Abdelmajid Benamara

Idealization of CAD model for a simulation by a finite element method

Nowadays, numeric simulation becomes one of the most important activities of the product development cycle. To accelerate the design and simulation tasks, it is necessary to adapt the CAD model before the simulation process. This paper presents a method based on an original algorithm in order to adapt and simplify the design geometric model to a simulation by finite elements method. It consists in the idealization of the CAD geometry by eliminating details (holes, chamfers, etc.). These details increase the computing time due to a refined mesh in these details, which are considered as stress hubs, without providing more precision in the simulation. An implementation of the proposed algorithm using the Open Cascade platform is also presented. The last part of this paper presents two examples of mechanical parts, which are simulated before and after idealization. The results of simulation illustrate the major contribution of the proposed method in terms of computing time gain, without so much changing the exactitude of results.

Automatic comparison and remeshing applied to CAD model modification

Automatically detecting modifications between CAD models has many potential applications in product development processes. Tracing modifications throughout the design and manufacturing cycle of a new product, based on CAD/CAM/CAE tools, is one of these applications. Easily retrieving and reusing existing designs, along with engineering data associated, is another very interesting perspective. In this direction, several methods have been proposed, aimed at the quantification of similarity between existing CAD models. These methods are based on using shape descriptors, with a specific focus on invariance to affine transformations. However, these methods are dedicated to discriminating, clustering and retrieving CAD models, and not to accurately identifying and locating differences between models. Such an automatic identification of differences between CAD models is of great practical interest for many applications but making it invariant to affine transformations is very complex. This paper proposes new shape descriptors that are focused on this invariance. These descriptors use vector-based representations of geometry, which can be successfully applied for accurate, local and automatic comparisons between CAD models. The potential of these descriptors is illustrated in the specific context of automatic remeshing, which is the initial purpose for which they have been designed. The result demonstrates that this vector-based representation of geometry can contribute, possibly in conjunction with other shape descriptors, to setting up powerful and efficient CAD model comparison tools.

Solution space reduction of disassembly sequences generated automatically via computer aids

To develop a simulation tool for automatic disassembly in computer aid design (CAD) environment two difficulties are found: the huge space of generated sequences and their feasibility especially in combinatory generation. This article deals with automatic sequence generation for selective disassembly of mechanical product. Starting from a CAD model a new appropriate connection tree of a target component is constructed. This tree aims at reducing space solution by eliminatory rules. The generation of sequence is based on reading of connection tree branches and eliminatory tests of feasibility. The feasibility is checked by updating the disassembly mobility of each sequence’s element. A case study is presented to prove the effectiveness of the proposed approach.

A Feature-Based Methodology for Eco-designing Parts on Detail Phase

Today it becomes necessary for manufacturers to adopt Eco-design to guard their place in the market. Eco-designing products, is reducing their environmental impact in the early design stages throughout all stages of their life cycle (raw material extraction, manufacturing process, use, transport and end of life treatments). In the literature, many tools and methodologies were developed to simplify the environmental task to the designer by helping him reducing the environmental impact of his products. The most of these works are based in features-based modeling to extract data for realizing environmental evaluation also we found that this technology is essentially used in selecting a green machining process trough Computer Aided Process Planning (CAPP). In this paper we propose a methodology based on feature technology and on the integrations realized on CAD systems such CAD/CAL/CAPP and CAD/PLM to generate alternatives scenarios in order to choose the most ecological one till feature’s selection. The environmental impact is calculated with Eco-Indicator method and shown to the designer as End-Points Indicators (Resources, Human Health, Eco-system damages) which are related to the designer’s Degrees of Freedom (DoFs).

Eco-Design of a Basin Mixer in Geometric Modeling Phase

Reducing the environmental impacts of products surrounding us in our daily lives has become a common concern for the industry as well as for consumers. The practice of a Life Cycle Assessment (LCA) allows determining not only the environmental impacts centers but also the overriding factors on which it is still possible to act at the design phase. The geometric modeling phase in the design process represents an important step to make the necessary changes on the product in order to reduce its environmental hotspots. In this paper, we have eco-designed a basin mixer by acting on its geometric modeling phase, after identifying its various environmental hotspots from a LCA practiced and determining the factors still editable on CAD phase. An environmental comparison between the eco-designed mixer and the original one has been established, which shows a 66% reduction of impacts linked only to the amount of material used.

Ecodesigning with CAD Features: Analysis and Proposals

The integration of environmental aspects in design frameworks has become a necessity for manufacturers to maintain their market position. This is especially true in the Computer Aided Design (CAD) phase, which is the last phase in the design process. At this stage, more than 80% of choices have been made. However, the environmental impacts generated by the remaining choices are significant. Features Technology (FT), the core of the CAD phase, is used to integrate environmental aspects. This paper presents a literature review of different works based on FT to ecodesign products. First, we present an overview of features in CAD systems. Second, we present a critical review of works done on ecodesigning with features that we divide into two subsections: the first one concerns CAD-Life Cycle Assessment (LCA) integration (methodologies, prototype tools, and commercial tools), and the second one, works using FT in CAD phase to reduce the environmental impact of one life cycle stage such as material selection or manufacturing. Finally, we propose an approach based on FT for ecodesigning products to promote simple new ecodesign tools which will help the inexperienced designer.

Automatic CAD Models Comparison and Re-meshing in the Context of Mechanical Design Optimization

A lot of research work has been focused on integrating FEA (finite elements analysis) with CAD (Computer Aided Design) over the last decade. In spite of improvements brought by this integration, research work remains to be done in order to better integrate all the operations led during the whole design process. The design process involves several modifications of an initial design solution and until now, in this context, the communication between CAD modules (dedicated to different tasks involved in the product design process) remains static. Consequently, there is a need for more flexible communication processes between CAD modules through the design cycle, if not through the product life cycle. Some approaches have been developed aiming at the reduction of the design process length when using FEA, and aiming at the automation of part’s data transfer from one step of the process to the next one. Automatic re-meshing is one of these approaches. It consists in automatically updating the part’s mesh around modifications zones, in the case of a minor change in the part’s design, without the need to re-mesh the entire part. The purpose of this paper is to present a new tool, aiming at the improvement of automatic re-meshing procedures. This tool basically consists in automatically identifying and locating modifications between two versions of a CAD model (typically an initial design and a modified design) through the design process. The knowledge of these modifications is then used to fit portions of the initial design’s mesh to the modified design (a process referred to as automatic re-meshing). A major benefit of the approach presented here is that it is completely independent of the description frame of both models, which is made possible with the use of vector-based geometric representations.

Model of mobility state of parts: The automation of feasibility test in disassembly sequence generation

Disassembly sequencing is a concurrent research subject in design for life-cycle. Many past and recent researches are made to give practical methods for disassembly sequencing. The problem of assembly information’s modeling is one of the important sub-problems of disassembly simulation. The problem includes connection determination, disassembly direction identification, and part mobility state definition. In the present paper, the authors propose a new representation model of disassembly directions, starting from geometric and assembly data of computer aid design models. This model is based on a mobility matrix definition for every part. This matrix is also called disassembly direction matrix. The model gives information about the mobility state of a part during disassembly sequencing by updating its mobility matrix. Mobility state data are used in a practical computing of disassembly sequence feasibility. In this paper, theoretical explication of this modeling is given and validated by computational results. In the validation section, the model is applied to a computer aid design mechanism using a selective disassembly.

An Environmental Impact/Cost Model for Evaluating Multiple Feature-Based Machining Methods

For a designed part, if different sets of features are used for machining, the manufacturing Environmental impacts (EIs) as well as cost may vary. In this research, a new methodology based on feature technology is proposed in order to help designer till detail design phase to choose the most optimal compromise Environmental Impact/Cost in manufacturing process. Hence an Environmental impact/Cost model is presented. This model follows the activities required for machining a set of features which are tool set-ups, fixturing set-ups and machining tool paths. The paper starts by presenting features based models which are the base of the methodology proposed. Then, a state of the art about using Feature technology in reducing on one side manufacturing cost and on the other side manufacturing environmental impacts is presented. Finally an environmental impact/cost methodology for evaluating multiple feature-base machining methods is proposed.

FEM Simulation Based on CAD Model Simplification: A Comparison Study between the Hybrid Method and the Technique Using a Removing Details

The simulation process is currently used in the design and dimensioning of mechanical parts. With the progress of computer materials, the Finite Elements Method (FEM) becomes the most used approach in the simulation of mechanical behavior. The simulation process needs multiple Design-FEM loops. In order to accelerate those analysis loops, an adaptation of Computer Aided Design (CAD) model is necessary. The adaptation step consists in the simplification of the CAD model geometry by eliminating details (holes, chamfers, fillet, etc.) and faces. In this paper, a new technique of simplification of the CAD geometry is developed. This technique is a hybrid method based on a combination of the elimination details and merging faces. With this approach, the computing time is reduced by the elimination of geometric details which do not boundary conditions. An implementation of the proposed algorithm on the Open Cascade platform is also presented. The results of the hybrid method are compared with a previous publication. The reduction of the computing time and the amelioration of the result precision highlight the efficiency of the hybrid method.