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Author Topic: Is a hollow tube stronger than a solid bar?  (Read 20906 times)

Offline thedoc

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Is a hollow tube stronger than a solid bar?
« on: 03/05/2013 02:30:01 »
John asked the Naked Scientists:
   
Hello,

Which is stronger/stiffer, a solid bar of,say,steel or a thick wall tube (same grade of steel, same outside diameter). Why are bones hollow, or are they?

Thank you,

John , Indianapolis

What do you think?
« Last Edit: 03/05/2013 02:30:01 by _system »


 

Offline RD

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Offline CliffordK

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Re: Is a hollow tube stronger than a solid bar?
« Reply #2 on: 03/05/2013 15:59:22 »
Say you had a 1/2" solid steel rod vs a 1/2" OD pipe, the solid steel rod will be much stronger in general.  However, it would also be much heavier.

If one used the same material, one might be able to make a 1" pipe that would be a little springier than the original solid rod, and also generally resisting bending better.

Bones, while generally hollow, they are filled with marrow including fat, water, and blood cells.  It does reduce weight somewhat because the marrow is a lower density than the solid bone.  It also provides an important function in the body where the blood cells are generated.  The solid part of the bones are also, in fact, living, with osteoclasts and osteoblasts constantly remodelling the bone and repairing small stress fractures.

In nature, one finds both solid and hollow structures.  Most trees are generally solid unless diseased.  Branch sizes, for the most part decrease as one gets further from the bottom of the trunk, and with more branch points.

Grasses, Bamboo, and many fast growing plants are hollow, giving more height, strength, and resistance to cracking with the use of less cellular material.
 

Offline wolfekeeper

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Re: Is a hollow tube stronger than a solid bar?
« Reply #3 on: 05/05/2013 00:31:59 »
It depends what you mean by 'stronger'.

If you mean which has the greater tensile strength, a solid rod, or a hollow pipe, with the same cross-section? It's actually the solid rod.

If you mean, which has the greater axial compressive strength, then it's usually the hollow pipe, because the thicker pipe defies buckling failure to much higher loads.

Also, the pipe is usually much stiffer.
 

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Re: Is a hollow tube stronger than a solid bar?
« Reply #3 on: 05/05/2013 00:31:59 »

 

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