Harmonic Analysis Loading
Harmonic Analysis Loading
(OP)
I have what is probably a simple question but one which for the life of me I cannot quite come up with on my own. I'm performing a harmonic analysis using Ansys 10 on an electronics chassis with some electrical components. My model consists of beams, solids, shells, and masses. There are four points at each of the chassis corners where it is fastened into an avionics rack. Ultimately, my goal here is to find the displacements in various places when it is excited with a 0.1g sine input from 0 Hz to 2000 Hz.
My question is how does one go about applying loads to these four attachment points? These could be considered the base of the model so to speak. I have tried applying only an inertial load of 0.1g at these points in the direction of interest and the model seems to diverge. In a harmonic analysis can one apply both loads (acceleration in my case) and constraints at the same point and both will be considered? Or is there a different methodology that needs to be taken here? It seems like until I add constraints convergence is something that is not in the cards for me.
Thanks for reading!
-Brian
My question is how does one go about applying loads to these four attachment points? These could be considered the base of the model so to speak. I have tried applying only an inertial load of 0.1g at these points in the direction of interest and the model seems to diverge. In a harmonic analysis can one apply both loads (acceleration in my case) and constraints at the same point and both will be considered? Or is there a different methodology that needs to be taken here? It seems like until I add constraints convergence is something that is not in the cards for me.
Thanks for reading!
-Brian





RE: Harmonic Analysis Loading
Input can be:
=> Harmonic loads (forces, pressures, and imposed displacements) of known magnitude and frequency.
=> May be multiple loads all at the same frequency.
=> Forces and displacements can be in-phase or out-of phase.
=> Surface and body loads can only be specified with a phase angle of zero.
Hope this helps.
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RE: Harmonic Analysis Loading
Thanks for the reply! I do have one question...how does one go about converting and acceleration to a displacement? Since I'm covering a frequency range here I don't believe that the displacement will be the same for each frequency even though the acceleration (0.1 g's) will be.
Would applying the harmonic force which would provide me with 0.1 g's acceleration be a better way of applying the load that I'm looking for?
Thanks for your help,
-Brian
RE: Harmonic Analysis Loading
CODE
C******************************************************
C***** NUMERICAL INTEGRATION OF A FUNCTION USING ******
c***** ANSYS APDL COMMANDS. REQUIRES TWO FILES ********
C***** TIME_AXIS.DAT and FUNC_AXIS.DAT, BOTH MUST *****
C***** BE WITHIN THE WORKING DIRECTORY WHICH **********
C***** INTEGRA.INP IS RUN. THE OUTPUT IS AN ***********
C***** INTEGRAL OF THE FUNCTION GIVEN IN **************
C***** FUNC_AXIS.DAT. CAN BE USED TO INTEGRATE ********
C***** TIME HISTORY (ACCELERATION ETC.) TO OBTAIN *****
C***** OTHER VARIABLES SUCH AS VELOCITY/DISPLACEMENT **
C******************************************************
C******************************************************
C******************************************************
C******************************************************
C**** MUST FIRST SET THE NUMBER OF DATA POINTS ********
C**** SEE THE "no_of_points" VARIABLE BELOW *************
fini
/cle
no_of_points=4096
*SET,XTIME
*SET,XFUNC
*SET,XINTE
*DIM,XTIME,,no_of_points
*DIM,XFUNC,,no_of_points
*DIM,XINTE,,no_of_points
*VREAD,XTIME(1),TIME_AXIS,dat,,1
(1f8.6)
*VREAD,XFUNC(1),FUNC_AXIS,dat,,1
(1f8.6)
C*** integrate
*VOPER,XINTE,XFUNC,INT1,XTIME
*VLEN,no_of_points
/output,OUTPUT_velocity,dat
*vwrite,XINTE(1)
(2f12.7)
/output
Converting acceleration-frequency to displacement-frequency is NOT easy, which is why using force is probably the preferred option.
------------
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