An important aspect of design for mechanical, electrical, thermal, chemical or other application is selection of the best material or materials. Systematic selection of the best material for a given application begins with properties and costs of candidate materials. For example, a thermal blanket must have poor thermal conductivity in order to minimize heat transfer for a given temperature difference. Industrial design is an applied art whereby the aesthetics and usability of products may be improved. ... In physics, thermal conductivity, k, is the intensive property of a material that indicates its ability to conduct heat. ...

Systematic selection for applications requiring multiple criteria is more complex. For example, a rod which should be stiff and light requires a material with high Young's modulus and low density. If the rod will be pulled in tension, the specific modulus, or modulus divided by density E / ρ, will determine the best material. But because a plate's bending stiffness scales as its thickness cubed, the best material for a stiff and light plate is determined by the cube root of stiffness divided density . This article is about a physical property. ... Density (symbol: ρ - Greek: rho) is a measure of mass per volume. ... This page is a candidate to be copied to Wiktionary. ...

Ashby plots

An Ashby plot, named for Michael Ashby of Cambridge University, is a scatter plot which displays two or more properties of many materials or classes of materials.^[1] An Ashby plot useful for the example of the stiff, light part discussed above would have Young's modulus on one axis, and stiffness on the other axis, with one data point on the graph for each candidate material. On such a plot, it is easy to find not only the material with the highest stiffness, or that with the lowest density, but that with the best ratio E / ρ. Using a log scale on both axes facilitates selection of the material with the best plate stiffness . The University of Cambridge, located in Cambridge, England, is the second-oldest university in the English-speaking world. ...

The Ashby plot below shows density and Young's modulus, without a log scale. Metals are represented by blue squares, ceramics by green, and polymers by red. It was generated by the Material Grapher.^[2]

(Deleted image will be re-added following copyright discussion with Laura Bartolo of the Materials Digital Library Pathway, to happen by November 3 2006. In the meantime, see the Material Grapher reference.)

References

1. ^ Ashby, Michael (1999). Materials Selection in Mechanical Design, 3rd edition, Burlington, Massachusetts: Butterworth-Heinemann. ISBN 0-7506-4357-9.
2. ^ "Material Grapher", Materials Digital Library Pathway MatDL.org.