Connecting two surface on FEMAP using NEI NASTRAN

[UTHorn1374]

I was wondering if someone could guide me in the right direction. My issue is that I am trying to model a pipe with a damping wrap around it. My method to try and model this scenario has been to create the pipe and directly on top of it the layer of wrap. I am creating the two using plate elements with identical mesh sizes and mesh orientations. However, I am trying to connect the two to act together, thus leading me to try the glued connection feature on NEI NASTRAN. However, it does not give me any way to define the properties or enter any at all. I am assuming it is using default properties, yet I am not quite sure what they are or where to find them. Also, I would like to check whether or not they are connected considering I'm not looking at the stresses. Is there any way to know that without using the stresses. Also, Is this the best method to use to connect to surfaces together with similar meshes. It would be ideal considering I am going to glue the two in my physical testing, yet I would like to know the properties that NEI NAstran uses.

 

[kalinka]

Use offset weld type. The properties it needs to glue the parts together are determined automatically. It is easy to control bond stiffness using the SFACT value on the property, where 1.0 is full stiffness. It’s always good to make a simple test case to check your concept.

To check connections - without using the stresses: set the directive, TRSLMODLDATA=ON and import the .BDF file into a new instance of Femap and the contact generated should be visible (or let NEi Tech know,

http://nenastran.com/fea/techSupport).

Lastly, another option to connect surfaces would be to use CBUSH elements, if meshes are identical. They can be generated in Femap using MESH, CONNECT, CLOSEST LINK. The CBUSH property can be adjusted.

 

[BlasMolero]

Hello!,
My preferences are always to use the GLUE surface-to-surface contact, the solver takes care of glue stiffness definition automatically (I run NX Nastran). Glue is a simple and effective method to join meshes which are dissimilar. It correctly transfers displacement and loads resulting in an accurate strain and stress condition at the interface, creating stiff springs or a weld like connection to prevent relative motion in all directions. The grid points on glued edges and surfaces do not need to be coincident. You can adjust the glue algorithm using the corresponding glue control parameters.

You have a few alternatives :
• RBE2 elements to connect both shell mesh using the FEMAP macro under "CUSTOM TOOLS > MESHING > CONNECT NODES ON SURFACES WITH RIGID ELEMENTS".
• To mesh the pipe with laminate composite two-layer elements

I try to avoid when possible the use of both OFFSET & RBE2 resources in any FE model, this could be a limitation sometimes. For instance, offsets should not be used in beam, plate, or shell elements (except CQUADR/CTRIAR) for buckling analysis (SOL105).

Also in nonlinear analysis (SOL106) the specification of offset vectors is not recommended. When geometry nonlinear conditions exist (PARAM,LGDISP,1), the offset vectors remain parallel to their original orientation when computing the differential stiffness. And finally, rigid elements may cause problems if the connected grid points undergo large motions in nonlinear analysis, then take care!!.

Best regards,
Blas.



~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48011 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

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[kalinka]

NASTRAN can do, but NEi Nastran does much more.

In NEi Nastran the GLUE surface-to-surface contact is also handled by the Solver, which takes care of glue stiffness definition automatically. This is done at the Solver level with a PARAM or command.

Glue is a simple and effective method to join meshes, which are dissimilar. It correctly transfers displacement and loads resulting in an accurate strain and stress condition at the interface, creating a transitional stiffness which does not make the connection overly rigid yet prevents relative motion in all directions. The grid points on glued edges and surfaces do not need to be coincident either.

Note that you can adjust all aspects of glued connections in NEi Nastran using either PARAMs, the CONTACTGEN Case Control command (which automatically generated the contact definition based on face to face proximity), or using the BSCONP surface contact Bulk Data entry.