Bolt Connections ?

[ozzkoz]

Hi, I am trying to model a threaded cap using FEA. I've set up my loading, set up my mesh so I can do a convergence analysis, etc but am having trouble with the threaded connection.

I'm using the built in bolt connection (basically saying that I have a nut and it's threaded section is bolted to a rigig virtual wall). I split the face of my ID so that the bolt connection applies over the distance of the (un-modeld)threads. What I am finding is that I am getting a stress singularity at the edge of the face which I have defined as the threaded section.

I'm using Cosmos DesignStar but suspect that what I am seeing is not specific to this software. Any ideas on how I can eliminate this stress singularity from my model?

 

[ozzkoz]

After poking around a bit more it seems that my problem was comming from having selected the "tight fit" option. According to the hlep file the "tight fit" option makes the threaded contact face rigid and it only deforms as a rigid body with the virtual bolt.

Is it inappropriate to not use this option on my threaded cap?