Metal Foams: A Design Guide

Chapter 5
Design analysis for material selection
A material is selected for a given component because its property profile
matches that demanded by the application. The desired property profile characterizes
the application. It is identified by examining the function of the
component, the objectives which are foremost in the designer’s mind, and
constraints that the component must meet if it is to perform adequately.
The applications in which a new material will excel are those in which
the match between its property profile and that of the application are particularly
good. This chapter describes how property profiles are established. The
Appendix to this Guide lists material-property groups linked with a range of
generic applications. Metal foams have large values of some of these property
groups and poor values of others, suggesting where applications might be
sought.
5.1 Background
A property profile is a statement of the characteristics required of a material
if it is to perform well in a given application. It has several parts. First, it
identifies simple property limits which are dictated by constraints imposed
by the design: requirements for electrical insulation or conduction impose
limits on resistivity; requirements of operating temperature or environment
impose limits on allowable service temperature or on corrosion and oxidation
resistance. Second, it identifies material indices which capture design objectives:
minimizing weight, perhaps, or minimizing cost, or maximizing energy
storage. More precisely, a material index is a grouping of material properties
which, if maximized or minimized, maximizes some aspect of the performance
of an engineering component. Familiar indices are the specific stiffness, E/ ,
and the specific strength, y/ ,(whereE is Young’s modulus, y is the yield
strength or elastic limit, and is the density), but there are many others. They
guide the optimal selection of established materials and help identify potential
applications for new materials. Details of the method, with numerous examples
are given in Ashby (1999). PC-based software systems that implement
the method are available (see, for example, CES, 1999).