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Stiffness vs Weight

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Aerowerx

Well-Known Member
Joined
Dec 1, 2011
Messages
6,092
Location
Marion, Ohio
Although they are talking about telescope structures, I found this interesting. And thought it may be of interest to HBAers.

Of course, stiffness isn't the only thing we are concerned about with metal construction.

My emphasis

The stiffness to weight ratio of common materials used for telescope parts can be expressed as the ratio of the materials modulus of elasticity (Young's Modulus) divided by its density. If we then scale the resulting stiffness to weight ratio by dividing by the stiffness to weight ratio for steel, we find that most metals (with the exception of beryllium) have almost the same stiffness to weight ratio. Aluminum and titanium are 5% stiffer than steel per unit weight for example.

If all of the structural elements of a telescope were made from aluminum, the telescope structure (for the same stiffness telescope) would weigh only 5% less.
The "Figure of Merit" for the material including cost of the raw material, can be expressed as the stiffness to weight ratio divided by the cost per unit weight. Steel is 3.8 times more efficient than aluminum based upon this highly simplified analysis. A more detailed analysis must take into account the manufacturing process and the resulting labor costs associated with that process. Typically, the raw material cost for the telescope structure is only 20% of the total cost of the structure. The labor cost is the remaining 80%.


 
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