Material Selection

While the properties of candidate materials have been ascertained a short-list should be established. If it is immediately obvious that one material is outstandingly superior the choice is straightforward. Often there is one property requirement that outweighs all the others. When this is the case the choice is simplified. There may, however, be a number of possible materials, or none may meet all requirements.

A number of procedures have been proposed for eliminating all but one of a number of possible materials. These include an advantage/limitation table; an elimination grid, and ranking methods for properties (and the number of properties) that meet the requirements.

Local factors - using a material which is familiar locally, using a material which has a margin in one specific property that may be of value, or using a material that is suitable for a locally available fabricating or machining technique - will often influence the final choice.

When none of the materials meet the necessary requirements a careful re-examination may sometimes reveal that a change in design environment or operating condition can enable satisfactory performance at minimum extra cost. As a last resort it may be possible to arrange for easy replacement after a fixed time, and to hold a supply of spares.