Steady state dynamic

[Rain4127]

Dear Guys,
I have a question about the steady-state dynamic step.
I'm looking for a digram that Y-axis is the structure receptance,which is the displacement over the force put on it;and x-axis is the frequency rang that I'm interested.

What I did is apply a concentrated load at the structure and then create a Frequency step to get all the frequencies, and then create a steady-state dynamic step.

Now I already get the digram for displacement against the Frequency. My question is how to get the diagram for the force against the frequency. Because if I just plot concentrated force against frequency, I will just get a straight line with the value that I define earlier for the point load.

Thanks in advance!!!

 

[friedmind]

Hi,
In a Steady-state step, the magnitude of the force is constant for all frequencies. I think you have to divide the displacement value by the force applied (constant).
If you use a force of magnitude=1, the diagram you get is displacement/force on the Y-axis and frequency on the X-axis

hope it helps!

matias

 

[Rain4127]

Hi,Friedmind!Thanks for your help!
What you said is also what I'm secretly hoping is correct.But until now I still can not convince myself about that.The reason is :
The receptance, which is the dynamic diplacement per applied force, should be a curve that all the value is positive.

But now the Displacement against frequency Curve I get has both negative and positive value. So if I divide the displacement by the constant force 1N,NOTHING will change.That's why I'm asking help here,thinking maybe there is a way to find the harmonic force for each frequency.Or maybe there is an option I can choose directly to get the receptance.

Thanks again,Friedmind with big heart!!!

 

[yangkuang]

I have met this situation before. If there is no damping, I think that's becasue of phase shift. I used direct steady state to do simualation of piezoelectric material. I found that before and after the natural fruquency, there was a phase shift of 180. You can use node print to check the magnatitude and the phase.