Hollow cylinder vs Solid cylinder. Which has a better strength to weight ratio? (1 Viewer)

[CMCDragonkai]

Solid cylinder:
12 mm diameter
Second moment of area = 1.02 * 10^(-9) m^4
BM = 12 kNm

Hollow cylinder:
25 mm diameter
1.2 mm wall thickness
Second moment of area = 6.37 * 10^(-9) m^4
BM = 12 kNm

Which has a better strength to weight ratio?
What the maximum bending stress of each?

Why would anyone ever use a hollow cylinder for a simply supported beam?

 

[David Spade]

work out how much a 12mm dia solid weights compared to a hollow 25mm dia 1.2mm thickness and the lightest wins lol

 

[CMCDragonkai]

Taken from Yahoo answers:

Of course a hollow cylinder will have a better strength: weight ratio than a solid cylinder. The section of a cylinder bearing the most stress in terms of bending is the section furthest from the central axis. So getting rid of most of the inner material affects the overall strength very little. On the the other hand it reduces the weight considerably. It would normally be uneconomic to use a solid cylinder for structural support rather than a hollow cylinder, unless the cylinder is very small in diameter.