Once the candidate DOF set has been determined, the characteristic matrices of the candidate set TAM should be extracted from Nastran for use with GA. The first step is to create an ASET card for each DOF in the candidate set and include the ASET cards in a standard SOL 103. Figure 1 shows the two changes that are required to a standard SOL 103 Nastran deck to create the TAM and extract the characteristic matrices. In this example, the candidate DOF ASET cards are included in the file candidate_set.aset. By default Nastran creates a Guyan (Static) TAM based on the DOF on the ASET cards whenever they are present, and the characteristic matrices are written to the punch file in DMIG format using Nastran’s standard parameter EXTOUT[3]. The punch file containing the DMIG mass and stiffness matrices will be imported into the GA.
If the user wishes to use the triaxial accelerometer selection option, the candidate set TAM must include all translational degrees of freedom for all grids in the model. Otherwise, a warning will be issued and the triaxial accelerometer selection option will not be available.
SOL 103 CEND $ TITLE = CANDIDATE DOF SET TAM SUBTITLE = PUNCH MASS AND STIFFNESS MATRIX $ ………………………Standard Case Control data ……………………… $ BEGIN BULK PARAM, EXTOUT, DMIGPCH $ ………………………Standard parameters, model, and solution data ……………………… $ $ File containing ASET cards of the candidate set INCLUDE ‘candidate_dof.aset’ $ ENDDATA |
Figure 1. Sample Nastran deck showing changes to export the mass and stiffness matrices in DMIG format.