I want to compare the normal modes implied by a reduced representation with those implied by a full analysis.i have a cantilever beam fixed at one end meshed using 3 20-node hex elements. The variables at 24 equally spaced nodes are selected as masters and a guyan reduction is performed. The normal modes of the reduced system are produced and compared with the normal modes of the full system using the MAC.
1.how do i perform this in NX/FEMAP ?
2. after performing guyan reduction will the natural frequencies differ or be same as the frequencies without guyan reduction ?
Performing MAC requires a DMAP alter and appropriate license. The alter is provided in the NX Nastran installation directory:
The related files are ones named premac and postmac
Only an experenced Nastran user would be likely to get through this method successfully.
Femap does not support this directly, but would allow you to include the DMAP alters etc.
Guyan reduction only is not likely to give the same answers as full model for normal modes and dynamic response, Femap does allow creation of an ASET to set up a guyan reduction. You can also use Femap to add CMS(craig bampton) modes to the guyan reduction and increase the accuracy.