Akış, Tolga
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Name Variants
Akis T.
Akis,Tolga
Tolga, Akış
Akış,T.
Akis,T.
T., Akış
Akis, Tolga
Akış, Tolga
Tolga Akış
T., Akis
T.,Akış
Akış T.
T.,Akis
Akiş T.
A.,Tolga
A., Tolga
Tolga, Akis
Akis, T
Akis,Tolga
Tolga, Akış
Akış,T.
Akis,T.
T., Akış
Akis, Tolga
Akış, Tolga
Tolga Akış
T., Akis
T.,Akış
Akış T.
T.,Akis
Akiş T.
A.,Tolga
A., Tolga
Tolga, Akis
Akis, T
Job Title
Profesör Doktor
Email Address
tolga.akis@atilim.edu.tr
ORCID ID
Scopus Author ID
Turkish CoHE Profile ID
Google Scholar ID
WoS Researcher ID
Scholarly Output
48
Articles
31
Citation Count
399
Supervised Theses
13
48 results
Scholarly Output Search Results
Now showing 1 - 10 of 48
Article Citation Count: 0İKİ KATMANLI DOLU BİR SİLİNDİRİN ELASTİK DAVRANIŞININ FARKLI UÇ VE SINIR KOŞULLARI İÇİN ANALİTİK OLARAK İNCELENMESİ(Turkish Soc thermal Sciences Technology, 2020) Akış, Tolga; Akış, Tolga; Eraslan, Ahmet N.; Civil Engineeringİki katmanlı dolu silindirlerin zamana bağlı termoelastik davranışlarının farklı uç ve sınır koşulları için belirlenmesi amacıyla analitik modeller geliştirilmiştir. Söz konusu silindirler, aralarında mükemmel temas olan ikikatmandan oluşmaktadır. Başlangıçta sıcak olan silindir, yüzeyinden konveksiyon yolu ile sıfır derecelik çevreselsıcaklığa veya önceden daha düşük olarak belirlenen yüzey sıcaklığına ulaşana kadar enerji kaybetmektedir. Tümdurumlarda soğuma yavaş bir biçimde gerçekleştiğinden problemde kuplajsız elastisite teorisinin kullanılması mümkünolmuştur. Genelleştirilmiş düzlemsel şekil değiştirme çözümü elde edilmiş ve bu çözüm, eksenel yöndeki birim şekildeğiştirmeyi sıfıra eşitleyerek düzlemsel şekil değiştirme durumuna ait çözüme indirgenmiştir. Bu çözümlere aitsonuçlar, sınır koşullarının serbest olduğu durumlarda radyal ve teğetsel yöndeki gerilmelerin uç koşullarına göredeğişmediğini göstermiştir. Ancak düzlemsel şekil değiştirme durumunda, eksenel gerilme baskın gerilme olmakta veuçların serbest olduğu duruma göre oldukça yüksek değerlere ulaşmaktadır. Kompozit silindirin eksenel ve radyalyönde yer değiştirmesinin kısıtlanması büyük gerilmelere yol açmasına rağmen ilgili gerilme durumu silindirde akmayayol açmamaktadır.Article Citation Count: 0On the Yielding of Two-Layer Composite Spherical Pressure Vessels(2017) Akış, Tolga; Civil EngineeringThe yielding of two-layer composite spherical pressure vessels under either internal or external pressure is investigated analytically in the framework of small deformations and von Mises yield criterion. It is shown for both pressure cases that depending on the material properties and sphere dimensions, different modes of plasticization may take place. Unlike the deformation behavior of a single layer spherical pressure vessel, yielding may commence at the inner layer or at the outer layer or simultaneously at both layers of the assemblyArticle Citation Count: 1Metaheuristic Optimization of Rotating Multilayer Composite Tubes Under Internal Heating and Pressure(Springer, 2022) Akış, Tolga; Akis, Tolga; Azad, Saeıd Kazemzadeh; Civil Engineering; Department of Civil EngineeringAlthough analysis/design of multilayer assemblies has been always an active field of research, works on the optimal design of rotating multilayer composite tubes are very limited. This paper addresses the design optimization of rotating multilayer composite tubes under internal heating and pressure. For determining the structural responses, analytical solutions are provided based on different boundary conditions. The automated selection of optimal material as well as thickness optimization of pressurized multilayer assemblies is carried out under different angular speed and internal heating conditions using a metaheuristic algorithm. The corresponding optimum design for each angular speed as well as internal heating condition is sought, and the numerical results are discussed. The study provides general guidelines for conceptual design of rotating multilayer composite tubes subjected to internal heating and pressure.Article Citation Count: 2Yielding of Radially Pressurized Functionally Graded Long Tubes Based on Von Mises Criterion(Gazi Univ, 2015) Akış, Tolga; Eren, Omur; Civil EngineeringThe elastic behaviour of functionally graded long tubes with axially constrained ends subject to either internal or external pressure is investigated analytically. The modulus of elasticity and the yield limit of the tube material are assumed to vary radially in nonlinear forms. Making use of von Mises yield criterion, the effect of grading parameters on the yielding behavior of the tube is investigated and it is observed that for both pressure cases, the plastic flow may commence at the inner surface, at the outer surface or simultaneously at both surfaces depending on the functionally grading parameters.Article Citation Count: 2On the Yielding of Two-Layer Composite Spherical Pressure Vessels(Gazi Univ, 2017) Akış, Tolga; Civil EngineeringThe yielding of two-layer composite spherical pressure vessels under either internal or external pressure is investigated analytically in the framework of small deformations and von Mises yield criterion. It is shown for both pressure cases that depending on the material properties and sphere dimensions, different modes of plasticization may take place. Unlike the deformation behavior of a single layer spherical pressure vessel, yielding may commence at the inner layer or at the outer layer or simultaneously at both layers of the assembly.Article Citation Count: 3Influence of Cement Replacement by Calcinated Kaolinitic and Montmorillonite Clays on the Properties of Mortars(Springer Heidelberg, 2023) Akış, Tolga; Akis, Tolga; Civil EngineeringThis study aims to investigate the decomposition and pozzolanic reactivity of two different clays (kaolinitic and montmorillonite) from different origins and to determine their effects after calcination on the properties of cement mortars when used to replace Portland cement partially. Mineralogical and chemical compositions of the clay samples were determined using XRD (X-ray Diffractometer) and XRF (X-ray Fluorescence) tests, respectively. TG-DTA (Thermogravimetry-Differential Thermal Analyses) was used to determine the temperature profiles and the burning temperatures of the clays. The density and fineness of the burnt clays were also determined. In order to investigate the optimum material properties, different burning temperatures and replacement levels were considered. It was found that for all temperatures, the two burnt clays possess good pozzolanic activity. The highest compressive strength and lowest water absorption capacity were achieved when the clay determined as kaolinitic was burned at 700 & DEG;C and with 10% replacement level. While for the clay determined as montmorillonite, the optimum properties were obtained at 700 & DEG;C with a 20% substitution level. Kaolinite had better pozzolanic reactivity than montmorillonite, achieving higher strength performance with lower water absorption when partially replaced with cement. Moreover, it had compressive strength values even higher than plain cement.Article Citation Count: 2Modeling of Asymmetric Shear Wall-Frame Building Structures(Architectural inst Japan, 2009) Akış, Tolga; Tokdemir, Turgut; Yilmaz, Cetin; Civil EngineeringBased on the conventional wide column analogy, two different three-dimensional shear wall models for open and closed sections are proposed. These approximate models are verified in comparison to not only the results available in the literature but also the ones obtained by Using models containing shell elements. With the help of these new models five different groups of shear wall-frame structures with different floor plans and different heights are analyzed. The first three natural vibration periods are determined and time history analyses are performed. The results Of these computations are observed to be in good agreement with those obtained by detailed models containing shell elements.Master Thesis Atık Döküm Kumu ile Üretilen Polimer Betonun Hızlıtamir Malzemesi Olarak Kullanımının Araştırılması(2020) Aghı, Anas; Akış, Tolga; Akış, Tolga; Akış, Tolga; Akış, Tolga; Şengönül, Cemal Merih; Civil Engineering; Civil EngineeringPortland çimentosu, çakıl, kum ve sudan oluşan Portland çimentolu beton (PÇB) inşaat sektöründe yaygın olarak kullanılmaktadır. Yangın, sülfat etkisi veya sismik kuvvetlerden dolayı PÇB zarar gördüğünde, hızlı onarım sağlama özelliğinden dolayı polimer beton (PB) iyi bir tamir malzemesi adayıdır. PB, agrega ve bağlayıcı görevi gören termoset bir reçineden meydana gelmektedir. Bu çalışmada atık döküm kumu, epoksi reçine ve pirinç çeltiği külünden üretilen özel bir tip polimer betonun hızlı tamir malzemesi olarak kullanımı araştırılmıştır. Bunun yanı sıra, yüzey pürüzlülüğünün onarım malzemesinin PÇB'ye yapışmasına etkisi de, PÇB yüzeye uygulanan farklı seviyelerdeki yapay pürüzlülükler üzerinden incelenmiştir. Eğimli kesme, yarmada çekme ve çift yüzey kesme gibi deneyler uygulanarak dört farklı yüzey pürüzlülük seviyesine sahip PÇB ile PB arasındaki yapışma dayanımı belirlenmiştir. Yüzeyler, pürüzlülük seviyelerine göre (a) pürüzsüz, (b) tel fırça ile pürüzlendirilmiş, (c) delik delinerek pürüzlendirilmiş ve (d) kumlamayla dövülmüş yüzeyler olarak adlandırılmıştır. Deneylerde genel olarak adhesiv, kohesiv ve karışık türde üç farklı tip hasar gözlenmiştir. Yapılan çalışmada, uygulanan kuvvet tipi ve yönüne bağlı olarak, yüzey pürüzlülüğü alanı kadar geometrisinin de bağ dayanımında etkili olduğu tespit edilmiştir. Bunlara ek olarak neredeyse tüm numunelerde, PÇB kısmında küçük veya büyük çatlaklar gözlenmiştir ve bu durum kullanılan PB'un yapışma gücünün dikkate değer olduğunu göstermektedir.Article Citation Count: 92On the Plane Strain and Plane Stress Solutions of Functionally Graded Rotating Solid Shaft and Solid Disk Problems(Springer Wien, 2006) Eraslan, AN; Akış, Tolga; Akis, T; Akış, Tolga; Akış, Tolga; Civil Engineering; Civil EngineeringClosed form solutions to functionally graded rotating solid shaft and rotating solid disk problems are obtained under generalized plane strain and plane stress assumptions, respectively. The nonhomogeneity in the material arises from the fact that the modulus of elasticity of the material varies radially according to two different continuously nonlinear forms: exponential and parabolic. Both forms contain two material parameters and lead to finite values of the modulus of elasticity at the center. Analytical expressions for the stresses at the center are determined. These limiting expressions indicate that at the center of shaft/disk: (i) the stresses are finite, (ii) the radial and the circumferential stress components are equal, and (iii) the values of the stresses are independent of the variation of the modulus of elasticity. It is also shown mathematically that the nonhomogeneous solutions presented here reduce to those of homogeneous ones by an appropriate choice of the material parameters describing the variation of the modulus of elasticity.Article Citation Count: 10Automated Selection of Optimal Material for Pressurized Multi-Layer Composite Tubes Based on an Evolutionary Approach(Springer London Ltd, 2018) Azad, Saeid Kazemzadeh; Akış, Tolga; Akis, Tolga; Azad, Saeıd Kazemzadeh; Civil Engineering; Department of Civil EngineeringDecision making on the configuration of material layers as well as thickness of each layer in composite assemblies has long been recognized as an optimization problem. Today, on the one hand, abundance of industrial alloys with different material properties and costs facilitates fabrication of more economical or light weight assemblies. On the other hand, in the design stage, availability of different alternative materials apparently increases the complexity of the design optimization problem and arises the need for efficient optimization techniques. In the present study, the well-known big bang-big crunch optimization algorithm is reformulated for optimum design of internally pressurized tightly fitted multi-layer composite tubes with axially constrained ends. An automated material selection and thickness optimization approach is employed for both weight and cost minimization of one-, two-, and three-layer tubes, and the obtained results are compared. The numerical results indicate the efficiency of the proposed approach in practical optimum design of multi-layer composite tubes under internal pressure and quantify the optimality of different composite assemblies compared to one-layer tubes.
