Rbe3 Um Flag Correction

Chayan
Chayan
Altair Employee
edited April 2022 in Altair Exchange

Overview

Optistruct errors out incorrect UM flag in the model which may be used due to Potential AMLS - Nastran limitation where it cannot handle load acting on more than 500 Independent Nodes, Usually load is applied on an dependant Node of an RBE3 and then use the UM flag to assign the dof of a single Independent node Atleast 6 dof needs to be assigned to constrain 6 Rigid Body Modes *** ERROR #  337 ***  Number of dependent d.o.f.s 3 not equal to  Number of reference point d.o.f.s 6 in RBE3 element 20341169

Usage/Installation Instructions

The attached macro is used to correct the number of dof of Independent grids so that the total dof of independent grid matches with the total DOF of dependent grid.

Steps:

1. Place the macro "RBE3_DOF_Reduction_HT.tcl" and "vector_lib.tcl" in the same directory

2. Isolate all the RBE3 which has UM flag assigned to them.

3. Run the macro "RBE3_DOF_Reduction_HT.tcl" and select the RBE3 elements isolated in Step 2

4. Now the macro would scan trough every single RBE3 and update its dof by assigning other independent grids such that the Total dof match with Dep nodes dof

 

Limitation

Currently if the macro finds a RBE3 which has no UM flag assigned it may throw an error, so please make sure one selects only the RBE3 that has UM flag activated.

Functionality

Interface

Subfunctionality

Utilities

Interface

Nastran, OptiStruct

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