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3D GIS
Published in Christopher M. Gold, Spatial Context: An Introduction to Fundamental Computer Algorithms for Spatial Analysis, 2018
This is the basis for traditional CAD (Computer Aided Design) systems based on a ‘b-rep’ (boundary representation) of the object being modelled. A key aspect here is the ability to build or modify the model one edge at a time without risking invalid topological connections – the validated operations for this are called ‘Euler Operators’. Probably the simplest way to construct these is by using the Quad Edge structure: valid sets of operators can be constructed entirely with ‘Make-Edge’ and ‘Splice’ as described previously. A valid set of operators is shown below: the names specify the number of edges, vertices, faces and shells (new models) added (‘Made’) or removed (‘Killed’) on the model while preserving the topology and the Euler Formula. Each operator has its inverse operation to undo its effect. Other sets of operators are possible.
Rapid manufacturing of metallic objects: A challenge for research and industry
Published in Paulo Jorge Bártolo, Artur Jorge Mateus, Fernando da Conceição Batista, Henrique Amorim Almeida, João Manuel Matias, Joel Correia Vasco, Jorge Brites Gaspar, Mário António Correia, Nuno Carpinteiro André, Nuno Fernandes Alves, Paulo Parente Novo, Pedro Gonçalves Martinho, Rui Adriano Carvalho, Virtual and Rapid Manufacturing, 2007
FGM deposition: FGM has controlled variation of material composition throughout the matrix leading to the desired distribution of material composition leading to obtain the desired patterns of properties such as color, density, hardness, porosity etc. in the matrix. RP enables manufacture of FGM. The inherent inhomogeneity of RP is exploited to build FGMs by focusing the inhomogeneity in a desired way. Z-Corp’s 3DP can produce color prototypes. Laser Engineered Net Shaping (LENS) supports the same for metals. Therefore, the manufacturing technologies today exist for FGM but the designers are unable to incorporate these in their designs for want of CAD tools supporting FGM. Existing CAD packages use Constructive Solid Geometry (CSG) and/or Feature Based Modeling (FBM) as the front end representation and Boundary Representation (B-Rep) internally. As they store only the boundary of the object, they fail to capture the definition of the interior of the components. Voxel representations are suitable for this application but are memory-intensive. Voxel representations of uniform and adaptive sizes are under development at various research centres. When these representations become available, designers can incorporate FGMs in their design.
Recognition and decomposition of rib features in thin-shell plastic parts for finite element analysis
Published in Computer-Aided Design and Applications, 2018
Jiing-Yih Lai, Ming-Hsuan Wang, Pei-Pu Song, Chia-Hsiang Hsu, Yao-Chen Tsai
Many commercial CAD systems already provide CAD feature trees to record the structure of a CAD model, which also includes the structure of many existing features. However, the commonly used CAD data file formats, such as IGES and STEP, do not record such a constructing structure. For a solid model, the boundary representation (B-rep) data structure is commonly used and its data can be rebuilt from the CAD data file. However, the B-rep data does not record the constructing structure of a CAD model. Thus, when a CAE system inputs such a CAD data, all it can access is the topological and geometric information of the CAD model. On the other hand, in CAE analysis, a hybrid combination of different types of solid meshes has been proved to be better than conventional tetrahedral meshes. It requires the recognition of each interesting region and decomposing it from the rest of the model. A feature in the CAD design may not directly represent a region that can be meshed. In fact, most commonly used features are too complex in geometry, and virtual faces may exist across multiple features, so they cannot be meshed directly. We aim to develop an independent feature recognition and decomposition method that can be implemented in a CAE system or used as a pre-processing tool for a better generation of solid meshes.
Interoperability of CAD geometry and product manufacturing information for computer integrated manufacturing
Published in International Journal of Computer Integrated Manufacturing, 2020
Satchit Ramnath, Payam Haghighi, Adarsh Venkiteswaran, Jami J. Shah
Major CAD systems define a solid model in terms of faces, edges, vertices, etc., collectively called the Boundary Representation (B-Rep). However, this representation does not give any information about the type of features or functionality of the part to be manufactured. The information about features has a lot of applications down the line and can aid manufacturers, process planners, designers, CNC programmers, etc.