×
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

Bolted Connections

Bolted Connections

Bolted Connections

(OP)
I have six panels to make a box.  These six panels are bolted together.  The panels are built with Solid elements (Hexa and Penta).  I am trying to figure out the best modeling method of the bolted connection from one panel to adjacent panel.  The mesh density of the panels is a minumum of 3 through the thickeness.  At the bolt locations i have removed the elements to simulate the bolt hole.  I then place a center node at the center of each opening through the thickness of the hole.  I use cbar elements to simulate the bolt shaft (minor diameter).  I then spider (wagon wheel) to the outside edge of the hole using rbe3's.  Is there a better or more acurate way of modeling the connection of the panles? Is it better to use rbe2's, springs? Also keep in mind that i have to look at isothermal conditions.  Some elements just jack the stresses up unrealistically.  

I need to determine the loads that are running through the joint so i can determine the stress resulting in the bolt with it preload which would be a hand calculation.  

RE: Bolted Connections

I use RBE2 elements for simulating bolts. And constrain all 6 dofs. RBE3 actually distributes the forces to the connection points by inversly propotional to the RBE3 element length. So I would not prefer using RBE3s. Depending on the stiffness of the materials, only rotational dofs can be constrained.  

RE: Bolted Connections

If all you want from the model is the loads in the fasteners, do the following
1) convert to a plate model (solids are overkill, more complicated to deal with, and not necessaryily more accurate
2) do not bother modelling the hole (overly complicated and you probably won't get the correct bearing deformation anyway).
3) model each plate with separate nodes; locate a node at each fastener location in each plate, these can be at the same location or offset by the plate thicknesses.
4) connect each pair of fastener location nodes with spring elements connecting the in-plane degrees of freedon and bar elements (if the nodes are not coincident) and springs (if the nodes are coincident) for the out-of-plane degree of freedom.
5) use fastener flexibility formulas to calculate the spring/bar stiffnesses; note that you have to include the plate bearing flexibility in the in-plane spring stiffness
6) I recommend making a small model of a one fastener joint loaded axially; use this model to calibrate/test your fastener flexibility values (spring stiffnesses).  If you don't go with the above approach you should make a small model using your solid element/bar approach for the joint and use it to verify your joint idealization.
7) rigid elements in a model at fastener locations are almost always too stiff and will not give correct results unless used very carefully and with a full understanding of their behavior and effects.

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