bluuebunny/crossref_metadata_2025 huggingface dataset:
Improvement of High Pressure Turbine Air Systems by De-Swirl Nozzles
Authors: Friedl Winfried-Hagen , Peitsch Dieter , Negulescu Dimitrie
Published: June 2008

Conventional two-stage high pressure turbine (HPT) air system concepts usually are based on exclusive use of compressor delivery air to cool HPT blades and vanes and to seal the gaps between rotors and stators. This air is expensive in terms of engine efficiency, since work has been done on it from all stages of the compressor and the air is lost for the main thermodynamic engine cycle. It is also very hot, leading to strong thermal loading of the turbine material. Improvements in this area thus lead to an immediate reduction of fuel consumption and increased cycle life of the turbine discs. On static components, it is common practice to use pre-swirl nozzles in order to reduce the relative total temperature of downstream disc and blades. To feed the interstage cavity between both HPT discs, the air is transferred through the first rotor disc or drive arm. In a conventional system, the air is passed on through straight holes, thus no benefit is taken from the internal energy potential of the cooling air, where work output from the flow would lead to an immediate air temperature reduction. The advanced air system presented in this paper uses de-swirl nozzles in the rotating part to extract energy from the fluid. By this, the air temperature for the downstream static part is reduced on the one hand and in addition, the overall turbine efficiency is increased due to the contribution from the fluid. This paper will cover the effects of an air system design change from a conventional to an advanced HPT air system on the Rolls-Royce BR715 aeroengine based on numerical analysis and test data. An overview of the change to the flow field and prospect of current research programmes in this field will be given.
Structural Fire Modeling With the Zone Method
Authors: Kim Hyeong-Jin , Lilley David G.
Published: June 2008

The development of the fire analytical modeling has accelerated over the last 30 years. As a result, fire modeling can often be used to appraise the effectiveness of the protective measures proposed when one designs a building. Fire behavior is extremely important in fire protection engineering and building design engineering. The ultimate goal of modeling studies is to improve scientific and technical understanding of fire behavior leading to flashover in structural fires. The zone modeling approach to multi-room structural fire modeling is emphasized in this study. This paper also summarizes the theory and methodology of the CFAST (Consolidated Model of Fire Growth and Smoke Transport) model, and its simpler variant the FASTLite model, which are zone type approaches being widely used by the authors. Studies of this type assist in the understanding of structural fires, and the development of computer modeling studies, and assessment of their predictive capability.
Master Assembly Model for Real-Time Multi-User Collaborative Assembly Modeling on the Internet
Authors: Chen Li , Song Zhijie , Liavas Billy
Published: June 2008

In this paper, an information model, known as Master Assembly Model (MAM), is introduced to support real-time multi-user collaborative assembly modeling on the Internet. By using UML class diagrams, the MAM is described in detail according to four key aspects: (1) Collaborative Assembly Representation, (2) Multi-View, (3) Coordination Control and (4) Collaborative Session. Finally, a real-time multi-user collaborative assembly modeling system based on this model is suggested. This system makes it possible for different organizations at geographically different locations to work together concurrently and synchronously on the design and modeling of an assembly.
Knowledge-Based Development of Mechatronic Products
Authors: Welp E. G. , Bludau C.
Published: June 2008

The development of mechatronic products, which are composed of mechanical and non mechanical elements and components, is a special challenge for interdisciplinary and geographically distributed engineering teams. Efficiency and quality of such development processes can significantly be increased by methods and tools, which help to cope with the different tasks of early design stages and rule the occurring complexity. Being aware of this facts, two interacting software applications have been developed, realizing a knowledge-based approach in the field of mechatronics. ModCoDe (modeling system for conceptual design) enables engineers of different disciplines to create a comprehensive mechatronic concept, based on so called “wirk”-structures. WISENT(system for knowledge archiving and processing) supports this iterative concept creation by providing relevant information and knowledge. Beyond this, these systems can be coupled with commercial simulation software like MATLAB/Simulink, which allows evaluation of the generated results.
Web-Based Innovation Alert Services to Support Product Design Evolution
Authors: Gupta Satyandra K. , Lin Edward , Lo Alexander J. , Xu Changxin
Published: June 2008

Technological innovations provide an opportunity to improve product performance and reduce cost. Therefore, design organizations are interested in monitoring technological innovations. A large number of innovations are announced every year. Monitoring them manually is very time consuming. We are developing web-based innovation-alert services that can be used to monitor and communicate information about innovations relevant to a particular product design. In this paper, we discuss the required infrastructure, relevant design issues, and our approach to developing web-based innovation alert services to support product design evolution. We also describe a prototype innovation monitoring service for computer components and an interactive tool to transform semi-structured web contents into semantic representations in XML.
Architecture and Implementation of a Design Repository System
Authors: Szykman Simon
Published: June 2008

This paper describes the design and development of a design repository software system. This system is a prototype implementation intended to demonstrate the role of design repositories as part of a vision for the next generation of product development software systems. This research involves not only the creation of a prototype software system, but is part of a broader effort that also includes the development of a core product knowledge representation, and that seeks to address terminological and semantic issues associated with computer-aided product development. This paper focuses on the interfaces that have been developed to support authoring and navigation of the product models stored in design repositories, as well as the software architecture and associated rationale that provide the framework on which the system is built.
CADDAC: Multi-Client Collaborative Shape Design System With Server-Based Geometry Kernel
Authors: Agrawal Abhishek K. , Ramani Karthik , Hoffmann Christoph M.
Published: June 2008

New and efficient paradigms for web-based product design will be driven by increased outsourcing in a global economy, increased competition, and a reduction in product development time. We have developed a three-tier (client-server-database) architecture based collaborative shape design system, Computer Aided Distributed Design and Collaboration (CADDAC). CADDAC has a centralized geometry kernel and constraint solver. The server-side provides support for solid modeling, constraint solving operations, data management, and synchronization of clients. The server also holds the master copy of the CAD model that is used to update the local version of the shape model on the clients. The client-side performs real-time creation, modification, and deletion of geometry over the network. The clients are also capable of viewing three-dimensional model and manipulating it by applying rotational, translation, and scaling transformations. In order to keep the clients thin, many computationally intensive operations, such as solid modeling and constraint solving, are performed at the server. Only the graphics rendering pipeline operations comprising of matrix transformations, clipping, viewport mapping, rasterization, and pixel operations, are performed at the client-side. Our work lead to a thin client-side that is capable of geometry and constraint creation, modification, and deletion over the network.
Digital Interfaces: The Key to Effective Decision-Making in Distributed Collaborative Design and Manufacturing
Authors: Ferna´ndez Marco Gero , Rosen David W. , Allen Janet K. , Mistree Farrokh
Published: June 2008

In product development, the interfaces between distinct phases of a design process are not well defined and largely misunderstood. The same ambiguity holds true for interactions among distributed stakeholders engaged in shared, concurrent design tasks. Such vagueness fosters poor communication, problematic changeovers, and hard-to-manufacture designs. Resulting design processes tend to be iterative and not only increase product development costs and extend time-to-market, but also ultimately impede collaboration. What is needed is the ability to propagate decision-critical, up-to-date information alongside design knowledge for both sequential and concurrent design tasks. This is particularly important for dependent and interdependent decisions that cannot be made in isolation. To address this need, digital interfaces are being developed as key components to successful collaboration in distributed design and manufacture applications. Such digital interfaces will constitute a means of communicating critical information and will address the need for allocating responsibility for decisions. The potential implementation of a digital interface is illustrated in an example focusing on the production of a functional prototype of a disposable camera spool.
Remeshing Based Mesh Smoothing by 2D Sketches Input
Authors: Wang Charlie C. L. , Wang Yu , Yuen Matthew M. F.
Published: June 2008

This paper presents an interactive 3D mesh smoothing method, which is useful for intuitive, efficient geometric modeling of freeform polygonal models. With our method, users can remove unwanted bumps and cavities, or smooth creases by drawing two strokes to map out the smoothing area. Discrete fairing is applied on the surrounded area to minimize its membrane energy and its thin plate energy. During the process of fairing, an umbrella operator smoothes the vertices in the surrounded area one by one; and a remeshing scheme is used to optimize the topology structure of the mesh inside the surrounded area during smoothing. Compare to other well-known approaches, our method will not be influenced by the topology structure of the smoothing mesh. Thus, it can be applied to any triangular mesh surface. At the end of this paper, examples of our mesh smoothing implementation are shown to demonstrate its functionality.
An Automatic Technique for CAE Analysis With a 3D-CAD Model
Authors: Nonaka Norihiko , Nishigaki Ichirou
Published: June 2008

A CAE (computer-aided engineering) analysis system, consisting of a 3D-CAD (three-dimensional computer-aided design) modeler, a pre-processor, an analysis solver, and a post-processor, was developed. This system uses automated procedures for solid modeling, definition of analysis models (i.e., defining boundary conditions and material properties, traditionally done manually), mesh generation, numerical simulation, and visualization of results. The CAE analysis system has two key features: it can greatly reduce the analysis time, and it uses a 3D-CAD model as the geometric model for numerical analysis. It was found that the developed automatic system reduces the analysis time by 50% compared with that for manual operation.
Supporting Design Refinement in MEMS Design
Authors: Sinha Rajarishi , Paredis Christiaan J. J. , Khosla Pradeep K.
Published: June 2008

We present a framework to support design refinement during the virtual prototyping of microelectromechanical systems (MEMS). By instantiating MEMS components and connecting them to each other via ports, the designer can both configure complex systems and simulate them. We examine design refinement in the context of ease of use and representation of the virtual prototype. We propose the use of a common, formal grammar representation for the design entities in the virtual prototype—MEMS components, behavioral models and CAD models. We show that the formal grammar approach leads to easy creation of virtual prototypes. In this paper, we focus on ports—the fundamental building blocks of a virtual prototype. Ports mediate all interactions within and between aspects of the virtual prototype. For even moderately complex designs, there can be many interactions present. The representation and organization of all possible ports is important in the context of design refinement. We provide a set-theoretic formalism that defines the algebra of ports. We present a formal grammar for ports that represents a port as a set of attributes, and provide a design refinement mechanism that involves adding or modifying attributes in the port. We illustrate our framework with a MEMS example. We demonstrate that the MEMS designer can evaluate multiple design alternatives quickly and accurately with our framework.
Estimating the Optimal Number of Alternatives to Be Explored in Large Design Spaces: A Step Towards Incorporating Decision Making Cost in Design Decision Models
Authors: Gupta Satyandra K. , Xu Changxin
Published: June 2008

Exploration of design spaces is an important step in decision-based design. In consumer product development, precise design specifications are not known at the beginning of the design process. It is usually design team’s responsibility to find out the specifications as a part of the design process. This results in large design spaces in consumer product development. Furthermore, market window is usually limited. Thus, it is impractical to examine all possible design alternatives. As part of the design process, design teams need to determine how many alternatives to examine and how much evaluation time should be devoted to examining each alternative. This paper presents a model for estimating the optimal number of alternatives to be explored and the optimal evaluation time for each alternative by incorporating cost of decision-making in the overall design decision model. We also describe a design case study and investigate how characteristics of design task parameters influence the optimal number of alternatives and the optimal evaluation time. Our results indicate that it is difficult to intuitively identify the optimal values of the number of alternatives and the evaluation time for even very simple design tasks. We describe the practical issues that need to be addressed to make these decisions and discuss how the model proposed in this paper can be extended to handle more general cases of design tasks.
Offset Slices for Layered Manufacturing
Authors: Singh Prabhjot , Dutta Debasish
Published: June 2008

Layered Manufacturing (LM) techniques build a part by adding thin layers of material. In this process overhangs need to be supported by sacrificial supports, resulting in an increase in the build time, wastage of material and requiring costly post-processing. Metal based LM machines with the capability to deposit material along multiple directions resolve most of the above problems. These machines have the capability to deposit non-planar slices. In this paper we study such slices and present a task framework for their use with multi-directional LM machines. A solution methodology is presented for the 2 dimensional domain which can be extended to 3 dimensions.
Feature Simplification in Surface Models for Efficient Finite Element Mesh Generation
Authors: Joshi Nikhil , Dutta Debasish
Published: June 2008

Sheet metal components are typically modelled as freeform surface models. Finite element meshes generated automatically for such models have poor quality around small detailed features. These features need to be simplified in order to obtain an acceptable mesh. Simplification involves recognition of the feature and modification of its geometry or complete suppression of the feature. This paper proposes techniques to directly query the CAD data structure to recognise and suppress two basic features, viz. holes and fillets in freeform surface models. Results of a software implementation for the same are discussed with suitable examples.
Pneumatic Calligraphy Manipulator and Web-Based Tele-Operation
Authors: Hu Xudong , Yu Hong , Shen Weiping , Wu Chuanyu
Published: June 2008

Pneumatic devices are typically used as actuators in the engineering. Because of the compressibility and less stop position, they were considered hard to control in a precise motion control system. The servo-pneumatic positioning systems change people’s concept. Engineers find that with the help of new pneumatic servo control technology, it is just as easy of using electro-servo system as to use servo-pneumatic positioning controller. The SPC-200 Axis Controller being wildly used is a good example. This article discusses the Web-based calligraphy manipulator control. Authors had built an experimental calligraphy robot in the Lab. It could mimic human calligraphy. In this test robot system, it contained Web-based control ability. User could move robot manipulator through Web page. The critical issue of Web-based control is the requirement of a language environment, which characterize script. This experimental system ran under Ch language environment. The details of system building and executing are described in this paper. It concluded that pneumatic devices could be used as accurate position control and could be possible to control through Web.
Thermal Robustness and Mass Optimization of Heat Pipe Shape for Spacecraft Panel Using a Combination of Response Surface Methodology and Monte Carlo Simulation
Authors: Kobayashi Takashi , Nomura Takehide , Kamifuji Masaki , Yao Akira , Ogushi Tetsurou
Published: June 2008

A commercial spacecraft should survive on orbit for more than 10 years under the severe circumstances without any maintenance. To realize this subject, not only performance but also other design factors such as reliability, mass, robustness, cost, etc. should be taken into consideration. From point of the thermal design, it is very important to obtain the robust thermal control subsystem with matrix heat pipe layout while minimizing the mass (weight). A new thermal optimization method without compromising the thermal robustness and the mass of thermal subsystem is highly anticipated. This paper proposes a robust thermal design approach for optimizing the heat pipe shape to minimize the mass of the spacecraft panel. We apply a combination of Design of Experiments (DOE), Response Surface Methodology (RSM) and Monte Carlo Simulation to determine the robust design parameters that minimize the mass of the heat pipe structure. Dimensions of the heat pipe design parameters were determined with rationally in a short time and practical robust optimization method was established.
Dual Stage Input Coupled Split Power Transmission Efficiency Optimization
Authors: Fussner Doug , Singh Yesh P.
Published: June 2008

Split power continuously variable transmissions can offer clutchless transitions from reverse through park and into the forward driving mode. The advantages of these transmissions can include elimination of a launch device while maintaining the continuous variability and fuel economy benefits of conventional CVTs. This paper offers further improvements to the transmission by providing an efficiency optimization methodology. Models for the transmission are constructed. A genetic algorithm is developed for the optimization routine. The effects of the gear material strength, gear module, gear tooth width, and shaft offset on the efficiency are determined. The bearing diameters and gear parameters are calculated and reviewed. Power loss contributions are presented in conjunction with their effect on the overall transmission efficiency. Recommendation for further improvements to the methodology is made.
Artificial Immune System Based Isomorphism Identification Method for Mechanism Kinematics Chains
Authors: Xiao Renbin , Wang Lei , Fan Zheng
Published: June 2008

An Artificial Immune System (AIS in short) based Isomorphism Identification method for Mechanism Kinematic Chains (IMKC) is proposed in this paper. The problem of IMKC has puzzled the scholars in the field of mechanical design for a long time, however, most researchers have omitted one important fact that this problem can be viewed as a Traveling Salesman Problem (TSP) and solved with relevant approaches. AIS is a newly developed bionic paradigm of information processing and problem solving, with powerful ability in recognition, memory and feature extraction. Temporally, AIS has been employed in solving many combinatorial optimization problems like TSP. In view of the existing problems of IMKC, we introduce the definition of Structural Code and convert the problem of computation on IMKC to a similar TSP. Then an AIS based algorithm is utilized to solve the problem and the result shows AIS is a powerful tool in solving IMKC problem and the numerical experiment shows that the AIS based method is better than the one used GA and both of the two methods are highly efficient in solving IMKC problems.
Use of Constrained Viscoelastic Layers in the Design of Satellite Panels to Predict the Amplification Factor
Authors: Potvin Marie-Jose´e , Coˆte´ Andre´ , Charbonneau Eric , Aguilar Maria-Elena
Published: June 2008

A critical aspect of the design of a space structure is the prediction of the amplification factor. This factor is often estimated from comparison with similar structures, which can lead to costly errors. Adding viscoelastic patches enables an accurate prediction of the damping level of the structure since the viscoelastic patches become the main cause of damping for the structure. In this project, a test panel similar to large satellite feed panels is damped using five small viscoelastic patches. The location of the patches is optimized using the strain energy method. The amplification factor is obtained through a complex eigenvalue finite element analysis. The complex eigenvalue method is shown to be as accurate as the direct frequency analysis, but it runs much faster. The predicted amplification factor is within 15% of the experimental value which is a very good estimation for such a complex structure.
Determination of Geometric Distortions in Automotive Lamps Using Non-Linear Parametric Estimations
Authors: Usman Asad A. , Usman Mohammad
Published: June 2008

In automotive lamps, an ideal paraboloid is the reflector shape of choice when lens optics is utilized. However, geometric distortions occur among manufactured automotive lamps. This paper discusses the effects of geometric distortions on spread, packing, and gradient of reflected light from automotive lamps. Relevant legal requirements set by Federal Motor Vehicle Safety Standard on the performance of automotive lamps are also discussed. A new parametric mathematical model is developed to represent the geometry of an ideal lamp reflector. A non-linear parametric estimation problem is formulated using the Box-Kanemasu modification of the Gauss method. An application of methodology is also presented in this paper. The results show significant distortions of paraboloidal reflector with respect to the ideal design-intent reflector geometry. The numerically calculated deviations of focal point, focal length and paraboloidal axis from the ideally designed reflector necessitate improvements in the tooling and the manufacturing process for better dimensional control.
Macroscopic Shape-Information as a Curve Design-Guideline
Authors: Ujiie Yoshiki , Matsuoka Yoshiyuki
Published: June 2008

In curve design, controlling the characteristics of the overall shape is difficult using conventional microscopic shape-information such as dimension. Curvature entropy as calculated by the distribution of curvature was proposed as the macroscopic shape-information, and was confirmed to represent the complexity of a shape. In order to adjust the shape recognition of human beings, a Markov process was introduced into the definition of the macroscopic shape-information. Shape-generation method using the macroscopic shape-information was developed, and was applied to the design of an automobile side-view. Thus, the possibility of curve design-support using the macroscopic shape-information was indicated.
Collaborative Decision Making Across Digital Interfaces
Authors: Xiao Angran , Choi Hae-Jin , Allen Janet K. , Rosen David W. , Mistree Farrokh
Published: June 2008

In distributed product realization problems, new paradigms and accompanying software systems are necessary to support the collaborative work of geographically dispersed engineering teams from different disciplines who have different knowledge, experience, tools and resources. In the context of prototyping product using SFF technologies, digital interfaces are constructed between engineering teams, especially between design and manufacturing teams, to separate their product realization activities. Across digital interfaces, each engineering team holds its own perspective towards the product realization problem, and each controls a subset of design variables and seeks to maximize its own payoff function subject to individual constraints. That is, engineering teams act like players in a team sport (i.e., a game) cooperating to achieve a set of overall goals. Hence, we postulate the use of principles from game theory to model the relationships between engineering teams. In this paper, a decision template is used as a digital interface enabling information about product realization activities to be transferred between engineering teams. Three game protocols are used to facilitate collaborative decision making without iteration across digital interfaces. A simple product realization scenario is introduced to demonstrate the efficacy of inserting digital interfaces between design and manufacturing teams.
Local Least Squares Fitting for Surface Mesh Fairing in Automobile Panel Design
Authors: Vieira Miguel , Shimada Kenji , Furuhata Tomotake
Published: June 2008

Three-dimensional laser scanning equipment is being used more frequently to convert clay model automobile designs to large, detailed meshes for computer-aided design of outer-body panels. The panels are generally composed of large, constant curvature patches with small local features, called character lines, superposed to give the car a distinctive look. Although modern laser scanners are very accurate and precise, their tolerances nevertheless admit meshes with geometric flaws that destroy the constant curvature of patches and make character lines nearly invisible in a reflection simulation. Thus, we require an algorithm to fair the mesh by restoring the intended curvature while minimizing the vertex displacemtents. Existing approaches such as Laplacian and curvature flow operators are not suitable because they tend to shrink the mesh and introduce a bias toward planar geometries. Our approach aims to solve both of these problems by fitting a least squares surface to a set of vertices adjacent to the target vertex and moving the target vertex vertically onto the least squares surface in a local coordinate system. This algorithm has linear time complexity in the number of vertices and makes convergence likely while eliminating the planar bias of other operators. We show the effectiveness of our operator with both geometric and real-world mesh examples.
A Benchmark Comparison of Curvature Matched Machining versus Three- and Five-Axis Machining Methods Applied to Industrial Part Surfaces
Authors: Hill J. K. , Cheatham R. M. , Jensen C. G.
Published: June 2008

Parts representing the aerospace, automotive, and power generation industries were machined using Curvature Matched Machining, Sturz milling, and traditional 3-axis ball-end methods. The performance of these methods were compared using the benchmarks of tool path length, surface finish, and post-machining finishing time. Curvature Matched Machining proved to be superior method for the parts studied. Significant reductions in tool path length were observed (over 80% in some instances). Improvements were also realized in surface finish and post-machining operations.
Development of Adaptive Range Genetic Algorithms Considering Inheritance of Searching Range
Authors: Arakawa Masao , Ishikawa Hiroshi
Published: June 2008

For several years, adaptive range genetic algorithms have been developed and it turned out to be very efficient in treatment of both discrete variables and continuous variables. That means it is useful tools for mixed variable problem, which was thought most daunting problem in design engineering. We have shown its effectiveness through benchmark problems and outperformed the other method in its accuracy. In this paper, we will newly develop a new type of Adaptive Range Genetic Algorithms, which will consider inheritance of searching range. We have demonstrated its effectiveness through benchmark problem and showed its characters. Through numerical example, we showed the stability and effectiveness of the proposed method compared with the conventional method.
Using Genetic Algorithms With Niche Formation to Solve the Minimum Distance Problem Among Concave Objects
Authors: Carretero J. A. , Nahon M. A. , Ma O.
Published: June 2008

In this paper an optimization approach is used to solve the problem of finding the minimum distance between concave objects, without the need for partitioning the objects into convex sub-objects. Since the optimization problem is not unimodal (i.e., has more than one local minimum point), a global optimization technique, namely a Genetic Algorithm, is used to solve the concave problem. In order to reduce the computational expense of evaluating the constraints at runtime, the objects’ geometry is replaced by a set of points on the surface of the body. This reduces the problem to a combinatorial problem where the combination of points (one on each body) that minimizes the distance will be the solution. Additionally, niche formation is used to allow the minimum distance algorithm to track multiple minima rather than exclusively looking for the global minimum.
Shape Optimization of NURBS Modeled 3D C-Frames Using Hybrid Genetic Algorithm
Authors: Hegazi Hesham A. , Nassef Ashraf O. , Metwalli Sayed M.
Published: June 2008

The present paper introduces a new methodology for designing machine element shapes. The element is represented using non-uniform rational B-Spline (NURBS) in order to give it a form of shape flexibility. A special form of genetic algorithms known as real-coded genetic algorithms is used to conduct the search for the design objectives. Shape optimization of 3D C-frames are used as an application of the proposed methodology. The design parameters of these frames include the dimensions of their cross-sections, which should be chosen to withstand the applied loads and minimize the element’s overall weight. In a further development, the hybridization of different optimization methods has been used to find the optimum shape of the element. Real coded genetic algorithm is used as a random search method, while Nelder-Mead is used as a direct search method, where the result of the genetic algorithm search is used as the starting point of direct search. The results showed that the use of Nelder-Mead with Real coded Genetic Algorithms has been very significant in improving the optimum shape of a solid 3D C-frames subjected to a combined tension and bending stresses. The hybrid optimization method could be extended to more complex shape optimization problems. For the purpose of analysis, curved beam theory is applied on local cross-sections on the NURBS surface. A finite elements analysis was conducted on SDRC-IDEAS for verifying the results obtained using the curved beam theory.
Theoretical Evaluation of the Integrated Structure and Control Design Approach by Optimization Theory
Authors: Fu Ke , Mills James K.
Published: June 2008

Comparing to the traditional sequential design approach, the integrated structure and control design approach integrates the mechanical structure design and the control system design by formulating the design as an optimization problem. This paper investigates two important questions pertaining to the integrated structure and control design approach: Why and when should the integrated design approach be used rather than the traditional sequential design approach? In this paper, we have formulated both approaches as optimization problems. The benefit of the integrated design approach over the sequential design approach is proved in this paper. The conditions for when the integrated design approach will result in better closed-loop system performances are also given. A simple example is given to illustrate the theoretical results derived. The conclusion is given following this example and the simulation results are shown at the end of the paper.
Finding the Shortest Path for Quality Assurance of Electric Components
Authors: Kageura Masaru , Shimada Kenji
Published: June 2008

This paper presents a computational method for calculating the shortest path along the surface of a product assembly between two components. The goal of this method is to check whether or not there is sufficient distance between two electrical components to prevent the occurrence of a spark between them. Our approach is an approximating method using a discrete weighted graph. To improve accuracy we have added two methods, geometric improvement and K-shortest path. Through experiments, we show that our method is effective for the quality assurance of electric components.
Sequential Optimization and Reliability Assessment Method for Efficient Probabilistic Design
Authors: Du Xiaoping , Chen Wei
Published: June 2008

Probabilistic optimization design offers tools for making reliable decisions with the consideration of uncertainty associated with design variables/parameters and simulation models. In a probabilistic design, such as reliability-based design and robust design, the design feasibility is formulated probabilistically such that the probability of the constraint satisfaction (reliability) exceeds the desired limit. The reliability assessment for probabilistic constraints often involves an iterative procedure; therefore, two loops are involved in a probabilistic optimization. Due to the double-loop procedure, the computational demand is extremely high. To improve the efficiency of a probabilistic design, a novel method – sequential optimization and reliability assessment (SORA) is developed in this paper. The SORA method employs a single-loop strategy where a serial of cycles of optimization and reliability assessment is employed. In each cycle optimization and reliability assessment are decoupled from each other; no reliability assessment is required within optimization and the reliability assessment is only conducted after the optimization. The key concept of the proposed method is to shift the boundaries of violated deterministic constraints (with low reliability) to the feasible direction based on the reliability information obtained in the previous cycle. Hence the design is quickly improved from cycle to cycle and the computational efficiency is improved significantly. Two engineering applications, the reliability-based design for vehicle crashworthiness of side impact and the integrated reliability and robust design of a speed reducer, are presented to demonstrate the effectiveness of the SORA method.
Model Validation via Uncertainty Propagation Using Response Surface Models
Authors: Baghdasaryan Lusine , Chen Wei , Buranathiti Thaweepat , Cao Jian
Published: June 2008

Model validation has become a primary means to evaluate accuracy and reliability of computational simulations in engineering design. Mathematical models enable engineers to establish what the most likely response of a system is. However, despite the enormous power of computational models, uncertainty is inevitable in all model-based engineering design problems, due to the variation in the physical system itself, or lack of knowledge, and the use of assumptions by model builders. Therefore, realistic mathematical models should contemplate uncertainties. Due to the uncertainties, the assessment of the validity of a modeling approach must be conducted based on stochastic measurements to provide designers with the confidence of using a model. In this paper, a generic model validation methodology via uncertainty propagation is presented. The approach reduces the number of physical testing at each design setting to one by shifting the evaluation effort to uncertainty propagation of the computational model. Response surface methodology is used to create metamodels as less costly approximations of simulation models for uncertainty propagation. The methodology is illustrated with the examination of the validity of a finite-element analysis model for predicting springback angles in a sample flanging process.
An Evolutionary Multi-Objective Optimization Approach to the Topology Optimization of Auxetic Structures
Authors: Nassef Ashraf O.
Published: June 2008

Auxetic structures are ones, which exhibit an in-plane negative Poisson ratio behavior. Such structures can be obtained by specially designed honeycombs or by specially designed composites. The design of such honeycombs and composites has been tackled using a combination of optimization and finite elements analysis. Since, there is a tradeoff between the Poisson ratio of such structures and their elastic modulus, it might not be possible to attain a desired value for both properties simultaneously. The presented work approaches the problem using evolutionary multiobjective optimization to produce several designs rather than one. The algorithm provides the designs that lie on the tradeoff frontier between both properties.
An Interactive Virtual Environment for 3D Model Assembly With Video Immersion
Authors: Klar Thomas , Baladi Miranda , Fadel George , Almer Mathias
Published: June 2008

Virtual Reality (VR) applications will become increasingly important as the need to link several locations in the product development process arises. This motivates research in advanced techniques for the visualization of remotely located participants within a computer-generated environment. This research ports an existing application, which allows the assembly of predefined objects, into a virtual environment (VE). A further extension allows the user’s hands to be filmed and superimposed onto the computer-generated VE. To create this effect, live video was combined with a projection display and the “blue-box” technique. This combination enabled the texture of the hands to be untied from the background without the effort of putting up blue walls. The image is sent over the network to a high-end graphics computer generating the VE. The knowledge gained in this research will be the basis for future work on distributed multi-user access to a shared VE.
Prediction of Workpiece-Fixture Contact Forces Using the Rigid Body Model
Authors: Wang Michael Yu , Pelineascu Diana M.
Published: June 2008

Prediction of workpiece-fixture contact forces is important in fixture design since they define the fixture stability during clamping and strongly influence workpiece accuracy during manufacturing. This paper presents a solution method for predicting the normal and frictional contact forces between workpiece-fixture contacts. The fixture and workpiece are considered to be rigid bodies, and the model solution is solved as a constrained quadratic optimization by applying the minimum norm principle. The model reveals some intricate properties of the passive contact forces, including history dependency during a sequence of clamping and/or external force loading. Model predictions are shown to be in good agreement with known results of an elastic-contact model prediction and experimental measurements. This presented method is conceptually simple and computationally efficient. It is particularly useful in the early stages of fixture design and process planning.
Automated Manufacturability Evaluation of Sheet Metal Components: A Review
Authors: Ramana K. V. , Rao P. V. M.
Published: June 2008

Accounting for manufacturability considerations at the product design stage is not only important but earlier they are considered in the design cycle, better it is. When computers are used extensively for design and manufacturing, automated manufacturability evaluation is a powerful option. This paper presents a review on automated manufacturability evaluation of sheet metal parts. While a large number of technical papers including reviews have been published on the general subject of Design For Manufactuarability (DFM), there is no paper in the literature that provides a review of automated manufacturability evaluation of sheet metal parts. In this work existing automated manufacturability evaluation systems for sheet metal parts are reviewed. The product, process and resource information models together with integration issues for automated manufacturability evaluation are discussed. Some of the future research challenges in this area are presented at the end.
Concurrent Design for Optimal Production Performance
Authors: Wei Yu-Feng , Thornton Anna C.
Published: June 2008

In this paper we propose a quantitative method for optimizing the design tasks at the product, process, and system level based on predicted system performance. We develop a set of models for a production system that comprises two plants: manufacturing and assembly, with a finished-good inventory in between, and seek to optimize the part design, tolerancing, production and inventory control concurrently. Such an approach provides an efficient manufacturing feedback loop for the design tasks and can significantly shorten the product development lead-time. A case study of an aircraft tube production system is used to illustrate this methodology.
RPBloX Rapid Prototyping: More Than Just Layers
Authors: Lim T. , Corney J. , Ritchie J. M. , Davies B. J.
Published: June 2008

Rapid Prototyping and Manufacturing (RP&M) technologies are increasingly being applied to produce functional prototypes and directly manufacture small batches of components (where the “prototype” is itself the final product). Although there are various forms of RP&M, almost all rely on a layered manufacturing approach. However despite the flexibility of these systems, they have common drawbacks such as slow build rates, a limited number of build axes (typically one) and the need for post processing, i.e. removal of support structures and finishing. This paper reports the preliminary research that aims to combine sophisticated CAM software and automated assembly technologies to demonstrate that a non-layered method of RP can be engineered. The system under development is referred to as RPBloX. This novel technique has the potential to not only supplement current RP techniques but also act as a standalone method in which products can be brought to market within a shorter design-manufacture cycle time. Essentially, the RPBloX methodology involves a cellular approach to building up a part. Rather than slicing up the CAD model into numerous thin sheets, RPBloX segments the model into 3D cells (or Bloxes) of varying sizes. In contrast to current RP technology, conventional machine tools such as CNC machines and robots are employed for manufacturing and assembly work. Consequently, production costs could be significantly reduced without the forfeiting accuracy and timeliness.
Speed Control for Flexible Blade Cutting of Thick Foam Layers
Authors: Broek J. J. , Horva´th I. , Kooijman A.
Published: June 2008

The FF-TLOM (Free Form Thick Layered Object Manufacturing) process is based on heated flexible blade cutting of thick foam layers in a free form manner. Both blade ends are supported in a U-shaped tool frame. During cutting the blade is shaped in a minimal strain energy curve. Positioning the tool in an optimal orientation is provided by pitch, roll, yaw and positioning of the tool frame. A restriction of the FF-TLOM cutting is the cutting speed. The cutting speed depends on melting of the foam at the blade location and does not allow outside forces on the blade. Nevertheless the manufacturing time must be as rapid as possible. In this paper an estimation method is proposed for the overall speed setting along a tool path. Hereto the blade is subdivided in blade segments and each segment is analyzed for the encountered speed and in the same time to prevent that the maximum allowable cutting speed is exceeded.
A Normative DFM Framework Based on Benefit-Cost Analysis
Authors: Zhao Zuozhi , Shah Jami
Published: June 2008

Design for Manufacturing (DfM) involves trade-offs between design objectives and manufacturing cost/efficiency. However, contemporary software packages consider DfM in a unilateral (manufacturing centric) way. Ad-hoc rating systems used in these packages can lead to bad decisions. Also, uncertainty in estimating design attributes and manufacturing costs must be accounted for. This paper presents a theoretical framework for DfM that incorporates the above factors. The applicability and rationality of Benefit-Cost analysis to DfM is demonstrated. Present value of net benefit is proposed as the only rational measure of DfM. A domain independent shell for DfM analysis is developed. The shell can be customized for evaluating both technical feasibility and economics of manufacturing.
Modeling of Wrinkles and Its Application in Footwear Design
Authors: Jing Fu , Joneja Ajay , Tam Angela , Yuen W. F.
Published: June 2008

We develop a parametric description of a wrinkle as a shape feature that may be superposed upon selected regions of a 3D surface defined by B-splines or NURBS. We show the use of such a feature in footwear design. We found that the shape modification operator for such a feature can be developed using geodesic offsets. A computer program has been implemented providing such a feature, and some examples of the output of the program are presented in this paper. We also address the need for automatically generating 2D surface developments of 3D shapes with superposed wrinkles. A finite-element style iterative algorithm is outlined for the performing this task; a new distortion energy model is developed for this algorithm in this paper.
Graphical Feedback for Improved Product Design and Production
Authors: Henderson Mark , Shunmugam Umadevi , Krishnamurthi Siddharth
Published: June 2008

Time and cost have been two of the leading factors contributing to a product’s success or failure in the market place. Cost to design, produce and market add to a product’s success or failure. Any savings in cost or time during the design process can make the difference between success and failure. This paper deals with the concept of feedback in design that will help improve the quality of the end product. This feedback system is called Feedback for Automated Manufacturability Evaluation (FAME). With the output from FAME, the user can change the design and the manufacturing process to help reduce the cost and time in the making the component.
Budding Assembly Accuracy in the Presence of Workpiece Surface Roughness and Dimensional Error
Authors: Yu Grace H. , Ceglarek Dariusz , Lee Neville K. S.
Published: June 2008

In this paper, simulation methods with improved surface generation techniques are used to study the accuracy of budding assembly processes. Our analysis shows that both the dimensional error and surface roughness together with surface waviness have significant effect on the budding assembly accuracy. In addition, we have found that even for the same parts with given dimensional errors, surface roughness and waviness, the budding assembly accuracy can still vary significantly depending on the different approaches of the alignment processes.