceği ortaya konulmuştur. Bu modelle ayrıca farklıkalıp geometri ve kalıp derinliğinde, istenilen sıcaklığa ulaşabilmek içingereken ısıtma süresi kolaylıkla belirlenebilir. Çalışma sonucundainfrared ısıtıcı ile kalıbın ön ısıtıma işleminin homojen ve verimli birşekilde yapılabiliceği gösterilmiştir.
Analysis of mechanical behavior of termoplastic composites
(Necip Fazıl YILMAZ, 2022-03-04) Kuzu, Ali Taner; Kosemen, Elifnur; Yücel, Aysu Hande; Bakkal, Mustafa
This paper presents the effect of fiber orientation on the tensile, compression, impact, and flexuralproperties of glass fiber reinforced acrylic-based thermoplastic composites. The mechanical behaviorof three different composite plates, produced by the resin transfer molding (RTM) method, with0°/90°/45°, 0°/90° and ±45° glass fiber orientations were investigated by carrying out tensile,compression, three-point bending and Charpy impact tests. A Weibull distribution model wasimplemented to explain the variation in mechanical properties of the acrylic-based composite.According to Weibull analysis results with 63.2% probability, the highest tensile strength (561 MPa),compressive strength (293 MPa) and impact values (19.44 J) were obtained when the plate with0°/90° glass fiber orientation was tested, whereas the highest flexural strength was obtained when theplate with 0°/90°/45° was tested.
Eksenel çıkışlı radyal fan sistemi tasarımı
(TMMOB Makina Mühendisleri Odası, 2021-11) Develi, Salih Deniz; Sönmez, Olgun; Ayder, Erkan
Radyal fanlar hava veya gaz nakline gerek duyulan klima santralleri, havalandırma tesisatları vb. gibi pek çok yapıda kullanılmaktadır. Son zamanlarda radyal fanların performans artırımlarına yönelik pek çok çalışma yapılmakta ve fan kanatları üzerinde yapılan değişiklikler ile yüksek performanslı fanlar elde edilebileceği vurgulanmaktadır. Bilindiği üzere radyal fanlarda, akış fanın içerisine eksenel olarak girip 90° dönerek ve radyal olarak çıkmaktadır. Klima santrallerinde çoğunlukla çift emişli salyangozlu radyal vantilatörler ve salyangozsuz plug fanlar kullanılmaktadır. Plug fanlar, salyangozlu vantilatörlere göre daha düşük verimli olsa da sağladığı montaj kolaylığı ve yer tasarrufu üstünlüğü nedeniyle daha yaygın olarak kullanılmaktadırlar. Plug fanlarda, rotorda basınçlandırılmış hava, çıkışta enerjisinin önemli bir kısmını yitirmekte ve hava hızındaki büyük değişim sistemin gürültü seviyesinin artması ile sonuçlanmaktadır. Birden fazla fanın dizilmesi ile oluşturulan fan demeti uygulamalarında, fanların birbirleriyle etkileşimini ortadan kaldırma amacıyla fanların aralarına belirli uzaklıklarda ayırıcı duvarlar yerleştirilmekte ve bu nedenle sistem boyutları büyümektedir. Rotor çıkışına bir eksenel yönlendirici yerleştirilmesiyle plug fanların bu dezavantajlarının ortadan kaldırılabileceği öngörülmektedir. Plug fan çıkışındaki akışın eksenel hale getirilmesi, klima santrallerindeki diğer ekipmanların (filtre, eşanjör, nemlendirme ünitesi vb.) performanslarını da arttıracaktır. Bu nedenle bu çalışma kapsamında radyal fanın hemen çıkışına konumlandırılan, akışı 90° döndürerek eksenel hale getiren bir yönlendirici bileşen tasarlanmış ve performansı hesaplamalı akışkanlar dinamiği (HAD) analizleri ile incelenmiştir. Ayrıca tasarlanan bu yönlendiricinin fan performansı üzerindeki etkisi de çalışılmıştır. Varılan sonuç yönlendiricinin sistemin debisini ve verimini arttırdığı yönündedir.
A cooperative neural network control structure and its application for systems having dead-zone nonlinearities
(Springer International Publishing Ag, 2022-03) Dinçmen, Erkin
An adaptive control structure utilizing two feed-forward neural networks (NN) is proposed to deal with systems having unknown nonlinearities. One of the networks is trained to mimic the nonlinear system dynamics. Its training will be repeated with periods in order to keep it an updated valid model of the system all the times since the parameters and/or nonlinearities of the system may change during time. The other network, which is the Controller NN, adapts itself continuously by collaborating with the Model NN. The stability-convergence analysis of both networks is performed via Lyapunov method. An example system is chosen to show the applicability of the control algorithm. This example system is created by combining a linear dynamics model with a dead-zone function to represent a nonlinear system to be controlled. It should be noted that the proposed control structure can be used in any nonlinear system without knowing the system dynamics. The only information required by Model NN is the training set consisting input-output data pairs of the system. The Model NN is trained offline with this training set, and afterward the Controller NN adapts its weights online continuously during the control task with the help of Model NN. The performances of PD and PID controllers are also given for comparison purposes.
Transient multi-domain thermal modeling of interrupted cutting with coated tools
(Springer Science and Business Media Deutschland GmbH, 2021-09) Karagüzel, Umut
Interrupted cutting operations, such as milling, produce fluctuating tool temperatures which directly affect the process outputs. Thus, prediction of cutting tool temperatures enables process planning, selection of materials for tool substrate and coating layers, and tool geometric design for improved productivity in machining operations. Theoretical analysis of temperature is a cost effective way to predict the tool temperatures. Considering the industrial needs, a theoretical model should be fast, easy to implement, and reliable. To that end, a novel hybrid model, which assembles analytical and numerical methods, is proposed in this study. This novel transient thermal model simulates the interrupted cutting with coated cutting tools. The proposed model includes an analytical heat flux calculation at the tool-chip interface considering the sticking-sliding contact behavior. The determined heat flux is, then, used to perform a numerical solution of the transient heat conduction problem in the cutting tool geometry with temperature-dependent thermal properties. The developed model is validated with experimental results found in literature under different cutting conditions. The results show that the model can predict the maximum temperatures generated in a thermal cycle with an accuracy of 2–10%. Thus, the proposed model can be further used to determine the process parameters, properties of coating layers, and tool geometric design.
Effect of scanning strategies and laser parameters on metal-composite joining
(Bellwether Publishing, 2021-07-27) Kuzu, Ali Taner; Karagüzel, Umut; Erbay, Batıray; Bakkal, Mustafa
This study presents an investigation on the effectiveness, automation characteristics, and mechanics of joints between different material types namely glass ?ber reinforced plastics (GFRPs) and SS304 stainless steel using an industrial Nd: YAG continuous-wave laser welder and a 2-axis custom design jig. The custom design jig includes computer-controlled (CNC) step motors, which provide high accuracy position control of the selected laser patterns. Four different patterns (Linear Curve, Hilbert Curve, Triangle Weave, and Curlique Weave) are investigated under different process parameters (laser power, lap joint length, and traveling speed) to obtain more robust joints. The strength of the joint is examined by variance analysis and found that the laser power and the pattern are the most important factors. Tensile shear tests present that the best-resulted joint carried around 4000 N before fracture. Polymer vaporization resulted in sub-millimeter sized bubbles that are widely formed inside the molten zone of the GFRP specimen. Therefore, a strong joint between GFRP and SS304 stainless steel could be obtained by a direct laser joining process at low power, with load adaptable space-filling curve patterns and without needing surface pretreatment, sophisticated clamps or high clamping forces.
Ti6Al4V Alaşımının talaşlı imalatı sırasında termal kamera ile sıcaklık ölçümü ve sonlu elemanlarla modellenmesi
(Süleyman Demirel Üniversitesi Mühendislik Fakültesi, 2019-06-26) Karagüzel, Umut
Talaşlı imalat en yaygın kullanılan imalat yöntemlerinden biridir. Talaşlı imalatta en önemli problemlerin başında yüzey bütünlüğünü, parça toleransını ve takım ömrünü dolayısıyla maliyeti etkilemesi nedeniyle kesme sıcaklığı gelmektedir. Özellikle titanyum, nikel gibi kesilmesi zor alaşımların işlenmesinde kesme sıcaklığının etkileri daha belirgin olmaktadır. Bu amaçla, bu çalışmada Ti6Al4V alaşımının kesilmesi sırasında sıcaklıkların belirlenmesine çalışılmıştır. Kesme sıcaklıkları deneysel olarak termal kamera ile ölçülmüştür. Termal kamera ile yapılan ölçümlerde karşılaşılan en büyük problem uygun yayma katsayısı (emissivite) değerinin seçilmesidir. Bu nedenle çalışmada yayma katsayısının belirlenmesi için bir deney düzeneği tasarlanmıştır. Sonrasında ise bu sıcaklıklar sonlu elemanlar yardımı ile modellenmiştir. Deneysel ve teorik sonuçlar karşılaştırılmış ve birbirine oldukça yakın sonuçlar elde edilmiştir.
Modelling and simulation studies on adaptive controller for alt-azimuth telescopes despite unknown wind disturbance and mass
(SAGE Publications, 2020-09-15) Keskin, Onur; Ünal, Ali Cem; Kararsız, Gökhan; Yılmaz, Tuğrul; Yeşilyaprak, Cahit
Numerous ground-based observatories are using small sized ground telescopes for scientific research purposes. The telescopes that are available on the market have three main problems. These issues can be listed as: positioning repeatability, tuning requirement according to different wind speeds for different seasons, and the mass changing via different scientific equipments added to the telescope. This study is aimed at resolving these issues for ground based small alt-azimuth telescopes. Establishing of a set and forget system is performed by designing an adaptive controller. Motor dynamics are taken into consideration for a realistic mathematical model. The Wind-Gust model that consists of a sum of sinusoidal disturbances with unknown phase, amplitude and frequency is used for the wind model. The purposed controller cancels the disturbance effects on the plant while operational positioning and also the makes the plant insensitive to mass changes. The Lyapunov approach is utilised when proving the asymptotic stability. The proposed controller’s success is illustrated with thorough numerical evaluation.
Experimental analysis on drilling of Al/Ti/CFRP hybrid composites
(Bellwether Publishing, 2021-01-25) Kayihan, Mete; Karagüzel, Umut; Bakkal, Mustafa
Carbon fiber reinforced composites (CFRP) have superior mechanical properties such as high strength/density ratio, and good damping ability. CFRP which is frequently used in parts in the aviation industry can also be single or stacked together with titanium and aluminum alloys. However, delamination could occur on the CFRP surfaces after drilling which leads to deterioration in mechanical properties. Therefore, in this paper, the effect of process parameters and stack order on cutting force, torque are investigated. The tests were carried out at three different drilling speeds and feed rates on a CNC vertical machine tool by using a solid carbide cutting tool. The results of hole quality indicate that the process outputs are significantly affected by process parameters and stack order. The force and torque values obtained at high drilling speeds and low feed rates are independent of the stack order. However, the stacking order is determined to be the most effective parameter for the thrust force and torque values. The force generated during the Ti/CFRP/Al stack in which the highest force value is approximately 50% higher than the lowest force which occurs on Al/Ti/CFRP stack. The surface roughness value measured during the Al/Ti/CFRP stack is approximately half of the other stack order.
Computational and asymptotic methods in aeroacoustics with applications
(Işık University Press, 2011) Delale, Can Fuat; Zafer, Baha; Aslan, Alim Rüstem
In this article the computational and asymptotic methods used in aeroacoustics are reviewed. In particular, two different aeroacoustic applications are demonstrated.In the first problem we investigate the first and second order asymptotic predictions of the thickness and loading noise of a subsonic B-bladed helicopter rotor in the far field and compare the SPL noise results with those of full numerical computations. The results of the second order asymptotic formula seem to be in better agreement with full numerical computations than the first order asymptotic formula. In the second problem, the effect of acoustic wave propagation in transonic nozzle flow is investigated by solving the unsteady quasi-one-dimensional transonic nozzle equations in conservative form using high order computational aeroacoustic schemes, where a novel non-reflecting boundary condition is implemented in addition to the standard non-reflecting boundary condition using characteristics. Excellent agreement with the exact solution is obtained in each case.
Optimal ABS frenleme kontrolcüsünün geliştirilmesi
A thermo-mechanical model of drill margin-borehole surface interface contact conditions in dry drilling of thick CFRP laminates
(Elsevier Ltd, 2020-04-23) Karpat, Yiǧit; Karagüzel, Umut; Bahtiyar, Onur
Dry drilling of thick carbon fiber reinforced polymer (CFRP) laminates requires careful selection of process parameters in order to obtain acceptable borehole surface quality. Complex contact conditions between the drill margin and the borehole surface determine the integrity of the borehole surface depending on the process parameters and temperature-dependent viscoelastic material properties. Temperature rise during dry drilling reduces the elastic modulus of the CFRP and causes thermal expansion of the drill, resulting in considerable contact length at the drill margin and borehole surface interface. Manufacturers need a better understanding of the interaction among contact pressure, sliding velocity, temperature at the interface, and temperature-dependent material properties to develop predictive models for drilling CFRPs. To examine this complex interaction, this study develops a novel, hybrid model that combines a time-based analytical modeling of drilling process with a finite element-based modeling of temperature rise. Drilling experiments were performed in which thrust force, torque, and temperature were measured as a function of feed, and these measurements were used to identify unknown hybrid model parameters. The results revealed that a significant change in friction conditions occurs when increased temperatures at the margin and borehole surface interface approach and exceed the glass transition temperature of the CFRP laminate at a large feed rate. These findings show the benefit of increasing feed during dry drilling, which is nonetheless limited by the temperature-dependent material properties of the work material.
Effects of turn-milling conditions on chip formation and surface finish
(Elsevier Science BV, 2019-04-24) Rahimzadeh Berenji, Kaveh; Karagüzel, Umut; Özlü, Emre; Budak, Erhan
Turn-milling operations performed on mill-turn machines offer significant advantages provided that appropriate conditions are used. Compared to conventional machining processes, kinematics and geometry of turn-milling are more complicated due to additional parameters such as speed and diameter ratios of the tool and workpiece as well as eccentricity between them. In this study, the effects of process conditions on chip formation and surface generation are investigated. A novel approach is presented in order to select turn-milling conditions and related machine tool parameters using the relationship between the process and the machine tool.
Extremum seeking control of uncertain systems
(Işık University Press, 2017) Dinçmen, Erkin
Extremum seeking is used in control problems where the reference trajectory or reference set point of the system is not known but it is searched in real time in order to maximize or minimize a performance function representing the optimal behaviour of the system. In this paper, extremum seeking algorithm is applied to the systems with parametric uncertainties.
Frezeyle tornalamada takımda ortaya çıkan termal deformasyonların modellenmesi
(Gazi Universitesi Muhendislik-Mimarlik, 2017) Karagüzel, Umut; Bakkal, Mustafa; Budak, Erhan
Frezeyle tornalama işleminde işlemiş parça doğruluğu ve üretkenliği arttırarak işlem performansını iyileştirmek kesme kuvvetlerini ve takım ucundaki ısı kaynaklı deformasyonları kontrol etmekle mümkündür. Bu çalışmanın amacı frezeyle tornalama sırasında ortaya çıkan ısı kaynaklı deformasyonları belirlemek ve bunları basınçlandırılmış soğuk hava kullanarak azaltmaktır. Kesme kuvvetleri, takım sıcaklıkları ve deformasyonlar sonlu elemanlarla modellenmiş ve deneylerle doğrulanmıştır. Kuru kesme koşullarında bu deformasyonların paso derinliğinin %40’ı kadar olabileceği ve bunun sonlu elemanlarla tahmin edilecebileceği gösterilmiştir. Ayrıca bu deformasyonlar soğuk hava ile %65’e kadar azaltılabilir. Termal deformasyonlara ek olarak çalışmada takım aşınması ve işlenen parçada yüzey pürüzlülüğü değerleri de ölçülmüştür ve özellikle frezeyle tornalamada yüzey pürüzlülüğü değerlerinin taşlamadaki kadar iyi olabileceği gösterilmiştir.

Güncel Gönderiler