cancel
Showing results for 
Search instead for 
Did you mean: 

MODAL ASSURANCE CRITERION

Creator
Creator

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. how do i perform this in NX ? thank you.

3 REPLIES

Re: MODAL ASSURANCE CRITERION

Siemens Phenom Siemens Phenom
Siemens Phenom

Dan,

 

You can use NX FE Model Correlation do do this.

 

http://www.plm.automation.siemens.com/en_us/products/nx/for-simulation/structural-analysis/index.sht...

 

 

There is a detailed tutorial in the NX online documentation. Navigate to Home>CAE>Advanced Simulation>NX FE Model Correlation>Introduction to Correlation

 

 

Re: MODAL ASSURANCE CRITERION

Creator
Creator
many thanks jim. i have used SOL 103- SUPERELEMENT and put the 24 nodes in a-set and ran the analysis for guyan reduction. the frequencies after guyan reduction are way different than the frequencies without guyan reduction. is this correct ? most of the numbers in my MAC table are 0.

Re: MODAL ASSURANCE CRITERION

Creator
Creator

This is not correct. The natural frequencies of the superelement, with identical boundary conditions to the full model, should be very similar, though probably not exact, and the higher frequency modes will start to diverge. Check to make sure you have defined SPOINTS and designate them as members of the QSET to define the modal DOF in the superelement. There should be one SPOINT for each mode requested.