CWELD with NX Advanced Simulation

[potrero]

NX7.5.2, Win7-64

Does anyone (@blasmolero, maybe?) have experience applying CWELD through the NX Advanced Simulation application? I'm having trouble with a very simple test case consisting of two overlapping, rectangular coupons spot-welded at a single point in the middle of their overlapping region. It seems that no matter what options I try (changing mesh offset, mesh size, search distance, Shell definition in Type dialogue, etc), I always get the same error: "Failed element creation: Could not create elements at the highlighted locations. Output group created with failed points.", ... and the Information window says: "Could not find more than one shell PID within specified search distance."

For clarity, I'm attaching an image showing the tool I'm using; it's accessed through the "Connection" drop-down in Advanced Simulation; the Command is called "CFAST/CWELD Connection". I cannot find any documentation of this function in the NX7.5 Help files. There is documentation of CWELD and CFAST in the Nastran help files, of course, but not in the FEM pre-processor help.

Thank you.

 

[louis1m]

Do both coupons have different Physical Properties(PID's)?

 

[potrero]

@louis1m,
That's an excellent point. I'm making good progress towards understanding how this works, and having separate PID's was the 1st mandatory thing I discovered. In NX Advanced Simulation parlance, this means that:
* both shell meshes must have different material property definition (even if it's just a copy of the same property), and therefore:
* both shell meshes must be in different Mesh Containers.

Another important factor is that both shell meshes must have independent nodes in the region you're trying to connect. The out-of-box default for 2D Shell meshes is to attempt to "Match Edges", which will merge coincident nodes. This will cause the CWELD mesh creation to fail. So, uncheck "Match Edges" when creating the shells.

Yet another important factor is the "Search Distance", relative to the mesh size near your CWELD point. I haven't figured out exactly how this works but will try to update if I do.

 

[louis1m]

Since this capability is new in NX752 it will be documented in the "What’s New and Help", which are separate from the 7.5 help.

 

[potrero]

@louis1m,
Good point. I'd missed that this is new in NX7.5.2