In the literature, a large number of metaheuristic search techniques have been proposed up to present time and some of those have been used in structural optimization. Scatter search is one of those techniques which has proved to be effective when solving combinatorial and nonlinear optimization problems such as scheduling, routing, financial product design and other problem areas. Scatter search is an evolutionary method that uses strategies based on a composite decision rules and search diversification and intensification for generating new trial points. Broodly speaking, this thesis is concerned with the use and application of scatter search technique in structural optimization. A newly developed optimization algorithm called modified scatter search is modified which is computerized in a software called SOP2012. The software SOP2012 is integrated with well-known structural analysis software SAP2000 using application programming interface for size optimum design of steel structures. Numerical studies are carried out using a test suite consisting of five real size design examples taken from the literature. In these examples, various steel truss and frame structures are designed for minimum weight according to design limitations imposed by AISC-ASD (Allowable Stress Design Code of American Institute of Steel Construction). The results reveal that the modified scatter search technique is very effective optimization technique for truss structures, yet its performance can be assessed ordinary for frame structures.

This paper deals with the Java bytecode size optimization. It describes the Java Virtual Machine and the Java class file format. It also presents some tools for the bytecode manipulation. Using these tools, I have analyzed selected data and found sequences of instructions, that could be optimized. Based on the results of the analysis, I have designed and implemented methods for bytecode size optimization. The bytecode size of the selected data was reduced by roughly 25%.

Design optimization of truss structures is a popular topic in aerospace, mechanical, civil, and structural engineering due to benefits to industry. Common design problem for the structures is the weight minimization. Especially in aerospace engineering the minimization of the weight of the total structure gets the highest importance in the design. This study focuses on the design optimization of 2D and 3D truss structures. The objective function is the total mass of the structure which is subjected to stress and nodal displacement constraints. To optimize the design, Genetic Algorithm (GA) is preferred due to its efficiency in dealing with problems with discrete design variables as in the case of truss structures. This technique yields more realistic results than linear programming methods. In the thesis, a finite element code is developed for the analysis of planar and space truss structures. The developed finite element solver is coupled with a genetic algorithm optimization code which is also developed as a part of the thesis study. Different truss optimization case studies are performed to demonstrate the performance of the finite element solver and the genetic algorithm optimization code that are developed. It is shown that with the use of adaptive penalty function employing scaled fitnesses, the arbitrariness issue of the factor multiplying the error term in the augmented fitness function can be resolved. It is also shown that significant weight reduction can v be achieved by employing shape optimization together with size optimization compared to pure size optimization.

The objective of this study is to investigate the use and efficiency of Differential Evolution (DE) method on structural optimization. The solution algorithm developed with DE is computerized into software called SOP2011 using VB.NET. SOP2011 is automated to achieve size optimum design of steel structures consisting of 1-D elements such as trusses and frames subjected to design provisions according to ASD-AISC (2010) and LRFD-AISC (2010). SOP2011 works simultaneously with the structural analysis and design software SAP2000 in order to find the global or near optimum designs for real size truss and frame structures in which the optimization problem is classified as constrained, discrete size optimization. Software interacts with SAP2000 through the Open Application Programming Interface (OAPI), which provides an access to information of SAP2000 inputs and outputs. It is programmed for finding reasonable and optimized results for truss and frame steel structures by choosing appropriate ready sections for structural members considering the minimum weight via DE technique. Based on the comparison of the obtained results with the literature, DE algorithm with penalty function implementation is proved to be an efficient optimization technique amongst several major methods used for discrete constrained size optimization of real size steel structures. Also, it has been shown that by using optimized designs obtained by DE, weight of the structures can be reduced up to 67.9% for steel truss structures and 41.7% for steel frame structures compared to SAP2000 auto design procedure, hence resulting a significant saving of materials, cost, work hours and energy required for the project.

Este trabalho apresenta um estudo de transdutores piezelétricos de potência usados em máquinas de estampagem e soldagem de tecidos sintéticos por ultra-som, através de modelos de elementos finitos implementados no software ANSYS e verificações experimentais. O transdutor é do tipo sanduíche e está acoplado a um amplificador mecânico e a um sonotrodo. Os comportamentos elétrico e vibracional do transdutor tipo sanduíche foram analisados em relação à quantidade de discos de piezocerâmicas em modelos axi-simétricos com quatro e oito discos. Comparam-se os resultados numéricos da resposta em frequência da impedância elétrica e do coeficiente de acoplamento eletromecânico com resultados experimentais de protótipos. Apresentam-se também análises numéricas do comportamento vibracional do amplificador mecânico e de dois tipos de sonotrodos, um cilíndrico e outro com o formato de uma lâmina larga, usados no processo de corte e soldagem de tecidos por ultra-som. É feita uma análise da distribuição de amplitude de vibração ao longo da face de trabalho dos dois sonotrodos. Os resultados simulados são comparados com os resultados experimentais de uma varredura feita na superfície de trabalho de cada protótipo usando-se um vibrômetro laser Doppler. Mostra-se que a vibração na face do sonotrodo cilíndrico ocorre com maior amplitude em uma região na sua borda. Considerando que para o processamento adequado do tecido é necessário que todos os pontos ao longo da face de trabalho do sonotrodo vibrem com a mesma amplitude, verifica-se a necessidade de modificar a forma do sonotrodo visando obter uma distribuição uniforme de deslocamentos em sua face. Para isso utiliza-se a modelagem do sonotrodo com a técnica de otimização paramétrica disponível no ANSYS, com o objetivo de se obter uma distribuição de vibração uniforme ao longo de sua face de trabalho. Os resultados experimentais do protótipo do sonotrodo cilíndrico otimizado são comparados com os resultados numéricos da distribuição de vibração ao longo de sua face de trabalho mostrando uma boa concordância e, portanto, validando o modelo numérico. / This work presents a study of high power piezoelectric sandwich transducers used in ultrasonic cutting and welding of thermoplastic textiles using finite element models with ANSYS and experimental verifications. The electrical/vibrational behaviour of transducers with four and eight piezoceramics is analysed using axisymetric models. The numerical results of electrical impedance frequency response and electromechanical coupling factor are compared with experimental results of prototypes. There are presented the numerical analysis of the vibrational behaviour of an acoustical amplifier and two types of sonotrodes, a cylindrical and an wide blade shape, used in the ultrasonic cutting and welding of thermoplastic textiles. It is performed an analysis of the distribution of vibration amplitude along the work surface of both sonotrodes and the simulated results are compared with esperimental measurements of the prototypes using a laser Doppler vibrometer. The results show that the amplitude of vibration of the cylindrical sonotrode is not uniform on its working surface. A maximum of amplitude occurs in its border. In order to guarantee the process quality it is necessary that all points along the working surface vibrate with the same amplitude. It is used the parametric optimization technic of ANSYS in order to obtain an uniform amplitude of displacement on the working surface of the cylindric sonotrode. The simulated and experimental results optimized prototype of the cylindric sonotrode are compared showing good agreement and therfore validating the numerical model.

Este trabalho apresenta um estudo de transdutores piezelétricos de potência usados em máquinas de estampagem e soldagem de tecidos sintéticos por ultra-som, através de modelos de elementos finitos implementados no software ANSYS e verificações experimentais. O transdutor é do tipo sanduíche e está acoplado a um amplificador mecânico e a um sonotrodo. Os comportamentos elétrico e vibracional do transdutor tipo sanduíche foram analisados em relação à quantidade de discos de piezocerâmicas em modelos axi-simétricos com quatro e oito discos. Comparam-se os resultados numéricos da resposta em frequência da impedância elétrica e do coeficiente de acoplamento eletromecânico com resultados experimentais de protótipos. Apresentam-se também análises numéricas do comportamento vibracional do amplificador mecânico e de dois tipos de sonotrodos, um cilíndrico e outro com o formato de uma lâmina larga, usados no processo de corte e soldagem de tecidos por ultra-som. É feita uma análise da distribuição de amplitude de vibração ao longo da face de trabalho dos dois sonotrodos. Os resultados simulados são comparados com os resultados experimentais de uma varredura feita na superfície de trabalho de cada protótipo usando-se um vibrômetro laser Doppler. Mostra-se que a vibração na face do sonotrodo cilíndrico ocorre com maior amplitude em uma região na sua borda. Considerando que para o processamento adequado do tecido é necessário que todos os pontos ao longo da face de trabalho do sonotrodo vibrem com a mesma amplitude, verifica-se a necessidade de modificar a forma do sonotrodo visando obter uma distribuição uniforme de deslocamentos em sua face. Para isso utiliza-se a modelagem do sonotrodo com a técnica de otimização paramétrica disponível no ANSYS, com o objetivo de se obter uma distribuição de vibração uniforme ao longo de sua face de trabalho. Os resultados experimentais do protótipo do sonotrodo cilíndrico otimizado são comparados com os resultados numéricos da distribuição de vibração ao longo de sua face de trabalho mostrando uma boa concordância e, portanto, validando o modelo numérico. / This work presents a study of high power piezoelectric sandwich transducers used in ultrasonic cutting and welding of thermoplastic textiles using finite element models with ANSYS and experimental verifications. The electrical/vibrational behaviour of transducers with four and eight piezoceramics is analysed using axisymetric models. The numerical results of electrical impedance frequency response and electromechanical coupling factor are compared with experimental results of prototypes. There are presented the numerical analysis of the vibrational behaviour of an acoustical amplifier and two types of sonotrodes, a cylindrical and an wide blade shape, used in the ultrasonic cutting and welding of thermoplastic textiles. It is performed an analysis of the distribution of vibration amplitude along the work surface of both sonotrodes and the simulated results are compared with esperimental measurements of the prototypes using a laser Doppler vibrometer. The results show that the amplitude of vibration of the cylindrical sonotrode is not uniform on its working surface. A maximum of amplitude occurs in its border. In order to guarantee the process quality it is necessary that all points along the working surface vibrate with the same amplitude. It is used the parametric optimization technic of ANSYS in order to obtain an uniform amplitude of displacement on the working surface of the cylindric sonotrode. The simulated and experimental results optimized prototype of the cylindric sonotrode are compared showing good agreement and therfore validating the numerical model.

Ride and handling are important areas for safety and improved vehicle control during driving. To meet the demands on ride and handling a number of measures can be taken. This master thesis work has focused on the early design phase. At the early phases of design, the level of details is low and the design freedom is big. By introducing a tool to support the early vehicle body design, the potential of finding more efficient structures increases. In this study, topology optimization of a vehicle front structure has been performed using OptiStruct by Altair Engineering. The objective has been to find the optimal topology of beams and rods to achieve high stiffness of the front structure for improved ride and handling. Based on topology optimization a proposal for a beam layout in the front structure area has been identified. A vital part of the project has been to describe how to use topology optimization as a tool in the design process. During the project different approaches has been studied to come from a large design space to a low weight architecture based on a beam-like structure. The different approaches will be described and our experience and recommendations will be presented. Also the general result of a topology-optimized architecture for vehicle body stiffness will be presented.

Aluminum Cross-Car Beam is significantly lighter than the conventional steel counterpart and presents superior energy absorption characteristics. The challenge is however, its considerably higher cost, rendering it difficult for the aluminum one to compete in the automotive market. In this work, using material distribution techniques and stochastic optimization, a Multidisciplinary Design Optimization procedure is developed to optimize an existing Cross-Car Beam model with respect to the cost. Topology, Topography, and gauge optimizations are employed in the development of the optimization disciplines. Based on a qualitative cost assessment, penalty functions are designed to penalize costly designs. Noise-Vibration-Harshness (NVH) performance is the key constraint of the optimization. To fulfill this requirement, natural frequencies are obtained using modal analysis. Undesirable designs with respect to the NVH criteria are gradually eliminated from the optimization cycles. The new design is verified by static loading scenario and evaluated in terms of the cost saving it offers.

Aluminum Cross-Car Beam is significantly lighter than the conventional steel counterpart and presents superior energy absorption characteristics. The challenge is however, its considerably higher cost, rendering it difficult for the aluminum one to compete in the automotive market. In this work, using material distribution techniques and stochastic optimization, a Multidisciplinary Design Optimization procedure is developed to optimize an existing Cross-Car Beam model with respect to the cost. Topology, Topography, and gauge optimizations are employed in the development of the optimization disciplines. Based on a qualitative cost assessment, penalty functions are designed to penalize costly designs. Noise-Vibration-Harshness (NVH) performance is the key constraint of the optimization. To fulfill this requirement, natural frequencies are obtained using modal analysis. Undesirable designs with respect to the NVH criteria are gradually eliminated from the optimization cycles. The new design is verified by static loading scenario and evaluated in terms of the cost saving it offers.

Composite monocoque frames are becoming increasingly more popular inperformance cars. Compared to their steel and aluminum counterparts theyprovide additional torsional stiffness at the cost of less weight. This thesiscovers the complex optimization process of a monocoque applied within theregulations of a Formula Student competition. It aims to give the reader a goodunderstanding of the rules and how they affect the optimization process whilegenerating an optimized design used in the competition of Formula StudentGermany -21 by KTH Formula Student. The rules of Formula Student dictate the structural requirements on themonocoque based on a steel space frame. All materials except low carbon steelused in the structure require proof of equivalence through regulated testingmethods. However, this thesis shows that the regulated setup can severelyaffect results through a deep analysis of the testing methodology.The torsional stiffness of the monocoque is analyzed and optimized accordingto the results of a free-size optimization. Both through slight adjustmentsin chassis geometry and the laminate, resulting in a theoretical torsionalstiffness of 9.9 kNm/deg, more than five times as much as the old space frame.Weighing in at 20 kg, a significant weight reduction of about 10 kg, eventhough it was larger, with a surface area of about 4.2 m2. This design will be the first monocoque manufactured within KTH FormulaStudent since 2010. Therefore, a lot of focus was put on analyzing the rulesand lay the ground for future development by conducting tests on optimizedpanels. These results have the potential to further reduce the weight of a futuremonocoque with a different geometry. / Allt fler sportbilar använder självbärande karosser i komposit. Till skillnadfrån deras stål och aluminium motsvarighet så tillåter kompositkonstruktionenen styvare konstruktion för samma vikt. Denna rapport går igenom denkomplicerade optimeringsprocessen för en självbärande kaross i kolfiber appliceratinom tävlingen Formula Student. Målet med rapporten är att läsaren ska fåen bättre förståelse av reglerna och dess påverkan på optimeringsprocessensamtidigt som en optimerad design presenteras för användandet i “FormulaStudent Germany -21” åt KTH Formula Student. Reglerna inom Formula Student ställer strukturella krav på den självbärandekarossen baserat på en standard för stålrörsramar. Alla material förutomlåg kols stål som används i strukturen kräver att ekvivalens bevisas genomspecifika tester. Denna rapport visar att dessa tester kan generera olika resultatgenom en djup analys av metodiken. Torsions styvheten av karossen analyseras och optimeras enligt reglernagenom en så kallad free-size optimization". Genom att variera geometri ochkomposit utvecklades en kaross som var mer än 5 gånger så styv som dentidigare stålrörsramen med en teoretisk torsions styvhet på 9.9kNm/deg. Meden vikt på 20 kg reducerades även vikten 10 kg, även om den var större, ochhade en area på cirka 4.2m2. Denna design kommer att vara den första självbärande komposit karossentillverkad inom KTH Formula Student sedan 2010. Efter den djupa analysen avreglerna, testas då de optimerade panelerna, vilket lägger grunden för framtidautvecklingen. Dessa resultat har potential att reducera vikten ytterligare av enframtida kaross, genom ändringar i geometrin.