NX Nastran DMAP Programmer's Guide - Kxcad.net

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Extracts real symmetric system eigenvaules
• For maximum efficiency in the Lanczos method, it is recommended that
USET, SIL, and EQEXIN data blocks and SETNAME parameter are specified.
If the size of KAA is not the same as the size of the set indicated by
SETNAME, then PARTVEC should also be specified.
12. If SID=-2, then NE is used to modify the ND parameter. ND is modified
accordingly:
ND*(1+NE/100)
13. For the Lanczos (METH='LAN') and Householder (METH='HOU', 'MHOU', and
'AHOU') methods, if the problem can fit into memory then a "QL" Householder
eigensolution will be performed. If the problem cannot fit in memory then the old
method is used because the "QL" method does not have spill capability.
The criterion for switching from the requested method to the "QL" method is
controlled system cell 359 and the NE parameter. The default value for system cell
359 is 1 which means:
• if METH='LAN' is requested, the program wil automatically switch to
AHOU when the size of the problem less than or equal to NE.
• if METH='HOU', 'MHOU', and 'AHOU' then the program will automatically
switch to the "QL" solution if the problem will fit in memory.
Examples:
1. Suppose the user has a matrix [A] for which he or she wishes to extract
eigenvalues via the classical equation [ A – λI ] { u}
=
0 . Presuming [A] is input
via DMI Bulk Data entries and there is an EIGR or EIGRL Bulk Data entry that is
selected in Case Control (METHOD), the following DMAP sequence will be
sufficient:
PARAML A//’TRAILER’/1/S,N,NCOLA $
MATGEN ,/IDEN/1/NCOLA $
READ A,IDEN,,,DYNAMICS,,CASECC,,,,,,,,/LAMA,VECTOR,MI,
OEIGS,/’MODES’/S,N,NEIGS/1 $
OFP LAMA,OEIGS//$
IF(NEIGS>-1) MATPRN VECTOR// $
2. Suppose that the user wishes to now calculate 5 modes of the equation
[[A] - lambda [I]]{phi} = 0 in a subDMAP where the DYNAMICS and CASECC
data blocks are not available:
$ GENERATE IDEN AS SHOWN IN THE PRIOR EXAMPLE
READ A,IDEN,,,,,,,,,,,,,/LAMA,VECTOR,MI,
OEIGS/'MODES'/S,N,NEIGS////-1////5 $
OFP LAMA,OEIGS//$
IF (NEIGS > -1) MATPRN VECTOR// $
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