Stronger or Stiffer? Tube vs Rod: Answers Here!

[saravananrame]

I have some serious confusion regarding the title for the following issue .

I have read on plethora of forums and sites, giving the explanation of why hollow tubing is stronger than solid rod of the same dia or weight by justifying as to why it bends the least .

This makes me ponder ! Stronger or stiffer ? Isn’t that least bending property under a given load ( of hollow tubing ) attributed to stiffness ?

I would also like to clear if these conclusions of mine are right ?

1. Of the same dia – Hollow tubing is stiffer but Solid rod is stronger (owing to the more material present in it )

2. Of the same weight – Hollow tubing is stiffer but both have the same strength (owing to the same amount of material in it - assuming the yield strength is independent of the geometry )

Would be very helpful if someone could kindly throw some light on the same !

Thanks

 

[Chestermiller]

Strength refers to the state of stress necessary to cause a material to fail when it is placed under load. This is very different from stiffness. The key word is failure.

 

[CWatters]

I would also like to clear if these conclusions of mine are right ?

1. Of the same dia – Hollow tubing is stiffer but Solid rod is stronger (owing to the more material present in it )

The rod is stiffer and stronger. Hint: you didn't specify the ID of the tube so the wall thickness could be near zero.

2. Of the same weight – Hollow tubing is stiffer but both have the same strength (owing to the same amount of material in it - assuming the yield strength is independent of the geometry )

Would be very helpful if someone could kindly throw some light on the same !

Thanks

I believe the tube would be stiffer and stronger. One reference say a tube can be twice as strong.