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Author Topic: which of these will be stronger 2cm sq. tubular pipe or 10mm threaded rod  (Read 1076 times)

Offline jrmfiambic

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if we use vertically both materials and hang 500 kg weight on each, which will be stronger enough (10mm threaded rod or 2cm square tubular pipe?


 

Offline evan_au

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Some more information, please?
- Are both objects made of the same material?
- How thick are the walls of the square pipe? (ie does it have the same area of material as the circular rod?)
- I assume it is in tension? (not compression)
- Are there any sideways forces on it (is it swinging in the wind?)

Note that most square objects are not perfectly square, but are slightly rounded. This is because a sharp point concentrates stress, and is likely to result in cracking and failure at this point.
 

Offline Tim the Plumber

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10mm threaded rod will do the job.

I don't know what the other stuff will do. Have you asked the manufacturer? It's also very important how you attach to the rod or bar. This is generally the point of failure.
 

Offline ProjectSailor

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if used vertically, we are looking at tensile forces, and therefore the pipe would be stronger due to greater surface area (of course wall thickness matters if you used tinfoil it would be no good)
 

Offline William McC

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The problem with engineering today is that modern engineers pick and choose what they want from older data, and then design things from that small section of knowledge, that often fail.

As other posters mentioned you would need to know how the materials are fastened. What the materials are made of, and their exact dimensions or else there is no engineering question.

Engineering is where the theories meet the pavement, literally, in both amazing and often catastrophic ways. So you need to really get into some high level understanding of the shapes, sizes, hardness, intended environment, and use of the product.

So often I have seen this theory of round or square pipe verses solid square bar or rod, misused to cause catastrophe. In life there is no scenario where something is just suspended vertically, without, some motion, if only the motion caused by passing nearby motor vehicles. Or the setting of the weight when originally placed, often referred to as the jostle load.

Also consider all materials bend and stretch as you apply force to them. The hardest materials even Tungsten Vanadium used to stamp coins, bend and give regularly. Your automobile in the cold months of winter where temperatures reach freezing, will shrink one eight of an inch from the hot summer days. Now consider that tube in a sudden cold front, it will suddenly shrink while the solid bar may not, because the solid bar can store heat with its mass and limited surface area. Depending on the length, the weights involved, you could create massive forces.

Also consider that when you get near materials give point, which should never happen if you engineered it properly, there is mechanical hardening. Mechanical hardening causes the the thin walled, tube, to harden quickly as it is stretched, apparently increasing its strength. However the cost of this strength increase is done at the expense of the fracture of the metals molecular structure. That material although it did not break is now very brittle and not fit for service. So all of this is really splitting hairs because if you are building things you should not be anywhere near these limits. Elevators used to be designed to 10 times the most outrageous conditions that the elevator might encounter its service.



Sincerely,

William McCormick

 



 
 

Offline William McC

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I also believe you will find that the cross section of the material if equal, in both the tube and solid, will give you approximately the same strength when stretched. That as an earlier poster mentioned would be needed to make an engineering decision on this subject.

These two videos might give you some insight into different shapes and structures interacting with destructive forces. Size, shape, placement, angle of destruction, mounting, can mean nothing or everything.

youtube.com/watch?v=M-SuV6egdeA


youtu.be/SRAh1uDgOwM


Sincerely,

William McCormick


« Last Edit: 06/08/2016 16:26:01 by William McC »
 

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