Response to impulse cantilever beam

Francesco Porcari

Hello,
I have modeled a beam with a rectangle of L=200mm and H=10mm. Material steel, property shell with thickness = 8mm.
It is a cantilever, so I constrained it in one side. On the other side, I want to apply an impulsive force downward of 1000N.
I create a tabled1 with this value in time domain: 

The load is applied at 0.95s and has a duration of about 0.1s, so I approximate an impulse (it's the correct method?).After that I create a tstep of 0.01s and 20000 steps, because I want to study the motion of the free extreme node of the beam subjected to impulse for the next 20 seconds. 
I insert a tload1, and a loadstep with transient direct response.
At the end, I create a displacement control card for the extreme free node and add a viscous general damping (alpha2 parameter) of 1e-4.

However, the plot of displacement of the node hasn't the aspected behavior: I aspect a damping oscillation down to zero for time tending to infinite.

The model file is at the end of this post. 

 

Thanks to anyone who help me!

Kory

Hi Francesco,

 

I took a look at your model setup and results. Everything seems to be correct. The behavior you are seeing would be expected for a damped oscillation. Hope this helps. Feel free to reach out separately to discuss!