I don't get from your sketch not the text what is the circle - I thought that is just marking a plan blow-out picture, but then talking about an unintended gap maked no sense?

If you wish advice on modelling your geometry, I suggest you first explain what you are modelling and what is the purpose/target of your analysis (including sketches/photos, see also Troubleshooting, 2.1.1).

Regards.

I have been learning how to use GiD and Atena recently and I have now faced my first problem. I was hoping someone could take a look and advise:

1. I have two parts, a blue part and a green part.
2. The green part bites in the blue part as the green part is pulled (in real life).
3. I can model the components of the blue section but when I to create the outer diameter I obtain a gap (red).

How do I eliminate this gap and create a section that fits the inside green part?

Here is a link to the image:

https://s15.postimg.org/u0ulu5j8r/finite.jpg

Regards,
MuhendisAus