When we define a RBE2 or RBE2 in nastran, the dof is defined only in gloal coordinate system, is there a way that I can define the RBE2 dof in local coordinate system. My RBE2 element is along a line that is iclined to X and Y axis and I want to keep the rotation about that line as free, but in dof I only get global dof and not local dof to put constraints to.
Is there a way to do it, like for a CBUSH element, I can orient a CBUSH along a local coordinate system and define the stiffnesses in local coordinate system. I sthere a similar way for RBE2 as well.
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I think you're confusing the Nastran Global cordinate system with the Basic coordinate system (a common source of confusion).
In Nastran, "Global" is the collection of nodal displacement coordinate systems (not a single coordinate system). "Basic" is the reference or fixed coordinate system from which everything else is referenced.
See Comparing the Basic and Global Coordinate Systems in the online help.
Therefore, the DOF on an RBE2 are defined in the nodal displacement coordinated system at each node on the RBE2. You need to define a coordinate system with an axis parallel to the line you described, then modify the displacement coordinate system for the grids on the RBE2 to be that local csys.