During our last meeting we decided that an aluminium alloy could be used to create the legs of the crane. So I have done some research and found that there are two main categories of alloys, Wrought and cast. We will be using a cast alloy as it is stronger. However, as there are thousands of variations of cast aluminium alloys, I thought it best to find out the upper and lower strength limits of most cast aluminium alloys rather than to find these values for a specific alloy.
Facts on aluminium alloys
Tensile strength = 320-550 mpa
Yield strength = 250-450 Mpa
Density = 2626-2790 kg/m3
Young’s modulus = 70-74 Gpa
Advantages
· Aluminium alloys have a high strength to weight ratio so using them would make the crane easier to carry.
· Has a low fatigue limits which isn’t a problem as it fits the criteria of our crane perfectly.
· Excellent corrosion resistance
Disadvantages
· Has a lower tensile strength than steel so if a metal pipe (ie. The tripod legs) is to built out of an aluminium alloy. The diameter of the pipe would have to be larger then a pipe made out of steel to be able to deal with the same amount of stress.
· Cost is higher then that of steel.
Sources:
R.E. Sanders, Technology Innovation in aluminium Products, The Journal of The Minerals, 53(2):21–25, 2001.
Metals reference book(5th edn, Butterworths 1976)
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