unit2notes - Unit 2 Screening and ranking: the key to...

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Unit 2 Screening and ranking: the key to optimised selection
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2 CES EduPack Notes for Instructors Frame 2.1 Outline Description Selection has four basic steps. 1. Translation of design requirements into a prescription for a material, identifying the constraints that it must meet and the objective that is desired. 2. The screening out of all materials that fail to meet the constraints. 3. The ranking of those that remain by their ability to meet the objective 4. A search for supporting information for the top-ranked candidates, allowing them to be documented in depth.
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Unit 2: Screening and Ranking 3 Frame 2.2 The design process Description Design starts with the identification of a market need. Concepts (general working principles) are identified to fill the need, and the most promising of these are developed into sketches or diagrams indicating configuration, lay-out and scale (“embodiment”). One or more of these is selected for detailed development, analysing performance, safety and cost. The output is a set of design requirements enabling the construction of a prototype that, after testing and development, goes to manufacture. The product is produced, marketed, sold and used, and – at the end of its life, recycled, incinerated or sent to land fill. Material information enters all stages of the design. At the concept stage the design is fluid and all materials are candidates. Here the need is the ability to scan the World of Materials, but at a low resolution. As the design gels and the requirements become sharper, the need becomes that for information about fewer materials but at a higher level of precision. In the final, detailed, stage when finite-element, optimisation and other analyses are undertaken, the need is for data for just one or a very few materials at the highest precision. We need a procedure of providing this information. The first step is that of translating the design requirements into a specification for materials selection. Further Information More on the design process: The Text, Chapter 2, p.8 - 19
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4 CES EduPack Notes for Instructors Frame 2.3 Design requirements material specification Description This frame summarises the way that design requirements are translated into a specification for selecting materials, elaborated in the frames that follow. The steps are summarised here. Identify the function of the component for which the material is sought. Identify and list the constraints it must meet: ability to carry loads safely, satisfy limits on thermal or electrical properties etc. Identify the objective guiding the design: for aerospace it might be to minimise mass, for a mobile phone it might be to minimise volume, and always there is the objective of minimising cost. Finally, identify the free variables – those that the designer is free to change: usually dimensions or shape, and, of course, the choice of material.
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This note was uploaded on 02/01/2012 for the course MSEG 302 taught by Professor Snively during the Spring '08 term at University of Delaware.

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unit2notes - Unit 2 Screening and ranking: the key to...

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