FINITE ELEMENT MODEL VALIDITY CHECK 4.
Unit Temperature Increase
The Unit Temperature Increase validity check verifies that the model will provide accurate displacements due to temperature loading. This check should be performed on all models used for thermal distortion analyses.
The displacements should be compared to the theoretical solution of alpha*l*deltaT. This comparison can be done easily when a sorted bulk data deck of the model is run through the program THDEF, located on "merger" in MERGER::SYS$SYSDISK:[USER,THDEF]. The program will provide a file containing the theoretical displacements for the model. The displacements from NASTRAN should be the same as the displacements from the THDEF program. The model must contain a kinematic mount to run the THDEF program. Also, the NASTRAN model should contain a kinematic mount for this validity check. A limitation to the THDEF program is that it does not handle local coordinate systems.
The grid point force balance should be zero for all grid points and only forces at the mounting locations should be output when SPCFORCES=ALL is included in the CASE CONTROL. Look at the displacements of the model in your post-processor to make sure it expands as expected.
It is suggested you create a kinematic mount for your model, e.g., one GRID point constrained in all 6 DOFs.
EXECUTIVE DECK must include the following information:
CASE CONTROL must include the following information:
SPCFORCES=ALL DISP=ALL GPFORCES=ALL SPC=100 (both normal plate rotations and kinematically mounted structure) TEMP=50
BULK DATA must include the following information:
TEMPD 50 21. (reference temperature + 1.)
RBE2s that are not joined by coincident nodes should not be used.
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