Learning Forum

[sbrusca]

Hello to everyone, 

The question is relative to management of participation factor. 

Is it possible to use a Command APDL for avoiding to exctract frequency with a low value of PF? I remember that I did it in Mechanical but I don't remember the snippet. 

Can you help me? 

Thank you 

[Ankush Choudhary]

Hi,

You can use the MXPAND and MODSELOPTION commands for that. Please check out the below link on this approach.

https://innovationspace.ansys.com/courses/wp-content/uploads/sites/5/2024/01/Considering-specific-modes-in-the-Harmonic-analysis.pdf

[Erik Kostson]

 

 

 

 

Hi

There is also a native setting in wb mechanical and a harmonic response system (MSUP – so modal MSUP harmonic response). It is under analysis settings and is called:

Mode Selection Method – set that to Modal Effective Mass and then set a threshold for the Ratio of Effective Mass to Total Mass (so if set to say 0.2 it will take modes with a Ratio of Effective Mass to Total Mass higher than 0.2).

 

See here for more info on the above:

Coupled Field Harmonic, Harmonic Acoustics, and Harmonic Response Options (ansys.com)

See here how to aview the above help link:

https://innovationspace.ansys.com/forum/forums/topic/how-to-access-the-ansys-online-help/

 

 

 

 

[sbrusca]

Hello to everyone and thank you for your responses. 

I can apply the second method (with a filter in Harmonic Response Options). 

I can not appy the first method because I have this error: 

MXPAND,20,,,NO,0.2,YES,MODM,,
modseloption,no,yes,no,no, no,no, 

With this commands I think that must extract only modes with a PF>0.2 in Y direction. 

And I can not see the participation factors and the simulation does not extract the right frequencies. 

Can you help me? 

Thank you 

[sbrusca]

Maybe I found the reason: 

! Obtain the Modal Solution
/solu
antype, MODAL
modopt, LANB,12 ! Block Lanczos
solve
finish

! Perform the modal selection and expansion
/solu
antype, MODAL, RESTART
mxpand,,,,yes,0.1,, MODM ! Mode selection is based on the modal effective mass, and element
! results are requested
modseloption,no, no,yes, no,no,no ! Only direction X is selected, a minimum of 90% of the total
! mass is requested in this direction
solve
finish

I need to perfom a pre-modal simulation and after I can apply my filters. 

Is it the only solution right? 

Thank you