The State of Current Practice in Engineering Design Optimisation
This document provides an introductory level overview of ‘Engineering Design Optimisation’as a technology area and is based, in large measure on an earlier paper summarising material on Product and System Optimisation delivered during the four years of the FENet Thematic Network. Here the concentration is mainly upon ‘product’ and it is understood that what is being considered are things that are technical in nature and require the use of Engineering Analysis at some stage in their design.
FENet was a Thematic Network, funded by the European Commission from August 2001. The network sought to co-ordinate activities within Europe aimed at improving both the quality of industrial applications of finite element (F.E.) technology and the level of confidence that can be placed in the computed results. In excess of 110 organisations were members of FENet,representing eight separate industry sectors:
The activities of the network were focussed on three technology areas: Durability and Life Extension, Multi-Physics & New Technology and Product and System Optimisation.A principal objective of FENet was to collate and structure existing information and to facilitate the efficient exchange of experience and knowledge within, and between, different industrial sectors within the European Community. Whilst in outline this material is drawn from the FENet final report, the applications reported here reflect an expansion in the usage of optimisation that has occurred since that time.
An engineering product is seen as an assembly or an individual part whose form is determined through the design process, such as the wing of an aircraft or a single rib of the wing or even a single rivet fastener connecting the rib to the wing. This product has to perform in such a manner as to meet design requirements and to survive within its operating environment for its design life. The emergence of computational methods in the areas of structural mechanics and fluid dynamics over the past half-century has led to the present day situation in which substantial reliance is placed upon such numerical simulations for the purpose of predicting product performance characteristics and for building safety cases.
In parallel with developments in the areas of engineering analysis, corresponding progress has also been made on optimisation techniques to support the design process but here the take-up has not been as widespread. While in the well-established world of “simulation” the principles are clear (build a model able to reproduce numerically the physics of a phenomenon), in the design optimisation arena the driving force is to first establish a feasible design and subsequently to improve the design. As will be shown, the formulation of a design optimisation process is open to interpretation to a far greater extent.
In conjunction with the above definition of a product, the word ‘system’ encompasses both the behaviour of the product within an assembly to perform a wider set of functions and the production/manufacture/processing that goes into making the product. This may also require extensive use of Flow Solvers and Finite Element Analysis as the resulting strength, stiffness and longevity of the product can be as much dependent upon the processes by which it is made,as upon the design itself. Most of these complex processes are Multi-Physics and their optimisation goals are multi-criteria.
What this book seeks to achieve is firstly to describe the methodologies that are currently available for design optimisation and secondly to review the range of applicability for each method and, if possible, to define which techniques are best suited to any given circumstances.
In Section 2 of the book, design optimisation is placed in an historical context by reviewing the development of the subject, structural optimisation in particular, up to the point of the widespread availability of digital computer resources. The section also introduces a classification of the forms design optimisation problems might take. Section 3 is more mathematical in nature and provides a basic introduction to the techniques of optimisation traditionally referred to as ‘mathematical programming’.
The central element of this State of the Art Review is to be found in Section 4 which links theoptimisation strategies in widespread use to the forms of design problems introduced in Section 2. Finally the emerging role of process integration frameworks is discussed in Section 5.