Topology Optimization Applications on Engineering Structures

Over the years, several optimization techniques were widely used to find the optimum shape and size of engineering structures (trusses, frames, etc.) under different constraints (stress, displacement, buckling instability, kinematic stability, and natural frequency). But, most of them require continuous data set where, on the other hand, topology optimization (TO) can handle also discrete ones. Topology optimization has also allowed radical changes in geometry which concludes better designs. So, many researchers have studied on topology optimization by developing/using different methodologies. This study aims to classify these studies considering used methods and present new emerging application areas. It is believed that researchers will easily find the related studies with their work

Radial basis and LVQ neural network algorithm for real time fault diagnosis of bottle filling plant

U ovom je radu razvijena umjetna neuronska mreža (ANN) za brzo pronalaženje grešaka na pneumatskom sustavu. Podaci su prikupljeni i procijenjeni smatrajući da sustav radi savršeno, a greške su unaprijed predviđene. Greške uključuju manjak boce, ne funkcioniranje cilindra B za stavljanje poklopca, neispravni cilindar C za stavljanje poklopca na boce, nedovoljan tlak zraka, voda se ne puni i nizak tlak zraka. Tijekom postupka prikupljeni su signali šest senzora te je za ANN kodirano 18 najkarakterističnijih obilježja podataka. Primijenjene su dvije različite umjetne neuronske mreže (ANN) za interpretaciju kodiranih signala. Umjetne neuronske mreže testirane u ispitivanju bile su "learning vector quantization (LVQ)" i "radial basis network (RBN)". Ustanovilo se da te dvije vrste umjetnih neuronskih mreža dobro funkcioniraju u primijenjenim postupcima u sustavu u kojem se sekvencijski podaci ponavljaju.In this study, an Artificial Neural Network (ANN) is developed to find faults rapidly on a pneumatic system. The data were saved and evaluated considering system is working perfectly and faults are predetermined. These faults include having no bottle, a nonworking cap closing cylinder B, a nonworking bottle cap closing cylinder C, insufficient air pressure, water not filling and low air pressure faults. The signals of six sensors were collected during the entire sequence and the 18 most descriptive features of the data were encoded to present to the ANNs. Two different ANNs were applied for interpretation of the encoded signals. The ANNs tested in the study were learning vector quantization (LVQ) and radial basis network (RBN). The performance of LVQ and RBN was found to be fine with the presented procedures for a system having very repetitive sequential data

Studies on fuzzy decision making in Turkish Universities: An overview

Fuzzy sets theory bridges the gap between boolean logic and human logic which is including a high degree of ambiguity. It has been used to accomplish different tasks (to control, to optimize, to make decision etc.) in different areas (education, management, medicine, technical, military etc.). Many fuzzy decision making methods have been proposed over the years. Classification of these methods and their applications can be found in literature. However, most of these studies concern only one method or one specific application area or one certain time interval. From this point of view, this study aims to show the studies on application of fuzzy decision making in Turkish universities. It is expected that this study will help the researchers on working fuzzy decision making as it is beneficial to know the previous studies on their topic, in an organized way and there is no similar study on this area. It mainly surveys the PhD and MSc Theses in Turkey on fuzzy decision making and the unclassified studies are not given to limit the study. Classified studies are summarized, compared and future recommendations are given for new researchers

Experimental observation of tool wear, cutting forces and chip morphology in face milling ofcobalt based super-alloy with physical vapour deposition coated and uncoated tool

Cobalt base superalloys are used extensively in applications requiring good wear, corrosion and heat resistance. The main goal of this study is to examine the effect of machining conditions (cutting speed, feed rate and depth of cut) on tool wear, chip morphology and cutting forces in symmetric face milling of cobalt base superalloy with physical vapour deposition coated and uncoated inserts. with the aim of achieving to achieve this goal, 90 milling experiments were carried out with different cutting speeds, feed rate and depth of cut under dry cutting conditions. The settings of machining parameters were determined by using general full factorial design method. Chip morphology, cutting forces and tool wear were compared by using PVD coated and uncoated hard metal inserts which are obtained dependent on feed rate, cutting speed and cutting depth. The cutting forces increase as the feed rate and depth of the cut increases, but cutting speeds' effect on cutting forces has not been observed for symmetric face milling. (C) 2006 Elsevier Ltd. All rights reserved

Multicriteria optimization of cutting parameters in turning of UD-GFRP materials considering sensitivity

In this paper, a new multicriteria optimization approach is proposed for the selection of the optimal values of cutting conditions in machining. This approach aims to handle the possible manufacturing errors in design stage. These errors are taken into consideration as change in design parameters and the design most robust to change is selected as the optimum design. Machining of a glass fiber composite material is chosen in case studies. Experiments on the unidirectional glass fiber reinforced composite material are performed to investigate the effect of cutting speed, feed, and cutting depth on the cutting forces. Also, material removal rate values are obtained. Minimizing cutting forces and maximizing the material removal are considered as objectives. It is believed that the used method provides a robust way of looking at the optimum parameter selection problems

Multiobjective optimization of axially loaded non- prismatic columns

Son otuz yıldır yapısal dizayn optimizasyonu en etkin araştırma alanlarından biridir. Yapısal dizayn optimizasyonu yardımıyla yapının ağırlığının yada kullanılan malzemenin azaltılmasının yanında dayanım, burkulma ve yapıyla ilgili diğer özellikler verimli bir şekilde geliştirilebilir. Burkulma problemlerine genel olarak yapı mühendisliğinde, özellikle de sıkıştırma üniteleri, kabuk yapılar veya ince cidarlı basınç kaplarında karşılaşılır. Burkulmayla ilgili dizayn yapının statik dayanımına göre daha zor olduğundan, dizayn optimizasyon metodları özellikle bu tür problemler için faydalıdır. Burkulmayı göz önüne alan yapısal optimizasyon problemleri ilk araştırmalardan oluğundan bu problemlerle ilgili çok çalışma vardır. Bu tezde, burkulma yükü altındaki prizmatik olmayan kolonlar çeşitli kesit şekilleri için incelenmiştir. Bu problemde her farklı durum için iki kriter göz önüne alınmıştır: Ağırlığı minimum ve Yükü maksimum yapmak. Ağırlıklı fonksiyon metodu kullanılarak, Pareto setler bulunmuştur. Pareto setler arasından parametrelerdeki değişimden en az etkilenen nokta optimum nokta olarak seçilmiştir. Bu metodla bulunan sonuçlar daha dayanıklı ve güvenilir dizaynlar oluşturmaktadır. Sonuçlar hassasiyet ve dayanıklılık açısından Global Criterion metodunun sonuçları ile karşılaştırılmıştır. ABSTRACT MULTIOBJECTIVE OPTIMIZATION OF AXIALLY LOADED NON-PRISMATIC COLUMNS Structural design optimization has been an active research field during the past three decades. By means of the design optimization methods, not only the weight and materials of structures can be reduced, but also the strength, buckling stability, and other performances of structures can be improved efficiently. Buckling problems extensively exist in structural engineering, in particular, in the design of structures such as compression members, shells and thin-walled pressurized containers. Since the design of buckling performance is more difficult than static strength of structures, the design optimization methods are particularly useful for this kind of design problem. Since the early research of structural design optimization with buckling constraint there has much work on these problems. In this thesis, non-prismatic columns under buckling loads are investigated for various cross-sectional shapes. For each case, two objectives are taken into account for this multicriteria problem: Minimizing Weight and Maximizing Load. By using weighted function method, the optimum Pareto sets is found. The optimum point is chosen by finding the least sensitive point to variable changes among the obtained Pareto sets. The results obtained from this methodology yield highly insensitive, robust and reliable designs. Results are compared with Global Criterion Method from point of sensitivity and robustness

Comparison and Determination of Efficient Techniques For Fuzzy Multiobjective Design Optimization of Mechanical Systems

ÖZETMEKANİK SİSTEMLERİN ÇOK KRİTERLİ BULANIK MANTIKLA TASARIM OPTİMİZASYONUNDA VERİMLİ TEKNİKLERİN KARŞILAŞTIRILMASI VE BELİRLENMESİÇok kriterli bulanık mantıklı optimizasyon metotlarının kullanılabileceği uygulamalar çeşitli alanlara yayılmıştır. Bu çalışmada, mekanik sistemlerin bulanık mantıklı çok kriterli optimizasyonu için etkin tekniklerin belirlenmesi hedef alınmıştır. Bu amaca ulaşmak için, mevcut tekniklerin kapsamlı bir sınıflandırılması yapılmış, kullanılacak karşılaştırma kriterleri ve bulanık optimizasyon teknikleri belirlenmiş ve çok kullanılan tasarım problemlerine uygulanmıştır. Mevcut tekniklerin kapsamlı incelenmesi sonucu, Verdegay, Werner, Xu ve tek katmanlı kesim yaklaşımları kullanılacak teknikler olarak belirlenmiştir. Üç çubuk mekanizması, helis yay tasarımı, kaynaklı kiriş ve redüktör tasarımı optimizasyonda kullanılacak örnekler; CPU hesaplama zamanı, hassaslık, fonksiyon hesaplama sayısı, yakınsama ve iterasyon sayısı karşılaştırma kriterleri olarak seçilmiştir. En etkin tekniğin belirlenmesi amacıyla karşılaştırma kriterlerinin sonuçlarını tek bir sayı altında toplamak için bir tatmin endeksi tanımlanmış ve uzaklık ölçütü kullanılmıştır.Tez çalışmalarından elde edilen sonuçlara göre, üç çubuk mekanızması için, düşük hassasiyet değerlerinde Xu’nun tekniği, fakat yüksek hassasiyet değerlerinde Werner’in tekniği en etkin teknik olarak ortaya çıkmaktadır. Yay tasarım probleminde, Xu’nun tekniği her hassasiyet değerinde en etkin teknik olarak görülmektedir, fakat Werner’in ve Verdegay’ın teknikleri de çok yakın değerler vermektedir. Kaynaklı kiriş probleminde, Werner’in tekniği en etkin teknik olarak görülmektedir. Redüktör tasarımı probleminde ise, tek katmanlı kesim tekniği her hassasiyet değerinde en etkin teknik olarak görülmektedir, fakat Werner’in ve Verdegay’ın teknikleri de çok yakın değerler vermektedir.ABSTRACTPotential applications for the most fundamental fuzzy multi-objective optimization methods span a variety fields. In this study finding efficient techniques for fuzzy multiobjective design optimization of mechanical systems is considered. To reach this objective, a comprehensive classification of methods is done, comparison criteria and fuzzy optimization techniques are determined, and these are applied to significant engineering design problems to determine the efficient techniques.From comprehensive investigation of methods, Verdegay’s, Werner’s, Xu’s and single level cut approaches are determined as the techniques to be used. Three-bar truss design, spring design, welded beam design and speed reducer design cases are selected as benchmark cases. Computation time, accuracy, number of function evaluations, convergence and number of iterations are selected as comparison criteria. A satisfaction index which combines all criteria into one is also developed to get a single comparison result and used to determine the most efficient technique. According to the results of the thesis, for three bar truss design problem, Xu’s method is the most efficient one for lower accuracy, but Werner’s method for high accuracy. For spring design problem, Xu’s method is the overall winner, but Werner’s and Verdegay’s methods also give close results. For welded beam design problem, Werner’s method is the most efficient one. For speed reducer design problem, single level cut method is the overall winner, but Verdegay’s method also gives close results

A new severe plastic deformation method: thin-walled open channel angular pressing (TWO-CAP)

In this study, a novel severe plastic deformation method, named as thin-walled open channel angular pressing (TWO-CAP), was developed and applied to AZ31 magnesium alloy beams in U-type cross-sectional shape. First of all, the principles of the method with all parameters were determined, and the analytical model of the system was generated, and then the study was supported with the numerical analysis. Then, a proper experimental setup was established by considering theoretic outputs. After that, AZ31 magnesium alloy specimens were machined from bulk material in U-type shape as to fit the die channel, and then these specimens were annealed and pressed along the TWO-CAP die. Following the experimental studies, the specimens were tested in order to define the changes in mechanical and microstructural properties. In this stage, the tension test and hardness test were applied to determine the mechanical properties, while optical microscope, scanning electron microscope, energy dispersive spectrometry, X-ray diffraction, and transmission electron microscope analyses were applied to see the changes in microstructure. As a result, an improvement on strength, hardness, and toughness was observed depending on the changes on the microstructure and grain refinement due to the large plastic deformation