Harmonic analysis- base acceleration

[HilaryE]

Hi,

I am looking for some tutorials or example analyses for 'base acceleration'- with use of APDL commands (not Workbench).
The links to the best websites in this regard that I have came across so far are pasted below.
Nevertheless, most of the stuff in those links (and other found) refers to Workbench whereas I need APDL commands (and guidelines how to do it).

http://www.ansys-blog.com/harmonic-analysis/

https://caeai.com/sites/default/files/WB_harmonic_shaker_table.pdf

Under this link there is one example of APDL coding:

http://www.simutechgroup.com/FEA/fea-tips-tricks-ansys-base-acceleration-harmonic-analysis.html

Please help.
Thank you.

Regards

 

[FEAdesserve]

What kind of harmonic load are you applying? Are you looking for a mode superposition analysis or a full harmonic analysis code?
I can provide.

Thank you

 

[HilaryE]

@FEAdesserve
Thank you for your response.
The load which is applied to the model is either the displacement or the axial force.

For the axial force loading the coding is as follows:
/SOLU
ANTYPE,HARMIC,NEW !Starts a new harmonic analysis
HROPT,AUTO !Auto pick the best solution method
HROUT,OFF !Print complex displacements as amplitude and phase angle (in degrees)
EQSLV,SPARSE !Select sparse direct solver
ASEL,S,AREA,,area number here !Select area to which the axial force is to be applied
NSLA,S,1 !Select nodes associated with selected area
F,ALL,FZ,4 !Apply axial force
ALLSEL,ALL !Re-select all
NSUBST,25 !Get harmonic response at n equally-spaced frequencies within the analysis range
KBC,1 !Use stepped loading within load steps
HARFRQ,5000,5010 !Freq range for harmonic analysis
ALPHAD,0.00001 !Damping coefficient
SOLVE

For the displacement loading the coding is:
ASEL,S,AREA,,area number here !Select area for load application
DA,ALL,UX,0 !Sets UX to 0
DA,ALL,UY,0 !Sets UY to 0
DA,ALL,UZ,-12E-9,12E-9 !Sets displacement in Z axis
DA,ALL,ROTX,0 !Sets ROTX to 0
DA,ALL,ROTY,0 !Sets ROTY to 0
DA,ALL,ROTZ,0 !Sets ROTZ to 0
ALLSEL,ALL !Re-select all
/SOLU
ANTYPE,HARMIC,NEW !Starts a new harmonic analysis
HROPT,AUTO !Auto pick the best solution method
HROUT,OFF !Print complex displacements as amplitude and phase angle (in degrees)
EQSLV,SPARSE !Select sparse direct solver
NSUBST,25 !Get harmonic response at n equally-spaced frequencies within the analysis range
KBC,1 !Use stepped loading within load steps
HARFRQ,5000,5010 !Freq range for harmonic analysis
ALPHAD,0.00001 !Damping coefficient
SOLVE

Thanks.

 

[FEAdesserve]

Do you know that a mode superposition method is faster?
You try performing modal first and then perform Harmonic. Make sure you extract modes for frequencies upto 2 times of that required in Harmonic and then perform harmonic on modal results.

Regards,
Desserve Engineering Solutions

 

[EHen]

@FEAdesserve

I've been looking into this as well; I'd like to model a:
1x1/8x8" aluminum beam,
clamped-free boundary conditions,
accelerating at 0.981 m/s^2,
subject to damping from Q (DMPRAT = 1/(2Q), if I'm not mistaken)
with a frequency sweep scanning +/- 2% of 2nd Bend
I'd prefer a MSUP to a full analysis because this is the simple problem, not the complex that this will expand to.

This seems very trivial, but it's not matching my experimental data and hopefully someone has good insight here.

Thanks in advance!