1,720,963 research outputs found
Milestones in the 150-Year history of topology optimization: A review
Get PDFStructural optimization is one of the most intensively investigated research areas in engineering. Recently, topology optimization has become the most popular engineering subfield. The starting date of structural optimization cannot be precisely determined. Michell's optimization paper, published in 1904, is considered as the first publication in this subfield. However, his paper starts with a statement that his work is a generalization of Maxwell's idea presented in the paper published in 1870. The authors of this review paper consider that this date can be accepted as the starting date of topology optimization. This paper is an overview of subjectively selected state-ofart achievements in topology optimization during its history of 150 years. The selection of the achievements is a rather difficult task because, in the early period of the history of topology optimization, a lot of meetings were classified and the results were not available for the public. The optimization community has almost no knowledge about the publications in topology optimization in the 1950s. Around that time, one can find some information on workshops and meetings connected to the Cambridge University or Oxford University with researchers such as Foulkes, Cox, Hemp, and Shield, who published significant results and these communications are generally not known for the reason mentioned above. After the 1970s, this situation has changed and there were more possibilities to find publications due to the changes and thanks to digitalization. As indicated earlier here subjectively selected works are overviewed from the 150-year history focusing on the first hundred twenty years
Topology Optimization for Loads with Multiple Points of Application
Get PDFThe optimal design for loads with multiple points of application is herein investigated by using a formulation of displacement-constrained minimum volume topology optimization. For each one of the several points in which a moving force may be applied, a static load case is introduced, and a local enforcement is implemented to control the relevant displacement. Inspired by some recent contributions in stress-based topology optimization of large-scale structures, an Augmented Lagrangian approach, is adopted to handle efficiently the arising multi-constrained problem, in conjunction with mathematical programming. The results of some numerical simulations are shown to comment on optimal shapes for loads with multiple points of application, as compared to classical solutions for fixed loads
Topology optimization with graded infill accounting for loading uncertainty
Get PDFThe optimal design of composite structures made of a solid phase and a given fraction of graded infill is addressed, using homogenization-based topology optimization and accounting for uncertainty in loading amplitude. A two-phase material law with void is implemented to control the amount of graded infill to be distributed, along with its admissible density range. Numerical homogenization is used to derive the macroscopic elastic properties of an isotropic and two orthotropic infills that are commonly used in additive manufacturing. A minimum weight problem is endowed with a set of deterministic displacement constraints that are equivalent to stochastic displacement enforcements in case of normal distributions of the amplitude of the applied forces. Sequential convex programming is adopted to solve the arising multi-constrained problem. Numerical simulations are performed to assess the proposed algorithm and point out peculiar features of the achieved optimal solutions with respect to layouts found in case of deterministic loads. When a fraction of graded infill is prescribed, coated structures are retrieved, whose shape may be remarkably affected by the selected type of lattice
Form-finding of reticulated shells for a given plan layout with geometric constraints
Get PDFA numerical tool is implemented to address the design of reticulated shells through funicular analysis. As discussed in the literature, the force density method can be conveniently implemented to cope with the equilibrium of funicular networks, using independent sets of branches in the case of grids having fixed plan projection. In this contribution, optimal networks are sought not only in terms of an independent set of force densities, but also in the vertical coordinates of the restrained nodes. Constraints are enforced on the coordinates of the nodes, to prescribe a feasible design domain, and on the geometry of the members, to control their length and inclination with respect to a given reference direction. Due to its peculiar form, the arising multiconstrained problem can be efficiently solved through techniques of sequential convex programming that were originally conceived to handle formulations of size optimization for elastic structures. Networks that are fully feasible with respect to the enforced local constraints are retrieved in a limited number of iterations, with no need to initialize the procedure with a feasible starting guess. The same algorithm applies to general networks with any type of geometry and restraints
Lightweight design with displacement constraints using graded porous microstructures
Get PDFA multi-scale approach of topology optimization is proposed to design lightweight components for given loads and displacement limits. Hexagonal close-packed arrangements of circular/spherical holes allow defining 2D/3D isotropic/transversely isotropic microstructures whose macroscopic elastic properties depend on the radius of the cavities, namely the density of the porous material. An interpolation law is implemented to handle two-material structures with void, distributing both solid and graded material within a certain density range. An Augmented Lagrangian approach is adopted to handle multiple displacement constraints, along with the enforcement of a minimum amount of graded porous microstructure to be used in the optimal design. The proposed method defines: (i) boundaries of the component, and, (ii) possible internal arrangements of circular/spherical holes with graded radius. Also, when boundaries of a hollow component are prescribed, the method can be used to equip it with an optimal infill. Numerical examples are presented, concerning two- and three- dimensional problems, for different types of loads. Features of the proposed procedure are discussed, as well as peculiar properties of the optimal solutions, with special regard to coated structures. Fabrication of the porous layouts by means of additive manufacturing techniques is outlined
Comparative Study on the Optimal Topologies
Get PDFThe topology optimization is a leading tool in structural design. Due to the rapidly spreading need of the industry, commercial software are available in the market. Generally, these software are suitable for solving one subtask (preprocessing, postprocessing, stress calculation, etc.) but need some user manipulation to interconnect to one that is better for some other subproblem. This is the reason why we write a study on the available software and make suggestions on their usability. The purpose of this research is to briefly introduce selected software such as Rhino 3D, Grasshopper, Peregrine, Karamba, Galapagos, polyTop and PolyStress using topology optimization theory. Due to the demand to apply them for industrial applications, the additional goal is to make suggestions to make these software programs more user-friendly and to create algorithms to connect with software used in the industry, such as Consteel. This work also discusses the connected algorithms and optimization methods such as layout optimization by Peregrine, and topology optimization by polyTop and PolyStress. Several illustrative videos are provided as supplements. In addition to the text of this paper one can see demonstrations of the applications by the use of the provided YOUTUBE links
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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