Learning Forum

[mohan.kola]

Hi, I am doing modal modal analysis of a mass which is hung on to dampers that is compressed by 1mm by bolts. When I am doing this by spring and mass system, the freq is not matching with the test results with my FEA data. Can anybody tell how to model the system in this case and i also tried with damping and without damping and the results same.

Thanks,

Mohan

[Erik Kostson]

Can you please expand more on what you are doing also show as many images as needed in order for someone to understand what you are doing and what the question is.

Thank you

Erik

[mohan.kola]

Hi Erik
thanks for the reply...
here is the details of my work, I have a mass which is hung on to the springs at 8 location (4 on the top and 4 on the bottom side) that is compresses by 1mm.
I have used 3 longitudinal springs (blue line) to represent the damper stiffness along 3 direction at each location and like I said the springs are compressed from 8mm to 7mm (1mm recompressed) using bolts.
first, I am not sure whether I have modelled in the right way and second please tell weather the damper's damping coefficient works in modal analysis, if so what would the effect of 0.1 damping coefficient on the modal behavior.

Thanks Mohan

[Erik Kostson]

Hi

I can not help with this, but have a look on the documentation about damping and damped solvers (DAMP, and QRDAMP) - normally moderate damping (at least as far as I have seen) has little effect on the freq., but that is not always the case. Good luck.

Erik

[mohan.kola]

Hi Erik can you provide the sample APDL code of the damper spring modal analysis .

Thanks Mohan

[Erik Kostson]

HI

We can not provide any sample code - the only I can suggest is to look in the help manual to see if you find anything.

Erik