Bolted Joints in ANSYS

[MrRogers1987]

I am very familiar with Nastran solver codes, but a recent client of mine prefers ANSYS and I am currently trying to bridge the gap between these two software packages. One area in particular that I was curious about is modeling bolted joint connections. Typically in my experience with Nastran it isn't necessary to explicitly model the bolt itself - instead I'll do something like use rigid bodies (RBEs) to connect to the rest of the mesh structure and have a spring element (CBUSH) between these rigid bodies to control stiffness in each DOF.

Example

I came across contact elements and pretension elements, which could be used to explicitly define the bolted connection, but this is more "refined" then I currently need for my analysis. Is it common to implement simplified methods like the one I described above to model these connections? If yes, what are some methods that you've employed?

 

[Nexxon]

Yes, it is common such methods with ansys to simplify the fasteners connections. You can use a "bushing" type of joint, then you can defines the stiffness coefficients in each directions.
The Ansys help describes the procedure to apply it, here is the path:
// Mechanical Application User's Guide // Features // Connections // Joints // Types of Joints

 

[flash3780]

If you're using Ansys Workbench Mechanical, there's a magical feature for modeling solid bolts: The program will automagicly cut the shank of the bolt in half then apply constraint equations and a displacement which gives the desired preload. The only downside is that large displacements can produce odd results with constraint equations. Alternatively, you can apply a contact offset underneath the bolt head to achieve the desired amount of preload.

Of course, there are simpler ways of modeling bolts depending on your desired level of accuracy. Here is a paper that describes various ways of representing bolts in your ANSYS model:

http://www.ansys.com/staticassets/A...elibrary/confpaper/2002-Int-ANSYS-Conf-38.PDF