Aiming to redundant parallel mechanism, on the basis of the kinetic energy method, virtual work principle and perturbation method, the generalized mass matrix and generalized stiffness matrix are obtained, respectively. Two indices on inertial coupling and elastic coupling are defined to measure the decoupling level of the redundant parallel mechanism in terms of two generalized matrices. Furthermore, an algebraic solution method for natural frequency equation of the mechanism is utilized to obtain the natural frequency by means of the Cholesky decomposition method. And then, in order to minimize inertial coupling and elastic coupling, and maximize the natural frequency of the mechanism, two indices and natural frequency are taken as objective functions to optimize the structural parameters of the redundant mechanism, so that optimal dynamic performance of the mechanism is acquired. In the optimization of natural frequency, two optimal solutions are selected. One is to consider inertial coupling and elastic coupling and the other is to ignore inertial coupling and elastic coupling. Finally, the dynamic performance of the two indexes is better by comparing the dexterity of the two solutions

The simulation of complex geometries and non-linear deformation has been a challenge for standard simulation methods. There has traditionally been a trade-off between performance and accuracy. With the popularity of additive manufacturing and the new design space it enables, the challenges are even more prevalent. Additionally, multiple additive manufacturing techniques now allow hyperelastic materials as raw material for fabrication and multi-material capabilities. This allows designers more freedom but also introduces new challenges for control and simulation of the printed parts. In this paper, a novel approach to implementing non-linear material capabilities is devised with negligible additional computations for geometry-based methods. Material curves are fitted with a polynomial expression, which can determine the tangent modulus, or stiffness, of a material based on strain energy. The moduli of all elements are compared to determine relative shape factors used to establish an element's blended shape. This process is done dynamically to update a material's stiffness in real-time, for any number of materials, regardless of linear or non-linear material curves.

Process uncertainty can have negative effects on part quality and is, therefore, critical to the safety and performance of products. Those effects are manifested in the dimensional measurement uncertainty associated with those parts and products. To minimize the effects of process uncertainties, the sources of dimensional uncertainty must be identified and clearly communicated to collaborators and suppliers. A principal source of dimensional uncertainty is the measurement equipment itself. This paper presents an activity model, rule types, and sample rules for selecting dimensional-metrology equipment. The activity model represents key operations and information flows associated with dimensional measurement. Analysis of the included activity model facilitates the development of rule types for measurement-equipment selection as described in the Quality Information Framework (QIF) standard. Rule types are based on design information and measurement requirements. Standard rule types enable industrial metrologists to capture, exchange, and share equipment-selection rules with their collaborators. Example QIF rules are defined for successful and cost-saving use in planning a measurement process with functionally complex and appropriate dimensional-measurement equipment.

Computer-aided design/computer-aided manufacturing/computer-aided engineering (CAD/CAM/CAE) integration offers designers, analysts, and manufacturers the opportunity to share the data throughout the product development process. Finite element (FE) meshing applications integrated with the solid model data from CAD systems represent a major subset of CAD/CAM/CAE integration. In an earlier paper, it was demonstrated that virtual persistent identifiers (VPIs) can be used to assure or repair sustained integration with successive versions of neutral-format solid models. From that article, several follow-on issues become apparent. The geometry as per the CAE model often differs from the CAD model, so even with cross-format issues resolved, significant obstacles to sustained CAD/CAE integration remain. Along with simplification, the current article investigates additional techniques for further automating the recognition of changes between CAD models, reducing the manual interaction to just a few minutes. The article goes on to demonstrate how associativity can be sustained when using current versions of neutral formats like STEP and IGES. The overall point of the paper is to show that given a precise recognition of the differences between two solid models, a generalized means of ad-hoc integration is possible. This point is demonstrated through two case studies where simplifications of the CAD geometry are made to facilitate the meshing of the part. The integration is shown to be maintained across successive versions and to address a range of simplification processing. A summary of best practices for efficiently accommodating sustained CAD/CAE integration is also presented.

Explicit dynamic analysis has proven to be advantageous when simulating shock and impact loading, and very small time-scale events. In this article, the feasibility of using a background mesh of B-spline elements for immersed boundary explicit dynamic simulation is studied. In this approach, the geometry is immersed in a background mesh consisting of uniform regular shaped elements to avoid mesh generation difficulties. The boundary conditions are applied using the step boundary method, which uses the equations of the boundaries to construct trial functions that satisfy the essential boundary conditions. An isoparametric formulation is presented for quadratic and cubic B-spline elements and their shape functions are derived from the classical recursive definition of B-splines. The effectiveness of mass diagonalization for B-spline elements is also explored. This approach is validated using several examples by comparing with modal superposition solutions as well as past work using traditional finite element analysis (FEA) and analytical solutions when available.

This paper presents the current issues and trends in meshing and geometric processing, core tasks in the preparation stage of computational engineering analyses. In product development, computational simulation of product functionality and manufacturing process have contributed significantly toward improving the quality of a product, shortening the time-to-market and reducing the cost of the product and manufacturing process. The computational simulation can predict various physical behaviors of a target object or system, including its structural, thermal, fluid, dynamic, and electro-magnetic behaviors. In industry, the computer-aided engineering (CAE) software packages have been the driving force behind the ever-increasing usage of computational engineering analyses. While these tools have been improved continuously since their inception in the early 1960s, the demand for more complex computational simulation has grown significantly in recent years, creating some major shortfalls in the capability of current CAE tools. This paper first discusses the current trends of computational engineering analyses and then focuses on two areas of such shortfalls: meshing and geometric processing, critical tasks required in the preparation stage of engineering analyses that use common numerical methods such as the finite element method and the boundary element method.

The long-standing goal of computer aided design (CAD)/computer aided engineering (CAE) integration demands seamless interfaces between geometric design and engineering analysis/simulation tasks. The key challenge to this integration stems from the distinct and often incompatible roles geometric representations play, respectively, in design and analysis. This paper critically examines and compares known mesh-based and meshfree approaches to CAD/CAE integration, focusing on the basic tasks and components required for building fully integrated engineering applications. For each task, we identify the fundamental requirements and challenges and discuss how they may be met by known techniques and proposed solutions.

This paper presents a semantic approach that uses ontologies to share knowledge related to product data in CAD/CAE applications and for integrating the design evaluation information that these applications individually provide. Our overall approach is the ontology-based adaptive design evaluation, also coined as OADE. This paper reports a piece of our ongoing work in the area of knowledge representation and ontology mapping methods. Here we design ontologies for representing product design and analysis, instantiate a source ontology with the product data, create formal ontology mapping methods, and then apply these methods to transfer the product data from the source ontology to the target one. A prototype implementation has been created using technologies such as OWL (representation language), JENA (ontology API), and PROTÉGÉ (ontology editor) to demonstrate the approach for integrating product design and assembly simulation analysis applications. This work is significant because heuristic methods based on geometry attributes, composition, and inheritance for determining mapped concepts in engineering ontologies is still very new, and not much work has been done in this area. This work will lead to the ability to create, share, and exchange knowledge for solving design evaluation challenges involving multiple applications and viewpoints.

This paper introduces the idea of extending quality assurance efforts in the processes of development of computer aided design (CAD) software systems to include formal review or testing of underlying engineering principles, theories, methods, or physical phenomena. It stems from the principle of disembodiment of CAD software systems and incorporates elements of existing well-established methodologies such as participatory design, extreme programming, and spiral software development. Under this approach, ideas’ generation, theories’ selection or creation, methods’ development, algorithms’ design, and pilot prototype implementation are the intermediate tasks in the early stages of the process of development of CAD software. Theories, methods, algorithms, and pilot prototypes are the deliverables of these tasks. Each task involves stepwise translation of requirements into a respective deliverable. Application experiences have shown that this procedure enlarges the scope of requirements’ acquisition and quality assurance of CAD software.

In this paper, we propose a new triangular finite element mesh generation scheme from various kinds of triangular meshes using the multiresolution technique. The proposed scheme consists of two methods: a mesh quality improvement method and a mesh property control method. The basic strategy of these methods is a combination of the mesh subdivision and simplification. Given mesh is first subdivided to obtain enough degree of freedom for a property change, then by simplification using edge collapse for the resulting mesh to change the mesh properties, we can easily improve and control the mesh properties required for finite element analysis.

This paper describes a new algorithm for contouring a medial surface from CT (computed tomography) data of a thin-plate structure. Thin-plate structures are common in mechanical structures, such as car body shells. When designing thin-plate structures in CAD (computer-aided design) and CAE (computer-aided engineering) systems, their shapes are usually represented as surface models associated with their thickness values. In this research, we are aiming at extracting medial surface models of thin-plate structures from their CT data for use in CAD and CAE systems. Commonly used isosurfacing methods, such as marching cubes, are not applicable to contour the medial surface. Therefore, we first extract medial cells (cubes comprising eight neighboring voxels) from the CT data using a skeletonization method to apply the marching cubes algorithm for extracting the medial surface. It is not, however, guaranteed that the marching cubes algorithm can contour those medial cells (in short, not “marching cubeable”). In this study, therefore we developed cell operations that correct topological connectivity to guarantee such marching cubeability. We then use this method to assign virtual signs to the voxels to apply the marching cubes algorithm to generate triangular meshes of a medial surface and map the thicknesses of thin-plate structures to the triangle meshes as textures. A prototype system was developed to verify some experimental results.

In today’s fast-changing economy, product designs are becoming increasingly complex while demands for faster design cycles never cease. Tighter collaboration among business partners and streamlined integration of engineering processes are becoming essential elements to succeeding in the competitive global environment. Modern computer-aided design/engineering solutions and revolutionary Internet technologies facilitate such real-time business-to-business (B2B) design collaboration. This paper discusses various emerging technologies that enable a true B2B virtual collaboration of an aircraft engine combustor design between GE Aircraft Engines, a jet engine manufacturer, and Parker Hannifin, a gas turbine fuel nozzle supplier. A case study involving the collaborative design and analysis of a fuel nozzle is also presented, which demonstrates the realistic implementation of these new technologies.

This paper describes a system for the automatic recognition of assembly features and the generation of disassembly sequences. The paper starts by reviewing the nature and use of assembly features. One of the conclusions drawn from this survey is that the majority of assembly features involve sets of spatially adjacent faces. Two principle types of adjacency relationships are identified and an algorithm is presented for identifying assembly features which arise from “spatial” and “contact” face adjacency relationships (known as s-adjacency and c-adjacency respectively). The algorithm uses an octree representation of a B-rep model to support the geometric reasoning required to locate assembly features on disjoint bodies. A pointerless octree representation is generated by recursively sub-dividing the assembly model’s bounding box into octants which are used to locate: 1. Those portions of faces which are c-adjacent (i.e. they effectively touch within the tolerance of the octree). 2. Those portions of faces which are s-adjacent to a nominated face. The resulting system can locate and partition spatially adjacent faces in a wide range of situations and at different resolutions. The assembly features located are recorded as attributes in the B-rep model and are then used to generate a disassembly sequence plan for the assembly. This sequence plan is represented by a transition state tree which incorporates knowledge of the availability of feasible gripping features. By way of illustration, the algorithm is applied to several trial components

Virtual reality applications are making valuable contributions to the field of product realization. This paper presents an assessment of the hardware and software capabilities of VR technology needed to support a meaningful integration of VR applications in the product life cycle analysis. Several examples of VR applications for the various stages of the product life cycle engineering are presented as case studies. These case studies describe research results, fielded systems, technical issues, and implementation issues in the areas of virtual design, virtual manufacturing, virtual assembly, engineering analysis, visualization of analysis results, and collaborative virtual environments. Current issues and problems related to the creation, use, and implementation of virtual environments for engineering design, analysis, and manufacturing are also discussed.

This article reviews various mechanisms in languages and operating systems for deterministic real-time computing. Open-architecture systems will be defined and their applications in manufacturing will be addressed. Market directions for open-architecture manufacturing systems will be surveyed. Performance issues based on real-time, reliability, and safety will be discussed relating to manufacturing factory automation designed and implemented with component-based, plug-and-play open-architecture.

This article presents an overview of the state-of-the art in modeling and simulation, and studies to which extent current simulation technologies can effectively support the design process. For simulation-based design, modeling languages and simulation environments must take into account the special characteristics of the design process. For instance, languages should allow models to be easily updated and extended to accommodate the various analyses performed throughout the design process. Furthermore, the simulation software should be well integrated with the design tools so that designers and analysts with expertise in different domains can effectively collaborate on the design of complex artifacts. This review focuses in particular on modeling for design of multi-disciplinary engineering systems that combine continuous time and discrete time phenomena.