37,369 research outputs found

    Study of lightweighting structural design considering 3D printing constraints

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    One of the current challenges of the aerospace industry is the exploration of new lightweighting structures to reduce fuel consumption and limiting the environmental impact. The use of numerical methods concerning topology optimization techniques allows the obtaining of such weight reduction, also minimizing both design time and costs, and hence accelerating the design process. Nevertheless, current structural optimization leads to the apparition of complex shapes and volumes with unintuitive holes, thus needing the use of additive manufacturing constraints - minimum length scales and overhanging - to ensure manufacturability. Considering the background exposed above, the aim of this project is to study the feasibility of heuristic designs concerning lightweighting structures, materialized with additive manufacturing and considering 3D printing constraints. The design stage will be developed by means of topology optimization techniques, applied to anisotropic filtering. The methodology employed has considered all details concerning Computational Solid Mechanics (CSM) techniques used in structures optimization, as well as additive manufacturing techniques, different case studies definition and their feasibility study. More specifically, in the context of CSM, the use of Finite Element Methods (FEM) in the classical elastic problem is reviewed, as well as current topology optimization techniques, so as to implement FEM in optimization algorithms. Thus, theoretical basis in additive manufacturing techniques are reviewed, along with the mathematical formulation of length scale and overhang constraints. Lastly, the programming stage is performed by previously defining the working environment, consisting in the use of Object-Oriented Programming within the git Version Control System, and hence establishing the computational domain definition for all cases, the meshing process and the simulation setup. In the end, the present project has accomplished the main objectives, giving a positive answer to the creation of lightweighting structures and fulfillment of 3D printing constraints. Indeed, FEM combined with topology optimization techniques has led to the obtaining of optimized designs, fulfilling an objective function and a set of constraints, considering both design variables approaches, density and level set. Besides, an additional shape functional has been defined as a penalty contribution to the main cost function in order to fulfill 3D printing constraints - the anisotropic perimeter - being the evolution of the standard isotropic one, both applied to total and relative perimeters. This shape functional self-penalizes length scale constraints and keeps control in overhanging phenomena by orienting the topologies with the definition of a virtual anisotropic stiffness matrix. Results obtained show that the apparition of local features with small length scales has been avoided when including either isotropic or anisotropic perimeter as a penalty term. Furthermore, vertical tendency orientation of topologies has been generally obtained with the anisotropic cases, along with penalization of horizontal features. Overall, this project has become clearly relevant for the exploration of new lightweighting structures, achieving weight reduction with topology optimization techniques. Further exploration remains in the course of PhD professionalization, specially when considering phase-field models, high-performance computing and large-scale optimization inside the non-linear regime

    Structural and thermal performances of topological optimized masonry blocks

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    Structural topology optimization is the most fundamental form of structural optimization and receives an increasing attention from engineers and structural designers. The method enables the exploration of the general topology and shape of structural elements at an early stage of the design process and gives rise to inspiring and innovative improvements. In this paper, topology optimization as a principle is used to design new types of insulating masonry blocks. Two main objectives are addressed: maximizing the structural stiffness and minimizing the thermal transmittance. The first part of this paper uses these objectives to create new block topologies. A general problem is formulated and the influences of boundary conditions, external loading, and filter value on the resulting geometry are discussed. In general, maximizing the stiffness is in strong contrast to minimizing the thermal transmittance. This causes problems not encountered in conventional topology optimization. Nevertheless, by adjusting the interpolation schemes and adding multiple load groups, convergent solutions are found. An isotropic material model with an enforced solid-or-empty distribution is considered as the primary method. The optimized block topologies are then thoroughly analyzed to review their structural and thermal performance using the commercial finite element software Abaqus. The direct compressive strength of the block is a measure of the structural performance and the equivalent thermal conductivity gives an indication of the thermal performance. The second part then gives some thoughts on three-dimensional optimization and the incorporation of mesostructures in the design

    Robust topology optimization of three-dimensional photonic-crystal band-gap structures

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    We perform full 3D topology optimization (in which "every voxel" of the unit cell is a degree of freedom) of photonic-crystal structures in order to find optimal omnidirectional band gaps for various symmetry groups, including fcc (including diamond), bcc, and simple-cubic lattices. Even without imposing the constraints of any fabrication process, the resulting optimal gaps are only slightly larger than previous hand designs, suggesting that current photonic crystals are nearly optimal in this respect. However, optimization can discover new structures, e.g. a new fcc structure with the same symmetry but slightly larger gap than the well known inverse opal, which may offer new degrees of freedom to future fabrication technologies. Furthermore, our band-gap optimization is an illustration of a computational approach to 3D dispersion engineering which is applicable to many other problems in optics, based on a novel semidefinite-program formulation for nonconvex eigenvalue optimization combined with other techniques such as a simple approach to impose symmetry constraints. We also demonstrate a technique for \emph{robust} topology optimization, in which some uncertainty is included in each voxel and we optimize the worst-case gap, and we show that the resulting band gaps have increased robustness to systematic fabrication errors.Comment: 17 pages, 9 figures, submitted to Optics Expres

    Computer-Aided Conceptual Design Through TRIZ-based Manipulation of Topological Optimizations

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    Organised by: Cranfield UniversityIn a recent project the authors proposed the adoption of Optimization Systems [1] as a bridging element between Computer-Aided Innovation (CAI) and PLM to identify geometrical contradictions [2], a particular case of the TRIZ physical contradiction [3]. A further development of the research has revealed that the solutions obtained from several topological optimizations can be considered as elementary customized modeling features for a specific design task. The topology overcoming the arising geometrical contradiction can be obtained through a manipulation of the density distributions constituting the conflicting pair. Already two strategies of density combination have been identified as capable to solve geometrical contradictions.Mori Seiki – The Machine Tool Compan
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