Velocity-Mobilty FRF's
Velocity-Mobilty FRF's
(OP)
Hello,
Iam trying to get a mobility plot (velocity/frequency) from my ansys model. I ran a full harmonic analysis and I have the displacements.
I would like to convert these displacements to velocities, to plot mobility FRF's.
Could anyone tell me how to do it in ANSYS?
Sorry if its a basic 101 question, new to dynamics..and ansys.. :(
Emily
Iam trying to get a mobility plot (velocity/frequency) from my ansys model. I ran a full harmonic analysis and I have the displacements.
I would like to convert these displacements to velocities, to plot mobility FRF's.
Could anyone tell me how to do it in ANSYS?
Sorry if its a basic 101 question, new to dynamics..and ansys.. :(
Emily





RE: Velocity-Mobilty FRF's
2*pi*frequency*i
where i is the square root of -1
M
--
Dr Michael F Platten
RE: Velocity-Mobilty FRF's
If I may, are you trying to get these mobility FRFs from FE to compare against experimental FRFs? I ask this because I am trying to update an FE model by comparing FRFs from FE and expt FRFs.
RE: Velocity-Mobilty FRF's
Good luck with your correlation. If you /can/ get good correlation then it is a piece of work to be proud of.
Cheers
Greg Locock
RE: Velocity-Mobilty FRF's
I have the computed displacements using ansys, so I now probably need to write a little code to multiply my displacements by 2*pi*frequency*i
RE: Velocity-Mobilty FRF's
Emily
RE: Velocity-Mobilty FRF's
Dr Michael F platten already responded to your thread.
This is regarding your statement
"I have the computed displacements using ansys, so I now probably need to write a little code to multiply my displacements by 2*pi*frequency*i"
No need to write a code, mathematical manipulation can be carried out in ANSYS time history post processor-Post 26.
Regards,
Logesh.E
RE: Velocity-Mobilty FRF's
Thank you for your response.
Yes, I need to create variables in time-history post processor and then plot the same.
Meanwhile, I was reading a book, and it said:
{v}=j*omega*{u}
I dont see the 2*Pi .. Is that to convert rad/s to Hz?
Thank you..
Sorry again, if the question was too simple..
Emily.
RE: Velocity-Mobilty FRF's
Cheers
Greg Locock
RE: Velocity-Mobilty FRF's
Thanks for helping me with the Mobility FRF problem.
Once I got my displacements from my ANSYS model, I created the following variables (working in Hz.)
created variable 100 (-1*Pi)
created variable 101 (100*freq)
created variable 102 (101*disp)
Variable 102 is mobility..
Does this look corrrect? I did implement it in ANSYS, and it looks like I have got my Mobility FRF.
Emily.
RE: Velocity-Mobilty FRF's
100 needs to be sqrt(-1)*2*pi
Cheers
Greg Locock
RE: Velocity-Mobilty FRF's
But Iam already working with Hz. during my harmonic analysis.
Do I still need to convert to radians?
Instead I thought it (variable 100) needs to be just sqrt(-1)
Please advice me if Iam wrong.
Emily.
RE: Velocity-Mobilty FRF's
Cheers
Greg Locock