Dynamic tailoring of beam-like structures. Application to High Aspect Ratio unitized box-beam and internal resonant structures

This work is a journey into the dynamic tailoring of beam-like structures which aims to exploit unconventional couplings and nonlinearities to enlarge the design space and improving the performances of engineering systems. Particularly, two examples pertaining dynamic tailoring of aerospace and mechanical systems are investigated in depth. In the first case, the work aims to attain a desired structural performance exploiting typical nonlinear structural phenomena and unconventional couplings offered by the unitized structures. As for the unitized structures, the present work, derives two equivalent plate models of curvilinear stiffened panels namely, constant (or homogenized) stiffness model and variable stiffness model. The models are assessed through finite element analysis. In the spirit of CAS (Circumferentially Asymmetric Stiffness), the equivalent plate stiffness’s are used to determine the cross- sectional beam stiffness’s. The governing equations for the Euler-Bernoulli, anisotropic beam with variable stiffness are derived and then used to address the optimization problem. The objective of the optimization is to attain a desired static or dynamic performance of the unitized beam exploiting the enlarged design space which arises from the stiffness variability and the unconventional couplings. In the second type of system analyzed, the aim is synthesize meaningful topologies for planar resonators. The topology optimization is addressed using as initial guess a ground structure. Motivated by the results of the optimization, a generalized reduced order model is derived for multi-members beam structures. The generalized model have been then specialized for three cases namely, V- Y- and Z-shaped resonators. The analytical solution for the V-shaped resonator is also derived along with the electro-mechanical equations of motion. Different solutions are studied aiming at investigating the effect of the folding angle on to the performances of a V-shaped harvester. Beside the study of the static and dynamic behavior of the systems, the thesis presents two novel optimization algorithms namely, the Stud^P GA and the GERM. The Stud^P GA, is a population based algorithm conceived to enhance the exploration capabilities, and hence the convergence rate, of classical GA. The Stud^P GA has been preliminary assessed through benchmark problems for composite layered structure and then used for the optimization of the stiffeners' path aiming at attaining a desired static or dynamic performances. The GERM (Graph-based Element Removal Method), is a double filtering technique conceived for the topology synthesis of planar ground structures. The GERM has been used, in combination with a standard GA, to address the topology optimization problem of the two types of system namely, planar resonator and compliant structures. The work introduces also the concept of trace-based scaling for predicting the behavior of anisotropic structures. The effectiveness of the trace-based scaling is assessed through comparison between scaled and analytical performances of anisotropic structures

Structural optimization in steel structures, algorithms and applications

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Algorithm selection in structural optimization

Thesis (Ph. D.)--Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2013.Cataloged 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 learningby Rory Clune.Ph.D

Fundamentals for the Dimensioning and Optimization of Prestressed Segmented Girders for Application in Bridge Crane Systems

Bridge cranes are widely used as discontinuous material handling systems in industrial environments. The so-called crane bridge plays a central role in the overall construction. With increasing span widths and load capacities, the dimensions of the crane bridge also increase. The core of this work is the design and optimization of a new type of bridge crane system, which consists of individual segments and is eccentrically pretensioned by a tensile member

Reduced Order Modeling based Inexact FETI-DP solver for lattice structures

This paper addresses the overwhelming computational resources needed with standard numerical approaches to simulate architected materials. Those multiscale heterogeneous lattice structures gain intensive interest in conjunction with the improvement of additive manufacturing as they offer, among many others, excellent stiffness-to-weight ratios. We develop here a dedicated HPC solver that benefits from the specific nature of the underlying problem in order to drastically reduce the computational costs (memory and time) for the full fine-scale analysis of lattice structures. Our purpose is to take advantage of the natural domain decomposition into cells and, even more importantly, of the geometrical and mechanical similarities among cells. Our solver consists in a so-called inexact FETI-DP method where the local, cell-wise operators and solutions are approximated with reduced order modeling techniques. Instead of considering independently every cell, we end up with only few principal local problems to solve and make use of the corresponding principal cell-wise operators to approximate all the others. It results in a scalable algorithm that saves numerous local factorizations. Our solver is applied for the isogeometric analysis of lattices built by spline composition, which offers the opportunity to compute the reduced basis with macro-scale data, thereby making our method also multiscale and matrix-free. The solver is tested against various 2D and 3D analyses. It shows major gains with respect to black-box solvers; in particular, problems of several millions of degrees of freedom can be solved with a simple computer within few minutes.Comment: 30 pages, 12 figures, 2 table

Mastering Uncertainty in Mechanical Engineering

This open access book reports on innovative methods, technologies and strategies for mastering uncertainty in technical systems. Despite the fact that current research on uncertainty is mainly focusing on uncertainty quantification and analysis, this book gives emphasis to innovative ways to master uncertainty in engineering design, production and product usage alike. It gathers authoritative contributions by more than 30 scientists reporting on years of research in the areas of engineering, applied mathematics and law, thus offering a timely, comprehensive and multidisciplinary account of theories and methods for quantifying data, model and structural uncertainty, and of fundamental strategies for mastering uncertainty. It covers key concepts such as robustness, flexibility and resilience in detail. All the described methods, technologies and strategies have been validated with the help of three technical systems, i.e. the Modular Active Spring-Damper System, the Active Air Spring and the 3D Servo Press, which have been in turn developed and tested during more than ten years of cooperative research. Overall, this book offers a timely, practice-oriented reference guide to graduate students, researchers and professionals dealing with uncertainty in the broad field of mechanical engineering

Otimização estrutural multi-objetivo de treliças planas e espaciais considerando aspectos dinâmicos e de estabilidade global

This dissertation presents the formulation of structural optimization problems (SOPs) containing three to six objective functions applied to plane and spatial trusses, focusing on considering objectives and constraints regarding the natural frequencies of vibration and the critical load factors. Solving SOPs helps engineering professionals find solutions and make decisions in developing a project. The application of multi-objective SOPs allows the decision-maker to find structural configurations that simultaneously serve all the desired criteria without solving several single-objective problems individually. To reduce costs and material consumption, the first objective, analyzed in all proposed problems, is to minimize the weight of the trusses. To avoid the resonance effect and find solutions with better dynamic behavior, other objectives used are the maximization of the first natural frequency of vibration and the maximization of the differences between the structure’s natural frequencies to avoid the superposition of their vibration modes. To guarantee the structural stability of the trusses, SOPs are also proposed with the objective functions of maximizing their first critical load factors related to global stability and maximizing the difference between their first two critical load factors. The meta-heuristics used to solve the optimization problems of this study are the GDE3 (Third Evolution Step of Generalized Differential Evolution), the SHAMODE (Success History–based Adaptive Multi-objective Differential Evolution), the SHAMODE-WO (Success History–based Adaptive Multi-objective Differential Evolution with Whale Optimisation) and the MM-IPDE (Multi-objective Meta-heuristic with Iterative Parameter Distribution Estimation). The non-dominated solutions obtained for each SOP are presented by graphs of the Pareto fronts and normalized parallel coordinate graphs (for the cases with more than three objective functions). A multi-criteria tournament decision-making method is applied to extract the desired solutions for each problem, according to the designer’s preferences. Finally, the performances of the four algorithms are compared through performance indicators found in the literature.O presente trabalho de dissertação apresenta a formulação de problemas de otimização estrutural (POEs) com três a seis funções objetivo, aplicados em treliças planas e espaciais, destacando-se a consideração de objetivos e restrições referentes às frequênciais naturais de vibração e fatores de carga crítica. A resolução de POEs auxilia os profissionais de engenharia na determinação de soluções e na tomada de decisões no desenvolvimento de um projeto. A aplicação de POEs multi-objetivo permite ao tomador de decisões encontrar configurações estruturais que atendam simultaneamente a todos os critérios desejados, sem a necessidade de resolver vários problemas mono-objetivo individualmente. Visando diminuir os custos e o consumo de materiais, o primeiro objetivo, abordado em todos os problemas propostos, é a minimização do peso das treliças. Para evitar o efeito de ressonância e encontrar soluções com melhor comportamento dinâmico, outros objetivos utilizados são a maximização da primeira frequência natural de vibração e a maximização das diferenças entre as frequências naturais da estrutura, evitando a sobreposição de seus modos de vibração. Com a intenção de garantir a estabilidade estrutural das treliças, também são propostos POEs com as funções objetivo de maximizar o primeiro fator de carga crítica relacionado à estabilidade global e maximizar a diferença entre os dois primeiros fatores de carga crítica. As meta-heurísticas de busca utilizadas na resolução dos problemas de otimização deste estudo são o GDE3 (Third Evolution Step of Generalized Differential Evolution), o SHAMODE (Success History–based Adaptive Multi-objective Differential Evolution), o SHAMODE-WO (Success History–based Adaptive Multi-objective Differential Evolution with Whale Optimisation) e o MM-IPDE (Multi-objective Metaheuristic with Iterative Parameter Distribution Estimation). As soluções não-dominadas obtidas para cada POE são apresentadas por meio de gráficos das frentes de Pareto e gráficos de coordenadas paralelas normalizadas (para os casos com mais de três funções objetivo). Um método de tomada de decisão de torneio multicritério é aplicado para extrair as soluções desejadas de cada problema, de acordo com as preferências do projetista. Por fim, as performances dos quatro algoritmos utilizados são comparadas através de indicadores de desempenho presentes na literatura.PROQUALI (UFJF

Proceedings of the ECCOMAS Thematic Conference on Multibody Dynamics 2015

This volume contains the full papers accepted for presentation at the ECCOMAS Thematic Conference on Multibody Dynamics 2015 held in the Barcelona School of Industrial Engineering, Universitat Politècnica de Catalunya, on June 29 - July 2, 2015. The ECCOMAS Thematic Conference on Multibody Dynamics is an international meeting held once every two years in a European country. Continuing the very successful series of past conferences that have been organized in Lisbon (2003), Madrid (2005), Milan (2007), Warsaw (2009), Brussels (2011) and Zagreb (2013); this edition will once again serve as a meeting point for the international researchers, scientists and experts from academia, research laboratories and industry working in the area of multibody dynamics. Applications are related to many fields of contemporary engineering, such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, mechatronic and autonomous systems, smart structures, biomechanical systems and nanotechnologies. The topics of the conference include, but are not restricted to: ● Formulations and Numerical Methods ● Efficient Methods and Real-Time Applications ● Flexible Multibody Dynamics ● Contact Dynamics and Constraints ● Multiphysics and Coupled Problems ● Control and Optimization ● Software Development and Computer Technology ● Aerospace and Maritime Applications ● Biomechanics ● Railroad Vehicle Dynamics ● Road Vehicle Dynamics ● Robotics ● Benchmark ProblemsPostprint (published version