Finite element mesh generation

The capabilities of a geometric modeller are extended towards finite element analysis by a mesh generator which extracts all its geometric and topological information from the model. A coarse mesh is created and subsequently refined to a suitable finite element mesh, which accomodates material properties, loadcase and analysis requirements. The mesh may be optimized by adaptive refinement, ie according to estimates of the discretization errors.A survey of research and development in geometric modelling and finite element analysis is presented, then an implementation of a mesh generator for 3D curvilinear and solid objects is described in detail.     

Finite element mesh deformation with the skeleton-section template

To develop fast finite element (FE) adaptation methods for simulation-driven design optimization, we propose a radial basis functions (RBF) method with a skeleton-section template to globally and locally deform FE meshes of thin-walled beam structures.The skeleton-section template is automatically formulated from the input mesh and serves as a hierarchical parameterization for the FE meshes. With this hierarchical parameterization, both the global and the local geometries of a thin-walled beam can be processed in the same framework, which is of importance for designing engineering components. The curve skeleton of the mesh is constructed with Voronoi decomposition, while the cross-sections are extracted from the mesh based on the curve skeleton.The RBF method is employed to locally and globally deform the mesh model with the cross-sections and the skeleton, respectively. The RBF method solves the spatial deformation field given prescribed deformations at the cross-sections. At the local scale, the user modifies the cross-sections to deform a region of the surface mesh. At the global level, the skeleton is manipulated and its deformation is transferred to all cross-sections to induce the mesh deformation.In order to handle curved mesh models and attain flexible local deformations, the input mesh is embedded into its skeleton frame field using an anisotropic distance metric. In this way, even strip-like features along arbitrary directions can be created on the mesh model using only a few cross-sections as the deformation handles. In addition, form features can be rigidly preserved at both deformation levels.Numerical examples demonstrate that intuitive and qualified FE mesh deformations can be obtained with manipulation of the skeleton-section template.     

A knowledge base for finite element mesh design

The finite element method (FEM) is the most successful numerical method, that is used extensively by engineers to analyse stresses and deformations in physical structures. These structures should be represented as a finite element mesh. Defining an appropriate geometric mesh model that ensures low approximation errors and avoids unnecessary computational overheads is a very difficult and time consuming task. It is the major bottleneck in the FEM analysis process. The inductive logic programming system GOLEM has been employed to construct the rules for deciding about the appropriate mesh resolution. Five cylindrical mesh models have been used as a source of training examples. The evaluation of the resulting knowledge base shows that conditions in the domain are well represented by the rules, which specify the required number of the finite elements on the edges of the structures to be analysed using FEM. A comparison between the results obtained by this knowledge base and conventional mesh generation techniques confirms that the application of inductive logic programming is an effective approach to solving the problem of mesh design.     

A workplace design expert system

Although there is an abundance of reference material available, most facility design engineers lack the proficiency required to design ergonomically sound workplaces. This may be due to several factors. This paper presents an initial knowledge-based system to assist a design engineer in achieving an ergonomic workplace design. The developed system is, in reality, a subsystem consisting of the primary module of the knowledge base as a prototype. The root context, Dimensional Design, was selected for prototyping using the Texas Instruments Personal Consultant. A total of 41 parameters were defined for use by the prototype with 13 of those being goal parameters. In addition 57 rules are imbedded into the system.     

Finite element simulation of stretch forging using a mesh condensation method

In order to reduce the computation time of finite element simulations of stretch forging process,a mesh condensation method is presented and applied to a three-dimensional rigid-viscoplastic finite element program.In this method,a conventional mesh for the whole zone of a workpiece is condensed to a computational mesh for the active deformation zone.Two vital problems are solved,which are automatic construction of the computational mesh and treatment of interfaces between the deformation zone and the rigid ...     

A model-based expert system for digital system design

An expert system that generates digital system design from high-level specifications is described. It is called MBESDSD, short for model-based expert system for automated digital systems. The system is based on a three-phase model of digital system design. First, the high-level behavioral specifications are translated into a sequence of primitive behavioral operations. Next, these primitive operations are grouped to form intermediate-level behavioral functions. Finally, structural function modules are selected to implement these functions. The advantages of this model-based reasoning technique is that more design solutions are possible and the design is easier to optimize. The design of a popular peripheral device, the ART asynchronous receiver/transmitter, is used to demonstrate the proposed design process using MBESDSD     

Finite element analysis and optimization in fixture design

Fixturing locating point synthesis considers the workpiece and the fixturing elements to be rigid, but however they are elastic and deformable. To ensure sustained quality of manufacture to meet the design tolerances, fixture design must be predictably repeatable. This paper is concerned with minimizing deformation of the workpiece due to machining loads about fixturing support positions, especially in thin castings. Finite element analysis is used in simulating the deformation of the workpiece at selected points. An optimization algorithm is developed to minimize deflections at these selected nodal points by considering the support and tool localtions as design variables. The resulting support locations and tool point designs ensure part support, kinematic closure and minimal workpiece deflections during machining.     

Finite element optimal design of transverse web frames

The objective of this paper is to propose an intergrated computerized method aimed at the structural design of web frames subjected to symmetrical loading.The design problem is approached by a three phase procedure employing the finite element method as an analysis strategy and mathematical programming techniques for the synthesis phase.The change of boundary conditions during the optimization is accounted for by an approximate method.     

An expert system to automate timing design

Presents a novel approach for automating the timing design of interfaces between VLSI chips in microcomputer systems. The Prolog-based expert system, called TDS (for timing design system), incorporates the heuristic knowledge of the hardware designer. TDS is a rule-based system that interprets the specification sheets of VLSI chips and can synthesize, diagnose, and verify timing charts at the expert's level. The system uses a functional model based on timing specifications, not the structural information. TDS can model other interfaces that are based on timing specifications, such as standard bus interfaces     

Feature-based design and finite element mesh generation for functional surfaces

This paper describes an approach to feature-based design and feature-based mesh generation for multi-featured functional surfaces. Unlike standard free-form parametric surface representation where the parametric surface patch plays the key role in both surface design and finite element mesh generation, we propose an approach to these two tasks which proceeds from the level of a complete feature (for example, a pocket or channel). The result is a more direct method for modeling functional surface characteristics and a more efficient feature-based implementation of Delaunay surface triangulation.     

Advisory expert system for flexible pavement design

The adoption of an expert system approach to flexible pavement design could be especially useful, because of the complexity of the design algorithm involving numerous possible combinations of pavement material types and traffic data, and the heavy reliance on empirical correlations, which can vary from one region or state to another. This paper describes the development of an advisory expert system for flexible pavement design that attempts to mimic the design process of pavement engineering specialists. The highly interactive microcomputer expert system was developed, using an expert system shell.     

BDES: A bridge design expert system

The expert system described here designs superstructures for small to medium span highway bridges. The system addresses a domain within the engineering design consultation paradigm. It is installed in a personal microcomputer environment. This paper examines the nature of the bridge design domain as practiced in the United States and its suitability for expert system application. The architecture, the context structure, the knowledge base, the control module, and the implementation of the expert system are presented.     

"MDZY型，冲压模方案设计专家系统的设计与实现

作为一种先进的金属零件加工方法,冲压生产在工业领域中已经得到了广泛的应用,但其生产效率的进一步提高却由于冲压模具设计的复杂性和耗时性而受到了较大程度制。CAD技术的引入虽然简化了图形的绘制和处理工作,但对冲模设计当中普遍存在的推理、判断等非数值问题却无能为力。文中利用人工智能技术,在Visual C 5．0环境下实现了一个冲压模方案设计专家系统,用来帮助设计者在模具设计前期完成合理的方案设计。系统在执行设计任务时采用了实例匹配和归纳推理两种不同手段,系统中的设计知识分别采用了数据库记录、链表以及集成了框架、规则和方法的对象等多种形式来表示,各类知识的学习和修改采用了包括神经网络在内的多种机制。     

A generalized expert system for database design

Generalized Expert System for Database Design (GESDD) is a compound expert system made up of two parts: (1) an expert system for generating methodologies for database design, called ESGM; and (2) an expert system for database design, called ESDD. ESGM provides a tool for the database design expert to specify different design methodologies or to modify existing ones. The database designer uses ESDD in conjunction with one of these methodologies to design a database starting from the requirement specification phase and producing a logical schema in one of the well-known data models, namely, the hierarchical data model, the network data model, or the relational data model. The system is evolutive in the sense that an existing methodology can be modified or a novel methodology can be added to the existing ones. GESDD is a menu-driven system and it is coded in Prolog     

Using an expert system for design diagnosis and design synthesis

Abstract This paper describes the concepts which allow an expert system to be used for both design diagnosis and design synthesis. An example of the implementation of these concepts is presented in the domain of preliminary design of domestic kitchens in the expert system PREDIKT. PREDIKT carries out both design diagnosis and design synthesis using the same knowledge base and utilises an existing expert system shell which has forward- and backward-chaining capabilities. The significance of graphical interaction with expert systems in design domains is demonstrated.     

Finite element mesh for a complete solution of a problem with a singularity

It is well known that the stress field at the tip of a crack in an elastic body exhibits a singularity. In this paper, a complete elastic solution for a center cracked plate loaded under uniform tension is obtained by a finite element plane-stress analysis using constant strain elements. No a priori assumptions about the form of the stress singularity are required. The numerical results are compared with the exact analytic solution. It is shown that a particular mesh arrangement in which the size of the elements decreases in a geometric series as the crack tip is approached yields stress and strain fields which are accurate over the entire plate, even at distances very close to the crack tip. The effects of changes in mesh arrangements on the accuracy of the solution are considered. The computations are carried out on the CRAY-1 computer and the advantages of vectorization are discussed for this problem.     

Developing an expert system to assist in control system design

This paper addresses the problem of how to develop an expert system that is able to design or to assist in the design of a control system. The discussion includes how to structure the expert system, how to choose the relationship between the symbolic and numerical processor and how to divide the work among the expert system, the computer aided control systems analysis package and the design engineer. A prototype intelligent design associated is presented and an example of a compensator design is given.     

An expert system for design for robotic assembly

In recent years, due to the various advantages associated with automation and robotics, much work has been done in developing robotic systems for assembly operations. Since part design plays a major role in assembly, this paper deals with the design of parts for ease of robotic assembly. Considerable knowledge is available in the form of design for robotic assembly rules. In addition, a large amount of data is required for decisions regarding suitability of parts for robotic assembly. The implementation of design for robotic assembly rules would be much easier with the help of an expert system, which would guide the designer toward choosing the design alternative that can best facilitate ease of assembly from a robotic point of view.To this end, a prototype expert system for design for robotic assembly is developed and presented in this paper. The expert system was implemented as a production system, which consists of rules and Object-Attribute-Value (O-A-V) triplets to represent domain knowledge. In order to best utilize the domain specific knowledge, a state space search-based inference mechanism was employed. The implementation of the prototype system is illustrated with examples.