Mechanical Engineering / Makina Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4129
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Article Citation - WoS: 5Citation - Scopus: 5Investigation and Validation of the Flow Stress Equation and Damage Model Parameters of an Electron Beam Melted Ti6al4v Alloy With a Martensitic Phase(Elsevier, 2023) Güden, Mustafa; Bin Riaz, Arslan; Toksoy, Ahmet Kaan; Yıldıztekin, Murat; Erten, Hacer İrem; Çimen, Gülden; Hızlı, BurakThe Johnson and Cook flow stress and damage model parameters of an electron beam melt (EBM)-Ti64 alloy composed of & alpha;' (martensite) and & alpha;+& beta; and an extruded-annealed conventional Ti64 alloy were determined experimentally. The validities of the determined flow stress equations and damage model parameters were then verified by the numerical simulations of the compression tests on the Body Centered Cubic lattices produced using the same EBM parameters with the solid EBM samples. In addition, a compression flow stress equation was extracted from the small-size test specimens (1 and 2 mm diameter) taken directly from the struts of the as-built lattices. The microscopic observations, XRD analyses and hardness tests confirmed the presence of & alpha;& PRIME; phase in the EBM solid samples and in the struts of the BCC lattices, which reduced the ductility of the EBM solid specimens and struts compared to the conventional Ti64. Furthermore, the partially melt particles on the surfaces of the struts acted as the stress concentration sides for micro-cracking; hence, the compression flow stresses of the struts were found to be significantly lower than those of the as-built EBM solid specimens. The flow stress equation derived from the struts predicted more accurately the compression behavior of the lattices. The compression tests and models showed that early damage formation in the lattices was noted to decrease the initial peak and post peak stresses. As with the experiments, the initial damage occurred in the models with the separation of the nodes at the lattice cell surface edges. This resulted in an abrupt reduction in the stresses after the peak stress. The numerical lattices without damage showed a localized lattice deformation at the mid-sections and the stress increased continuously as a function of normal strain.Research Project Otomobil endüstrisi için mukavemeti yüksek seramik katkılı kapalı hücre alüminyum köpük metallerin geliştirilmesi(2009) Güden, Mustafa; Taşdemirci, Alper; Yüksel, Sinan; Toksoy, Ahmet Kaan; Gültürk, Elif; Karsu, Nurettin DenizFarklı seramik ve metal toz katkılarının Al toz tabletlerinde köpükleşme ve mekanik davranışlara etkileri incelenmiştir. Katkı malzemesi olarak sıvı Al ile ıslatılan Ti6Al4V ve diyatomdan elde edilen silika parçacıkları ve Al tarafından yarı ıslatılan SiC parçacıkları, SiC nano toz ve SiC viskır kullanılmıştır. Ti6Al4V parçacıklarının sıvı Al içerisinde küçük boyutlu TiAl3 intermetalik fazı oluşturması ile artan sıvı tablet viskozitesi köpüğün kararlılığını artırmakta; fakat, köpükleşmeyi azalmaktadır. Köpük kararlılığı ve köpükleşme uzaması kullanılan Ti6Al4V toz boyutu ve yüzdesi ile değişmektedir. Sıvı Al tarafında ıslatılan bir diğer toz olan diyatom SiO2 katkısında ise düşük yüzdelerde köpükleşme maksimum uzamaya kadar artmaktadır. Artan katkı yüzdelerinde ise viskozite artışı ile tabletlerin köpükleşmesi azalmaktadır. SiC katkılı tabletlerde köpükleşme, kullanılan tozların toplam yüzey alanı ile değişmektedir. Optimum parçacık toplam yüzey alanında (~100000 mm2), SiC içeren tabletlerin uzamaları katkısız tabletlere göre daha yüksektir. Küçük boyutlu tozlarda artan yüzey alanı düşük parçacık yüzdelerinin, büyük parçacık boyutlarında ise daha yüksek parçacık yüzdelerinin kullanılmasının gerekliliği gösterilmiştir. Mikroskobik çalışmalar SiC parçacıklarının çoğunlukla hücre duvar yüzeylerinde asılı, Ti6Al4V ve SiO2 parçacıklarının ise tamamen hücre duvar içlerinde yer aldığını göstermiştir. Çalışılan parçacık boyu ve yüzdelerinde SiC katkısı plato gerilmesi ve enerji emme miktarlarını sırası ile %35 ve %20 artırmaktadır. Simülasyon sonuçları kritik köpük yoğunluğunun altında ticari olarak kullanılan boş 6063 T6 Al ve çelik tüplerin köpük dolu tüplerden maliyet ve ağırlık açısından daha avantajlı olduğunu göstermiştir.Article Citation - WoS: 9Citation - Scopus: 10Investigation of Hybridization Effect on Ballistic Performance of Multi-Layered Fiber Reinforced Composite Structures(Sage Publications Ltd, 2022) Üstün, Hikmet Sinan; Toksoy, Ahmet Kaan; Tanoğlu, MetinThe aim of this study is enhancing the ballistic performance of multi-layered fiber reinforced composite structures by hybridization approach against fragment simulating projectile (FSP). For manufacturing of homogeneous and hybrid composite structures, 170 g/m2 twill weave aramid and 280 g/m2 plain weave E-Glass fibers were used with epoxy resin systems and two different thickness values for each composite panel were fabricated and tested to obtain a relationship between areal density and V50 parameters. Tensile, 3-point bending, and short beam strength tests of composite panels were performed, and ballistic performance of composite structures were measured by V50 test method with 1.1 g FSP threat. Ballistic performance of hybrid composite structures was compared with high-performance composite ballistic panel test results reported in literature. As a result, it was found that E-Glass fabric layers together with aramid fabrics increased the energy absorbing capability of hybrid composite panels and ballistic performance was enhanced to be similar or higher than ballistic fiber reinforced composites. Hence, hybridization was found to be an effective way to enhance ballistic performance of fiber reinforced composite structures.Conference Object Citation - Scopus: 2Characterization of Swarm Behavior Through Pair-Wise Interactions by Tsallis Entropy(CSREA Press, 2005) Can, Fatih Cemal; Bayram, Çağdaş; Toksoy, Ahmet Kaan; Avşar, Hakan; Özdemir, SerhanThis paper tries to look at the interactions of a swarm of two at an elementary level. The change in the swarm entropy during the interactions is investigated. The characterization of swarm behavior has been subsumed in four modes, i.e. normal-free, normal-swarm, feeding and obstacle modes. Based on these modes, an entropy based algorithm is constructed to observe pair-wise interactions for each mode. For these modes, individuals of swarm are taken into account as self-driven interacting particles in the mathematical model. Statistical entropy definitions are used to control individual's behavior in feeding and obstacle modes. Individuals lose interactions enabling swarm behavior in feeding mode because of the priority of feeding for individuals as in nature. On the other hand, when swarm confronts an obstacle, individuals interact as much as they can. However they may lose interaction, depending on the size of the obstacle and position of the individuals. For feeding and obstacle modes, it is observed that Tsallis Entropy fits in the simulation better than other entropy definitions such as Shannon and Renyi.Conference Object Axial Compression of Aluminum Closed-Cell Foam Filled and Empty Aluminum Tubes(Uludağ Üniversitesi, 2002) Toksoy, Ahmet Kaan; Güden, Mustafa; Hall, Ian W.Aluminum closed-cell foam filled aluminum tubes with a polyester bonding layer between foam core and tube wall have been compression tested in ord er to detemiine specific energy absorption for the crash box applications. Aluminum foam, empty and foam filled tubes without bonding layer were also tested for comparison purposes, Preliminary results have shown that interaction effect has been found in foam filled tubes with polyester layer. In order to identify deforiDation mechanisms involving with tube deforination, deformed empty and foam filled tubes crosssections were microscopically analyzed and operative defoimationmechanisms were determined.Conference Object Ekstrude Polistiren Köpüklerin Basma Davranışları(Pamukkale Üniversitesi, 2004) Toksoy, Ahmet Kaan; Güden, MustafaMikroskobik ve mekanik test çalışmalarının yardımı ile ekstrude polisitren köpük malzemelerin yapı ve mekanik davranışları belirlenmiştir. Mekanik davranışları üzerindeki anistropi, yoğunluk ve deformasyon hızlarının etkilerini bulmak için polisitren köpükler üç farklı yönde test edilmiştir; bunlar Yükseklik (R), En (W) ve Ekstrüzyon (E) olarak belirlenmiştir. Mikroyapı çalışmaları göstermiştir ki polisitren köpük malzemeler 14 yüzlü (tetrakaidecahedral) kapalı hücrelerden oluşmakta ve bu hücreler R-yönünde uzatılmıştır, diğer iki yönde ise hücre boyutları birbirine çok yakındır. Basma testleri sonucunda en yüksek basma mukavemeti R yönünde olup, tüm yönlerdeki mukavemet değerleri yoğunluk ve basma hızlarının artması ile artmıştır. Deformasyon hızının köpük malzemenin basma davranışı üzerindeki etkisi deformasyon hızı atlama testleri ile kanıtlanmıştır. Son olarak da deformasyon bandı oluşumları ve hücre deformasyonu su içinde ve optik mikroskop altında yapılan basma testleri sonucunda belirlenmiştir.Conference Object Alüminyum Kapalı Hücreli Köpüklerin Toz Metalürjisi Yönetimi ile Üretilmesi(Pamukkale Üniversitesi, 2004) Güden, Mustafa; Kavi, Halit; Toksoy, Ahmet KaanSon şekle yakın Alüminyum kapalı hücreli yapılar, örneğin otomobil tampon ve kapıları, tabletlerin köpükleştirilmesi metodu olarak bilinen toz metalürjisi yöntemi ile hazırlanmaktadır. Metot tozların karıştırılması, sıcak preslenmesi ve elde edilen toz tabletlerin kullanılan alaşımın ergime sıcaklığının üstüne ısıtılması suretiyle köpükleştirilmesi süreçlerinden oluşmaktadır. Bu çalışmada, toz metalürjisi metodu ile kapalı hücreli alüminyum köpük metal üretim parametreleri ve üretim sonucu ortaya çıkan mikroyapılar, köpüğün yoğunluğuna bağlı mekanik özellikleri ile birlikte özetlenmektedir. Son olarak, alüminyum köpük metalin yuvarlak tüplerde dolgu malzemesi olarak kullanımına yönelik deneysel çalışmaların sonuçları otomobil ezilme kutularında kullanımına yönelik örnek olarak verilmiştir.Article Citation - WoS: 71Citation - Scopus: 78The Strengthening Effect of Polystyrene Foam Filling in Aluminum Thin-Walled Cylindrical Tubes(Elsevier Ltd., 2005) Toksoy, Ahmet Kaan; Güden, MustafaThe strengthening effect of foam filling in thin-walled circular tubes, deforming in diamond and concertina modes, was investigated in polystyrene foam filled aluminum tubes. Empty tubes of two different diameters (16 and 25 mm) deformed in diamond mode, while foam filling changed the deformation mode into concertina in 25 mm tube due to thickening effect of foam filling. The strengthening coefficient in concertina mode was found around unity, while in diamond mode it was greater than unity. In concertina mode, foam and tube were observed to deform independently. However, in diamond mode, foam was compressed in between the folds, leading to a higher strengthening coefficient. The effects of deformation rate and the use adhesive on the average crushing loads of the filled tubes were also determined.Article Citation - WoS: 29Citation - Scopus: 32The Optimisation of the Energy Absorption of Partially Al Foam-Filled Commercial 1050h14 and 6061t4 Al Crash Boxes(Taylor and Francis Ltd., 2011) Toksoy, Ahmet Kaan; Güden, MustafaPartially Alulight and Hydro Al closed-cell foam-filled commercial 1050H14 Al and 6061T4 Al crash boxes were optimised using the response surface methodology in order to maximise specific energy absorption (SEA). The quasi-static crushing of empty and filled crash boxes was simulated using LS-DYNA, and the results were further confirmed with experimental quasi-static crushing testing of empty and Alulight foam-filled commercial 1050H14 Al crash boxes. Results showed that partial foam filling of commercial crash boxes increased both SEA and mean load because of foam filler axial and lateral deformation in between the progressing folds of the crash box. Within the studied constraint range of box mean load, box wall thickness and foam filler density, the optimised Alulight and Hydro foam-filled 1050H14 and 6061T4 crash boxes resulted in 26%–40% increase in total energy absorption as compared with empty crash boxes. Considering the same weight basis, the use of a higher yield strength box wall material and higher plateau stresses of Al foam filler resulted in higher energy absorptions in partial foam-filled boxes at relatively low displacements.Article Citation - WoS: 54Citation - Scopus: 62Sic-Particulate Aluminum Composite Foams Produced by Powder Compacts: Foaming and Compression Behavior(Springer Verlag, 2003) Elbir, Semih; Yılmaz, Selahattin; Toksoy, Ahmet Kaan; Güden, Mustafa; Hall, Ian W.The foaming behavior of SiC-particulate (8.6% by volume) aluminum composite powder compacts contained Titanium Hydride blowing agent was investigated by heating above the melting temperature (750°C) in a pre-heated furnace. Aluminum powder compacts were also prepared and foamed using similar compaction and foaming parameters in order to determine the effect of SiC-particulate addition on foaming and compression behavior. The linear expansions of the compacts at various furnace holding times were ex situ determined. Optical and scanning electron microscopy techniques were used to characterize prepared and deformed foams microstructures. The SiC-particulate addition was found to increase the linear expansion and reduce the extent of the liquid metal drainage and cell coarsening of the aluminum compacts. The composite foam samples also showed higher compressive stresses, but a more brittle behavior as compared with aluminum foams.