Philip Sargent

Shared memory in design: A unifying theme for research and practice

This paper presents a new unifying theme for design theory by emphasizing the importance of context. We arrive at our conclusions by examining and then criticizing the legitimacy of universal methods in design upon which the critical importance of context emerges. The collaborative aspects of design focuses attention on the conception of shared meaning. We introduce and elaborate the concept of shared memory as the embodiment both of context and of shared meaning. Using the concept of shared memory in vertical and horizontal forms, within and between disciplines, respectively, we both account for past observations of design in practice and recommend actions to improve design in the future. We examine several practical implications of the growing importance of shared memory in industrial firms and for design teams. We then consider and recommend specific research programs which will help designers capture and make better use of this critical resource.

Genetic algorithm representations for laminate layups

Abstract The design of laminate layups using a genetic algorithm (GA) search-based function optimizer has been investigated using both a generate-and-test evaluation function and the layup-synthesis rule-base from a knowledge based design system. (The small rule-base from the laminate design was translated into a procedural evaluation function which could be called by the GA.) A simple coding of plies to genes is shown to be applicable in each case, but only when coupled with a penalty function which constrains genetic search to permissible layup candidates. Two experiments have been performed: a comparison of the GA search algorithm with a random/greedy search algorithm and a comparison of the GA with a rule based design system. Comparative tests with the rule based laminate design system are presented for four different load types. These demonstrate the robustness and accuracy of the system for the design of small scale asymmetric laminates.

Design of laminate composite layups using genetic algorithms

Fibre-reinforced laminate composites have attractively high stiffnesses and strengths and low densities. However, designing with laminate composites is more difficult than designing with metals because (a) it involves the design of the material itself, and its manufacturing route, at the same time, (b) laminates are highly anisotropic, and (c) they have complex failure modes. The failure modes and anisotropy combine to make design details unintuitively important and small detailed-design oversights have been responsible for most failures in composite structures. Design is ‘the process of converting an idea into information from which a product can be made’. Thus the central role of information processing in any design activity implies that software should be able to help. Here we show three different ways in which laminate stacking sequences can be designed.

A deformation mechanism map for IN738LC superalloy

This letter reports new data on the isothermal creep properties of the DS alloy IN738LC, which is used as a blading material for the first-row high-pressure stage of gas turbines

Inherently flexible cell communications: A review

Abstract The first generations of Flexible Manufacturing Systems (FMS) are flexible only with respect to implicity predefined types of parts and assemblies: determined by the machines and software comprising the FMS. A more radical form of flexibility is the ability to be readily adapted to produce unforseen product types. It is this inherent flexibility which is becoming a primary, rather than a secondary, requirement of new manufacturing systems architectures. The burden of this flexibility falls almost entirely on software which is the glue that defines what machines constitute an FMS and how they work together. This paper reviews current computer science research which addresses these issues. This paper explores the issue of devising programs and architectures that support their own replacement within the real-time, heterogeneous factory environment. Formal computable specifications for reconfiguration have been proposed as a way of producing flexibility, but this paper argues that self-referential systems based on independently communicating agents are both more flexible and more acceptable in practice. Requirements for long-term, inherent flexibility are shown to share more features with fault-tolerance and error recovery needs than with short-term flexibility. Five partial, complementary solutions are suggested which together should improve the inherent flexibility of future software systems: (1) global information services, (2) high-level standardization such that only the standards actually needed are generated, (3) distributed agent heterarchical architectures, (4) dynamic updating of configuration-oriented software, and (5) computational reflection.

Materials data interchange for component manufacture

Computer-based materials information is vital to the integration of design with manufacture. While some of the challenges associated with representing materials property data in computerized data banks are now well known, development of completematerials information systems still involves many complex and intractable difficulties.There are many conflicting goals in representing materials information and, as yet, there is no generally usefuldata model for describing materials data. A central issue in the data model and in the design of materials information systems is the useful transfer of data from one part of the system to another. This paper discusses the current status of property data interchange and the related data modeling activities.

Data quality in materials information systems

Abstract Materials information systems, especially those used in engineering design, are largely felt to be less useful than they could be. One major reason is that the quality of the systems, and more especially the quality of the data within them, is ‘felt’ to be either low or indeterminate (where ‘data quality’ is taken to mean ‘fitness for use’). Traditional ways of using materials information in design and analysis have not led to the same concern that appears when computerized systems are considered. This is peculiar, since, often, exactly the same data is used in both cases. The survey in the paper takes the view that traditional methods inevitably involve extensive manual reevaluation of the data, and that simplistic computerized methods, by speeding up the process, reduce the degree of personal involvement and the ‘feeling’ for the validity of the data. The sources and deriviations of materials parameters used in finite-element analyses are a particular cause for concern now that this type of software has become much more widely used over the past three years. The quality of materials property data is intimately bound up with the use and perception of data by organizations in the real world. Therefore, the review takes a historical perspective, and records where and by whom insights and conclusions were reached. The presentation of a mere discussion of technical points would have meant that the worth of the review was itself indeterminate; it is important to realize how much of the paper represents a consensus.

Engineering materials information systems

Materials properties information systems are poorly understood. Many databases of materials properties and designations have been produced but, except in the most modest of cases, they have been less successful than their creators had hopedKnowledge based systems (KBS) are subject to exactly the same problems as data based materials information systems and it is important to realize what these are before the special character of KBSs can be used to alleviate them.This paper surveys the unusual and difficult aspects of engineering materials information that must be handled by any organizing methodology, whether manual or computerized, data based or knowledge based, handling information which is stored or inferred.

Superconducting wire turns to electrical power

The discovery of superconductivity at 39K in the metallic compound magnesium diboride two years ago created quite a stir. Since then, physicists and chemists have come a long way in understanding the curious set of circumstances that lead to such a high critical temperature in this widely available material (see Physics World January 2002 pp29–34). At the same time, metallurgists, engineers and entrepreneurs have been focusing on the commercial potential of magnesium diboride as superconducting wire, which was the subject of a one-day meeting in Cambridge, UK, in April.

DATA MODELS AND DICTIONARIES FOR MATERIALS INFORMATION

Some of the same basic elements of materials information and the relationships between them are required in computerized systems designed to support many different kinds of users: materials designers, failure analysts, materials selectors and laboratory and database administrators. A materials information specialist, when first given a problem of representing and relating families of metal alloys, a variety of mechanical properties, test methods and potential processing routes, is inclined to start by sketching some kind of tree-like (hierarchical) representation, perhaps with cross-links (multiple-inheritance networks). Much later it may become apparent that for transferring this information between different software systems, some tabular method based on relational databases becomes necessary because the full generality of the relational algebra is required. The specialist then has much devious reinterpretation of definitions to do to achieve this transformation. However the generality of a relational system, as the lowest common denominator of several materials information systems, then produces problems of its own: it is at too elementary a level to represent clearly some important relationships. The problems are these: hierarchical representations are easy at first, but become difficult and arbitrary at detailed levels, i.e. different people produce different trees. But the relational database approaches fail to capture many hierarchical associations explicitly leaving many functional dependencies only implicit in the tabular structure. What is required is some better representation. What this paper offers is only some understanding of the useful limits of trees and tables, it does not provide a solution.