Press fit seal between two BeCu cylinders, *pics*

[random_guy]

Hi All,

I have two beryllium copper parts that are to be placed together with a gap of .005 in between the OD of the inner and the ID of the outer. Approx 1200 psi of force will press on one side, expanding the inner cylinder to create a seal with the other. Check the pic for a better explanation:

http://files.engineering.com/getfil...a13c-4bd0-affe-7eec4098bc2e&file=settings.JPG

The problem is, I cannot get the inner part to expand and meet the outer unless the ID and the OD are the same (no gap). When a gap is placed between them, the inner part is compressed until it begins to expand through the outer, as if the outer cylinder does not exist. Any ideas on how to avoid this?

http://files.engineering.com/getfile.aspx?folder=c01b1180-0234-4007-a23f-ce3ec832bd11&file=min.JPG

http://files.engineering.com/getfile.aspx?folder=42040ed9-0c24-42b2-bf49-fd5ffaf11e5f&file=max.JPG

With no gap:

http://files.engineering.com/getfil...d-fc76-4389-b9d9-95fca0b301f5&file=CYL_VM.JPG

Thanks in advance.

 

[mgage]

I ran into this problem very recently. When you created your design study, did you check the "nonlinear" checkbox. Doing this opens up the "include contacts" checkbox. I wasted a whole day trying to get anything but bonded contact to work until I discovered this.

Marcus

 

[random_guy]

Marcus,

Thank you very much for your help. I spent some time trying to find these options, and found that non-linear features are available only in the advanced version of Mechanica; we only have the basic.

I will try to make some worthwhile assumptions so that I may use the basic package to give a ballpark figure.

Thanks again,

Nick

 

[random_guy]

Turns out we have the advanced version, the option was only greyed out because I hadn't inserted an interface. Here is the process:

Insert > Connection > Interface
*Select Surface*
Type > Contact
Check “Infinite Friction” Checkbox

Click "Run a Design Study"
File > New Static
Check “Include Contacts”

Hope that helps anyone looking for help.