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General Mechanical

General Mechanical

Topics related to Mechanical Enterprise, Motion, Additive Print and more.

Management of Participation Factor

    • sbrusca
      Subscriber

      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
      Ansys Employee

      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
      Ansys Employee

       

       

       

       

      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
      Subscriber

      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
      Subscriber

      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 

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