Thin Walled Tube around a 180deg bend

  • Thread starter Thread starter rogueracing
  • Start date Start date
  • Tags Tags
    Bend Tube
AI Thread Summary
The discussion revolves around the viability of a thin-walled polyimide tube subjected to UV exposure and a load of approximately 4 kg around a 180-degree bend. There are concerns about the tube's dimensions, specifically the conflict between the outer diameter and wall thickness, which needs clarification. The tube is expected to maintain its integrity under load despite potential UV-induced capacity loss of up to 33%. Participants suggest that while the tube may stretch under the weight, it should hold as long as sharp clips are avoided to prevent tears. For added safety, a thicker-walled tube is recommended for applications requiring more margin.
rogueracing
Messages
2
Reaction score
0
Hey guys any help you can help me solve a problem at work. I've been UV testing some polymide tubing and I need to know if it will survive one of our manufacturing processes post UV exposure. The OD is 21 (0.91 mm) thou and wall thickness is 3 (6.4 mm) thou. It will be loaded with approx 4kg, say 40N around a 180 degree bend/support of 50 mm in diameter. Now in looking for the principal stress am I looking for hoop stress * 2? Been a long day not sure why I am struggling with this one some direction would be lovely. Thanks boys n gals :)
 
Engineering news on Phys.org
The dimensions need a check, 0.91 mm OD conflicts with 6.4 mm wall thickness, although 3 thou (mil?) thickness works with 21 thou OD.
Hanging 10 pounds on a thin polyimide tube will cause it to collapse. Is that an issue?
Is the tube supposed to be load bearing or is the question about internal pressure? What is the extent and duration of the UV exposure?
 
Sorry about the dimensions, I was just leaving and typed it in haste. 0.021'' OD with 0.003'' wall thickness. The tube will have a mandrel line inside, collapse is not an issue as long as the tube does not fail in being loaded with the 4kg for a short period of time on both sides. I am still working out the UV exposure but worst case scenario we are looking to loose a max of 33% in original load carrying capacity. The question is about the resulting stresses as it is in the jig and how the load is distributed.

I have attached a quick sketch to give you an idea. Thank you!

PS: Attached picture should be CW 90 degrees.
 

Attachments

  • 20131106_203722.jpg
    20131106_203722.jpg
    26.5 KB · Views: 659
Last edited:
So we have a plastic tube effectively holding about 20 pounds (2 x 4kg, with a 1/3rd capacity cut).
I'm still iffy on the tube dimensions, .003' is 3/1000 foot is about .91mm wall thickness and .021' then is the OD, about 6.4 mm, about a quarter inch.
If that is correct, it is a pretty puny tube, which I expect would surely stretch with the weight applied, but should hold, provided there are no sharp clips holding it which could start tears.
As long as some stretching is ok for your application there should be no problem, but if you need more margin, a 2 mm or thicker walled tube would give much more leeway.
 

Thread 'Query on Isentropic relationships (such as PV^gamma = constant)'

Hi all, I have a question. So from the derivation of the Isentropic process relationship PV^gamma = constant, there is a step dW = PdV, which can only be said for quasi-equilibrium (or reversible) processes. As such I believe PV^gamma = constant (and the family of equations) should not be applicable to just adiabatic processes? Ie, it should be applicable only for adiabatic + reversible = isentropic processes? However, I've seen couple of online notes/books, and...
View full post »
Thread 'How can I find the cleanout for my building drain?'

Thread 'How can I find the cleanout for my building drain?'

I am a long distance truck driver, but I recently completed a plumbing program with Stratford Career Institute. In the chapter of my textbook Repairing DWV Systems, the author says that if there is a clog in the building drain, one can clear out the clog by using a snake augur or maybe some other type of tool into the cleanout for the building drain. The author said that the cleanout for the building drain is usually near the stack. I live in a duplex townhouse. Just out of curiosity, I...
View full post »

Hot Threads

Recent Insights

Back
Top