by Professor Mike F. Ashby
Engineers make things. They make them out of materials. What do they need to know to choose and use materials successfully? First, a perspective of the world of materials - polymers, glasses, ceramics, composites and so forth - and of processes that can shape, join and finish them. Second, an understanding of the origins of these properties and of the ways that they can be manipulated. Third, they need methods for selecting from these menus the materials and processes that best meet the requirements of a design. Fourth, they need access to data for material attributes and - since the quantity of data is large - computer-based tools to enable their implementation. And, of course, they need common sense: the ability to use experience and knowledge of the world at large to recognise inspired choices and to reject those that are impractical.
Material selection involves seeking the best match between the property-profiles of the materials and that required by the design. In collaboration with colleagues at Cambridge University and Granta Design Ltd, UK we have developed material property charts, selection methodologies that enable this match, and that interface with other engineering design tools.
The first task is that of translation: converting the design requirements into a prescription for selecting a material and process to shape it. Any engineering component has one or more functions: to support a load, to contain a pressure, to transmit heat, and so forth. This must be achieved subject to constraints: that certain dimensions are fixed, that the component must carry the design loads without failure, that it insulates or conducts, that it can function in a certain range of temperature, and many more. In designing the component, the designer has one or more objectives: to make it as cheap, or as light, or with as low a carbon footprint as possible. Function, constraints objectives define the boundary conditions for selecting a material and - in the case of load-bearing components - a shape for its cross-section.
The methods and their application to mechanical design, design for the environment and industrial design are documented in the books listed below. Granta Design provides the CES Selector software, enabling engineers and designers to apply these systematic selection methods via an easy-to-use and highly visual tool on their personal computer. An educational version of this selection software is one component of Granta Design's CES EduPack teaching resources, now used in over 700 Universities and Colleges worldwide. Granta also provides the GRANTA MI software system, which helps engineering organizations to manage their materials data.
Ashby M.F., Shercliff, H. and Cebon, D. (2010) "Materials: Engineering, Science, Processing and Design", 2nd edition, Butterworth Heinemann, Oxford, UK. ISBN 978-1-85617-895-2.
Ashby, M.F. (2005) "Materials Selection in Mechanical Design", 3rd edition, Butterworth Heinemann, Oxford, UK. ISBN 0-7506-6168-2.
Ashby, M.F. (2009) "Materials and the Environment - Eco-informed material choice" Butterworth Heinemann, Oxford, UK. ISBN978-1-85617-608-8.
Ashby, M.F. and Johnson, K. (2009) "Materials and Design, the Art and Science of Material Selection in Product Design", 2nd edition, Butterworth Heinemann, Oxford, UK. ISBN978-1-85617-497-8.
The CES EduPack 2010 (2010), Granta Design Ltd., Cambridge, UK (www.grantadesign.com ). (Software and materials teaching resources designed for College and University teaching at all levels)
Copyright AZoM.com, Professor Mike F. Ashby (The University of Cambridge)
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