Forced Vibration Analysis in F.E. software

[EngTipX]

Hi All,

I am not sure how to use FE software and specifically ANSYS to conduct Forced vibration analysis.
ANSYS has the following types of Analysis:
Modal Analysis (basically calculates natural frequencies and mode shapes)
Harmonic Analysis (provides the harmonic response under a range of frequencies)
I thought harmonic response would be the most suitable type of analysis. However, I tried using it and got weird results. Let us say I am applying a force of +10Pa this force is tensile and its frequnecy (forced frequency) is omega-f=6e5 rad/sec.

First, the harmonic frequency is a range. I would like to study the response at specific forced frequencies.

Second, let us say I would like to study the response while the applied force is +10Pa "while the force is tensile" or in other words the response at the begining of the harmonic cycle.

Third, what if I would like to apply a shear force of the same frequency.

I did a search and found this thread (not exactly what I was looking for however very helpful)

http://eng-tips.com/viewthread.cfm?qid=140528

 

[EngTipX]

if I may add to Harmonic response analysis. Not only it is a range of frequencies but also it does not apply the harmonic frequency to the force.

What would be the best way to study harmonic forced vibration?

 

[hacksaw]

the explore the forced response you need to include damping

there are several damping models ranging from linear to nonlinear

good luck

 

[EngTipX]

Thanks hacksaw,
I did not understand

the explore the forced response you need to include damping

Let us say you wish to model
m (dx/dt2)+ c (dx/dt)+ k x = F
and F is F=F0*sin(omega*t)
what type of analysis would you use?

 

[EngTipX]

I think I figured it out. However, got more questions
For harmonic Forced vibration you can use Harmonic response analysis. Yes harmonic response solves for a range of frequencies. If you desire a specific frequency
F=F0*sin(omega*t). Then, see the results for that particular frequency. The harmonic response provides results for a range of frequencies.


Now to my question, the harmonic response did not work when the boundary conditions were fixed cylinder around its axis! Why?