Using Measured Damping as Input to Mechanical Abaqus Model

[Astentine]

Good morning everyone. I was hoping I could get some help using damping in Abaqus.

A little background is appropriate first I assume. I have a fairly basic model. It's a cantilever beam enclosed in a box frame. The entire system is excited at the base using a shaker, which causes the beam to bend in it's first bending mode. I drive the system at it's resonance frequency. I am able to obtain Q values by comparing the measured tip acceleration to to base acceleration, and subsequently, get my zeta value.

I am using a modal dynamics - steady state analysis to pull out accelerations as a function of frequency.

Currently, I am using the Composite Damping in the Dynamics step and have it defined as:
Start Mode: 1
End Mode: 1
Damping: my zeta value

This approach, however, does not yield a perfect correlation between the Abaqus-predicted tip acceleration and the experimentally measured acceleration. My advisors and I expect the comparison to be exact since we are using the measured damping in the model.


Can anyone tell me if I input the damping correctly, or have any ideas as to what I should do?


Thank you!

 

[Astentine]

Whoops, I have to make an edit. I am using the Direct Damping option in the Modal Dynamics step.