Dynamic Response - resonance

[nathanb99]

I am currently trying to model forced vibration on a simple cantilever beam. I am looking to model a resonance scenario, and was wondering if anyone had some suggestions on how to do this in ABAQUS.

Currently, I have determined the natural frequencies and modal shapes of the beam (using the step->frequency). So far, to model the resonance scenario, I have simply taken one of those frequencies of concern, and used the step->Dynamic, Implicit. Then, I placed a symmetric load on the end of the beam, which is applied using a 'periodic amplitude'. This is where I believe I might be doing something wrong - I have the periodic amplitude circular frequency set at my natural frequency, starting time 0, initial amplitude 1, A=0, B=1.

When I run the job, it runs successfully. However, I don't really understand how to arrive at a resonance animation after this point. It seems like I can cycle through some sort of set time steps, each having a different vibration shape.

To summarize: Is there some proper way to create resonance conditions, and then how does one view this scenario?

(I am hoping to move on to dampening, and eventually changes in shape/weight distribution to combat resonance when we know the exciting vibration is very close to the natural frequency of the structure)

Thanks!

 

[Geof180]

If you are exciting it at its natural frequency, you should be at a condition of resonance.

To see it in Abaqus, if I am understanding you correctly, make a new "Set". Maybe select the point of the load application as the set.

At the step where the periodic load is applied, make a new history output request from this set.

Once the analysis is complete, load up the results. Go to your history outputs and select the spatial displacement. This will give you a plot of displacement vs. time.

Geof