Spring vs Gap Elements in Nastran

[Burner2k]

Hi,
I am trying to get a better understanding on Gap vs Spring elements in Nastran and their usage. Would appreciate some help with possible physical case for each item.

Per my current understanding, gap elements are more suited for cases where compression (contact) is expected. For example: fastener bearing and heel to toe interaction.

Springs can take both compression & tension and thus if one wants to model rope, a spring representation would be more effective.

Am I correct?

Edit: I trying to find tutorials on Patran's Linear Gap Tool. I've found MSC documents on Non-linear gap elements but nothing yet on Linear Gap Tool, expect a MSC powerpoint presentation dated Oct 2001. On Patran 2014, I am not able to find Linear Gap Tool PCL function. Would appreciate if someone could point me to a decent tutorial as well as finding Gap tool on Patran 2014.

Thanks

 

[aerostress82]

Gap elements are mostly used for sol106 where there will be some contact between parts. So, try to review examples of gap usage for sol106 eapecially.

Per linear gap element utility in patran, patran made a change in sol101 as I understand it. You can use contact card for sol101 in patran2014 and it will be less work to model and for accuracy compared to the patran 2005 linear gap elements utility. Hope this is clear enough. Just check msc website for case studies or google for patran 2014 version. You should be able to find more about the contact card for sol101 in patran2014.

Spaceship!!
Aerospace Engineer, M.Sc. / Aircraft Stress Engineer

 

[nlgyro]

Quoting:

>Springs can take both compression & tension and thus if one wants to model rope, a spring representation would be more effective.

I think you need to be careful before this conclusion is made. A rope works as a tension not in compression. So a spring element will not be ideal for this application.

The use of a GAP element (linear or non-linear) puts additional labor on the modeler to maintain an identical mesh at the region where the gaps are going to be used.

As mentioned by the previous poster, body contact is a good way to address such problems as they are a lot easier to set-up in terms of modeling time.