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Polyhedral models are widely used for applications such as manufacturing, digital simulation or visualization. They are discrete models; easy to store, to manipulate, allowing levels of resolution for visualization. They can be easily exchanged between CAD systems without loss of data. Previous works (Comput Aided Des 29(4):287–298, 1997, Comput Gr...
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Context 1
... processing proposed Fig. 2 Polyhedral model assembly and its corresponding bounding boxes label. The internal edges of the contact interface with significant curvature are also extracted. These edges identification is based on a mean curvature criterion computed on each internal edge. The discrete mean curvature H e [16] is defined for an edge (Fig. 9) ...
Context 2
... of distinct contact areas and handles all the cases of domain re-meshing. The geometry is preserved after processing the assembly, as the clearance distance. Even gaps created by tessellation of the CAD models are not changed during the process Fig. 17. The resulting re-meshed assembly (Fig. 18) has the same contact interfaces on both parts (Fig. 19), and a contact line can be easily ...
Context 3
... extraction of specific information from a polyhedral assembly is our purpose. A treatment of the assembly is necessary; the need of setting up conformity in the Fig. 19 Parts before and after Re-meshing, new tessellations take the boundary of the contact into account Fig. 20 Example of a polyhedral assembly translated by the I-DEAS CAD software assembly meshing is the first step. The second step is the contact detection, introducing tangency handling and clearance handling. Contact detection is here ...
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The rapid development of digital technology has made architecture a succession of different evolutionary design methodologies. As a result, the rise of computationally driven processes has gain popularity in research and shows a great potential to dramatically improve the design process and productivity that evoke innovations in design practices wh...
Citations
... The quality of the mesh elements is not ensured (c − ) and the shape of the modification tool is not respected (e − ). Chouadria et al. (2006) have proposed an approach for the treatment of digital mock-up assemblies (Chouadria and Veron, 2006). The modifications are local (a + ) but self-intersecting elements are not avoided (d − ). ...
... The quality of the mesh elements is not ensured (c − ) and the shape of the modification tool is not respected (e − ). Chouadria et al. (2006) have proposed an approach for the treatment of digital mock-up assemblies (Chouadria and Veron, 2006). The modifications are local (a + ) but self-intersecting elements are not avoided (d − ). ...
Purpose
– The purpose of this paper is to set up a new framework to enable direct modifications of volume meshes enriched with semantic information associated to multiple partitions. An instance of filleting operator is prototyped under this framework and presented in the paper.
Design/methodology/approach
– In this paper, a generic mesh modification operator has been designed and a new instance of this operator for filleting finite element (FE) sharp edges of tetrahedral multi-partitioned meshes is also pro-posed. The filleting operator works in two main steps. The outer skin of the tetrahedral mesh is first deformed to round user-specified sharp edges while satisfying constraints relative to the shape of the so-called Virtual Group Boundaries. Then, in the filleting area, the positions of the inner nodes are relaxed to improve the aspect ratio of the mesh elements.
Findings
– The classical mainstream methodology for product behaviour optimization involves the repetition of four steps: CAD modelling, meshing of CAD models, enrichment of models with FE simulation semantics and FEA. This paper highlights how this methodology could be simplified by two steps: simulation model modification and FEA. The authors set up a new framework to enable direct modifications of volume meshes enriched with semantic information associated to multiple partitions and the corresponding fillet operator is devised.
Research limitations/implications
– The proposed framework shows only a paradigm of direct modifications of semantic enriched meshes. It could be further more improved by adding or changing the modules inside. The fillet operator does not take into account the exact radius imposed by user. With this proposed fillet operator the mesh element density may not be enough high to obtain wished smoothness.
Originality/value
– This paper fulfils an identified industry need to speed up the product behaviour analysis process by directly modifying the simulation semantic enriched meshes.
... As a result, this common area can be used to generate conformal FE meshes in this area, which greatly improves the FE mesh generation process of an assembly model. In case of meshed or faceted CAD models, several approaches have been proposed [50,114] to compute the common areas between components representing their contact areas and to process FE meshes generated on a component basis so that their common area can be identified and their FE meshes in that region can be modified to produce a conformal mesh. Obviously, these approaches are of great interest to process assembly models for FEA. ...
The digital mock-up (DMU) of a product has taken a central position in the product development process (PDP). It provides the geometric reference of the product assembly, as it defines the shape of each individual component, as well as the way components are put together. However, observations show that this geometric model is no more than a conventional representation of what the real product is. Additionally, and because of its pivotal role, the DMU is more and more required to provide information beyond mere geometry to be used in different stages of the PDP. An increasingly urging demand is functional information at different levels of the geometric representation of the assembly. This information is shown to be essential in phases such as geometric pre-processing for finite element analysis (FEA) purposes. In this work, an automated method is put forward that enriches a geometric model, which is the product DMU, with function information needed for FEA preparations. To this end, the initial geometry is restructured at different levels according to functional annotation needs. Prevailing industrial practices and representation conventions are taken into account in order to functionally interpret the pure geometric model that provides a start point to the proposed method.
... To provide mesh compatibility connectivity, i.e., an interface between two components ensures the same mesh distribution in the interface area of each component, Lou [LPMV10] and Chouadria [CV06] propose to identify and re-mesh contact interfaces. Quadros [QVB * 10] establishes sizing functions to control assembly meshes. ...
Aeronautical companies face a significant increase in complexity and size of simulation models especially at the level of assemblies, sub-systems of their complex products. Pre-processing of Computer Aided Design (CAD) models derived from the digital representation of sub-systems, i.e., Digital Mock-Ups (DMUs), into Finite Elements Analysis (FEA) models requires usually many tedious manual tasks of model preparation and shape transformations, in particular when idealizations of components or assemblies have to be produced. Therefore, the purpose of this thesis is to make a contribution to the robust automation of the time-consuming sequences of assembly preparation processes. Starting from an enriched DMU with geometrical interfaces between components and functional properties, the proposed approach takes DMU enrichment to the next level by structuring components' shapes. This approach extracts a construction graph from B-Rep CAD models so that the corresponding generative processes provide meaningful volume primitives for idealization application. These primitives form the basis of a morphological analysis which identifies the sub-domains for idealization in the components' shapes and their associated geometric interfaces. Subsequently, models of components as well as their geometric representation get structured in an enriched DMU which is contextualized for FEA application. Based on this enriched DMU, simulation objectives can be used to specify geometric operators that can be robustly applied to automate components and interfaces shape transformations during an assembly preparation process. A new idealization process of standalone components is proposed while benefiting from the decomposition into sub-domains and their geometric interfaces provided by the morphological analysis of the component. Interfaces between sub-domains are evaluated to robustly process the connections between the idealized sub-domains leading to the complete idealization of the component. Finally, the scope of the idealization process is extended to shape transformations at the assembly level and evolves toward a methodology of assembly pre-processing. This methodology aims at exploiting the functional information of the assembly and interfaces between components to perform transformations of groups of components and assembly idealizations. In order to prove the applicability of the proposed methodology, corresponding operators are developed and successfully tested on industrial use-cases.
... Developments of ontology-based approaches take advantage of new capabilities to structure concepts and to connect them with component models [26,31] or at the level of 3D geometry entities [7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Some of these approaches have been applied to assemblies [7,23,31] and can take advantage of reasoners to set up inference rules to ensure the consistency of the assembly description or extract information that is not readily available in the dataset describing an assembly. ...
... Moreover, part naming identification used in this approach is not sufficient because it locates only individual components contained in the assembly without establishing relations with their adjacent components and their associate geometric model, i.e. replacing a bolted junction by an idealized fastener implies simplifying its nut, its screw as well as the hole connected to them in the tightened components. To provide mesh domains connectivity, Lou [28] and Choudria [10] proposes to identify and re-mesh contact interfaces. Quadros [30] establishes sizing functions to control assembly meshes. ...
Pre-processing of CAD models derived from Digital Mock-Ups (DMUs) into finite element (FE) models is usually completed after many tedious tasks of model preparation and shape transformations. It is highly valuable for simulation engineers to automate time-consuming sequences of assembly preparation processes. Here, it is proposed to use an enriched DMU with geometric interfaces between components (contacts and interferences) and functional properties. Then, the key concept of template-based transformation can connect to assembly functions to locate consistent sets of components in the DMU. Subsequently, sets of shape transformations feed the template content to adapt components to FE requirements. To precisely monitor the friction areas and the mesh around bolts, the template creates sub-domains into their tightened components and preserves the consistency of geometric interfaces for the mesh generation purposes. From a user-selected assembly function, the method is able to robustly identify, locate and transform groups of components while preserving the consistency of the assembly needed for FE models. To enlarge the scope of the template in the assembly function taxonomy, it is shown how the concept of dependent function enforces the geometric and functional consistency of the transformed assembly. To demonstrate the proposed approach, a business oriented prototype processes bolted junctions of aeronautical structures.
... replacing volume sub domains by either planar surfaces or lines when their mechanical behavior resembles a plate's or a beam's one, respectively. In addition to the modeling of each component individually, mechanical simulation requires to model the interfaces between components [3,4,2]. While the kinematic simulation of assemblies only requires knowledge about the type and spatial position of the contact surfaces, stress computations using FE simulations require the precise modeling of the imprint of one component on each other within each interface. ...
... More generally, components' geometric interfaces appear as key entities to process assemblies efficiently. However, these interfaces are not readily available in DMUs and specific geometry processing is needed to obtain them [3,4,6,5]. ...
... When it comes to large assemblies, this lack of detailed description of geometric interfaces becomes a real challenge. Low level interactive operators enabling the surface trimming of components' boundaries become too tedious for a practical computation of imprint faces [3,4,7]. To scale up this approach to highly complex assemblies, new and more automated approaches are necessary. ...
... Across the tasks involved in FE simulations, specific operators have been set up at the level of FE mesh generation [18][19][20] to process contact areas between components either from B-Rep CAD models [18] or faceted ones [19,20]. These operators are helpful to reduce the amount of interactive processing to transform component boundaries into geometric models suited for meshing but they are far from the function level to avoid repetitive selection operations and faceted representations can hardly be efficient to pro- cess DMUs during a design process. ...
... Across the tasks involved in FE simulations, specific operators have been set up at the level of FE mesh generation [18][19][20] to process contact areas between components either from B-Rep CAD models [18] or faceted ones [19,20]. These operators are helpful to reduce the amount of interactive processing to transform component boundaries into geometric models suited for meshing but they are far from the function level to avoid repetitive selection operations and faceted representations can hardly be efficient to pro- cess DMUs during a design process. ...
A digital mock-up (DMU), with its B-Rep model of product components, is a standard industrial representation that lacks geometric information about interfaces between components. Component shapes reflect common engineering practices that influence component interfaces with interferences and not only contacts.The proposed approach builds upon relationships between function, behavior, and shape to derive functional information from the geometry of component interfaces. Among these concepts, the concept of behavior is more difficult to set up and connect to the geometry of interfaces and functions. Indeed, states and design rules are introduced to express the behavior of components through a qualitative reasoning process. This reasoning process, in turn, takes advantage of domain knowledge rules and facts, checking the validity of certain hypotheses that must hold true all along a specific state of the product’s lifecycle, such as operational, stand-by or relaxed states. Eliminating configurations that contradict one or more of those hypotheses in their corresponding reference state reduces ambiguity, subsequently producing functional information in a bottom-up manner.This bottom-up process starts with the generation of a conventional interfaces graph (CIG) with components as nodes, and conventional interfaces (CIs) as arcs. A CI is initially defined by a geometric interaction that can be a contact or an interference between two components. CIs are then populated with functional interpretations (FIs) according to their geometric properties, producing potentially many combinations. A first step of the reasoning process, the validation against reference states, reduces the number of FIs per CI.Domain knowledge rules are then applied again to group semantics of component interfaces into one functional designation per component to connect together geometric entities of its boundary with its function.
... The quality of the mesh elements is not ensured (c -) and the shape of the modification tool is not respected (e -). The digital mock-up assembly presented in [7] ensures local modification (a + ) but selfintersecting elements are not avoided (d -). ...
Currently adopted process from Computer-Aided Design (CAD) product definition to numerical simulation could be improved by avoiding the return to the CAD model for model modification. To this aim, we propose a generic mesh modification operator whose architecture is detailed in this paper. A new instance of this operator for filleting finite element (FE) tetrahedral meshes is also proposed. The filleting operator works in two main steps. The external skin of the tetrahedral mesh is first deformed to round user-specified sharp edges. Then, in the filleting area, the positions of the inner nodes are relaxed to improve the aspect ratio of the mesh elements. Several examples illustrate the interest of such a CAD-less approach.
... 56 2.6 Surface triangulation over intersecting geometries [105] . . . . . . 57 2.7 Contact interface re-meshing in context of assembly collision detection [24] [117] . . . . . . . . . . 62 2.12 Interactive TIN modification with a cutting tool [31] . . . . . . . ...
... Chouadria et al. worked on the treatment of contact interfaces to simplify polyhedral assemblies [24]. The faces between interacting objects are identified and specific operators are applied to merge the two parts. ...
... This step aims at finding the faces that are potentially in contact. It consists in the detection of intersections between scaled bounding boxes built on each face of M esh1 and M esh2 [24]. The bounding box of a face is computed along the parametric directions and scaled with an empiric factor of 1.05 to avoid inaccuracy problems. ...
Behaviour analysis is largely performed on the virtual model of the product before its physical manufacturing. Anyhow, the process could be further optimised especially during the product behaviour optimisation phase. This process involves repetition of four main processing steps: CAD design, mesh creation, enrichment of physical semantics and Finite Element Analysis (FEA). The product behaviour analysis is performed on the first design solution as well as on the numerous successive product optimisation loops. Each design solution evaluation necessitates the same time as required for the first product design and it is particularly crucial in the context of maintenance and lifecycle assessment. This thesis proposes a new framework for CAD-less product optimisation through FEA, which reduces the mesh preparation and semantics enrichment activities. More concretely, the idea is to directly operate the firstly created FE mesh, enriched with semantics, to perform the product modifications required to achieve its optimised version. In this thesis, the underlying concepts and the devised components for the development of such CAD-less operator are discussed. A high-level operator specification is proposed according to a modular structure that allows an easy realisation of different mesh modification operators. Finally, four instances of this high-level operator are described: merging, cracking, drilling and filleting. These operators are prototyped and validated on academic and industrial FE mesh models, thus clearly showing the feasibility of our approach.
... Unfortunately, the fact that the transition surface is hardly controllable reduces its interest in the industrial context. Chouadria et al. have been working on the treatment of contact interfaces to simplify polyhedral assemblies [15]. The faces between interacting objects are identified and specific operators are applied to merge the two parts. ...
... This step aims at finding the faces that are potentially in contact. It consists in the detection of intersections between scaled bounding boxes built on each face of Mesh1 and Mesh2 [15]. The bounding box of a face is computed along the parametric directions and scaled with an empiric factor of 1.05 to avoid inaccuracy problems. ...
A new approach to the merging of Finite Element (FE) triangle meshes is proposed. Not only it takes into account the geometric aspects, but it also considers the way the semantic information possibly associated to the groups of entities (nodes, faces) can be maintained. Such high level modification capabilities are of major importance in all the engineering activities requiring fast modifications of meshes without going back to the CAD model. This is especially true in the context of industrial maintenance where the engineers often have to solve critical problems in very short time. Indeed, in this case, the product is already designed, the CAD models are not necessarily available and the FE models might be tuned. Thus, the product behaviour has to be studied and improved during its exploitation while prototyping directly several alternate solutions. Such a framework also finds interest in the preliminary design phases where alternative solutions have to be simulated. The algorithm first removes the intersecting faces in an n-ring neighbourhood so that the filling of the created holes produces triangles whose sizes smoothly evolve according to the possibly heterogeneous sizes of the surrounding triangles. The hole-filling algorithm is driven by an aspect ratio factor which ensures that the produced triangulation fits well the FE requirements. It is also constrained by the boundaries of the groups of entities gathering together the simulation semantic. The filled areas are then deformed to blend smoothly with the surroundings meshes.
... Concerning the geometric aspects, (Chouadria & Véron, 2006) present an approach to simplify poly- hedral assemblies. The contact faces between inter- acting objects are identified and specific operators are applied to merge the two parts. ...
... This step aims at finding the faces that are potentially in contact, either in the face/edge or face/face modes. The algorithm is based on the work of (Chouadria & Véron, 2006). It consists in the detection of the intersections between scaled bounding boxes built on each face of the two meshes. ...
... The algorithm used to compute the contact interface boundaries (case of the face/face merging mode) is not presented here. It exploits partially the work of (Chouadria & Véron, 2006) on the detection and merging of contact interfaces between two polyhe- dra. In their work, the authors do not take care of the aspect ratio criterion that is crucial for FE analyses. ...
Nowadays, most of the numerical product behavior analyses are carried out following four steps: Com-puter Aided Design (CAD) modeling, mesh defini-tion, Finite Element (FE) simulation and results anal-ysis. This process can be completed by optimization loops. In the context of current maintenance and life-cycle problems, the product is already designed, and its behavior has to be studied and improved during its exploitation. For the maintenance of the EDF power plants, it is critical to identify the problem source and to provide the adopted solution in a short time. In this paper, we propose a method to enable the di-rect modification of 2D FE models for fast and accu-rate FE simulation. This approach enables to avoid both multiple iterative updatings of the CAD model and the remeshing problems of complex shapes while reusing the exiting meshes together with the seman-tic data useful for FE simulation. Starting from ex-isting triangle meshes to be merged, the algorithm removes the intersected faces and fills in the created holes while ensuring that the semantics initially as-sociated to the meshes is preserved. The holes filling algorithm is driven by an aspect ratio factor which ensures that the produced triangulation fits well the FE requirements.
