Material Choices

We chose to use the Aluminium Alloy 7075-O because with zinc as the primary alloying element, It is strong, with strength comparable to many steels. It has good fatigue strength also. Its relatively high cost is why most of the design is not made of this material.

Many groups looked at using 7075 but we chose 7075-O in particular because it is un-heat treated has maximum tensile strength of no more than 276 MPa, and maximum yield strength of 145 MPa. This is more than enough for our crane. The material has elongation of 10% and therefore stretches before ultimate failure.

We decided to go with a mild carbon steel for pretty much the rest of the design but quite a lightweight carbon steel because of its cost benefits and strength. We did undergo stress analysis using aluminium but it was consistently failing and so we decided to go with the stronger, cheaper alternative. The graph above illustrates how much stronger steel is than other materials we considered.