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Sibai, Munira. "Optimization of an Unfurlable Space Structure". Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/99908.
Pełny tekst źródłaMaster of Science
Spacecraft, or artificial satellites, do not fly from earth to space on their own. They are launched into their orbits by placing them inside launch vehicles, also known as carrier rockets. Some parts or components of spacecraft are large and cannot fit in their designated space inside launch vehicles without being stowed into smaller volumes first. Examples of large components on spacecraft include solar arrays, which provide power to the spacecraft, and antennas, which are used on satellite for communication purposes. Many methods have been developed to stow such large components. Many of these methods involve folding about joints or hinges, whether it is done in a simple manner or by more complex designs. Moreover, components that are flexible enough could be rolled or wrapped before they are placed in launch vehicles. This method reduces the mass which the launch vehicle needs to carry, since added mass of joints is eliminated. Low mass is always desirable in space applications. Furthermore, wrapping is very effective at minimizing the volume of a component. These structures store energy inside them as they are wrapped due to the stiffness of their materials. This behavior is identical to that observed in a deformed spring. When the structures are released in space, that energy is released, and thus, they deploy and try to return to their original form. This is due to inertia, where the stored strain energy turns into kinetic energy as the structure deploys. The physical analysis of these structures, which enables their design, is complex and requires computational solutions and numerical modeling. The best design for a given problem can be found through numerical optimization. Numerical optimization uses mathematical approximations and computer programming to give the values of design parameters that would result in the best design based on specified criterion and goals. In this thesis, numerical optimization was conducted for a simple unfurlable structure. The structure consists of a thin rectangular panel that wraps tightly around a central cylinder. The cylinder and panel are connected with a hinge that is a rotational spring with some stiffness. The optimization was solved to obtain the best values for the stiffness of the hinge, the thickness of the panel, which is allowed to vary along its length, and the stiffness or elasticity of the panel's material. The goals or objective of the optimization was to ensure that the deployed panel meets stiffness requirement specified for similar space components. Those requirements are set to make certain that the spacecraft can be controlled from earth even with its large component deployed. Additionally, the second goal of the optimization was to guarantee that the unfurling panel does not have very high energy stored while it's wrapped, so that it would not cause large motion the connected spacecraft in the zero gravity environments of space. A computer simulation was run with the resulting hinge stiffness and panel elasticity and thickness values with the cylinder and four panels connected to a structure representing a spacecraft. The simulation results and deployment animation were assessed to confirm that desired results were achieved.
Denli, Huseyin. "Structural-acoustic optimization of composite sandwich structures". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 168 p, 2007. http://proquest.umi.com/pqdlink?did=1251904511&Fmt=7&clientId=79356&RQT=309&VName=PQD.
Pełny tekst źródłaPeters, David W. "Design of diffractive optical elements through low-dimensional optimization". Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/54614.
Pełny tekst źródłaPanayirci, Huseyin Murat. "Structural Optimization Using Ansys". Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607075/index.pdf.
Pełny tekst źródłaSchmidt, Martin-Pierre. "Computational generation and optimization of mechanical structures On structural topology optimization using graded porosity control Structural topology optimization with smoothly varying fiber orientations". Thesis, Normandie, 2020. http://www.theses.fr/2020NORMIR01.
Pełny tekst źródłaThis thesis studies and develops methods for mathematical modeling, numerical analysis and optimization applied to the generation of 3D objects. The proposed approaches are used to generate lattice structures and continuum structures with topology optimization
Mahfouz, S. Y. "Design optimization of structural steelwork". Thesis, University of Bradford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534650.
Pełny tekst źródłaHassani, B. "Homogenization and topological structural optimization". Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493797.
Pełny tekst źródłaClune, Rory P. (Rory Patrick). "Algorithm selection in structural optimization". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82832.
Pełny tekst źródłaCataloged from PDF version of thesis.
Includes bibliographical references (pages 153-162).
Structural optimization is largely unused as a practical design tool, despite an extensive academic literature which demonstrates its potential to dramatically improve design processes and outcomes. Many factors inhibit optimization's application. Among them is the requirement for engineers-who generally lack the requisite expertise-to choose an optimization algorithm for a given problem. A suitable choice of algorithm improves the resulting design and reduces computational cost, yet the field of optimization does little to guide engineers in selecting from an overwhelming number of options. The goal of this dissertation is to aid, and ultimately to automate, algorithm selection, thus enhancing optimization's applicability in real-world design. The initial chapters examine the extent of the problem by reviewing relevant literature and by performing a short, empirical study of algorithm performance variation. We then specify hundreds of bridge design problems by methodically varying problem characteristics, and solve each of them with eight commonly-used nonlinear optimization algorithms. The resulting, extensive data set is used to address the algorithm selection problem. The results are first interpreted from an engineering perspective to ensure their validity as solutions to realistic problems. Algorithm performance trends are then analyzed, showing that no single algorithm outperforms the others on every problem. Those that achieve the best solutions are often computationally expensive, and those that converge quickly often arrive at poor solutions. Some problem features, such as the numbers of design variables and constraints, the structural type, and the nature of the objective function, correlate with algorithm performance. This knowledge and the generated data set are then used to develop techniques for automatic selection of optimization algorithms, based on a range supervised learning methods. Compared to a set of current, manual selection strategies, these techniques select the best algorithm almost twice as often, lead to better-quality solutions and reduced computational cost, and-on a randomly-chosen set of mass minimization problems-reduce average material use by 9.4%. The dissertation concludes by outlining future research on algorithm selection, on integrating these techniques in design software, and on adapting structural optimization to the realities of design. Keywords: Algorithm selection, structural optimization, structural design, machine learning
by Rory Clune.
Ph.D.
Debenham, Shaun T. (Shaun Todd) 1973. "Optimization of outrigger structural systems". Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/80923.
Pełny tekst źródłaTayar, Memduh Ali. "Design approaches to structural optimization". Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/78067.
Pełny tekst źródłaMICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH.
Includes bibliographical references (leaves 84-86).
The objective of this thesis is to develop design approaches to structural optimization. In the example of three-dimensional grid structures, widely known as 'space frames', possible configurations are explored which maximize the load-bearing capacity of the system in relation to its weight. The study has been organized in two chapters: The first chapter starts with a brief review of structural concepts. Along with Gothic as a historical example to optimization, modem analytical methods to optimal structural design are presented which include Maxwell's Lemma, Michell's Fields and Ultimate Strength Analysis. In the second part of the thesis the design solutions are presented. The emphasis lies on a deployable space frame which is based on bar-joist like elements.
by Memduh Ali Tayar.
M.S.
Eppard, William M. "Integrated aerodynamic-structural design optimization". Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/90966.
Pełny tekst źródłaM.S.
Vogel, Ryan N. "Structural-Acoustic Analysis and Optimization of Embedded Exhaust-Washed Structures". Wright State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=wright1374833633.
Pełny tekst źródłaSaleh, Amgad. "Parallel algorithms for integrated structural/control optimization of large structures /". The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487940308432707.
Pełny tekst źródłaEkren, Mustafa. "Structural Optimization Strategies Via Different Optimization And Solver Codes And Aerospace Applications". Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610250/index.pdf.
Pełny tekst źródłaBoissier, Mathilde. "Coupling structural optimization and trajectory optimization methods in additive manufacturing". Thesis, Institut polytechnique de Paris, 2020. http://www.theses.fr/2020IPPAX084.
Pełny tekst źródłaThis work investigates path planning optimization for powder bed fusion additive manufacturing processes, and relates them to the design of the built part. The state of the art mainly studies trajectories based on existing patterns and, besides their mechanical evaluation, their relevance has not been related to the object’s shape. We propose in this work a systematic approach to optimize the path without any a priori restriction. The typical optimization problem is to melt the desired structure, without over-heating (to avoid thermally induced residual stresses) and possibly with a minimal path length. The state equation is the heat equation with a source term depending on the scanning path. Two physical 2-d models are proposed, involving temperature constraint: a transient and a steady state one (in which time dependence is removed). Based on shape optimization for the steady state model and control for the transient model, path optimization algorithms are developed. Numerical results are then performed allowing a critical assessment of the choices we made. To increase the path design freedom, we modify the steady state algorithm to introduce path splits. Two methods are compared. In the first one, the source power is added to the optimization variables and an algorithm mixing relaxation-penalization techniques and the control of the total variation is set. In a second method, notion of topological derivative are applied to the path to cleverly remove and add pieces. eventually, in the steady state, we conduct a concurrent optimization of the part’s shape and of the scanning path. This multiphysics optimization problem raises perspectives gathering direct applications and future generalizations
TAVARES, VINICIUS GAMA. "EFFICIENT STRUCTURAL TOPOLOGY OPTIMIZATION SYSTEM USING THE GROUND STRUCTURE METHOD". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=30728@1.
Pełny tekst źródłaCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Métodos de otimização topológica estrutural visam obter a melhor distribuição de material dentro de um dado domínio, sujeito a carga, condições de contorno e restrições de projeto, de forma a minimizar alguma medida especificada. A otimização topológica estrutural pode ser dividida em dois tipos: contínua e discreta, sendo a forma discreta o foco da pesquisa desta dissertação. O objetivo deste trabalho é a criação de um sistema para realizar todos os passos dessa otimização, visando a resolução de problemas com grandes dimensões. Para realizar esse tipo de otimização, é necessária a criação de uma malha densa de barras, esta definida como conjunto de nós cobrindo todo o domínio, conectados através de barras, além da especificação dos apoios e das forças aplicadas. Este trabalho propõe um novo método para geração da malha densa de barras, utilizando como entrada somente o contorno do domínio que se deseja otimizar, contrapondo com métodos que necessitam de um domínio já discretizado, como uma malha de poliedros. Com a malha gerada, este trabalho implementou a otimização topológica, sendo necessário resolver um problema de programação linear. Toda a parte de otimização foi realizada dentro do framework TopSim, tendo implementado o método dos pontos interiores para a resolução da programação linear. Os resultados apresentados possuem boa qualidade, tanto na geração quanto na otimização, para casos 2D e 3D, tratando casos com mais de 68 milhões de barras.
Structural topology optimization methods are used to find the optimal material distribution within a given domain, subject to loading, boundary conditions and design constraints, in order to minimize some specified measure. Structural topology optimization can be divided into two types: continuum and discrete, with the discrete type being the research focus of this dissertation. The goal of this work is the creation of a system to achieve all the steps of this optimization process, aiming problems with large dimensions. In order to perform the optimization, it is necessary create a ground structure, defined as a set of nodes covering the entire domain, connected by bars, with the supports and the applied loads. This work proposes a new method for the ground structure generation, using as input only the domain boundary, in contrast with methods that require a domain already discretized, such as a polyhedron mesh. With the generated mesh, this work has implemented the topological optimization, needing to solve a linear programming problem. All the optimization part was performed within the TopSim framework, implementing the interior point method for the linear programming resolution. The results presented have good quality, both in generation and optimization, for 2D and 3D cases, considering cases with more than 68 million bars.
Tan, Mengmeng. "Structural optimization of polypod-like structured DNA based on structural analysis and interaction with cells". Kyoto University, 2020. http://hdl.handle.net/2433/253233.
Pełny tekst źródłaSokmen, Ozlem. "Structural Optimization Of A Composite Wing". Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607715/index.pdf.
Pełny tekst źródłaTaskinoglu, Evren Eyup. "A Genetic Algorithm For Structural Optimization". Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607958/index.pdf.
Pełny tekst źródła) or by using in-house codes. The application of the algorithm is shown by a number of design examples. Several strategies for reproduction, mutation and crossover are tested. Several conclusions drawn from the research results are presented.
Wennhage, Per. "Structural-Acoustic Optimization of Sandwich Panels". Doctoral thesis, Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3161.
Pełny tekst źródłaForsberg, Jimmy. "Structural optimization in vehicle crashworthiness design /". Linköping : Dept. of Mechanical Engineering, Univ, 2005. http://www.bibl.liu.se/liupubl/disp/disp2005/tek940s.pdf.
Pełny tekst źródłaWolf, Matthew Dearing. "Structural optimization and properties of clusters". Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/30928.
Pełny tekst źródłaGao, Huanhuan. "Categorical structural optimization : methods and applications". Thesis, Compiègne, 2019. http://www.theses.fr/2019COMP2471/document.
Pełny tekst źródłaThe thesis concentrates on a methodological research on categorical structural optimizationby means of manifold learning. The main difficulty of handling the categorical optimization problems lies in the description of the categorical variables: they are presented in a category and do not have any orders. Thus the treatment of the design space is a key issue. In this thesis, the non-ordinal categorical variables are treated as multi-dimensional discrete variables, thus the dimensionality of corresponding design space becomes high. In order to reduce the dimensionality, the manifold learning techniques are introduced to find the intrinsic dimensionality and map the original design space to a reduced-order space. The mechanisms of both linear and non-linear manifold learning techniques are firstly studied. Then numerical examples are tested to compare the performance of manifold learning techniques mentioned above. It is found that the PCA and MDS can only deal with linear or globally approximately linear cases. Isomap preserves the geodesic distances for non-linear manifold however, its time consuming is the most. LLE preserves the neighbour weights and can yield good results in a short time. KPCA works like a non-linear classifier and we proves why it cannot preserve distances or angles in some cases. Based on the reduced-order representation obtained by Isomap, the graph-based evolutionary crossover and mutation operators are proposed to deal with categorical structural optimization problems, including the design of dome, six-story rigid frame and dame-like structures. The results show that the proposed graph-based evolutionary approach constructed on the reduced-order space performs more efficiently than traditional methods including simplex approach or evolutionary approach without reduced-order space. In chapter 5, the LLE is applied to reduce the data dimensionality and a polynomial interpolation helps to construct the responding surface from lower dimensional representation to original data. Then the continuous search method of moving asymptotes is executed and yields a competitively good but inadmissible solution within only a few of iteration numbers. Then in the second stage, a discrete search strategy is proposed to find out better solutions based on a neighbour search. The ten-bar truss and dome structural design problems are tested to show the validity of the method. In the end, this method is compared to the Simulated Annealing algorithm and Covariance Matrix Adaptation Evolutionary Strategy, showing its better optimization efficiency. In chapter 6, in order to deal with the case in which the categorical design instances are distributed on several manifolds, we propose a k-manifolds learning method based on the Weighted Principal Component Analysis. And the obtained manifolds are integrated in the lower dimensional design space. Then the method introduced in chapter 4 is applied to solve the ten-bar truss, the dome and the dame-like structural design problems
Ghisbain, Pierre. "Seismic performance assessment for structural optimization". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82833.
Pełny tekst źródłaCataloged from PDF version of thesis.
Includes bibliographical references (pages 223-228).
The economic impact of earthquakes has spurred the implementation of performance-based design to mitigate damage in addition to protecting human lives. A developing trend is to consider damage directly as a measure of seismic performance. In spite of the ability to estimate the cost of future earthquakes, adjusting the investment in seismic upgrades is impeded by the computational requirements of the probabilistic damage assessment. In this dissertation, we develop the damage assessment tools needed to implement structural optimization with an estimate of lifetime seismic damage in the objective function. A parametric study of the procedure to predict damage from earthquake simulation results is presented. By varying the procedure and analyzing the effects on the damage estimate, we identify simplifications that are beneficial for practical applications without losing important information about the behavior of the structure under seismic loads. The runtime of the probabilistic damage assessment is dominated by the response analysis of the structure to a range of earthquake scenarios. We consider alternatives to the standard but expensive nonlinear dynamic analysis, and we evaluate the error introduced by the faster analysis methods. The applicability of linear dynamic analysis is further investigated by detailing the effects of structural nonlinearities on the lifetime damage assessment. We determine that these effects are limited for the performance-based designed buildings, whose responses to the moderate but more frequent earthquakes remain essentially elastic. An application to the placement and sizing of viscous dampers in building frames is presented. A first procedure seeks the optimal trade-off between the investment in damping and the losses due to future earthquakes. For each level of damping considered, another optimization problem is solved to determine the most efficient damper layout considering the results of the damage assessment in a true performance-based design process.
by Pierre Ghisbain.
Ph.D.
Sun, Yongyan. "A Structural Optimization Scripted Software System". Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/88725.
Pełny tekst źródłaMaster of Science
Commercial structural optimization software packages which integrate modeling tools, optimization and extensive computational tools such as a finite element solver were developed and pushed to the market. However, some commercial approaches to structural optimization are not very general. In addition, the commercial codes are designed for a specific-purpose, and they may not be suitable in many cases. If the commercial codes do not properly represent the structural optimization problem, users have to write custom Python scripts to assist the software system in retrieving data from the .odb files generated by FEA software. This thesis introduces an optimization software system which supports two separate optimization approaches to solve structural optimization problems with small and large-scale finite element models. The optimization module of the system is performed by the MATLAB optimization toolbox and the Abaqus finite element program with scripts implemented in Python. This optimization software system allows users to extract and manipulate data for optimization without limitations. Furthermore, once the required parameters are input in the system, the scripting software creates the finite element model and proceeds with the optimization automatically.
Gao, Huanhuan. "Categorical Structural Optimization: Methods and Applications". Doctoral thesis, Universite Libre de Bruxelles, 2018. https://dipot.ulb.ac.be/dspace/bitstream/2013/278020/5/contrathg.pdf.
Pełny tekst źródłaDoctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
Unger, Eric Robert. "Integrated aerodynamic-structural wing design optimization". Diss., This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-09042008-063104/.
Pełny tekst źródłaBarton, Andrew Barton. "Integrating Manufacturing Issues into Structural Optimization". Thesis, The University of Sydney, 2002. http://hdl.handle.net/2123/857.
Pełny tekst źródłaBarton, Andrew Barton. "Integrating Manufacturing Issues into Structural Optimization". University of Sydney. Aerospace, Mechanical and Mechatronic, 2002. http://hdl.handle.net/2123/857.
Pełny tekst źródłaZHANG, Jingyao. "STRUCTURAL MORPHOLOGY AND STABILITY OF TENSEGRITY STRUCTURES". 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/49132.
Pełny tekst źródłaKyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第13385号
工博第2856号
新制||工||1420(附属図書館)
25541
UT51-2007-Q786
京都大学大学院工学研究科建築学専攻
(主査)教授 加藤 直樹, 教授 上谷 宏二, 准教授 大﨑 純
学位規則第4条第1項該当
Andersson, Maria, i Hanna Kristofferson. "Structural Optimization of Product Families : With Application to Vehicle Body Structures". Thesis, Linköping University, Department of Mechanical Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-6078.
Pełny tekst źródłaSome products share one or two modules and while developing these products, structural optimization with stiffness as the objective function can be a useful tool. There might be no or very little CAD-data available in the pre-development phase and it is not certain that existing designs can be, or is desirable to use as a reference. The main objective of this thesis is to establish an accurate and fast-to-use methodology which can be utilized while developing new cars.
In this thesis, the Volvo products S40, V50 and C70 serve as a basis for this case study. All the models are beam structures and the masses of components are added as point and line masses. Several optimization analyses are performed on one or three products exposed to seven load cases. Additional analyses with shell elements, more simplified models and changed load case balance achieved by normalization of the different load case compliances are also studied to investigate how these factors influence the results.
Analyses show that front crash to a great extent dominates the results while normalization increases the influence of the remaining load cases. Since front crash is dominating and the front area is shared in all products, the performance is remarkably similar when three products are optimized compared to separate analyses of one product. Analysis of models without added point or line masses gives a result which greatly differs from previous results and therefore shows that added masses are required. The methodology is applicable to develop products and detect new load paths through the car.
Pokharel, Rajib. "Structural Optimization of Offset Derrick Structure and Channel Endplate Connections Study". Thesis, University of Louisiana at Lafayette, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10002396.
Pełny tekst źródłaThis study is intended to focus on the optimization of offset derrick structures and to present a novel connection details for derrick structures. The overall goal of this study is to improve performance, ease fabrication, and reduce material and labor costs associated with derrick structures, and study the performances of Double Channel Endplate and Single Channel Endplate Connections using Finite Element Method (FEM) analysis.
Optimization of derrick structure is carried out by modeling different bracing systems with different parameters of design, for example, vertical panel height, bracing type, buckling restraint, and member orientation to come to optimum result in terms of structural weight, lateral stiffness, and number of joints. Eccentric bracing system, 2X-bracing system, X-bracing system, and K-bracing system are studied and comparisons are made among structures with similar vertical panel height to come to efficient geometry of that category. A Double Channel and Single Channel Endplate connection are developed and modeled to see the stress distribution, moments, and rotation capacities. Finally, behavioral plots (moment-rotation) are modeled to rate the performance of connections.
Structures with relatively shorter force path, uniform internal force distribution, and small internal forces are found to respond well and they are stiff, economical, and elegant as well. For 2X-bracing system, efficiency of offset derrick structure to resist the load is found to decrease for both small and large vertical panel height and optimum height was found in between. For this study, the optimum height was 20 ft. for 2X-bracing system. Thickness, and overlapping length of channel plate is found important for in-plane capacity of connection while stiffeners are more important for out-of-plane capacity. Connection is found to have higher in-plane bending stiffness than for out-of-plane.
Nunes, Eliana Ferreira. "Qualitative investigation of the performance of a structural membrane roof project". reponame:Repositório Institucional da UFOP, 2012. http://www.repositorio.ufop.br/handle/123456789/6036.
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This paper provides a qualitative investigation about the structural performance of the membranes, surface structures (with double curvature in opposite directions) with minimum thickness and weight, which absorb forces in form of tensile stresses in its own plane, considering two aspects: structural and design procedure. Initially, it involved the analyses of lightweight structure buildings and the observation of constructive work process in membrane roofs. These investigations allowed identifying strategies that contribute to achieve optimum system performance and the challenges encountered along the stages of designing and building. They also guided the qualitative analysis of the performance of a structural membrane roofing project, i.e., a particular situation, as example. This qualitative analysis was developed in two stages, guided by experimental and numerical data. The first stage involved the optimization procedure of the structural system under load action. This analysis showed that the flexible system performance is a result of the three-dimensional stability of the structural system (arrangement and geometry of all components), membrane surface stiffness (membrane geometry), as well as the cooperation of all components in pre-tension state. The second stage comprised the experimental investigation of the membrane material behaviour within the structure context in order to analyze the flattened membrane geometry. Such evaluation enabled to verify the difference between the theoretical model (shape of equilibrium) and the actual shape (consisting of flat panels), enabling the proper adjustment of the surface geometry so that the final shape can reveal not only the path of the forces, but also the best use of the material. The investigations, analyses and working procedure here adopted broadened the understanding of this system pointing possibilities to increase its performance and to minimize failures during the preliminary stage of design.
Descamps, Benoît. "Optimal shaping of lightweight structures". Doctoral thesis, Universite Libre de Bruxelles, 2013. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209362.
Pełny tekst źródłaPreviously proposed computational methods for designing lightweight structures focused either on finding an equilibrium shape, or are restricted to fairly small design applications. In this work, we aim to develop a general, robust, and easy-to-use method that can handle many design parameters efficiently. These considerations have led to truss layout optimization, whose goal is to find the best material distribution within a given design domain discretized by a grid of nodal points and connected by tentative bars.
This general approach is well established for topology optimization where structural component sizes and system connectivity are simultaneously optimized. The range of applications covers limit analysis and identification of failure mechanisms in soils and masonries. However, to fully realize the potential of truss layout optimization for the design of lightweight structures, the consideration of geometrical variables is necessary.
The resulting truss geometry and topology optimization problem raises several fundamental and computational challenges. Our strategy to address the problem combines mathematical programming and structural mechanics: the structural properties of the optimal solution are used for devising the novel formulation. To avoid singularities arising in optimal configurations, the present approach disaggregates the equilibrium equations and fully integrates their basic elements within the optimization formulation. The resulting tool incorporates elastic and plastic design, stress and displacements constraints, as well as self-weight and multiple loading.
Besides, the inherent slenderness of lightweight structures requires the study of stability issues. As a remedy, we develop a conceptually simple but efficient method to include local and nodal stability constraints in the formulation. Several numerical examples illustrate the impact of stability considerations on the optimal design.
Finally, the investigation on realistic design problems confirms the practical applicability of the proposed method. It is shown how we can generate a range of optimal designs by varying design settings. In that regard, the computational design method mostly requires the designer a good knowledge of structural design to provide the initial guess.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
Dersjö, Tomas. "Reliability based design optimization for structural components /". Stockholm : Skolan för teknikvetenskap, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11824.
Pełny tekst źródłaDersjö, Tomas. "Reliability based design optimization for structural components". Licentiate thesis, KTH, Solid Mechanics (Div.), 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11824.
Pełny tekst źródłaÖman, Michael. "Optimization and robustness of structural product families". Licentiate thesis, Linköping University, Linköping University, Solid Mechanics, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-17947.
Pełny tekst źródłaThis thesis concerns structural optimization of product families and robustness. The overall objective is to find a method for performing structural optimization of product families subjected to multiple crash load cases and to ensure a robust behavior.
A product family is a family of products where every product variant, or family member, shares at least one component with at least one other product in the family. Structural optimization of such a family is complex and for expensive function evaluations, e.g. crash simulations, the computing time to solve the problem with traditional methods gets unrealistically long. Therefore, a new optimization algorithm for product families is presented, called the critical constraint method (CCM), that reduces the number of required evaluations by only considering the active constraints in the optimal solution.
Traditionally optimized structures have a tendency of being sensitive to small variations in the design or loading conditions. As these kind of variations are inevitable, it is important to account for this sensitivity in the design process to ensure the robustness of the optimized design.
The thesis is divided in two parts. The first part serves as a theoretical background to the second part, the two appended articles. This first part includes introductions to the concepts of product families, optimization, meta modeling and robust design.
The first appended paper presents a new optimization algorithm for product families subjected to multiple crash loads. The method is compared to traditional methods and tested on two smaller product family examples.
The second paper is an application of an existing sensitivity analysis method on a large industrial application example. A sensitivity analysis is performed on a Scania truck cab subjected to an impact load in order to identify the most influencing variables on the crash responses.
Öman, Michael. "Optimization and Robustness of Structural Product Families". Doctoral thesis, Linköpings universitet, Hållfasthetslära, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-70372.
Pełny tekst źródłaDe, Hennin Stephen Robert. "Structural decisions in on-line process optimization". Thesis, Imperial College London, 1994. http://hdl.handle.net/10044/1/8355.
Pełny tekst źródłaRedhe, Marcus. "On vehicle crashworthiness design using structural optimization /". Linköping : Univ, 2004. http://www.bibl.liu.se/liupubl/disp/disp2004/tek863s.pdf.
Pełny tekst źródłaLeite, Joao Paulo de Barros. "Parallel adaptive search techniques for structural optimization". Thesis, Heriot-Watt University, 1996. http://hdl.handle.net/10399/1242.
Pełny tekst źródłaOLIVEIRA, ANDRE PIMENTEL DE. "APPLICATION OF TOPOLOGICAL DERIVATIVE IN STRUCTURAL OPTIMIZATION". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2018. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=36089@1.
Pełny tekst źródłaCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
A otimização topológica tem por objetivo buscar uma distribuição ótima de uma quantidade limitada de material em um dado domínio, de tal maneira a minimizar uma medida de desempenho, como, por exemplo, a flexibilidade da estrutura. Tradicionalmente, são utilizados algoritmos clássicos, baseados em gradiente, para se encontrar a solução deste problema de otimização. Este trabalho propõe a aplicação de uma técnica alternativa, baseada no conceito de derivada topológica, para a solução do problema de otimização topológica em domínios bidimensionais arbitrários, utilizando malhas de elementos finitos poligonais. Inicialmente, são apresentados os conceitos básicos da expansão assintótica topológica na solução de problemas de elasticidade linear em um domínio com pequenas perturbações. Usamos esse conceito para definir a derivada topológica a partir da solução desse problema e de um equivalente em um domínio sem perturbações. Em seguida, discutimos a obtenção da derivada topológica em problemas unidimensionais simples para depois estender este conceito para problemas de elasticidade linear bidimensional. Apresentamos uma implementação computacional da derivada topológica, em MATLAB, e aplicamos o código desenvolvido na solução de problemas de otimização topológica, conhecidos na literatura. Finalmente, apresentamos as conclusões sobre a qualidade dos resultados obtidos e a eficiência computacional da implementação proposta e sugerimos alguns tópicos para futuros desenvolvimentos.
The purpose of topology optimization is to find the optimum material distribution of a limited amount of material in a given domain, in such a way that it minimizes a performance measure, such as the structure s compliance. Traditionally, classical algorithms based on gradients are used to obtain the solution of optimization problems. This work proposes the application of an alternative technique, based on the topological derivative concept, for the solution of topology optimization problems in arbitrary two-dimensional domains, using polygonal finite element meshes. Initially, the basic concepts of topological asymptotic expansion of linear elasticity problems in a domain with small perturbations are presented. We use this concept to define the topological derivative from the solution of this problem and an equivalent one on a domain without perturbations. Then, we discuss how to calculate the topological derivative for one-dimensional problems before extending this concept to two-dimensional linear stability problems. We present a computational implementation of the topological derivative in MATLAB, and apply the developed code to solve topology optimization problems known in the literature. Finally, we present some conclusions about the quality of the results obtained and the computational efficiency of the proposed implementation and suggest some topics for future developments.
Chapman, Colin Donald. "Structural topology optimization via the genetic algorithm". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/35410.
Pełny tekst źródłaSmit, Charl Francois. "Reliability based optimization of concrete structural components". Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86329.
Pełny tekst źródłaENGLISH ABSTRACT: Standards define target reliability levels that govern the safety of designed structures. These target levels should be around an economic optimum for the class of structure under consideration. However, society may have safety requirements in excess of that required to achieve an economic optimum. The LQI criterion can be used to determine society’s willingness to invest in safety, thereby defining a minimum acceptable safety- or reliability level. This thesis determines economically optimised reliability levels for reliability class two concrete structures in South Africa, over a range of typical input parameters. Rackwitz’s (2000) approach is used here, adjusted for the South African context. The structure is described using a simple limit state function, defined as the difference between load and resistance, with resistance a function of a global safety parameter. South African construction costs, costs of increasing safety, failure costs and discount rates are used in the objective function for economic optimisation. Life Quality Index (LQI) theory is used as a basis to derive society’s willingness to pay (SWTP) for safety and the corresponding reliability level is found by applying the LQI criterion. In the South African context the derivation of SWTP presents some challenges, which is discussed. Situations where the minimum required reliability would exceed the economically optimum reliability level are discussed. Various reliability based cost optimization case studies are conducted covering a broad range of typical concrete design situations. From these case studies a range of target reliability indices are derived for typical concrete structural components and failure modes. Obtained values are compared to current South African target levels of reliability provided by the South African loading code and recommendations are made. The approach used by Rackwitz (2000) is compared with results obtained from case studies and used as basis to estimate optimum reliability levels for other types of buildings. Functions are written in MATLAB to allow replication of the study for others seeking to derive optimum reliability indices.
AFRIKAANSE OPSOMMING: Standaarde spesifiseer teiken betroubaarheidsvlakke wat die veiligheidsvlak van ontwerpte strukture bepaal. Hierdie teikenvlak moet rondom die ekonomiese optimum wees vir die klas van struktuur onder oorweging. Die samelewing verkies moontlik ‘n hoër veiligheidsvlak as wat deur die ekonomiese optimum dikteer word. Die LKI (Lewens Kwaliteit Indeks) maatstaf kan gebuik word om die samelewing se bereidwilligheid om in veiligheid te belê te bepaal en sodoende ‘n minimum veiligheidsvlak bepaal. Hierdie tesis bepaal die ekonomiese optimum betroubaarheidsvlak vir klas twee beton strukture in Suid-Afrika vir wisselende parameters. Rackwitz (2000) se benadering word in hierdie studie gebruik en is aangepas vir Suid-Afrikaanse omstandighede. Die struktuur word beskryf deur ‘n eenvoudige limiet staat funksie, gedefinieer as die verskil tussen die las en weerstand, met die weerstand as die funksie van ‘n globale veiligheidsparameter. Suid-Afrikaanse konstruksie koste, veiligheidsvermedering koste, falingskoste en diskonteer koerse word gebruik vir optimering. Die LKI teorie word gebruik om SBB (Samelewing Bereidheid om te Belê) vir veiligheid af te lei en die ooreenkomstige betroubaarheidsvlak word bepaal deur die LKI maatstaf toe te pas. In die afleiding hiervan vir Suid-Afrikaanse omstandighede is sekere uitdagings teegekom wat bespreek word. Situasies waar die minimum betroubaarheidsvlak hoer is as die ekonomiese optimum word bespreek. Verskillende betroubaarheids gebaseerde optimering gevalstudies word gedoen op tipiese beton struktuur elemente. Van hierdie gevalstudies is optimum betroubaarheidsindekse vir die tipiese beton elemente en galingsmodusie afgelei. Die betroubaarheidsindekse word vergelyk met huidige betroubaarheidsindekse soos wat voorgeskryf is in die Suid-Afrikaanse laskode (SANS10160-1(2011)). Rackwitz (2000) se benadering word vergelyk met die resultate van die gevallestudies en word gebruik as basis om optimum betroubaarheidsvlakke vir ander tipes geboue te voorspel. MATLAB funksies is geprogrameer om minimum en optimum betroubaarheidsindekse af te lei.
Stewart, Eric C. "Shape and Structural Optimization of Flapping Wings". Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/24808.
Pełny tekst źródłaPh. D.
Johansson, Robin. "Structural optimization of electronic packages using DOE". Thesis, KTH, Hållfasthetslära, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-285859.
Pełny tekst źródłaTillförlitligheten hos ett mekaniskt system med elektroniska kretsar påverkas starkt av miljön systemet används i. Skillnader och fluktuationer mellan omgivningens temperatur och arbetstemperaturen för de elektroniska kretsarna orsakar ackumulering av inelastiska töjningar, därmed förkortas det mekaniska systemets livstid. Dem vanligaste fel-moderna för en elektronisk krets har identifierats genom inspektion av felande maskiner som sprickbildning i lödfogarna och delaminering mellan processorn och dess lim. Kunskap hur förhållandet mellan parametrar som påverkar dessa fel-moder, vilka som är viktiga och vilka som inte är viktiga är av högt intresse vid utveckling av nya och redan existerande produkter. SAAB AB vill utveckla en metodik som utnyttjar statistisk försöksplanering för analyserande av elektroniska kretsar med hjälp av olinjära finita element metoder för att kunna spegla dess beteende på ett realistiskt sätt. En surrogatmodell skapades och parametriserades med hjälp av HyperMorph för att användas inom tre statiskt linjära varianter av statistisk försöksplanering, där både metodens prestanda och den relativa påverkan från parametrarna var av intresse. Ett kontaktvillkor implementerades för att tillåta relativ rörelse mellan komponenter samtidigt som nätet av finita element hölls intakt. Försöksplaneringsimuleringar utfördes med en Taguchi design, en Modified extensive lattice sequence design och en fractional factorial design, där de tre metoderna jämfördes mot varandra samt analyserades vad gäller respektive parametersignifikansen. Med optimering fanns sedan en optimal modell för att kunna jämföras med en nominell modell där en kryplag implementerades i lödfogen. Livslängden beräknades sedan för båda modeller.
Öman, Michael. "Optimization and robustness of structural product families /". Linköping : Department of Management and Engineering, Linköping University, 2009. http://www.bibl.liu.se/liupubl/disp/disp2009/tek1403s.pdf.
Pełny tekst źródłaRosyid, Daniel Mohammad. "Layout optimization of force transmitting structures". Thesis, University of Newcastle Upon Tyne, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315665.
Pełny tekst źródłaEsteban, Jaime. "A reliability-based method for optimization programming problems". Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-03302010-020045/.
Pełny tekst źródłaUlu, Erva. "Enhancing the Structural Performance of Additively Manufactured Objects". Research Showcase @ CMU, 2018. http://repository.cmu.edu/dissertations/1188.
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