Solid model abstraction using form features

Midsurface abstraction from 3D solid models: general theory and applications

A Case Study of 3D Printed PLA and Its Mechanical Properties

The authors review and categorize the research in applications of artificial intelligence (AI) and expert systems (ES) in new product development (NPD) activities. A brief overview of NPD process and AI is presented. This is followed by a literature survey in regard to AI and ES applications in NPD, which revealed twenty four articles (twenty two applications) in the 1990–1997 period. The applications are categorized into five areas: expert decision support systems for NPD project evaluation, knowledge-based systems (KBS) for product and process design, KBS for QFD, AI support for conceptual design and AI support for group decision making in concurrent engineering. Brief review of each application is provided. The articles are also grouped by NPD stages and seven NPD core elements (competencies and abilities). Further research areas are pointed out.

Due to the complex structure and massive volume of large equipment in petrochemical enterprises, it was very difficult to carry out inspection and maintenance work. The traditional expert system used a single knowledge base and reasoning machine, so the processing efficiency and prediction accuracy were low. In this paper, the dimensionality reduction which is used to process a large amount of physical information collected by the sensors, remove redundant components and extract main characteristic parameters. Meanwhile, combined with the powerful pattern recognition and judgment ability of fuzzy neural network, the forward reasoning mechanism and error back propagation keeping continuous training correction until meeting the accuracy requirements, the expert system gave the equipment fault prediction conclusion. Finally, taking main fan oil station circulating oil pump and motor of heavy oil catalytic cracking unit and nine stages of bearing damage as monitoring objects, the fault predictions was implemented by the following steps: data collection, feature extraction, dimension reduction of big data and expert system with the fusion of fuzzy neural network, and it is proved that the expert system with fuzzy neural network based on dimension reduction can greatly improve the convergence speed.

Current CAD systems have inherent bottlenecks, which diminish possible achievements for architectural practices. Among these shortcomings there are two the paper will deal with. Firstly, traditional CAD relies on a pure geometric model. All non-geometric information about objects of architectural interest has to be attached to these geometric entities. This restricts the ability to describe semantically dependent relationships. Secondly, the integration of different design tools for building and construction is still at its very beginning. The data exchange remains restricted, since it is based on a fairly low semantic level of a document-based exchange of information, such as geometric representation in DXF or IGES, rather than on a high semantic level of a model-based exchange.

An algorithm has been developed for the automated recognition of undercut features for determining the optimal parting direction of injection molded parts. On the basis of the 3-D solid model of a molded part described in Boundary Representation (B-Rep), the geometrical entities and the information of a solid model and their topological relationships are extracted. According to these information, the criteria under which the undercut feature is formed are set up and the undercut feature directions (the withdrawal directions of side-cores or side-cavities) are identified. The optimal parting direction is chosen based on the criterion of maximizing undercut feature volumes in each undercut feature group. Through the case studies on industrial parts, the methodology developed is found to be efficient and effective in determining the undercut features and the optimal parting direction automatically.mining the optimal parting direction of injection molded parts. On the basis of the 3-D solid model of a molded part described in Boundary Representation (B-Rep), the geometrical entities and the information of a solid model and their topological relationships are extracted. According to these information, the criteria under which the undercut feature is formed are set up and the undercut feature directions (the withdrawal directions of side-cores or side-cavities) are identified. The optimal parting direction is chosen based on the criterion of maximizing undercut feature volumes in each undercut feature group. Through the case studies on industrial parts, the methodology developed is found to be efficient and effective in determining the undercut features and the optimal parting direction automatically.

Kuwait Oil Company (KOC) is using several models to assist with the planning of the future of the Greater Burgan field. Integrated asset modelling (IAM) is being used to understand the dynamics of the full production system and find opportunities for optimisation. Abnormal declines have been observed in some of the surface facilities. Further investigation revealed scale deposits in some flowlines causing a restriction. IAM was then used to identify similar restrictions and quantify the overall benefit of their removal. Combining wells, flowlines and facilities of a field into a single integrated asset model in any organisation is always challenging. It requires a vast amount of inputs and a good understanding of the dynamics of the field. With an operating asset, such as the Greater Burgan field in South East Kuwait, it is likely that the inputs would have changed shortly after starting. Existing wells occasionally switch from high to low pressure systems and new wells are being connected on a regular basis. Bringing together 1000+ completions with an associated flowline network requires a disciplined approach. There should be careful attention to the benefits of modelling particular features and to what level of detail. For example, the internal diameter changes due to the completion accessories will take a long time to enter and offer little benefit to the overall result. Decisions need to be made to allow early and timely results. Sometimes a rough and quick model can help to proiritise the high impact items affecting the entire field. KOC has taken two approaches to create such a large scale model. One simple, one detailed. The purpose of both models is to understand where to focus investment by understanding the benefits of changes in the system like debottlenecking, routing options and expansions. By building a simplified multiphase flow simulation model with the latest field data KOC has identified a potential gain of 30,000 BOPD to the current field oil rate. This would come from the removal of restrictions of varying magnitudes in 93% of the flowlines. However, further analysis shows that about 90% of the gain comes from just 200 of the completions and flowlines. With further study using this model it is estimated that twice as much gain will come through careful optimisation. The advantage of the simplified model is that its building is easy to automate. It can be updated frequently using the latest field data in the company database. This means that the model can stay live as rebuilding can be done in less than 3 hours. The time required to build the process and initial model took 3 weeks. The detailed model is estimated to take 12 months and is nearing completion. Some of the same processes used in the simplified model have already helped to reduce its overall building time.

CAD Software such as CREO and SolidWorks are used to develop mechanical parts and assemblies and do not explicitly support the function of the feature, component, part or assembly. Therefore, the reasoning of why and how a design is developed has not been incorporated into current CAD systems. At the same time, CAD systems support sophisticated functions such automated routing, modelling and simulation of dynamic and geometric properties and design solutions tracking. In this paper we investigate (a) to what degree CAD tools have advanced beyond drafting tools to include cognitive supports that facilitate problem solving and (b) which possibilities exist to enhance CAD with cognitive tools that with focus on the intersection between cognitive psychology, interaction design and design engineering remain unexplored.

Much work has been carried out on the creation of protocols for the exchange of data between CAD systems, but very little on the transfer of knowledge. The knowledge behind the development of a product is vital if modifications and adaptations are to be made within a concurrent development environment. Current CAD systems only contain a limited level of product knowledge through user-defined parametric structures. It is the underlying relationships in these programs that need to be communicated between systems, rather than the form of their individual programming languages. A generic structure is proposed that is able to handle both the current level of parametric programming and is suited to the resolution of conflict through the use of constraint modelling procedures. The structure of a parametric description is described and decomposed into its fundamental components. These components are then re-formed within a truth maintenance structure to allow a transfer protocol to be created. The derived protocol structure is then demonstrated on a number of simple examples.

Computer simulation packages have had success in predicting filling behavior in extremely complicated geometries. However, most of the current numerical implementation is based on a hybrid finite‐element/finite‐difference solution with the middle‐plane model. This kind of model leads to some inconvenience in applications. Instead of using the middle‐plane as the datum plane, the surfaces of the cavity are used as datum planes in this article. Additional boundary conditions in the gapwise direction are employed to keep the flows in the surfaces at the same section coordinative. Comparisons with experimental results obtained with an instrumented test mold and C‐Mold results show good agreement in terms of pressure traces and melt‐front advancement. It is demonstrated that the present formulation is well suited to handle cavities generated directly by current CAD systems. © 2001 John Wiley & Sons, Inc. Adv Polym Techn 20: 125–131, 2001

An ideal product modeling system should support both part modeling and assembly modeling, instead of just either of them as is the case in most current CAD systems. A good basis for such integration is multiple-view feature modeling, as it allows focusing on different aspects of the product, while at the same time maintaining consistency of all model views. This paper presents a framework that supports synchronous collaborative sessions via Internet, among members of a distributed development team, with such a modeling system. The framework provides facilities for creating a hierarchical product structure, with single and compound components, and meanwhile assigning tasks to team members. The actual design of a single component is supported by a web-client specialized in part design, whereas the specification of assembly relations among components is supported by a web-client specialized in assembly design. All clients make use of the same server, which runs a multiple-view feature modeling system and maintains the complete product model, guaranteeing consistency of the part design and the assembly design views.

A new enhanced B-Rep for solids is introduced, using the concept of virtual topology in which the geometric and topological entity definitions as defined in the standard B-Rep are uncoupled, thus allowing topological entities not corresponding to geometric ones. The need for such enhancement is explained as well as the construction process starting with an object described as a standard B-Rep and resulting in the desired modified topology, suitable for the user needs.

Abstract. Advanced analysis of spatio-temporal data is improving our knowledge about natural phenomena such as landslides and volcanic activity. Furthermore, it can contribute to a deeper understanding of the built environment by predicting city development. However, the data produced by the modelling of these observations can easily rise to terra bytes of 4D (3D space plus time) data. Also, the repeatability of such analysis is essential. Thus, repeatable and reliable access to big spatio-temporal data, models and simulation results should be guaranteed. However, today´s Geographic Information Systems (GIS) are not prepared to meet these requirements. Therefore, we present a comprehensive spatio-temporal data model for GIS and geodatabase management systems that can be used as the “heart” of 4D GIS. The comprehensive model enables a flexible management of time-series-based geometric and topological data. It cares of storage reduction and computational efficiency when storing, retrieving, and processing surface- and volume-based data in 3D space plus time. Furthermore, the model can handle geometry and topology changes of 4D data, i.e., mesh changes of triangulated surfaces and tetrahedral volumes over time. The model also allows the attachment of detailed semantic information to geometric and topological entities. The various concepts, implementation and the benefits of our comprehensive model are presented. Finally, conclusions are drawn from the approach and an outlook is given on future research including demanding applications based on multiscale digital elevation models.

Column foot in traditional Chinese timber structures may be subjected to be uplifted due to the lateral load and subsequently reset under the vertical loads. The residual moment of the rocking column foot is the most important parameter representing the mechanical behaviors of column foot, and the simplification of joints is the basis of structural analysis of whole structure. The complicated mechanical behaviors of joint and the modeling of the column foot joint has been undertaken historically based on the experiments and numerical simulation. On the condition of limited application range of those models, a lack of simplified model to represent the mechanical behaviors of joint deserves attentions. There is a great need to undertake theoretical studies to derive the residual moment and make better simplified model of the joint. This paper proposes the residual moment and equivalent simplified model of the rotational stiffness for column foot joint. And, the timber frame is established based on the simplified model, which is verified by solid finite element model. Results show that a mutual agreement on the mechanical behaviors of the timber frame is obtained between the simplified model and the solid finite element model. This study can serve as the references of the structural analysis for the traditional timber structures.

A critical problem with existing computer-based geometric modeling is the labor intensive task involved in specifying data input for the description of three-dimensional (3-D) objects. This paper describes a new, 3-D input system aimed at alleviating this problem. It is based on the use of a three-dimensional digitizer for the direct input of spatial coordinates, and an intelligent interactive user interface. The intent of this system is to create a high level, intelligent interface between the designer and a geometric solid modeler which would lighten the designer's burden in performing arduous 3-D geometric description tasks. The user interface is developed around the Knowledge Craft expert system building tool, using the rule-based Carnegie Representation Language OPS5 (CRL-OPS). The system uses schematic networks or frames and production rules to encode knowledge about geometric primitive digitization methods, object feature operators, solid modeler requirements, and input command functions. It also employs a forward-chaining inference strategy to direct the knowledge. This ensures that only a minimal amount of valid data entry is required by the user. However, if excessive data is entered the intelligent interface has the capability to extract the required information. As a result, the solid modeler can automatically create the appropriate object “primitive” or the specific object “feature” upon recognition by the expert system. It will be demonstrated that these capabilities can simplify the 3-D model description process.