×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Cheater-bar moment capacity

Cheater-bar moment capacity

Cheater-bar moment capacity

(OP)
I am trying to determine the moment capacity of connection of two tubes where one tube fits tightly in the other. I attach a drawing to show how I mean.

Clearly the moment is transfered through friction and through surface pressure. In my particular case the the tubes are made of composite materials with low shear strenght and low transverse compression strength. I would therefore be especially interested in these quantities as a function of the bending moment.
 
The question is similar to the one discussed in thread507-274127: Nested Pipe Moment Capacity but I thought I'd have another go at it.

Thanks / David

http://www.durotec.se

RE: Cheater-bar moment capacity

I think I would consider the tubes a loose fit, disregard friction and consider the compressive force F acting at each of the four contact points between the two tubes.  

F = M/2(L-b) where b is the length of bearing required to resist the force.

If the outer radius at each corner of the tubes is 2t and the inner radius is t, the tubes are not in contact for a length of 2t from the inside of the outer tube wall.  If a is the required width of bearing, the bending moment in the wall of the outer tube would be F(2.5t + a/2) and the tension would be F.

It might be necessary to experiment with different ratios of a:b to find the best combination.

BA

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources