Feature based quadrilateral mesh generation for sculptured surface products

A successful approach to the generation of quadrilateral surface meshes for finite element analysis of sculptured surface products is presented. The free-form sculpted surface is divided into a feature based product anatomy which is used as the basis for defining regions of simpler shape that are related by the requirement for mesh continuity across their boundaries. Each surface region is meshed using a paving algorithm. Large surface areas are further subdivided to introduce new boundaries which improve contiol over mesh transitions and element distortion. A procedure, based on this approach, which generates well formed meshes on sculptured surface products is described using a hollow golf club head as an example. The approach is product specific and relies on initial user interaction to populate a feature based product data model. Thus, the data model contains, the attributes of a finite element mesh tailored to the product, which can be used to generate meshes on subsequent design iterations or other members of the product family with a high degree of automation, leading to reduced analysis cost.     

A methodology for planning experiments in robust product and process design

Robust design is an important method for improving product manufacturability and life, and for increasing manufacturing process stability and yield. In 1980 Genichi Taguchi introduced his approach to using statistically planned experiments in robust product and process design to U.S. industry. Since then, the robust design problem and Taguchi's approach to solving it has received much attention from product designers, manufacturers, statisticians and quality professionals. Although most agree on the importance of the robust design problem, controversy over some of the specific methods used to solve the problem has made this an active research area. Although the answers are not all in yet, the importance of the problem has led to development of a four-step methodology for implementing robust design. The steps are (1) formulate the problem by stating objectives and then listing and classifying product or process variables, (2) plan an experiment to study these variables, (3) identify improved settings of controllable variables from the experiment's results and (4) confirm the improvement in a small follow-up experiment. This paper presents a methodology for the problem formulation and experiment planning steps. We give practical guidelines for making key decisions in these two steps, including choice of response characteristics, and specification of interactions and test levels for variables. We describe how orthogonal arrays and interaction graphs can be used to simplify the process of planning an experiment. We also compare the experiment planning strategies we are recommending to those of Taguchi and to more traditional approaches.     

A particle‐in‐cell solution to the silo discharging problem

The problem of flow of a granular material during the process of discharging a silo is considered in the present paper. The mechanical behaviour of the material is described by the use of the model of the elastic–plastic solid with the Drucker–Prager yield condition and the non‐associative flow rule. The phenomenon of friction between the stored material and the silo walls is taken into account—the Coulomb model of friction is used in the analysis. The problem is analysed by means of the particle‐in‐cell method—a variant of the finite element method which enables to solve the pertinent equations of motion on an arbitrary computational mesh and trace state variables at points of the body chosen independently of the mesh. The method can be regarded as an arbitrary Lagrangian–Eulerian formulation of the finite element method, and overcomes the main drawback of the updated Lagrangian formulation of FEM related to mesh distortion. The entire process of discharging a silo can be analysed by this approach. The dynamic problem is solved by the use of the explicit time‐integration scheme. Several numerical examples are included. The plane strain and axisymmetric problems are solved for silos with flat bottoms and conical hoppers. Some results are compared with experimental ones. Copyright © 1999 John Wiley & Sons, Ltd.     

Hardware-in-the-loop simulation for a production system

This paper proposes a hardware-in-the-loop simulation (HILS) approach for the design and verification of a production system. The design of a production system involves two major activities: mechanical design (device specification and layouts) and electrical design (device behaviour and system control). Conventionally, the mechanical and electrical design activities have been performed sequentially, wasting time. We propose a concurrent procedure of mechanical and electrical design based on the HILS methodology to cope with this problem. The proposed HILS approach provides two major benefits: (1) the verified control program can be directly used for the real plant with minor adaptations; and (2) the verified 3D layout model can be used to generate the detailed drawings for the implementation of the plant. We can minimise the stabilisation time of a production system, since most mechanical and electrical errors can be found and fixed using HILS.     

An approach to the implementation and verification of abstract data

Abstract

The concept of abstraction can be used to simplify and formalize the design of software. However, most of the existing techniques based on abstraction only consider the control structure but not the data structures in the software. The transformation of a data abstraction, i.e., an abstract data type, to a physical data structure is a complicated process. It is composed of three major parts: a specification technique for describing a data abstraction; a deriving process for deriving the representation of the abstraction based on the specification; and a verification method for verifying the correctness of the specification and the representation of the abstraction. In this paper, we will concentrate on the last two problems, and it is assumed that the algebraic specification technique is used for describing abstract data types. Also, we will use examples to illustrate the use of the proposed approach.     

Concurrent optimization of the design and manufacturing stages of product development

The problem of concurrent optimization of the design and the process planning stages when a new product is developed is addressed. The paper advocates for a simultaneous approach rather than the traditional sequential one. A mathematical representation of this approach is given for these two stages. A mathematical programming technique is used to find the optimal values of the design and the process characteristics. The objective function is a quality loss function. The constraints are the customer requirements, the product's specification limits, the parts’ dimensional limits and the process capability. The traditional sequential approach of concurrent engineering is compared with the proposed simultaneous approach. A parametric analysis of the objective function is performed by applying an interactive multi-objective goal programming technique. A numerical example of a low-pass electrical circuit is given. It is shown that the proposed approach leads to better efficient solutions than the sequential approach. The decision-maker interacts with the optimization process and can choose the efficient solution that best satisfies the company's needs.     

基于主成分分析和模糊Kano模型的并条机造型设计研究

目的 为了更准确地获取并条机的用户需求,从生产实践中获取设计相关因素,提出一种并条机的设计开发流程。方法 采用主成分分析(Principal Component Analysis,PCA)和模糊Kano模型相结合的方法,综合两种方法各自的优势,通过PCA剔除信息重复和交叉的设计因素以降低数据维度,减少分析并条机设计因素的数量,依据模糊Kano模型中用户需求的计算方法和相关规范,结合各设计相关因素进行问卷设计,再对调研数据统计和分析后得到并条机各设计影响因素的用户需求类别,最后融入并条机的创新设计过程中。结论 以并条机造型设计为例,基于主成分分析和模糊Kano模型的分析结果进行了造型上的创新设计,验证了并条机设计开发流程的有效性和可行性,为并条机的设计提供依据,也为相关类别产品的设计提供量化分析参考。     

Resin infusion-based processes simulation : coupled Stokes-Darcy flows in orthotropic preforms undergoing finite strain

The aim of this paper is to present an overall model for the study of resin infusion based processes, in particular, the impregnation of a liquid resin through dry deformable fibrous reinforcements. This model can be appliedto a wide range of activities in many fields of engineering. Here, our approach based on a monolithic formulation in a level-set framework allows to strongly couple a Stokes-Darcy flow in low permeability media undergoing finite strains. The Stokes-Darcy coupled problem is solved using a mixed velocity-pressure formulation stabilized by a multi-scale method. A key feature of our approach is the fluid-solid interaction leading to couple a fluid/porous flow to a non-linear solid mechanics formulation. The interaction phenomenon due to the resin flow in the orthotropic highly compressible preform is based on both Terzaghi’s law and on explicit relation expressing permeability as function of porosity in finite strains mechanical framework. Finally, simulations of industrial design parts are performed to illustrate the abilities of our approach and the relevance of this fluid/porous-solid mechanics coupled problem for composite material process simulations.     

Mechanics of textile composites: Micro-geometry

Textile fabric geometry determines textile composite properties. Textile process mechanics determines fabric geometry. In previous papers, the authors proposed a digital element model to generate textile composite geometry by simulating the textile process. The greatest difficulty encountered with its employment in engineering practice is efficiency. A full scale fiber-based digital element analysis would consume huge computational resources. Two advances are developed in this paper to overcome the problem of efficiency. An improved contact-element formulation is developed first. The new formulation improves accuracy. As such, it permits a coarse digital element mesh. Then, a static relaxation algorithm to determine fabric micro-geometry is established to replace step-by-step textile process simulation. Employing the modified contact element formulation in the static relaxation approach, the required computer resource is only 1–2% of the resource required by the original process. Two critical issues with regards to the digital element mesh are also examined: yarn discretization and initial yarn cross-section shape. Fabric geometries derived from digital element analysis are compared to experimental results.     

Robust product development for multiple quality characteristics using computer experiments and an optimization technique

Conventional parameter or tolerance designs focus on developing exact methods to minimize quality loss or manufacturing cost. The inherent assumption is that the response functions which represent the link between controllable variables and response values of quality characteristics are known before a design is developed. Moreover, parameter and tolerance values are assumed to be independent controllable variables in previous works; namely, they are determined separately in design activities. Currently, advanced computer software, such as computer-aided engineering, can help engineers to handle design problems with unknown response functions, at the stage of product design and process planning. Therefore, in this study, the software ANSYS was employed to obtain simulation data which represent the response values of quality characteristics. These response values will be used to fit a set of response functions for later analysis. However, previous works in computer simulation for design and planning usually lack consideration of the noise impact from an external design system. To approximate a realistic design environment, various levels of controllable variables, in conjunction with artificial noises created from uncontrollable variables, are used to generate simulated data for statistical analysis via Response Surface Methodology (RSM). Then, an optimization technique, such as mathematical programming, is adopted to integrate these response functions into one formulation so that optimal parameter and tolerance values are concurrently determined, with multiple quality characteristics taken into consideration. A bike-frame design was used to demonstrate the presented approach, followed by multiple quality characteristics of interest: material cost, bike-frame weight, structure reliability, and rigidity dependability. The goal is to minimize material cost and bike frame weight and to maximize structure reliability and rigidity dependability. This approach is useful for solving any complex design problems in the early stages, while providing enhanced functionality, quality, economic benefits, and a shorter design cycle.     

Platform Design for Customizable Products as a Problem of Access in a Geometric Space

A product platform is a set of common components, modules or parts from which a stream of derivative products can be created. Product platform design is typically performed as redesign and consolidation of existing products to create more competitive product families by reducing part variety and standardizing components. The main disadvantage of such an approach is that the benefits of product platform design are achieved only after a number of parts have been designed and manufactured, with all the associated expenditure. A number of approaches, referred to as “top-down approaches”, have been proposed recently to design the platforms since the original design of the product families. However, current top-own approaches have two major limitations: (1) they do not enable multiple levels of commonality for different components and features, and (2) they have been applied to products that are variegated in one specification, whereas products are typically variegated in multiple specifications. This paper describes a rigorous top-down approach for synthesizing product platforms that facilitates the realization of a stream of customized product variants, and which accommodates naturally multiple levels of commonality and multiple customizable specifications. The proposed approach is based on the formulation of the platform design as a problem of access in a geometric space. The proposed approach is illustrated with a case example, namely, the design of a product platform for a line of customizable pressure vessels.     

Software design specification and analysis technique (SDSAT) for the development of safety-critical systems based on a programmable logic controller (PLC)

This paper introduces a Software Design Specification and Analysis Technique (SDSAT) for safety-critical systems based on a Programmable Logic Controller (PLC). During software development phases, the design phase performs an important role in connecting the requirements phase and the implementation phase, and it is a process of translating software requirements into software structures. In this work, the Nuclear FBD-style Design Specification and analysis (NuFDS) approach was proposed for nuclear Instrumentation and Control (I&C) software. The NuFDS approach is suggested in a straightforward manner for effective and formal software design specification and analysis. Accordingly, the proposed NuFDS approach is composed of a software design specification technique and a software design analysis technique. In addition, for tool support in the design phase, we developed the NuSDS tool based on the NuFDS approach; this tool is used specifically for generating software design specification and analysis for nuclear fields.     

A new infinite boundary element formulation combined to an alternative multi-region technique

The main objective of this work is to obtain an efficient three-dimensional boundary element (BE) formulation for the simulation of layered solids. This formulation is obtained by combining an alternative multi-region technique with an infinite boundary element (IBE) formulation. It is demonstrated that such a combination is straightforward and can be easily programmed. Kelvin fundamental solutions are employed, considering the static analysis of isotropic and linear-elastic domains. Establishing relations between the displacement fundamental solutions of the different domains, the alternative technique used in this paper allows analyzing all domains as a single solid, not requiring equilibrium or compatibility equations. It was shown in a previous paper that this approach leads to a smaller system of equations when compared to the usual multi-region technique and the results obtained are more accurate. The two-dimensionally mapped infinite boundary element (IBE) formulation here used is based on a triangular BE with linear shape functions. One advantage of this formulation over quadratic or higher order elements is that no additional degrees of freedom are added to the original BE mesh by the presence of the IBEs. Thus, the IBEs allow the mesh to be reduced without compromising the accuracy of the result. The use of IBEs improves the advantages of the alternative multi-region technique, contributing for the low computational cost and allowing a considerable mesh reduction. Furthermore, the results show good agreement with the ones given in other works, confirming the accuracy of the presented formulation.     

On the Reliable Solution of Contact Problems in Engineering Design

In this paper we examine briefly the reliability of solution needed for the accurate and effective analysis of engineering design problems involving contact conditions. A general finite element formulation for treating the frictional contact problem using constraint functions is first summarized. Then we address general reliability issues and those related to the selection of appropriate elements that provide optimal performance. These elements of course do not lock and would provide the best solution an analyst can expect when simulating a design problem. Reliability issues specific to the contact formulation are also presented. A promising procedure to increase the reliability of an analysis is the method of finite spheres. The method does not require a mesh and in particular can be used with a finite element discretization as described in the paper. Finally, the results of several illustrative analysis problems are given.     

Analysis of ground motion due to moving surface loads induced by high-speed trains

A three-dimensional time domain boundary element (BE) approach for the analysis of soil vibrations induced by high-speed moving loads is presented in this paper. An attenuation law is included in the formulation. By doing so, internal material damping can be taken into account. The characteristics of the BE model required for the study of travelling load problems are analysed. Thus, mesh size, type of elements, internal damping representation and the complete numerical approach are validated. Existing analytical solutions for some simple problems are used as a reference. Experimental results measured in a simple soil dynamic load problem are also accurately reproduced by the proposed model. The analysis of the type of BE mesh required for a good representation of high-speed train effects is carried out using different discretizations under the sleepers and the free field near the track. All these analyses allow to define a model very well suited for the study of soil vibration effects due to high-speed train passage. Vibrations produced by an Alstom (Thalys-AVE) train travelling at 256 and 300 km/h speed are evaluated at different locations near the track. Results show that the proposed numerical procedure and attenuation law allow for a realistic representation of the effects of the different passing loads. The BE approach presented in this paper can be used for actual analyses of high-speed train-induced vibrations. Layered soils, ballast or coupled vibrations of nearby structure can be included in the model in a straightforward manner.     

面向创新设计的科学效应库研究

概念设计是确定功能原理解的过程,创新设计主要在这个阶段完成。行为是联系功能与结构的纽带,起着承上启下的重要作用,使用科学效应是实现功能到行为映射的有效手段。根据概念设计的过程模型, 提出了功能、行为与效应的关系模型和一个以功能为核心的功能-效应（FE）模型。建立了面向创新设计的科学效应库原型系统,系统具有效应搜索、效应显示、效应组合和生成报告等功能,为产品创新设计功能原理解提供有效支持。科学效应库是计算机辅助创新设计软件系统的一个功能模块。     

Incorporation of high recyclability material selection in computer aided design

Manufacturing are now under increasing pressure of tighten environmental legislation to preserve natural resources. Product design, as a part of manufacturing activities, has to be more concern to deliver product specification with reduced environmental impact. Design for Recycling (DFR) is one of the promising approaches in prolonging material utilization of a product in the early stage of design. DFR focus on harmonizing product design with the recycling practices in order to minimize the loss of valuable materials and preventing unnecessary waste streams at the end of product’s life. In turn, it limits the usage of natural resources.To implement DFR, designers are faced with the challenge of compromising different design objectives such as cost, functional or technical requirements and product’s recyclability performance. This paper attempts to propose an intelligent approach that could facilitate designers to make an easy and quick recyclability assessment as well as selecting recyclable materials integrated with computer aided design. In this paper, the use of fuzzy inference system and genetic algorithm is proposed to optimize the multi-objective problem in the selection of recyclable materials. Case study on the actual conceptual design using computer aided design environment is demonstrated and showing that the proposed method successfully can be applied concurrently during product design. Comparison of proposed method with Sustainability Express Solid Work is also presented. The proposed method can assist product designers to design a high recyclability product without ignoring technical perspectives.     

Towards a human factors and ergonomics integration framework in the early product design phase: Function-Task-Behaviour

Considering the existing methodologies’ hysteresis and cost of the human factors and ergonomics (HF/E) integration in the design phase, this paper attempts to develop a time-saving, less expensive and standard approach for designers to integrate the HF/E from the early design phase. In this study, the HF/E information is embodied by a user manual, which will be continuously improved with the refinement of design. A Function-Task-Behaviour framework is proposed to restate the design process, which involves three steps: (1) Functional specification involves function definition and decomposition according to initial user manual and other requirements; (2) Embodiment refers to conducting task definition and planning to achieve the intended function. SysML is used for task definition and PERT method is applied for task planning; (3) Detailed design refers to the interactions analysis between user’s behaviour and product’s behaviour in the work area. A case study is shown at the end of this paper to illustrate the feasibility of the proposed method in integrating the HF/E from the early design phase to improve the final performance of both product and user.