DOF Springs???

[legersalazar]

Hello Forum,

I've been reading about modeling fasteners on the web and all sources suggest to use "spring/damper" elements (CBUSH) in lieu of DOF Springs.

My question to you is:

What are "DOF springs" used for???

Thank you,

Whyowhyowhy

 

[rb1957]

providing a elastic connection between pieces, like rivets.

 

[legersalazar]

@rb1957

Aren't "Spring/Damper" elements (CBUSH) preferred for any type of fasteners (including rivets)?

 

[rb1957]

CBUSH = dof spring ... CBUSH is the NASTRAN element (used to be CELAS), "dof spring" is FeMap modelling

 

[legersalazar]

I'm working with FEMAP Version 10.2.1A (preprocessor) and NX Nastran (solver) and it's telling me that my "DOF Springs" are CELAS, not CBUSH.

 

[rb1957]

does it matter ? if the data input for your dof spring is a single stiffness in a specific direction, then it's a CELAS. if the input is more generalised (mulitple stiffnesses, rotational stiffness, damping, ...) then that sounds like a CBUSH. looking at the f06 or your user manual should tell you the specific element used in analysis.

looking at the data entry i have (FeMap 10.3), "dof spring" has a single stiffness (= CELAS) and "spring/damper" multiple (= CBUSH).

look at the f06 to be sure.

 

[legersalazar]

I've noticed a difference in results obtained when using a CBUSH element vs using multiple CELAS elements to simulate a fastener with tension/shear capabilities.

Why and how is this different?

Thank you,

Whyowhy