Distributing coupling or MPCs in Optistruct

Altair Forum User

Hi,

I used RBE2 for creating spiders in my problem. However it stiffens the cross-section of the part. Is there any option to created deformable spiders or multi-point constraints?

I mean option similar to spiders in which all three Dofs of independent node should be transferred to all dependent nodes with any weight factor. I need option similar to distributing couplings in optistruct. Is the optistruct MPCs are similar to the option I require?

Will you give some guidelines on this? How to create this in optistruct?

Altair Forum User

have you tried with RBE3 elements? RBE3 elements do not increase the stiffness.

Altair Forum User

Just a question regarding RBE3.... I use to create 'adhesive-bondings' with the connectors-area-adhesive.

Once done, you have a solid bond connected with your shells by RBE3.

Those RBE3 have an assigned weight and DOF.

Some of them, anyway, become a 0.0 weight, so the optistruct or nastran solver doesn't run. Any ideas why is this with 0.0 weight happening?

regards,

N√∫ria

Altair Forum User

just modify the RBE3 element and add the proper weigth. For more information about RBE3, consult The Nastran or the Optistruct user manual.

Altair Forum User

yes, I can modidy the rbe3 elements ... but what if my mesh isn't regular, so I have different weighting for each node? Do I have to take each rbe3, look for the actual weighting and add the correct one? It can be very time-consuming... is there another possibility?

thanks,

N√∫ria

Altair Forum User

I've just cheked the macro xchange site.

I have found a very nice macro in there, doing exactly what I needed:

25. Januar 2008 Update RBE3 weights updates RBE3 element weights to standard connection use case (weight proportional to distance & sum of the weights = 1)

Great