Suitability of material

Now with the calculations completed I can compare the forces which the material will be under with its yield stress.

To recap the values for Aluminium 7075:

Specific Density: 2810 Kg/cb.m

Youngs Modulus: 72 Gpa
Yield Stress: 145 x10^6 pa
USD/LB: 0.97

The calculated stresses &forces:

Max stress experienced: 69 MPa

Max deflection: 0.015 m

As it can be seen the 69 Mpa is well below the materials yield stress of 145 MPa therefore this material will not deform when it is fully loaded which is very desirable. It will also not deform when the beam is at its max deflection as aluminium 7075 can deflect 9-10% before plastic deformation.

Therefore Aluminium 7075 is perfect for this crane as it is light, strong and reasonably priced.

Coating

Aluminium 7075 can also be easily anodized which increases the thickness of the naturally occurring oxidized layer. This layer increases corrosion and wear resistance, as well as creating a good base layer for paint primers and glues than bare metal. This is useful as the crane has to be transported, carried and repeatedly put up and taken down. This would mean that there would be a lot of wear on the crane and it might also be bumped by debris in the disaster zone.