Bending moment calculation

[s0r0s]

I have:
1. A flange with central hole. Anchored to virtual wall with foundation bolts.
2. A pipe inserted in the hole with one edge.
3. A loading applied to the other one.

According to specification, if a bending moment of 100J is reached, no damage should be made to the pipe, but if a bending moment is over 500J, the pipe should fail.

My goal is to find a suitable pipe wall thickness to meet specification.

Looking for some help with study setup...

 

[kellnerp]

What is a moment of 100J?

Moment is usually given in units of length times force. "J" is an unknown unit to most reading this forum.

What software are you using?

How is the pipe attached to the flange? That makes a big difference.

What is the failure mode of the pipe to be?

Looks like you might be an EE. A quick source of information on setting up this type of problem from a mechanical engineer's point of view would be Engineering Handbook.

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[s0r0s]

Thanks for your reply!

Yep, I'm not familiar with mechanical engineering. But I was also confused with units provided by specification.

Talking about specification, it's "Aerodrome Design Manual" Part 6 by ICAO.
Paragraph 4.9.2 says: <...>The yield point should be no more than 38 mm above the ground surface and should give way before any other part of the fixture is damaged. The yield point should withstand a bending moment of 204 J without failure but should separate cleanly from the mounting system before the bending moment reaches 678 J.<...>
This is the case i'm trying to simulate (with SW2010 SP4.0 Simulation).

 

[s0r0s]

Here are some sort of results I got with static study and Newtons applied. But when I've noticed that ICAO requires a bending moment in J, decided to ask Engineers.

 

[kellnerp]

I found this spec quoted elsewhere using commonly accepted units.

Static tests for verification of the maximum breaking force performed in a laboratory (breakable coupling) are allowed for installations with overall height not exceeding 1.2 m.
• The yield device must withstand a bending moment of 204 Nm but should separate before the bending moment reaches 678 Nm

Are you sure you don't mean N-m instead of J?

You have to predict fracture which means an elastic/plastic non-linear analysis and some idea of the stress-strain and fracture properties of the material in the fracture zone.


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CSWP, BSSE

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[kellnerp]

I was discussing this strange unit, "J", which is in your spec with an associate. Perhaps someone gave the unit of Joule to a N-m torque. This is a mistake. Energy and moment may have the same units but they are in no way equivalent and would make a huge difference in the meaning of the spec.

TOP
CSWP, BSSE

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[s0r0s]

Looks like I'm using preliminary and outdated revision of the document. I should buy a new one.

Thank you, kellnerp!

Now I have to setup my study properly...
1. How threaded connections are treated in COSMOS? For example, my frangible connection has threaded connection to flange? Should I reduce bolt dimensions to fit the hole w/o any intersections?

2. What kind of consideration should I take into account for fracture detection? It is good idea to rely on factor of safety (below 1)?

 

[kellnerp]

Cosmos doesn't have a threaded connection setting. That is up to the user/engineer to know how to do this. Perhaps this FAQ will help:

faq1183-1711

The second book covers the necessary steps to take to model fracture. It is normally part of a formal engineering school training in FEA with a prerequisite of mechanics of materials.

If you don't have any training in fracture mechanics you probably shouldn't be doing this without some mentoring or oversight. You are asking questions that don't rightly belong in a forum about how to use the software.

TOP
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