Page 464 - Corrosion Engineering Principles and Practice

CHAPTER 11

Materials Selection,

Testing, and Design

Considerations

11.1 Materials Selection
Materials are sometimes chosen by trial and error or simply on the
basis of what has been used before. While this approach frequently
works, it does not always lead to optimization or innovation. The
advent of computers has revolutionized the design process. It is now
possible to make design changes and prototype components rapidly
with very little effort. On the materials side, it is now possible to
generate databases of properties that allows instant retrieval of
desired properties which can in turn be integrated into the design
process. As a result, materials selection has undergone radical
transformation over the years.
An example of such an activity is the development of a materials
selection methodology by Michael Ashby of Cambridge University. In
this approach, materials selection is well integrated into the design
process. The constraints that are identified based on function and
design are used to identify the class of potential materials from the
broad spectrum of available materials. As the design is optimized and
detailed, additional high-precision data from this subset of materials
is considered in order to narrow down the choice to a single material.
Factors like cost and fabricability can also be introduced into the factor
that represents design and functional constraints thus making it a
rather powerful and cost-effective method for materials selection.
In Ashby’s model, a material has attributes: its density, strength,
cost, electrical properties, and so forth [1]. A design demands,
perhaps, a certain profile of low density, high strength, modest cost,
and high electrical conductivity. The problem is that of identifying
the desired attribute profile and then comparing it with those of real
engineering materials to find the best match.
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