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Structural Dynamics

Structural Dynamics

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  3. Can you limit the expansion of modes to only those modes with a high participation factors by using the MXPAND,,,,,,.01,,MODM command to ignore modes below a certain modal mass fraction?

Can you limit the expansion of modes to only those modes with a high participation factors by using the MXPAND,,,,,,.01,,MODM command to ignore modes below a certain modal mass fraction?

Tagged: MODM, MXPAND
    • June 6, 2022 at 9:58 am
      FAQFAQ
      Participant

      Yes, but you have to do the modal expansion is a separate solution pass as shown in the following input.

      /prep7
      et,1,185,,2
      mp,ex,1,1e7
      mp,nuxy,1,.3
      mp,dens,1,.0003

      block,,20,,2,,1
      esize,1
      vmesh,1
      nsel,s,loc,x,0
      d,all,all
      nsel,all
      fini
      ! 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,,, MODM ! Mode selection is based on the modal effective mass, and element
      ! results are requested
      modseloption,no, no,0.90, no,no,no ! Only direction X is selected, a minimum of 90% of the total
      ! mass is requested in this direction
      solve
      finish

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