Examinando por Materia "Mesh generation"
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Ítem FE-simulations with a simplified model for open-cell porous materials: A Kelvin cell approach(IOS Press, 2019-01-01) Montoya-Zapata D.; Cortés C.; Ruiz-Salguero O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEIn in-silico estimation of mechanical properties of open (Kelvin) cell porous materials, the geometrical model is intractable due to the large number of finite elements generated. Such a limitation impedes the study of reasonable domains. VoXel or Boundary representations of the porous domain result in FEA data sets which do not pass the stage of mesh generation, even for very modest domains. Our method to overcome such limitations partially replaces geometrical minutiae with kinematical constraints imposed on cylindrical bars (i.e. Truss model). Our implemented method uses node position equality constraints augmented with rotation constraints at the joints. Such a method significantly reduces the computational expense of the model, allowing the study of domains of 103 Kelvin cells. The results of the tests executed show the accuracy and efficiency of the Truss model in the estimation of Young's modulus and Poisson's ratio when compared with current procedures. The method allows application for materials which depart from Kelvin Cell uniformity, since the Truss model admits general configurations. As the simulation is made possible by the Truss model, new challenges appear, such as the application to anisotropic materials and the automatic generation of the Truss model from actual foam scans (e.g. tomographies). © 2019 - IOS Press and the authors. All rights reserved.Ítem Geometry simplification of open-cell porous materials for elastic deformation FEA(SPRINGER, 2019-01-01) Cortés C.; Osorno M.; Uribe D.; Steeb H.; Ruiz-Salguero O.; Barandiarán I.; Flórez J.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEEstimation of mechanical properties of porous materials is central for their medical and industrial application. However, the massive size of accurate boundary representations (B-Rep) of the foams makes the numerical estimations intractable. Even for small domain sizes, the mesh generation for finite element analysis (FEA) may not terminate. Current efforts for simulating porous materials use statistical predictions of the material structure. The simulated and actual materials present different geometry and topology, with consequences on the simulation results. To overcome these limitations, this manuscript presents a method, which (1) synthesizes an accurate truss abstraction from the raw geometry data, (2) executes efficient FEA simulations, and (3) processes nodal displacements to estimate apparent mechanical moduli of the porous material. The method addresses materials whose ligaments have circular cross-sections. The iso-surface present in the Computer Tomography (CT) scan of the porous material is used to synthesize a truss graph whose edges are truncated cones. Then, optimization and simplification methods are applied to produce a topologically and geometrically correct truss representation for the foam domain. Comparative FEA load simulations are conducted between the full B-Rep and truss representations of the material. The truss model proves to be significantly more efficient for FEA, departing from the Full B-Rep FEA by a maximum of 16% in the estimation of equivalent mechanical moduli. Geometric assessments such as porosity and Hausdorff distance confirm that the truss abstraction is a cost-effective one. Ongoing efforts concentrate on point set geometric algorithms for enforcement of standardized material testing. © 2018 Springer-Verlag London Ltd., part of Springer NatureÍtem Hessian eigenfunctions for triangular mesh parameterization(SciTePress, 2016-02-27) Mejia, D.; Ruiz OE; Cadavid, C.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEHessian Locally Linear Embedding (HLLE) is an algorithm that computes the nullspace of a Hessian functional H for Dimensionality Reduction (DR) of a sampled manifold M. This article presents a variation of classic HLLE for parameterization of 3D triangular meshes. Contrary to classic HLLE which estimates local Hessian nullspaces, the proposed approach follows intuitive ideas from Differential Geometry where the local Hessian is estimated by quadratic interpolation and a partition of unity is used to join all neighborhoods. In addition, local average triangle normals are used to estimate the tangent plane TxM at x ? M instead of PCA, resulting in local parameterizations which reflect better the geometry of the surface and perform better when the mesh presents sharp features. A high frequency dataset (Brain) is used to test our algorithm resulting in a higher rate of success (96.63%) compared to classic HLLE (76.4%). © Copyright 2016 by SCITEPRESS - Science and Technology Publications, Lda. All rights reserved.Ítem Hessian eigenfunctions for triangular mesh parameterization(SciTePress, 2016-02-27) Mejia, D.; Ruiz OE; Cadavid, C.; Mejia, D.; Ruiz OE; Cadavid, C.; Universidad EAFIT. Departamento de Ciencias; Matemáticas y AplicacionesHessian Locally Linear Embedding (HLLE) is an algorithm that computes the nullspace of a Hessian functional H for Dimensionality Reduction (DR) of a sampled manifold M. This article presents a variation of classic HLLE for parameterization of 3D triangular meshes. Contrary to classic HLLE which estimates local Hessian nullspaces, the proposed approach follows intuitive ideas from Differential Geometry where the local Hessian is estimated by quadratic interpolation and a partition of unity is used to join all neighborhoods. In addition, local average triangle normals are used to estimate the tangent plane TxM at x ? M instead of PCA, resulting in local parameterizations which reflect better the geometry of the surface and perform better when the mesh presents sharp features. A high frequency dataset (Brain) is used to test our algorithm resulting in a higher rate of success (96.63%) compared to classic HLLE (76.4%). © Copyright 2016 by SCITEPRESS - Science and Technology Publications, Lda. All rights reserved.Ítem Hybrid geometry / topology based mesh segmentation for reverse engineering(PERGAMON-ELSEVIER SCIENCE LTD, 2018-06-01) Mejia D.; Ruiz-Salguero O.; Sánchez J.R.; Posada J.; Moreno A.; Cadavid C.A.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEMesh segmentation and parameterization are crucial for Reverse Engineering (RE). Bijective parameterizations of the sub-meshes are a sine-qua-non test for segmentation. Current segmentation methods use either (1) topologic or (2) geometric criteria to partition the mesh. Reported topology-based segmentations produce large sub-meshes which reject parameterizations. Geometry-based segmentations are very sensitive to local variations in dihedral angle or curvatures, thus producing an exaggerated large number of small sub-meshes. Although small sub-meshes accept nearly isometric parameterizations, this significant granulation defeats the intent of synthesizing a usable Boundary Representation (compulsory for RE). In response to these limitations, this article presents an implementation of a hybrid geometry / topology segmentation algorithm for mechanical workpieces. This method locates heat transfer constraints (topological criterion) in low frequency neighborhoods of the mesh (geometric criterion) and solves for the resulting temperature distribution on the mesh. The mesh partition dictated by the temperature scalar map results in large, albeit parameterizable, sub-meshes. Our algorithm is tested with both benchmark repository and physical piece scans data. The experiments are successful, except for the well - known cases of topological cylinders, which require a user - introduced boundary along the cylinder generatrices. © 2018 Elsevier LtdÍtem Hybrid geometry / topology based mesh segmentation for reverse engineering(PERGAMON-ELSEVIER SCIENCE LTD, 2018-06-01) Mejia D.; Ruiz-Salguero O.; Sánchez J.R.; Posada J.; Moreno A.; Cadavid C.A.; Mejia D.; Ruiz-Salguero O.; Sánchez J.R.; Posada J.; Moreno A.; Cadavid C.A.; Universidad EAFIT. Departamento de Ciencias; Matemáticas y AplicacionesMesh segmentation and parameterization are crucial for Reverse Engineering (RE). Bijective parameterizations of the sub-meshes are a sine-qua-non test for segmentation. Current segmentation methods use either (1) topologic or (2) geometric criteria to partition the mesh. Reported topology-based segmentations produce large sub-meshes which reject parameterizations. Geometry-based segmentations are very sensitive to local variations in dihedral angle or curvatures, thus producing an exaggerated large number of small sub-meshes. Although small sub-meshes accept nearly isometric parameterizations, this significant granulation defeats the intent of synthesizing a usable Boundary Representation (compulsory for RE). In response to these limitations, this article presents an implementation of a hybrid geometry / topology segmentation algorithm for mechanical workpieces. This method locates heat transfer constraints (topological criterion) in low frequency neighborhoods of the mesh (geometric criterion) and solves for the resulting temperature distribution on the mesh. The mesh partition dictated by the temperature scalar map results in large, albeit parameterizable, sub-meshes. Our algorithm is tested with both benchmark repository and physical piece scans data. The experiments are successful, except for the well - known cases of topological cylinders, which require a user - introduced boundary along the cylinder generatrices. © 2018 Elsevier LtdÍtem Low altitude wind simulation over mount saint helens using NASA SRTM digital terrain model(2007-01-01) Garcia, M.J.; Boulanger, P.; Garcia, M.J.; Boulanger, P.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Mecánica AplicadaOn February 11, 2000, the Shuttle Radar Topography Mission (SRTM) was launched into space as part of one of the pay load of the Shuttle Endeavor. Using a new radar sweeping technique most of the Earth's surfaces was digitized in 3D in approximately 10 days. SRTM acquired enough data during its mission to obtain a near-global high-resolution database of the Earth's topography. This paper describe how this revolutionary data set can be used to simulate anywhere around the Earth low altitude wind conditions for various atmospheric conditions. More specifically, we will describe the various processing steps necessary to convert this high-resolution terrain model provided by the SRTM database into a Computational Fluid Dynamic (CFD) volumetric mesh that is compatible with an open source CFD solver called OpenFOAM running in parallel on large West-Grid supercomputers. This work is the result of a new virtual wind-tunnel under development at the University of Alberta. In the paper, we present wind flow over the MountSaint Helens in the United States for a simple wind flow boundary condition. © 2006 IEEE.Ítem Mesh Segmentation and Texture Mapping for Dimensional Inspection inWeb3D(Association for Computing Machinery, Inc, 2017-01-01) Mejia D.; Sánchez J.R.; Segura Á.; Ruiz-Salguero O.; Posada J.; Cadavid C.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAETraditionally, the data generated by industrial metrology so.ware is stored as static reports that metrology experts produce for engineering and production departments. Nevertheless, industry demands new approaches that provide ubiquitous and real time access to overall geometry, manufacturing and other data. Web3D technologies can help to improve the traditional metrology methods and o.er new ways to convey this information in web-based continuous friendly manner. However, enriched point clouds may be massive, thus presenting transmission and display limitations. To partially overcome these limitations, this article presents an algorithm that computes efficient metrology textures, which are then transferred and displayed through Web3D standards. Texture coordinates are computed only once for the reference CAD mesh on the server using in-house thermal-based segmentation and Hessian-based parameterization algorithms. The metrology data is then encoded in a texture le, which becomes available instantly for interactive visual inspection through the Web3D platform. © 2017 ACM.Ítem Weighted area/angle distortion minimization for Mesh Parameterization(EMERALD GROUP PUBLISHING LIMITED, 2017-01-01) Mejia D.; Acosta D.A.; Ruiz-Salguero O.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Desarrollo y Diseño de ProcesosPurpose: Mesh Parameterization is central to reverse engineering, tool path planning, etc. This work synthesizes parameterizations with un-constrained borders, overall minimum angle plus area distortion. This study aims to present an assessment of the sensitivity of the minimized distortion with respect to weighed area and angle distortions. Design/methodology/approach: A Mesh Parameterization which does not constrain borders is implemented by performing: isometry maps for each triangle to the plane Z = 0; an affine transform within the plane Z = 0 to glue the triangles back together; and a Levenberg-Marquardt minimization algorithm of a nonlinear F penalty function that modifies the parameters of the first two transformations to discourage triangle flips, angle or area distortions. F is a convex weighed combination of area distortion (weight: a with 0 = a = 1) and angle distortion (weight: 1 - a). Findings: The present study parameterization algorithm has linear complexity [O(n), n = number of mesh vertices]. The sensitivity analysis permits a fine-tuning of the weight parameter which achieves overall bijective parameterizations in the studied cases. No theoretical guarantee is given in this manuscript for the bijectivity. This algorithm has equal or superior performance compared with the ABF, LSCM and ARAP algorithms for the Ball, Cow and Gargoyle data sets. Additional correct results of this algorithm alone are presented for the Foot, Fandisk and Sliced-Glove data sets. Originality/value: The devised free boundary nonlinear Mesh Parameterization method does not require a valid initial parameterization and produces locally bijective parameterizations in all of our tests. A formal sensitivity analysis shows that the resulting parameterization is more stable, i.e. the UV mapping changes very little when the algorithm tries to preserve angles than when it tries to preserve areas. The algorithm presented in this study belongs to the class that parameterizes meshes with holes. This study presents the results of a complexity analysis comparing the present study algorithm with 12 competing ones. © Emerald Publishing Limited.Ítem Weighted area/angle distortion minimization for Mesh Parameterization(EMERALD GROUP PUBLISHING LIMITED, 2017-01-01) Mejia D.; Acosta D.A.; Ruiz-Salguero O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEPurpose: Mesh Parameterization is central to reverse engineering, tool path planning, etc. This work synthesizes parameterizations with un-constrained borders, overall minimum angle plus area distortion. This study aims to present an assessment of the sensitivity of the minimized distortion with respect to weighed area and angle distortions. Design/methodology/approach: A Mesh Parameterization which does not constrain borders is implemented by performing: isometry maps for each triangle to the plane Z = 0; an affine transform within the plane Z = 0 to glue the triangles back together; and a Levenberg-Marquardt minimization algorithm of a nonlinear F penalty function that modifies the parameters of the first two transformations to discourage triangle flips, angle or area distortions. F is a convex weighed combination of area distortion (weight: a with 0 = a = 1) and angle distortion (weight: 1 - a). Findings: The present study parameterization algorithm has linear complexity [O(n), n = number of mesh vertices]. The sensitivity analysis permits a fine-tuning of the weight parameter which achieves overall bijective parameterizations in the studied cases. No theoretical guarantee is given in this manuscript for the bijectivity. This algorithm has equal or superior performance compared with the ABF, LSCM and ARAP algorithms for the Ball, Cow and Gargoyle data sets. Additional correct results of this algorithm alone are presented for the Foot, Fandisk and Sliced-Glove data sets. Originality/value: The devised free boundary nonlinear Mesh Parameterization method does not require a valid initial parameterization and produces locally bijective parameterizations in all of our tests. A formal sensitivity analysis shows that the resulting parameterization is more stable, i.e. the UV mapping changes very little when the algorithm tries to preserve angles than when it tries to preserve areas. The algorithm presented in this study belongs to the class that parameterizes meshes with holes. This study presents the results of a complexity analysis comparing the present study algorithm with 12 competing ones. © Emerald Publishing Limited.Ítem Weighted area/angle distortion minimization for Mesh Parameterization(EMERALD GROUP PUBLISHING LIMITED, 2017-01-01) Mejia D.; Acosta D.A.; Ruiz-Salguero O.; Mejia D.; Acosta D.A.; Ruiz-Salguero O.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Procesos Ambientales (GIPAB)Purpose: Mesh Parameterization is central to reverse engineering, tool path planning, etc. This work synthesizes parameterizations with un-constrained borders, overall minimum angle plus area distortion. This study aims to present an assessment of the sensitivity of the minimized distortion with respect to weighed area and angle distortions. Design/methodology/approach: A Mesh Parameterization which does not constrain borders is implemented by performing: isometry maps for each triangle to the plane Z = 0; an affine transform within the plane Z = 0 to glue the triangles back together; and a Levenberg-Marquardt minimization algorithm of a nonlinear F penalty function that modifies the parameters of the first two transformations to discourage triangle flips, angle or area distortions. F is a convex weighed combination of area distortion (weight: a with 0 = a = 1) and angle distortion (weight: 1 - a). Findings: The present study parameterization algorithm has linear complexity [O(n), n = number of mesh vertices]. The sensitivity analysis permits a fine-tuning of the weight parameter which achieves overall bijective parameterizations in the studied cases. No theoretical guarantee is given in this manuscript for the bijectivity. This algorithm has equal or superior performance compared with the ABF, LSCM and ARAP algorithms for the Ball, Cow and Gargoyle data sets. Additional correct results of this algorithm alone are presented for the Foot, Fandisk and Sliced-Glove data sets. Originality/value: The devised free boundary nonlinear Mesh Parameterization method does not require a valid initial parameterization and produces locally bijective parameterizations in all of our tests. A formal sensitivity analysis shows that the resulting parameterization is more stable, i.e. the UV mapping changes very little when the algorithm tries to preserve angles than when it tries to preserve areas. The algorithm presented in this study belongs to the class that parameterizes meshes with holes. This study presents the results of a complexity analysis comparing the present study algorithm with 12 competing ones. © Emerald Publishing Limited.