When a material is to be used for a component, the allowed deformation of that component under the expected load is a design choice. For the tie of length, L, and lateral dimensions, t, subjected to a load, F, the permitted elongation is d.

The elongation is related to the applied stress through Hooke's law so that:
(F / t² ) = E (d/ L) , where E is Young's modulus. Also, the mass of the tie is determined by its density and volume: M = rLt².

The material's performance is measured by the force it can carry per unit mass while not extending by more than the permitted design elongation.
For this case: (F/M) = {d / L² } (E / r). The first term contains only the design qualities L and d, and the second term the material parameters.

To select the best material the quantity (E / r) should be maximized. All materials having the same value of this quantity are equivalent under this selection criterion.

From: Ashby and Jones, "Engineering Materials 1," Pergamon (1986)