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Öğe Al/B4C kompozitlerin karbür matkaplarla delinmesinin değerlendirilmesi(2016) Motorcu, Ali Rıza; Ekici, ErgünBu çalışmada, toz metalurjisi-sıcak presleme yöntemiyle üretilen yüksek yoğunluklu B4C parçacık takviyeli kompozitlerin kaplamalı ve kaplamasız karbür matkaplarla delinmesinde kesme kuvvetleri ve tork değerleri Taguchi metodu (TM) yardımıyla optimize edilmiştir. Kontrol faktörleri olarak kesme hızı (18, 25 ve 35 m/dk), ilerleme miktarı (0.08, 0.112 ve 0.16 mm/dev), kaplama özellikleri (kaplamalı ve kaplamasız) ve parçacık takviye miktarı (%5, %10 ve %15 B4C) kullanılmıştır. Artan ilerleme miktarı ve parçacık takviyesinin eksenel kuvvet ve torku arttırdığı, kesme hızını ise düşürdüğü görülmüştür. Kaplamasız matkaplar, kaplamalı matkaplara kıyasla daha iyi performans sergilemiştir. B4C takviye miktarının sırasıyla %96.6 ve %49.1 katkı oranları ile eksenel kuvvet ve tork üzerinde en etkili parametre olduğu görülmüştür. Ayrıca, eksenel kuvvet ve tork için geliştirilen birinci dereceden tahmini denklemlerin korelasyon katsayıları (R2) sırasıyla 0.895 ve 0.854 olarak hesaplanmıştır.Öğe An Experimental Study on Hole Quality and Different Delamination Approaches in the Drilling of CARALL, a New FML Composite(Belgrade University, 2021) Ekici, Ergün; Motorcu, Ali Rıza; Yıldırım, EnsarIn this study, the hole quality was investigated in the drilling of CARALL composite. In addition, the delamination factor calculation approaches of Chen, Davim, and Machado were compared in terms of the delamination damage at the hole entrance surface. Chen's approach is based on the conventional delamination factor (Fd) and Davim's on the adjusted delamination factor (Fda). Finally, Machado's approach is based on the minimum delamination factor (Fmin). The values closest to the nominal hole diameter value were obtained with the uncoated (T1), followed by the TiN-TiAlN-coated (T2) and TiAl/TiAlSiMoCr-coated (T3) carbide drills, respectively. The average circularity error values for the hole top and bottom surfaces were 6.184 µm, 7.647 µm, and 8.959 µm for T1, T2, and T3 tools, respectively. Delamination factor values varied between 1.174 and 1.804. The Fda values were found to be the highest, followed by Fd values, with Fdmin values determined as the lowestÖğe Delamination and thrust force analysis in GLARE: Influence of tool geometry and prediction with machine learning models(Sage Publications Ltd, 2024) Ekici, Ergün; Pazarkaya, İbrahim; Uzun, GültekinThe multi-layered (fiber/metal) structure of glass fibre aluminium reinforced epoxy (GLARE) makes it difficult to obtain acceptable damage-free holes that meet aerospace standards. This paper investigated the effects of tool geometry and drilling parameters on reducing delamination damage and uncut fibers at the hole exit surface in drilling GLARE. The hole surfaces were examined by scanning electron microscope (SEM) at various magnifications. In addition, deep neural network (DNN) and long-short-term memory (LSTM) machine learning models were used to predict delamination (Fda), uncut fiber (UCF), and thrust forces using experimental data. No positive contribution of the special geometry tool was observed, while the standard geometry tool was found to be ideal for drilling conditions. Analysis of variance (ANOVA) revealed that feed rate contributed 57.83% to delamination damage, while tool geometry contributed 74.31% and 92.33% for uncut fiber and thrust force, respectively. SEM analysis revealed high deformation zones in the aluminum layers and fiber fracture and separation in the glass fibre reinforced polymer (GFRP) layers. DNN and LSTM models were found to provide accurate predictions with R2 values greater than 95% and 98%, respectively.Öğe Elyaf Metal Tabakalı (FML) Kompozitlerin Delinmesinde Ortalama İtme Kuvveti ve Delaminasyon Faktörü Üzerinde İşleme Parametrelerinin Etkilerinin Değerlendirilmesi ve ARAS Yöntemiyle Çok Kriterli Optimizasyonu(Abdulkadir KESKİN, 2024) Motorcu, Ali Riza; Ekici, Ergün; Uzun, GültekinBu çalışmada bir Elyaf Metal Laminat (FML) türü olan Karbon Elyaf Takviyeli Alüminyum Laminat (CARALL) kompozitin delinmesinde işleme parametrelerinin ortalama itme kuvveti ve delaminasyon faktörü üzerine etkileri araştırılmış ve çok kriterli olarak optimize edilmiştir. İşlenebilirlik deneyleri Taguchi Metodu L18 (12x23) ortogonal diziye göre gerçekleştirilmiştir. İşlenebilirlik deneyleri kontrol faktörleri olarak seçilen kesici takım geometrisi, kesme hızı ve ilerleme miktarı işleme parametrelerinin farklı seviyelerinde kuru olarak yapılmıştır. Bu çalışmanın iki temel motivasyonu bulunmaktadır: birincisi ortalama itme kuvveti ve delaminasyon faktörü üzerinde kontrol faktörlerinin etkilerini ayrı ayrı belirlemek ikincisi ise aynı anda minimum ortalama itme kuvveti ve delaminasyon faktörünü sağlayan optimum işleme parametreleri seviyelerini çok kriterli optimizasyon yöntemi ile belirlemektir. İşleme parametrelerinin çok kriterli optimizasyonu ARAS tekniği ile gerçekleştirilmiştir. ARAS tekniği için ağırlıklandırılmış karar matrislerinin hesaplanmasında kullanılan ağırlıklar Entropi Metodu ile belirlenmiştir. Gerçekleştirilen çok kriterli optimizasyon sonucunda CARALL’ın delinmesinde aynı zamanda minimum ortalama itme kuvveti ve delaminasyon faktörü değerlerinin elde edilmesinde işleme parametrelerinin etki sırası takım geometrisi (%87.60), ilerleme miktarı (%8.39) ve kesme hızı (%0.28) şeklinde olmuştur. Minimum ortalama itme kuvveti ve delaminasyon faktörü değerlerinin elde edilmesi için işleme parametrelerinin optimum seviyeleri standart geometrili takım, 100 m/dak kesme hızı ve 0.06 mm/dev ilerleme miktarı olarak belirlenmiştirÖğe EVALUATION OF THE EFFECTS OF CUTTING PARAMETERS ON THE SURFACE ROUGHNESS DURING THE TURNING OF HADFIELD STEEL WITH RESPONSE SURFACE METHODOLOGY(2014) Ekici, Ergün; Uzun, Gültekin; Kıvak, TurgayHadfield çeliği (X120Mn12) sahip olduğu mükemmel aşınma direncinden dolayı mühendislik uygulamalarında yaygın olarak kullanılmaktadır. Bu çalışmada Hadfield çeliğinin tornalanmasında kesme parametrelerinin yüzey pürüzlülüğü üzerindeki etkileri araştırılmıştır. Deneyler 80, 110, 140 m/dak kesme hızı, 0.2, 0.3, 0.4 mm/dev ilerleme ve 0.2, 0.4, 0.6 mm kesme derinliğinde kaplamalı karbür takımlar kullanılarak gerçekleştirilmiştir. Halfield çeliğinin işlenebilirliğinin değerlendirilmesinde yanıt yüzey yöntemi (RSM) kullanılarak bir model oluşturulmuştur. Kesme parametrelerinin yüzey pürüzlülüğü üzerindeki etkilerinin belirlenmesinde merkezi tümleşik tasarım (CCD) ve varyans analizi (ANOVA) kullanılmıştır. Deneysel çalışma sonrasında oluşturulan modelle, yüzey pürüzlülüğü üzerinde kesme parametrelerinden ilerlemenin % 90,28 katkı oranı ile en etkili parametre olduğu ortaya konulmuştur. İlerlemenin artmasıyla yüzey pürüzlülüğünün arttığı görülmüştür. Yüzey pürüzlülüğü üzerinde etki bakımından ilerlemeyi % 3,12 katkı oranı ile kesme hızı, % 1,7 katkı oranı ile de kesme derinliği takip etmiştir.Öğe Evaluation of the effects of drilling parameters, tool geometry and core material thickness on thrust force and delamination in the drilling of sandwich composites(World Scientific Publishing, 2021) Ekici, Ergün; Uzun, Gültekin; Altaş, SedatThis study examined the effects of drilling parameters, tool geometry, and core material thickness (CMT) on thrust force and the delamination factor in the drilling of sandwich composites. Aluminum honeycomb (10 and 15mm in thickness) was used as the core material, with carbon fiber-reinforced polymer (CFRP) as the top and bottom surfaces. In the drilling experiments, three different cutting speeds (60, 78 and 100 m/min) and two different feed rates (0.05 and 0.075 mm/rev) were used. Drills having a diameter of 6.35 mm and three different geometries (candlestick drills, twist drills and dagger drills) were used in the experiments. At the end of the experiments, thrust force was seen to increase with increased feed rate and CMT. Increased cutting speed generally decreased the thrust forces and the minimum thrust force was achieved with the 10 mm thick core material, 0.05 mm/rev feed rate and 100m/min cutting speed using the dagger drill. The delamination factor at the entrance area was very low when drilling the sandwich composites and there was no significant difference based on drilling parameters, tool geometry, or CMT. Tool geometry was the main effective factor on exit delamination, and the highest delamination occurred with the use of the candlestick drill. Although increased feed rate increased delamination with all tools, with the dagger drill, increased cutting speed led to a severe increase. Delamination, tearing, and uncut fiber formation were observed when images of the exit areas of the drilled holes were examined.Öğe Fabrication and Machinability (Drilling) Properties of Fiber Metal Laminate (FML) Composites (CARALL and GLARE)(CRC Press, 2023) Ekici, Ergün; Motorcu, Ali RızaThe increasing need for lightweight and high-performance composite structures in the aerospace industry increases the demand for fiber metal laminate (FML) composite materials. This situation makes it necessary to improve existing FML materials’ mechanical properties and develop production and assembly conditions. In this section, the pre-production conditions of carbon fiber-reinforced aluminum laminates (CARALL) and glass laminate aluminum reinforced epoxy (GLARE) composites, which are currently under development, are evaluated. The effects of the metal group and fiber type on mechanical properties are presented. In addition to the traditional thermoset-based FML, the forming capabilities and mechanical properties of the new-generation thermoplastic-based fiber metal laminate (TFML) are also discussed. The effects of nanoparticles on the mechanical properties of FML were evaluated. FML production technologies are presented in detail. In FML composites, drilling is a common post-production joining method, as is the assembly of fiber-reinforced polymer (FRP) composite and metallic stacks. For this reason, the manufacturing processes required for assembling FML composites have been examined, and the drilling process has been comprehensively evaluated. © 2024 selection and editorial matter, Rajesh Kumar Verma, Shivi Kesarwani, Jinyang Xu and J. Paulo Davim.Öğe Green Machining of Ceramics(CRC Press, 2024) Ekici, Ergün; Bayraktar, ŞenolManufacturing is an important part of the production industry and different machining operations are frequently used in this process. Depending on the material type and machining operation, cutting fluids are often used in the manufacturing process to achieve the desired geometric and dimensional limits in the interaction between the tool and the workpiece or to increase the cutting tool’s life. However, in recent years, the use of chemical fluids has attracted more attention and has emerged as an environmental problem that needs to be solved. In this study, researches on more environmentally friendly machining of ceramic materials with different machinability properties than traditional engineering materials are included. These researches consist of two main parts. First, alternative applications for reducing the use of cutting fluids in conventional machining methods, which are harmful to the environment/human health and cause an additional serious burden on machinability costs. The second one consists of the use of non-conventional machining methods where the use of cutting fluids is reduced or eliminated in ceramic structures that are difficult to be machined by conventional methods. Thus, the study purposes to provide an in-depth contribution to the current literature and to provide support for industrial users to solve problems that may be encountered in applications. © 2024 CRC Press.Öğe Multi-Objective Optimization of Process Parameters for Drilling Fiber- Metal Laminate Using a Hybrid GRA-PCA Approach(Belgrade University, 2021) Ekici, Ergün; Motorcu, Ali Rıza; Uzun, GültekinThis study investigated the effects of drilling parameters and cutting tool coating conditions on the thrust force, surface roughness, and delamination factor in the drilling of fiber-reinforced carbon reinforced aluminum laminate (CARALL) composite, a commercial type of fibermetal laminate. Gray relational analysis (GRA) was used as a multiobjective optimization method to determine optimum processing parameters and principal component analysis (PCA) was used to determine the weights. According to the findings of this experimental study, the most effective control factors for the thrust force, surface roughnes, and delamination factor were the feed rate, tool coating conditioncutting speed interaction, and tool coating condition, with 93.87%, 66.504%, and 29.137% contribution rates, respectively. From the results of the GRA-PCA analysis, the optimum levels of the control factors were determined as 110 m/min cutting speed, 0.1 mm/rev feed rate, and the uncoated tool.Öğe Optimization of low-velocity impact behavior of FML structures at different environmental temperatures using taguchi method and grey relational analysis(Sage Publications Ltd, 2025) Dündar, Mustafa; Uygur, İlyas; Ekici, ErgünCarbon fiber-reinforced Aluminum Laminate (CARALL) is a new generation of Fibre Metal Laminate (FML) material. This study investigates the low-velocity impact behavior of CARALL structures at different environmental temperatures (-40 degrees C, 23 degrees C, and 80 degrees C). Two different groups of CARALL composite structures with varying fiber orientations were produced by hot pressing in a 3/2 arrangement: C1 (Al/0 degrees 90 degrees/Al/90 degrees 0 degrees/Al) and C2 (Al/0 degrees 0 degrees/Al/0 degrees 0 degrees/Al). Low-velocity impact tests were conducted at 23 J, 33 J, and 48 J energy levels using a & Oslash;20 mm spherical impactor tip. The area of damage was detected by ultrasonic C-Scan. In addition, analysis of variance (ANOVA) was applied to reveal the influential parameters and their effect levels. After conducting experiments using the Taguchi L18 test set, it was observed that the C2-coded specimen yielded better results in terms of maximum peak load, maximum displacement, and damage area. While the decrease in temperature increased the damage and maximum peak load, the increase in temperature did not cause a significant change in the maximum peak load. The primary damage mechanisms observed in damage investigations were matrix cracks and delamination between composite layers. Although delamination is present between the Al/CFRP layer, it is not significant. According to ANOVA results, impact energy was the most effective parameter for maximum impact force, maximum displacement, and damage area, with contribution rates of 81%, 74%, and 76%, respectively. The optimal experimental conditions (23 degrees C temperature and 23 J impact energy with the C1-coded sample) were determined using grey relational analysis based on principal component analysis.Öğe Performance of Multilayer Coated and Cryo-Treated Uncoated Tools in Machining of AISI H13 Tool Steel—Part 1: Tungsten Carbide End Mills(Springer, 2021) Çiçek, Adem; Kıvak, Turgay; Ekici, Ergün; Kara, Fuat; Uçak, NecatiThis paper focused on the performance of tungsten carbide end mills in machining of AISI H13 hot work tool steel under dry and wet conditions. The tool performance was evaluated in terms of resultant cutting force (Fc), average surface roughness (Ra) and tool life. In the milling tests, four categories of end mills were used: untreated (U), cryo-treated (CT), cryo-treated and tempered uncoated (CTT) and TiAlN/TiN multilayer coated (MLC). The tests were performed at four cutting speeds (80, 100, 120, 140 m/min), three feeds (0.08, 0.12, 0.16 mm/rev) and a depth of cut (2 mm). The test results showed that the lowest values of Fc and Ra were obtained with the use of MLC end mills. However, the cryogenic treatment was also effective on decreasing Fc and Ra. In addition, while the CTT end mills provided a slight improvement in tool life under dry conditions, they showed a remarkable improvement of 126.1% in comparison with the untreated ones under wet conditions. Although the CTT end mills exhibited a superior performance to U and CT ones, the MLC end mills were much more resistant to abrasive wear. This study is organized into two parts (WC-Co and HSS) to observe the effects of deep cryogenic treatment on performance of two different tool materials and to compare cryo-treated end mills with multilayer coated ones. This part is related to the cryogenic treatment of tungsten carbide end mills, whereas part two is regarding cryo-treated HSS end mills.Öğe Performance of Multilayer Coated and Cryo-treated Uncoated Tools in Machining of AISI H13 Tool Steel—Part 2: HSS End Mills(Springer, 2021) Çiçek, Adem; Ekici, Ergün; Kıvak, Turgay; Kara, Fuat; Uçak, NecatiThis part of the study aimed to investigate the effects of cryogenic treatment applied to uncoated high speed steel (HSS) end mills on cutting forces (Fc), surface roughness (Ra), and tool life. The milling tests were performed at four cutting speeds (40, 50, 60, and 70 m/min), three feeds (0.018, 0.024, and 0.03 mm/rev), and a depth of cut (2 mm) under dry and wet conditions. Three categories of uncoated HSS end mills were used in the tests: conventional heat treated (CHT), cryo-treated (CT), cryo-treated and tempered uncoated (CTT), and TiAlN/TiN multilayer coated (MLC) end mills. The test results showed that the lowest values of Fc and Ra were measured with the use of MLC end mills. However, the cryogenic treatment provided in a reduction in Fc and Ra values. In addition, under wet conditions, the CTT end mills exhibited better performance than the CHT ones by 71.4%. The test results showed while cryogenic treatment is a useful and cheap application in steels, it does not have the ability to compete with coating technology in terms of tool life in milling of hot work tool steel. This paper is organized into two sections. In the first section, cutting performance of cryo-treated and multilayer coated end mills is evaluated. In the second section, performance comparison of cryo-treated WC-Co (Part 1), HSS (Part 2), and MLC end mills in milling of AISI H13 hot work tool steel is presented.Öğe SANDVİÇ KOMPOZİTLERİN DELİNMESİNDE DELAMİNASYON FAKTÖRÜNÜN İNCELENMESİ(2017) Kuş, Abdil; Ekici, ErgünBu çalışmada bal peteği geometrisinde farklı çekirdek malzemelerden üretilen sandviç kompozitlerin delinmesinde delik giriş ve çıkış bölgesinde oluşan delaminasyon faktörü araştırılmıştır. Taguchi metodu L18 tasarımına göre yapılan deneylerde kontrol faktörleri olarak kesme hızı, ilerleme miktarı ve çekirdek malzeme tipi esas alınmıştır. Deneyler CNC dik işleme merkezinde 6,3 mm çapında TiAlN kaplı karbür matkap kullanılarak gerçekleştirilmiştir. Ayrıca %95 güven seviyesinde varyans analizi (ANOVA) uygulanmış, giriş ve çıkış bölgeleri hasarı için optimum parametreler belirlenmiştir. Her iki numunede delme işlemi sonrasında tüm deney şartlarında deliklerin optik görüntüleri alınmış ve en yüksek kesme parametreleri için delik çıkış bölgesinde oluşan hasar tipleri incelenmiştir. Delaminasyon faktörü üzerinde en etkili parametre delik giriş bölgesi için %46 katkı oranı ile kesme hızı, çıkış bölgesi içinse %32,8 katkı oranı ile ilerleme miktarı olmuştur. Özellikle delik çıkış bölgesinde oluşan hasar tipleri delaminasyon, kesilmemiş elyaf ve parçalanma olduğu görülmüştürÖğe WIRE ELECTRICAL DISCHARGE MACHINING OF A HYBRID COMPOSITE: EVALUATION OF KERF WIDTH AND SURFACE ROUGHNESS(2016) Kuş, Abdil; Motorcu, Ali Rıza; Ekici, ErgünBu çalışmada, Al/B4C-Gr karma kompozitin tel elektro erozyon tezgâhında işlenebilirlik karakteristikleri araştırılmıştır. Deneylerde; kesim genişliği (kerf) ve yüzey pürüzlülük değerlerini (Rz ve Rt) içeren işleme performansı etkilerinin incelenmesinde tel hızı, vurum süresi ve vurum ara süresi işleme parametreleri olarak seçilmiştir. Taguchi kalite tasarım konseptine göre, S/N oranını tanımlamak için bir L18 (21×37) ortogonal dizi ve işleme performansını etkileyen anlamlı işleme parametrelerini belirlemek için varyans analizi (ANOVA) ve F-testi kullanılmıştır. ANOVA ve F-testi sonuçlarından, işleme performansı kriterleri kerf, Rz ve Rt'nin her biri için anlamlı faktörler belirlendi. İşleme parametreleri ile kerf, Rz ve Rt'nin değişimleri regresyon analizi metodu yardımıyla istatistiksel olarak modellenmiştir. Kerf, Rz ve Rt için kontrol faktörlerinin optimum seviyeleri sırasıyla A1B1C1, A1B1C2 ve A1B1C2 olarak belirlendi. Kerf, Rz ve Rt için geliştirilen tahminsel denklemlerin korelasyon katsayıları sırasıyla 0.98, 0.828 ve 0.855 olarak hesaplanmıştır.
