Examinando por Materia "FEA (Finite Element Analysis)"
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Ítem Desarrollo de un sistema protésico para personas con amputación transfemoral en Colombia(Universidad EAFIT, 2006) Correal Franco, Sara; Palacio Delgado, Lía Judith; Salazar Gómez, Isabel Cristina; Torres Velásquez, Andrés; Correa Vélez, SantiagoÍtem Design of computer experiments applied to modeling of compliant mechanisms for real-time control(Springer London, 2013-07) Acosta, Diego A.; Restrepo, David; Durango, Sebastián; Ruíz, Óscar E.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis article discusses the use of design of computer experiments (DOCE) (i.e., experiments run with a computer model to find how a set of inputs affects a set of outputs) to obtain a force–displacement meta-model (i.e., a mathematical equation that summarizes and aids in analyz-ing the input–output data of a DOCE) of compliant mechanisms (CMs) -- The procedure discussed produces a force–displacement meta-model, or closed analytic vector function, that aims to control CMs in real-time -- In our work, the factorial and space-filling DOCE meta-model of CMs is supported by finite element analysis (FEA) -- The protocol discussed is used to model the HexFlex mechanism functioning under quasi-static conditions -- The HexFlex is a parallel CM for nano-manipulation that allows six degrees of freedom (x, y, z, hx, hy, hz) of its moving platform -- In the multi-linear model fit of the HexFlex, the products or inter-actions proved to be negligible, yielding a linear model (i.e.,linear in the inputs) for the operating range -- The accuracy of the meta-model was calculated by conducting a set of computer experiments with random uniform distribution of the input forces -- Three error criteria were recorded comparing the meta-model prediction with respect to the results of the FEA experiments by determining: (1) maximum of the absolute value of the error, (2) relative error, and (3) root mean square error -- The maximum errors of our model are lower than high-precision manufacturing tolerances and are also lower than those reported by other researchers who have tried to fit meta-models to the HexFlex mechanismÍtem Engineering design using evolutionary structural optimisation based on iso-stress-driven smooth geometry removal(2001) García, M.J.; Ruíz, O.E.; Steven, G.P.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThe main goal of Evolutionary Structural Optimisation (ESO) research has been to provide an easily applicable optimisation method for the engineering industry which assists the design process for product improvement -- Originally O was based on the concept of fully stressed structures and it is obtained by slowly removing, from a Finite Element mesh these elements that present the lowest stress value -- Following this heuristically-driven removal criteria, the initial topology evolves towards the optimum one -- Since its introduction in 1992, ESO has been developed and extended to several types of structural problems -- Initial weaknesses of ESO were (i) typically long solution times and (ii) topologies with jagged surfaces as a result of removing whole elements in the optimisation process -- These characteristics hindered its application to computer aided design and analysis -- In this investigation, these weaknesses have been addressed for 2D situations by (i) basing the stress computation on the Fixed Grid (FG) finite element method and (ii) removing material with the lowest values along iso-stress contours instead of removing whole elements -- A boundary representation (B-rep) of the structure is maintained at each iteration of the optimisation process -- Modification to the workpiece is made by identifying the stress contour lines and incorporating them into the evolving geometry -- The topological consistency of the B-rep is maintained via normalized 2D boolean operationsÍtem FEA-driven Geometric Modelling for Meshless Methods(Springer Paris, 2005-11) Ruíz, Óscar; Granados, Miguel; Cadavid, Carlos; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEOptimized Boolean Operations against orthogonal Fixed Grids (FG) for 2-manifold construction in quasi-meshless methods for Finite Element Analysis are presented -- A Piecewise Linear (PL) or Boundary Representation (B-Rep) B is assumed to be the boundary of a solid S ⊂ R3 -- On the other hand, R3 is partitioned into a 3-dimensional array of cubic, uniform cells Ci,j,k . Cells Ci,j,k with Ci,j,k ∩ S ≠Φ and Ci,j,k ∩ S ≠ Ci,j,k are particularly important for FG applications -- These are the cells Ci,j,k intersecting B, which happen to be Neither Inside nor Outside (NIO) of B -- The boundary ∂(Ci,j,k ∩ S ) of Ci,j,k ∩ S must be calculated from ∂Ci,j,k and B for a large number of cells Ci,j,k , which makes the normal boolean operations unpractical -- The article illustrates with examples the immersion of B-Rep models in Fixed Grids, visits the downstream results of the stress-strain calculations using FG and explains how this approach is used in Product Design OptimizationÍtem Geometric modeling in design of naval elements(2003) Ruíz S., Óscar E.; Leiceaga Baltar, Xoán; Rodrígez Pérez, Manuel; Prieto Villar, José; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEBoundary Representations (B-Reps) of actual solid parts are correct from the geometrical and topological points of view -- However, when the solid to model has extreme slender ratios, the rigid rules of the B-Rep force a large number of finite elements required to model the solid interior of a closed shell (also called a 2-manifold without border) -- In the practice, modelling is then pursued by using only a partial shell (2-manifold with border), excluding the “interior” of it -- For the same reasons, other slender elements (trusses or beams) must be modelled as 1-dimensional wires (1-manifolds with border) -- Assumptions are made in both cases to replace the solid model information left aside -- The scenarios in which both 2-manifolds and 1-manifolds must coexist are undesirable from the mathematical point of view, since they render flawed topologies and geometries -- However, in the engineering domain, they are required, and enabled, by replacing the information lost in the modelling with additional kinematic and structural constraints -- These constraints force the 1-manifolds and 2-manifolds to intervene together in the numerical solution, therefore rendering realistic results, without actually coexisting in the geometric model -- These techniques are discussed here and applied to examples of shipbuilding industry, where slender forms and extremely large models are ubiquitousÍtem Simulation of the evolution of floor covering ceramic tiles during the firing(Springer Verlag, 2013-04) Peris-Fajarnés, Guillermo; Defez, Beatriz; Serrano, Ricardo; Ruíz, Óscar E.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEIn the context of the firing of ceramic tiles the problem of simulating the final shape of the body is relevant because several defects can occur and the tile can be rejected if the conditions of the firing are inadequate for the geometry and materials of the tile -- The existing literature on this problem indicates that previous works present limitations in aspects such as not using a model characteristic of ceramics at high temperatures and oversimplifying the problem -- As a response to such shortcomings, this article presents a simulation with a 3-dimensional Norton’s model, which overcomes the difficulties because it is characteristic of ceramics at high temperatures -- The results of our simulated experiments show advantages with respect to the identification of the mechanisms that contribute to the final shape of the body -- Our work is able to divide the history of temperatures in stages where the evolution of the thermal, elastic and creep deformations is simplified and meaningful -- That is achieved because our work found that curvature is the most descriptive parameter of the simulation, the most important contribution of this article -- Future work is to be realized in the creation of a model that takes into account that the shrinkage is dependent on the history of temperatures -- The main shortcoming of the paper is the lack of physical experiments to corroborate the simulations